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NeilS
1st March 2019, 04:42 PM
I'm a bowl turner and don't really enjoy spindle turning. The longer the spindle and the smaller the diameter, the less I enjoy it.

From the bit of spindle turning I do, it seems to me that thin long pieces of wood don't like to be put into compression between centres; they naturally want to deflect sideway. It's like trying to move a piece of string by pushing on the end! String is much more manageable when pulled and not pushed.

If I could pull a thin spindle blank (ie put it into tension), instead of pushing it between the centres, I expect the turning experience would be better.

I've been looking for an off-the-shelf piece of kit that can do this for me. I'm aware of steadies (roller, string, etc), but I'm looking at a different approach here or at least one that is complementary to those methods.

The solution I'm after needs to provide both a holding and rotating grip at the tailstock end of the spindle.

My thinking is that I need:


A morse taper that is already threaded internally to take a draw bar. This will prevent the MT from being pulled away from the tailstock taper.
The MT needs to have a live centre that will work under tension. ie. not come apart when being pulled rather than pushed.
Some form of chuck attach to the live centre to grip and pull the spindle blank.

I have found the following that will do this for me provided they already have the internal thread ready for a draw bar. I'm yet to check with the suppliers about that. I'm also not sure that all of the international sellers will ship to Australia. Apologies if some of the following links have expired by the time later readers get to this post; if so, use the descriptor to search for new or similar listings.

Ready to go complete solutions:

Soba 2 MT Live Centre with 3 Jaw Chuck (https://www.chronos.ltd.uk/acatalog/info-154032.html)

50MM 3 JAW LATHE CHUCK ON A 2MT MORSE TAPER . M12 UNIMAT SL THREAD (https://www.ebay.co.uk/itm/50MM-3-JAW-LATHE-CHUCK-ON-A-2MT-MORSE-TAPER-M12-UNIMAT-SL-THREAD/301568893079?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D20160323102634%26meid%3Dda4086b6ae8d4d80bbe1aba57859b867%26pid%3D100623%26rk%3D1%26rkt%3D1%26sd%3D331318555354%26itm%3D301568893079&_trksid=p2047675.c100623.m-1)

MT2 3 Jaw Self Centering Lathe Chuck 50mm Morse Taper Shank (https://www.ebay.com/itm/MT2-3-Jaw-Self-Centering-Lathe-Chuck-50mm-Morse-Taper-Shank-for-CNC-Drilling/282993513852?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D20131003132420%26meid%3D396c164da95542b885764fc2e7154199%26pid%3D100005%26rk%3D6%26rkt%3D12%26sd%3D231495635119%26itm%3D282993513852&_trksid=p2047675.c100005.m1851)

2MT Shank Revolving Live Center M14x 1 with 50 mm 3 Jaw Self Centering Chuck (https://www.ebay.com/itm/2MT-Shank-Revolving-Live-Center-M14x-1-with-50-mm-3-Jaw-Self-Centering-Chuck/123308264437?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D20131003132420%26meid%3D396c164da95542b885764fc2e7154199%26pid%3D100005%26rk%3D8%26rkt%3D12%26sd%3D231495635119%26itm%3D123308264437&_trksid=p2047675.c100005.m1851)

This one doesn't ship to Australia
High Precision MT2 Shank Revolving Live Center M14x 1 with 65 mm 3 Jaws Self Centering Chuck (https://www.amazon.com/Precision-Shank-Revolving-Center-Centering/dp/B07CPWPVMW)

And, this one is already here in Australia, but looks like one of the above with a hefty mark-up.
2MT / 65mm Revolving Live Centre With 3 Jaw Chuck (https://www.lprtoolmakers.com.au/2mt-65mm-revolving-live-centre-with-3-jaw-chuck/)

There is also the option of adding an adaptor to a live centre to attach one of my existing
chucks.

Hurricane Turning Tools, Live Tailstock Chuck Adapter, 1" x 8 TPI, 2MT (https://www.amazon.com/dp/B079HL6HHR/ref=sr_1_fkmrnull_1?keywords=Hurricane+Turning+Tools+Live+Tailstock+Chuck+Adapter+1+x+8+TPI+2MT&qid=1551344413&s=gateway&sr=8-1-fkmrnull&tag=picclick0f-20)

PSI Woodworking Products LTCA18 Live Tailstock Chuck Adapter 1-Inch by 8TPI Male Thread Mounting to a 2 MT (https://www.amazon.com/PSI-Woodworking-Products-LTCA18-Tailstock/dp/B004CVJC1Q/ref=pd_lpo_vtph_tr_t_2?_encoding=UTF8&psc=1&refRID=D47GWVKH3CW2VTEEA073)


Does anyone know of any other off-the-shelf piece of kit for doing this?

Of course, putting the spindle blank into tension won't eliminate sideways deflection if too much sideways pressure is applied. Of course, all musical instruments that have their strings under tension do vibrate when struck or plucked, but I'm hoping with reasonable technique that turning thin section spindles might be a little more enjoyable (and less fiddly) when done under tension.

Do any of you have any experience to share on any of this?

NeilS
5th March 2019, 06:42 PM
OK, all of those suppliers got back, but none of their Morse Tapers come with a pre-threaded bore to take a draw bar from the rear of the tailstock.

A further search found only one assembly available that provides:


a chuck that attaches to
a live centre, with..... EDIT: I GOT THAT WRONG, IT DOESN'T!!
a MT that is pre-threaded to take a draw bar.

This one;

MT2 3 Jaw Self Centering Lathe Chuck 50mm Morse Taper Shank for CNC Drilling (https://www.ebay.com.au/itm/282993513852)

AS IT TURNED OUT, IT WAS THREADED TO TAKE A DRAW BAR, BUT DID NOT HAVE A LIVE CENTRE.

As always....

Skew ChiDAMN!!
5th March 2019, 07:21 PM
Are you sure that's on a live centre?

You may have more luck with locating such a chuck mounted on MT1 and a live centre that takes the MT1 mounted on a hollow MT2. (So you can use the draw bar.)

And even them you'd need some sort of bearing on the draw bar end to stop it unthreading itself. :think:

smiife
5th March 2019, 07:47 PM
Hi Neil , why not have a chuck on both ends ?
Get yourself one of these for the tailstock end .....

Colin62
5th March 2019, 08:03 PM
Are you sure that's on a live centre?

You may have more luck with locating such a chuck mounted on MT1 and a live centre that takes the MT1 mounted on a hollow MT2. (So you can use the draw bar.)

And even them you'd need some sort of bearing on the draw bar end to stop it unthreading itself. :think:
Then you’d need two draw bars, one to hold the MT1 in the MT2 and one to hold the MT2 in the tailstock. (That’s assuming I’ve understood what you meant).

Nubsnstubs
6th March 2019, 01:27 AM
Neil, what are your diameters of these spindles, and how long would they be when completed?? Also, how many are you looking to do? ............ Jerry (in Tucson)USA

NeilS
6th March 2019, 09:51 AM
Are you sure that's on a live centre?


Thanks Andy, you are absolutely right.

Of course, a live centre could not drill, which I realised half way through my morning shower. Not sure why that salient fact hadn't register with me sooner!

Back to the drawing board.

Acco
6th March 2019, 10:24 AM
Vermec do a live centre with a thread of which I’m sure if you ask, he could drill and tap for a drawbar.

Threaded Live Centres MT2 Revolving (http://www.vermec.com/store/p33/Threaded_Live_Centres%C2%A0_MT2_Revolving_.html)

Maybe he could make you one to your specs?

NeilS
6th March 2019, 10:32 AM
Get yourself one of these for the tailstock end .....

Smiife, that would be the ideal solution if the thread adaptor will not pull out of the live centre and the Morse Taper is already internally threaded to take a draw bar?

How is the thread adaptor held in that live centre that you have posted, Smiife?

So far, I haven't been able to find a MT2 with a live centre that is already threaded ready to take a draw bar. Then there is the issue with the thread adaptor being secured in the live centre so that it will not pull out under tension.

I have considered how I could drill and tap a MT that is not already threaded, but the challenge there is how do you hold and accurately drill the morse taper once it is attached to the live centre?

NeilS
6th March 2019, 10:44 AM
Vermec do a live centre with a thread of which I’m sure if you ask, he could drill and tap for a drawbar.

Threaded Live Centres MT2 Revolving (http://www.vermec.com/store/p33/Threaded_Live_Centres%C2%A0_MT2_Revolving_.html)

Maybe he could make you one to your specs?

I'm starting to think that might be the way I have to go, thanks, Acco.

tony_A
6th March 2019, 01:31 PM
I have a threaded live centre with the same thread as the spindle. With a vicmarc chuck on the tailstock there is a lot of force transmitted through the piece of turned wood to bring that chuck up to speed at startup. A soft start with a gentle ramp up would help.

Tony

NeilS
6th March 2019, 01:35 PM
Neil, what are your diameters of these spindles, and how long would they be when completed?? Also, how many are you looking to do? ............ Jerry (in Tucson)USA

Hi Jerry - Spindle turning is something that I only do occasionally as small jobs for family and fiends. eg, I recently turned some yarn spindles (abt. 8mm diam) for my daughter-in-law, just half a dozen of them, so not production turning.


450335


My next job is some drum sticks for a friend. I anticipate they will benefit from being turned under tension.

Even less occasionally I add small finials to lidded forms, but they are normally short enough to be turned between centres without any much trouble.


450336


This forum thread is really just me playing with the idea of how I can put a spindle blank into tension to see if it improves the spindle turning experience. If it works I will share that on the forum. After that I'm unlikely to use it very often myself, that is until the next grandchild's birthday comes around, etc, etc.

As always, I'm trying to...

NeilS
6th March 2019, 01:45 PM
I have a threaded live centre with the same thread as the spindle. With a vicmarc chuck on the tailstock there is a lot of force transmitted through the piece of turned wood to bring that chuck up to speed at startup. A soft start with a gentle ramp up would help.



Tony - I'm trying to visualise your setup.

Does your live centre have a male or female thread which is the same as your spindle size?

NeilS
6th March 2019, 02:26 PM
Vermec do a live centre with a thread of which I’m sure if you ask, he could drill and tap for a drawbar.

Threaded Live Centres MT2 Revolving (http://www.vermec.com/store/p33/Threaded_Live_Centres%C2%A0_MT2_Revolving_.html)

Maybe he could make you one to your specs?

OK, I have since spoken to Enzo at Vermec.

He will do a one-off for me with an M8 thread added to rear of MT2 and also add Loctite when he presses the bearings into the live centre to keep it in place under tension. As a once-off that will cost me an additional $20, so $119 all up + postage. Should there be enough interest and he were to do a batch of them he said he would setup the CNC machine to do a run and the additional unit cost would come down.

So, thanks again Acco for your suggestion.

If it proves its worth I'll explore a group buy, but that is getting a bit ahead of myself. It may just 'turn' out be a white elephant!

As always...

turnerted
6th March 2019, 03:51 PM
You can buy a transfer mandril from Mcjings for about $50 .This has an M2 taper and an m30x3.5 male thread .This will enable you to mount a chuck on your tailstock .It should not be a big job to drill and tap a thread in the end of the morse taper for a drawbar , after all it doesn't need to be dead acurate . Once you have a transfer mandril you will be suprised how many uses you find for it
Ted

tony_A
6th March 2019, 04:15 PM
Tony - I'm trying to visualise your setup.

Does your live centre have a male or female thread which is the same as your spindle size?

Male thread on the live centre, same as the male thread on the spindle, as per smiife's photo above.
Tony

Skew ChiDAMN!!
6th March 2019, 04:18 PM
OK, I have since spoken to Enzo at Vermec.

He will do a one-off for me with an M8 thread added to rear of MT2 and also add Loctite when he presses the bearings into the live centre to keep it in place under tension. As a once-off that will cost me an additional $20, so $119 all up + postage. Should there be enough interest and he were to do a batch of them he said he would setup the CNC machine to do a run and the additional unit cost would come down.

That's a pretty good price, considering it is a one-off. I'm guessing that Enzo is a tad curious about it himself. :D

I hadn't given any thought to the bearing slipping out under load; the Loctite is a good thought. Probably a good idea for the threaded section too, unless you devise a lock-washer or drill tap for a grub screw.

Tony_A makes a good point, anything turned that way will have to be thick enough to not twist until both ends are up to speed... and then be turned down to size in one sitting.

Colin62
6th March 2019, 06:20 PM
Tony_A makes a good point, anything turned that way will have to be thick enough to not twist until both ends are up to speed... and then be turned down to size in one sitting.
Slowing it down when you’re done will need to be carefully controlled too. If the lathe has a brake, the flywheel effect on the live spinning chuck at the tailstock could destroy the piece.

NeilS
6th March 2019, 06:58 PM
You can buy a transfer mandril from Mcjings for about $50 .This has an M2 taper and an m30x3.5 male thread .This will enable you to mount a chuck on your tailstock .It should not be a big job to drill and tap a thread in the end of the morse taper for a drawbar , after all it doesn't need to be dead acurate . Once you have a transfer mandril you will be suprised how many uses you find for it
Ted

Yes, Ted, I did consider the Mcjing offering. As you point out, theirs is a v. good price, but after contacting them they couldn't assure me that the thread adpator component would stay in place with the way I plan to use it. And, I didn't think I had the necessary skills to retro-engineer it myself. Some others on the forum may be more confident in doing so.

NeilS
6th March 2019, 07:21 PM
That's a pretty good price, considering it is a one-off. I'm guessing that Enzo is a tad curious about it himself. :D

Yes, I was prepared for it to be a lot more. Interestingly, one of the earlier sellers that I listed in my first post has since got back to me after saying their unit had no drawbar thread to ask me a few questions. They are now considering adding a drawbar thread to theirs in the next production run.


I hadn't given any thought to the bearing slipping out under load; the Loctite is a good thought. Probably a good idea for the threaded section too, unless you devise a lock-washer or drill tap for a grub screw.

Without it getting very complicated with an engineering solution and pushing the price way up, the Loctite fix will be good if it does hold up under reasonable tension. But, I'm glad Enzo is going to be doing it. If I were to attempt it I'm sure the bearings would be all glued together tight!


Tony_A makes a good point, anything turned that way will have to be thick enough to not twist until both ends are up to speed... and then be turned down to size in one sitting.

I expect that a variable speed lathe that can be slowly dialed up and down could be essential for long fine spindles. As Colin points out, long fine spindles will be at greatest risk when they are at their thinnest cross section near their completion and during the wind down. This is one of the reasons I was originally looking at the small 50mm chucks which have a lot less mass than a standard 100mm scroll chuck. I also considered Jacobs chucks with less mass again, but they also have a restricted gripping range.

smiife
6th March 2019, 07:50 PM
Smiife, that would be the ideal solution if the thread adaptor will not pull out of the live centre and the Morse Taper is already internally threaded to take a draw bar?

How is the thread adaptor held in that live centre that you have posted, Smiife?

So far, I haven't been able to find a MT2 with a live centre that is already threaded ready to take a draw bar. Then there is the issue with the thread adaptor being secured in the live centre so that it will not pull out under tension.

I have considered how I could drill and tap a MT that is not already threaded, but the challenge there is how do you hold and accurately drill the morse taper once it is attached to the live centre?

Hi Neil, not too sure how It is held together , pressed together I would imagine,
I don, t think it would pull apart if thats what you mean , why do you need a thread for a draw bar , surely a chuck tightened correctly and just a 1/4turn backwards on the tailstock would give enough "pull" for your experiment ?

NeilS
6th March 2019, 11:32 PM
I don, t think it would pull apart if thats what you mean , why do you need a thread for a draw bar , surely a chuck tightened correctly and just a 1/4turn backwards on the tailstock would give enough "pull" for your experiment ?

You could well be right, Smiife.

I'm just cautious about such matters. If I'm going to play about with a lump of metal spinning at 2k rpm, or more, I'd like to be confident that it is going to stay put in the tailstock. I'm getting too long in the tooth to lose any of them.... : - )




Sent from my ZTE T84 using Tapatalk

turnerted
7th March 2019, 11:18 AM
Neil
I just checked this morning and my Mcjing transfer mandril already has a small recess in the end of the morse taper and can be held in a 120 chuck with longnose jaws with the morse taper pointing to the tailstock .Drilling and tapping a hole should be a breeze .
I look forward to hearing the results if you get it set up . I had also thought about spindle turning with a "tension" system .
Ted

Skew ChiDAMN!!
7th March 2019, 11:44 AM
I don, t think it would pull apart if thats what you mean , why do you need a thread for a draw bar , surely a chuck tightened correctly and just a 1/4turn backwards on the tailstock would give enough "pull" for your experiment ?

I think you'll be surprised at how much tension you may need to pull out even a tiny deviation.

It's the classic "tension a cable to pull out sag" problem, except using centripetal forces rather than G in the equation. The straighter the "cable" the more tension is required to remove the same sag amount, quickly approaching infinite tension needed. On paper, anyway.

Of course, it's possible that on the scale we're talking about here the deviation can be brought into "acceptable" limits... I hope so, my fingers are crossed and I'll be quite content to be proven wrong. ;)

('Tis good to see someone actually testing it out; that's what makes the difference between a practical engineer and a University lecturer in the engineering dept. :D )

Bohdan
7th March 2019, 12:42 PM
Another thing to consider is that a thin piece under tension will try to resonate. This may result in chatter or worst the tool digging in and destroying the piece.

Colin62
7th March 2019, 06:12 PM
It's the classic "tension a cable to pull out sag" problem, except using centripetal forces rather than G in the equation. The straighter the "cable" the more tension is required to remove the same sag amount, quickly approaching infinite tension needed. On paper, anyway.
I think the benefit lies in not putting pressure on a long thin spindle which will definitely cause it to bow, more than using the tension to hold it perfectly straight.

NeilS
7th March 2019, 07:00 PM
I just checked this morning and my Mcjing transfer mandril already has a small recess in the end of the morse taper and can be held in a 120 chuck with longnose jaws with the morse taper pointing to the tailstock .Drilling and tapping a hole should be a breeze .
I look forward to hearing the results if you get it set up . I had also thought about spindle turning with a "tension" system .
Ted


Ted, thanks for that information on how the McJing device can be readily held in a woodturning chuck with long nose jaws. Also, that the end of its Morse Taper already has a centre recess hole into which to start the drilling. Any thoughts on how to keep the MT from rotating in the live centre while drilling? My earlier thinking when I thought I might have to do this was that enough masking tape wound around the two components would probably be sufficient if the drilling went up in small incremental sizes.


Interesting that you have also thought about some sort of tension holding system. I can understand why woodturning developed as it did between centres, coming as it from origins like pole lathe turning, but I'm surprised that there has not been any development of tension holding systems between centres since the introduction of clamping style chucks for woodturners, which we have had now for many decades.

There is theoretical support for the benefits of a tension system over compression, but almost no published experimental results, and no off-the-shelf workable system that I could find. The best article on the topic that I could find was Dennis Gooding's:


AN ENGINEER’S LOOK
AT TURNING SLENDER WOOD SPINDLES (http://www.aawforum.org/community/index.php?threads/an-engineer%E2%80%99s-look-at-turning-slender-wood-spindles.12266/)

Also, see this link (http://www.aawforum.org/community/index.php?threads/comparison-of-mounting-methods-for-turning-slender-spindles.12267/)

You will need to be logged on to that forum to see his tables and images. His experimental results showed that a spindle under tension is more rigid and can be turned to a smaller diameter over more length, but the apparatus he use to achieve tension was not a workable solution outside of the experiment.

I could try to replicate Dennis Gooding's results with his setup, but I though it would be more useful to try to find a workable setup that others can readily adopt if it proves to be worth it in terms of cost and greater turning satisfaction.

As always, at least try to......

NeilS
7th March 2019, 07:04 PM
Another thing to consider is that a thin piece under tension will try to resonate. This may result in chatter or worst the tool digging in and destroying the piece.

Yes, Bohdan, that is what this experiment is all about.

NeilS
7th March 2019, 07:33 PM
I think you'll be surprised at how much tension you may need to pull out even a tiny deviation.

In Dennis Golding's experiment he got up to 55 pounds of tension to get his result. This is why I think a drawbar will be a necessary component of a workable solution.


It's the classic "tension a cable to pull out sag" problem, except using centripetal forces rather than G in the equation. The straighter the "cable" the more tension is required to remove the same sag amount, quickly approaching infinite tension needed. On paper, anyway.

Right, as can be seen in any suspension bridge (https://en.wikipedia.org/wiki/Suspension_bridge)!


Of course, it's possible that on the scale we're talking about here the deviation can be brought into "acceptable" limits... I hope so, my fingers are crossed and I'll be quite content to be proven wrong. ;)

Me too, but if it proves to be a dumb idea then I'm also happy to put it too bed...:U

smiife
7th March 2019, 07:47 PM
You could be right, Smiife.

I'm just cautious about such matters. If I'm going to play about with a lump of metal spinning at 2k rpm, or more, I'd like to be confident that it is going to stay put in the tailstock. I'm getting too long in the tooth to lose any of them.... : - )




Sent from my ZTE T84 using Tapatalk

Good point Neil , best to be cautious , I was thinking about it today
And would be better to use a drawbar as you said , belt and braces !:U

artful bodger
7th March 2019, 08:20 PM
So where are the folk who usually turn long slender items, and what do they have to say to save the day?.
I dislike this sort of turning too. Even something as simple as balustrades tends to get the "handball the job to someone else impulse going".
Are you not meant to use the non preferred hand as a steady(on the spinning wood) as you slide along the tool rest (at the same time)to keep the show centered?.

Nubsnstubs
8th March 2019, 02:15 AM
Hi Jerry - Spindle turning is something that I only do occasionally as small jobs for family and fiends. eg, I recently turned some yarn spindles (abt. 8mm diam) for my daughter-in-law, just half a dozen of them, so not production turning.


450335


My next job is some drum sticks for a friend. I anticipate they will benefit from being turned under tension.

Even less occasionally I add small finials to lidded forms, but they are normally short enough to be turned between centres without any much trouble.


450336


This forum thread is really just me playing with the idea of how I can put a spindle blank into tension to see if it improves the spindle turning experience. If it works I will share that on the forum. After that I'm unlikely to use it very often myself, that is until the next grandchild's birthday comes around, etc, etc.

As always, I'm trying to...




Neil, Looking at the stick sticking out of that turned base, I can't imagine you are having a chatter problem. It looks over 1" diameter, and maybe 14" long. Sharp tools and higher speed would probably solve that issue. Another thing to look at maybe is if the wood was a bow making wood, there could be a spring effect that could possibly produce chatter.

I haven't turned very many spindles, but when I do, I tighten it between centers. I'll try to turn the live center by hand. If there is the pressure I think is need, I then turn the lathe on, and make one pass. I'll look at the live center to see if it still spinning. If it is, I'll touch it to see if I can stop it from spinning. I usually find that it does stop, so I just give the quill handle a small turn until I think enough pressure has been applied.

I've found it my case that the chatter I get is from a spindle that has lost the pressure from the tailstock......... Jerry (in Tucson)USA

Skew ChiDAMN!!
8th March 2019, 08:21 AM
I've found it my case that the chatter I get is from a spindle that has lost the pressure from the tailstock......... Jerry (in Tucson)USA

Oddly enough, it works t'other way around too.

Over-tightening the tailstock will "predispose" the blank to bowing out at the slightest touch of the tool, leading to automatic chatter while trying to cut.

I've actually tried doing this deliberately to texture spindles; sadly I cannot call my attempts successful. :B

turnerted
8th March 2019, 10:30 AM
Neil
The nonrotating part of the mandril is greater diameter than the rotating part, therefore holding it while drilling is not an issue .
Ted

jmk89
8th March 2019, 12:11 PM
I've been reading this thread with a great deal of interest and I wondered whether I have missed something in all of this, but if we are creating tension don't we really need to be thinking more about a thrust bearing in the set up rather than the usual live centre bearing that deals with rotary motion.


To explain what I have in mind, I attach a hand drawing which may help. There are four main pieces to this.




In the centre is a drawbar which has a flange on the end which in operation presses back against the forward part of the thrust race.
Bearing on the back of the thrust race is a circular square sided cup with an outside thread which suits your chosen chuck or other work holding device.
The third piece is a Morse taper sleeve that fits in the tailstock. It is not intended to do anything other than locate the device - no forces should be transmitted to it and hence it is a sliding fit on the drawbar. Similarly, the drawbar should not turn because the thrust race will isolate it from the turning motion experienced by the threaded cup transmitted from the work holding device.
My choice for a work holding device would be a four jaw chuck. The possibility of that coming off the threaded cup or the threaded cup working its way off the drawbar would be extraordinarily remote.



You will note that I have put a lock nut on the drawbar - once it has sufficient tension the locknut should be tightened so that the tension isn't lost by vibration or something like that, during turning.


In terms of manufacture, maybe this can be cobbled together from existing pieces (perhaps the drawbar could be a repurposed pen mandrel, the Morse taper sleeve should be relatively easy to drill out, the thrust bearing should be obtainable relatively and the treaded cup could be made from a piece of appropriate threaded rod by drilling through it at the same diameter as the drawbar and then counter boring from the front of the cup to the outside diameter of the thrust race.


The advantage of this is that there are no pieces that can let go accidentally, as far as I can see.


Any thoughts?450423450423

Skew ChiDAMN!!
8th March 2019, 05:35 PM
450423[/ATTACH]450423

That's pretty much the idealised version, yeah.

I'd used a tapered roller bearing instead of a plain thrust bearing, as though the major stresses would be axial there''d still be a fair radial component. Esp. when working close to the chuck. But that's a minor quibble.

NeilS
8th March 2019, 07:58 PM
Jeremy, thank you for your design contribution. With a few minor tweeks, I'm sure it would be effective. No doubt someone who is handy at engineering could readily cobble it together, but the cost of commercial manufacture might put it up market if it is only a limited run accessory.

One thought, a MT collet, as used in the following video (start at about the 2 min mark), might provide an off-the-shelf component for the back end of your design.


https://vimeo.com/114698045

On the bearing type, a live centre as used in the usual compression method between centres can experience as much axial as radial thrust. Some turners really wind up the pressure at the tailstock end to keep the drive spurs engaged at the headstock end. I'm not sure how much tension force will be required to get a desired benefit, but don't expect it will be significantly more than that involved in compression mode. Dennis Gooding's experiment used 55lbs. If necessary, a tapered bearing could be used, as Skew suggests.

NeilS
8th March 2019, 08:30 PM
Neil, Looking at the stick sticking out of that turned base, I can't imagine you are having a chatter problem. It looks over 1" diameter, and maybe 14" long. Sharp tools and higher speed would probably solve that issue.

Sorry, Jerry, I should have been more explicit. Not that 1" carrying post, but the small spindles holding the wool balls around the base. Yes, not that obvious....:roll:

NeilS
9th March 2019, 11:40 AM
One things leads to another.....

Looking for anything else that Dennis Gooding may have written on the subject, I stumbled upon the following article which had a reference to him.

An angle grinder isn't what I have in mind when I think of turning, but the article does address the key issue of how to put a spindle into tension. The article does offer an off-the-shelf solution by putting various components together, although when you add the cost of the components together it is not a cheap option (the A$ and CA$ are close to parity, but for US$ add half again).

Woodturning Slender Spindles (https://www.instructables.com/id/Woodturning-Slender-Spindles/)

Of interest are the comments in the last paragraph about axial oscillations and, although long, those spindles aren't exactly fine. As raised in our earlier discussions, the twist is definitely going to be a limiting factor with thinner spindles. The heavier the revolving part of the tailstock chucking device the more this will come into effect. The weight of the revolving component in the above implementation was about 1Kg.

Your standard 100mm scroll chuck will at that diameter have more momentum (rotational inertia) than a smaller diameter chucking arrangement. Something like a Beall chuck with a smaller diameter has some advantages there. Unfortunately Beall don't make theirs in our common M30x3.5 lathe thread size. Looking at alternatives...

For sizes up to 1/2" grip, the McJing 1/2" DRILL CHUCK WITH MT.2 LIVE TAILSTOCK SHANK (https://mcjing.com.au/categorybrowser.aspx?categoryid=64#DRILLCHUCKwithLIVECENTRE) at A$55 and overall weight of 1.2kg (so about 600gm in the rotating component), looks like the cheapest and lightest option. But, the MT would need to be drilled and tapped for a drawbar and the Jacobs chuck proven to hold to the live centre under tension if it is not threaded on.

Going up to 3/4" grip, the McJing COLLET CHUCK SET (https://mcjing.com.au/categorybrowser.aspx?categoryid=64#COLLETCHUCKSET) at A$125 matched up with their 1" X 8 LIVE THREAD ADAPTOR (https://mcjing.com.au/categorybrowser.aspx?categoryid=64#LIVETHREADADAPTOR) for A$50, with a combined rotating weighing of about 1kg, but taking into account that the MT would need to be drilled and tapped for a drawbar and the live thread may not be secured in the live centre against tension.

For up to 2" grip, the smaller diameter chucks from McJing like their 2-JAW PEN BLANK CHUCK (https://mcjing.com.au/categorybrowser.aspx?categoryid=64#2-JAWPENBLANKCHUCK) (not sure how well those jaws would hold under tension without adaption) or their 2" MINI 3-JAW CHUCK (https://mcjing.com.au/categorybrowser.aspx?categoryid=64#MINI3-JAWCHUCK) with just slightly more weight. The combined cost of live thread and chuck (A$130) is competitive if the same provisos above are met.

They also have a 3" version (1.3kg) which would have some advantage over a standard 4" chuck (at 2.5 to 3kg) in terms of rotational inertia.

In the above article, the Oneway live centre was reported to have managed 100lbs of tension without letting go. It would be good to know what the McJing and other locally available live centres can manage. Luggage scales can weigh up to about 50kg, which would be sufficient to compare it to the live centre reported on in the article. Does anyone have any of those and care to do a similar stress test to that shown in the article?

As always....

NeilS
9th March 2019, 12:23 PM
Neil
The nonrotating part of the mandril is greater diameter than the rotating part, therefore holding it while drilling is not an issue .
Ted

Yes, Ted, I can see that now that I look closely at the image of on their website. And, as you did say, if you hold it in a set of long nose jaws they will reach past the threaded component to the body of their live centre. I think I might even be able to manage that!

Their drill chuck with live centre is going to be more of a challenge.

Regards

Nubsnstubs
10th March 2019, 01:00 AM
http://www.woodworkforums.com/attachment.php?attachmentid=450335&d=1551837830&thumb=1 Sorry Neil. Until I enlarged the picture, I couldn't see the wool balls nor the spindles. You indicated the parts you want to make are 8mm, which is near 3/8" here. Why don't you just get yourself a dowel making jig, and produce your own in dowel. After you make them, cut to size, and reinsert into your chuck and detail whatever shape you choose, and then sand.

the dowel maker I referring to is made by Veritas. Veritas® Dowel and Tenon Cutters - Lee Valley Tools (http://www.leevalley.com/US/wood/page.aspx?p=52401&cat=1,180,42288&ap=1)

I have the 3/8" dowel maker, and then made a jig to be able to turn dowels on my lathe. I don't have pen jaws on the Nova G3 dedicated for making dowels, but I remove the jaws that enables the jaw slides to close down to 3/16" (4mm?). When I'm done making a dowel, if the dowel was going to be exposed as some type of stick with a detail, I just sand it to a better finish after detailing. If your headstock spindle has a through hole, it should be larger than the dowel's being made. Insert the dowel into the chuck and leave only what you want to turn. It's also a lot less expensive and complicated than the other options you are looking at.

I'm not trying to promote my videos, but I do have one on making dowels on Youtube. It's over 30 minutes long. https://www.youtube.com/watch?v=0A5Zo53URRI&index=13&list=UUNbQdo6Eey57sGg1jy04_zQ .............. Jerry (in Tucson)USA

Nubsnstubs
10th March 2019, 01:02 AM
Sorry Neil. Until I enlarged the picture, I couldn't see the wool balls nor the spindles. You indicated the parts you want to make are 8mm, which is near 3/8" here. Why don't you just get yourself a dowel making jig, and produce your own in dowel. After you make them, cut to size, and reinsert into your chuck and detail whatever shape you choose, and then sand.

the dowel maker I referring to is made by Veritas. Veritas® Dowel and Tenon Cutters - Lee Valley Tools (http://www.leevalley.com/US/wood/page.aspx?p=52401&cat=1,180,42288&ap=1)

I have the 3/8" dowel maker, and then made a jig to be able to turn dowels on my lathe. I don't have pen jaws on the Nova G3 dedicated for making dowels, but I remove the jaws that enables the jaw slides to close down to 3/16" (4mm?). When I'm done making a dowel, if the dowel was going to be exposed as some type of stick with a detail, I just sand it to a better finish after detailing. If your headstock spindle has a through hole, it should be larger than the dowel's being made. Insert the dowel into the chuck and leave only what you want to turn. It's also a lot less expensive and complicated than the other options you are looking at.

I'm not trying to promote my videos, but I do have one on making dowels on Youtube. It's over 30 minutes long. https://www.youtube.com/watch?v=0A5Zo53URRI&index=13&list=UUNbQdo6Eey57sGg1jy04_zQ .............. Jerry (in Tucson)USA

turnerted
11th March 2019, 04:26 PM
Neil
To drill the hole in the drill chuck , maybe you could bore a hole in a bit of wood equal to the diameter of the M2 taper about halfway up its length . then turn out the inside of the hole to aproximate an
M2 taper .Cut a slot from the side of the wood into the hole .Fit the shaft in to the hole , then put the whole thing in a vice and tighten it up .Then drill and tap your hole for the drawbar .It is not going to matter if the hole is not dead centre since this part is not going to rotate .Chances are it will have a centre point recess anyway .
Ted

turnerted
13th March 2019, 04:01 PM
Neil
I was driveing past Mcjings today so I called in to have a look at their rotating 1/2" drill chuck and it does have a centre point recess in the end of the morse taper .
Ted

NeilS
13th March 2019, 05:57 PM
.....Why don't you just get yourself a dowel making jig, and produce your own in dowel. After you make them, cut to size, and reinsert into your chuck and detail whatever shape you choose, and then sand.

[snip]

I'm not trying to promote my videos, but I do have one on making dowels on Youtube.

.............. Jerry (in Tucson)USA

Always happy to hear of other ideas, Jerry.

Also had a look at your video. Interesting! If I was going to be doing a lot of the same size I would definitely look at getting one of those 'pencil sharpeners'.

Have you found a use for those shavings?

NeilS
13th March 2019, 06:02 PM
Neil
I was driveing past Mcjings today so I called in to have a look at their rotating 1/2" drill chuck and it does have a centre point recess in the end of the morse taper .
Ted

Many thanks, Ted. And, also for your suggestion on how to hold the MT on the rotating drill chuck to drill for the drawbar.

I might give it a go.

Nubsnstubs
14th March 2019, 07:54 AM
Always happy to hear of other ideas, Jerry.

Also had a look at your video. Interesting! If I was going to be doing a lot of the same size I would definitely look at getting one of those 'pencil sharpeners'.

Have you found a use for those shavings?

If they are wet, I can get about an 8 foot strand. Someone doing Marquetry might have an interest, but they are way too thin. So far, just shavings to burn or toss........ Jerry (in Tucson)USA

NeilS
15th March 2019, 11:25 PM
The Vermec Threaded Live Centre arrived yesterday, with the customised thread added to the rear of the MT to take a drawbar and Loctite used when pressing in the live centre to (hopefully) ensure that it does not release under tension.

It was grandparenting yesterday and again today, so I haven't been able to use it yet, but did manage to go and get some allthread for the drawbar and give it a test reading to see if it will take the tension that I expect will be required without coming apart.

Dennis Gooding did his tension test at 55lbs (25kg). Stephen Kirby tested his rig up to 100lbs (45kg) but estimated that he was only using 15 to 20 lbs (7-9kg) on his spindles.

So, I split the difference and tested the Vermec up to 32kg (70lbs).


450878


Nothing let go at that tension. The modified Vermec may have taken more, but I couldn't see the benefit of doing so at this stage, especially if the required tension to get a desired benefit is substantially less than that. I should also mention that this was a static test, ie. the live centre was not spinning or any lateral forces applied, so under working conditions other factors will come into play. We will see.

I will probably get to try out some spindle work with it over the weekend to see if I can find any benefit from this technique and report back, one way or the other.

Until then...

NeilS
16th March 2019, 06:20 PM
Next step was to see what happens to the chuck in the tailstock live centre when stopping. If this is a problem it could be a party stopper. Stephen Kirby had reported that he was getting chuck oscillations at the tailstock end when stopping. If severe enough and the chuck heavy enough, these could damage a thin spindle.

Test setup: A 500mm length of 9mm dowel (from hardware shop) was use between two chucks of about equal weight and size (2kg and 100mm diam). The dowel was clamped firmly in the jaws of both chucks, but no pressure or tension was applied at the tailstock end.

First test was a running stop at 200rpm, which is not a practical speed for spindle turning, but a safe one to begin with. The previously reported oscillation was evident.

Next, how much more oscillation will there be with 3x that speed and what will be the impact be on the spindle. So, 2nd test, a running stop at 700rpm, ie, press the red stop button at full speed. Result: Almost the same as for 200rpm.

700rpm is still too slow for turning a 9mm spindle, so 3rd test, up the speed to 1500rpm. Press green button, wait until controller reaches full speed, stand back with face shield on and press red stop button. Result: Imperceptibly the same as for 200rpm and 700rpm.

Conclusion: The electronics is doing the all the work of gently slowing down the rpm until the lathe is almost stopped, then hitting the brakes at the very end with the result being the same oscillation happens across the above rpm range.

Unanswered question: Would the same apply at even higher RPMs? And, what would the impact be on a very thin spindle (eg down 2mm to 3mm); would it twist apart? What about a much longer spindle?

Anyway, here is a short video of the oscillation that I am getting on my lathe. It seems minor to me at this stage, but very thin spindles in some woods may object to that amount of twist.



450901


So, all ready to go ahead now and start experimenting with this setup to see if it provides any benefits over standard spindle turning techniques.

NeilS
16th March 2019, 07:52 PM
Using the same length (500mm) of crappy dowel that I used for the oscillation test, I turned the left half under compression with about the same amount of 'push' I would normally use with a live tailstock centre and the right half with some tension (perhaps less than 10kg). Lathe speed was about 1500rpm.

450902


I took the 9mm dowel down at both ends to about 7mm in several places. Closer to the chucks there was no obvious difference. As expected, the further away from the chucks the more deflection and vibration occurred. At this point I started to increase the tension on the right side and with that I experienced the first noticeable benefit, while on the left side, the compression end, typical unwanted candy stick spirals and vibration noises were starting to happen. The more tension that was applied to the right half the better it went with perhaps (I can only guess) a tension in the low teens.

It was time to go thin and at the mid-point where the spindle is at its weakest; down to 3mm, no trouble!



450903

Just a small section down to that size, but a promising initial result. Of interest, the thinnest section held up against the stop oscillations.

I will probably take a few more areas down to 3mm (or so) to see what happens next.

NeilS
19th March 2019, 12:21 PM
Using the same rig as above, I got the following results turning down 480mm long x 9.5mm pieces of dowel to the longest and thinnest cross section I could manage, with and without tension.

Under tension:The tension applied was approx* 3kg (⅛ turn of handwheel). I managed to get down to 3mm diameter over a span of 250mm while learning a few things along the way.

With compression: The pressure applied was similar to what I would normally use with a live centre; ie, as light a possible. I got comfortably down to about 5 to 6mm diameter over a span of about 250mm, but as you do, I pushed on to see if I could do better, but without any success. The middle ⅓ didn’t want to know about it..

Here are the two spindles as far as I could go with both of them. It is obvious which is which.


451006

451007


And here are closeups of the mid section of the two test spindles.


451008 451009


And a brief video to give more perspective on the 3mm spindle.



https://youtu.be/bTDRT8hjvrU

Others, especially those who do a lot more spindle work, could probably do better, but the above results summarise what I could achieve with the two methods of holding the test spindles.

Note: I did not turn down to final size starting from the tailstock and working in small steps towards the headstock, as would traditionally be done. I took 1mm off at a time over the full length working in from both ends. There is little benefit in the incremental approach if you have a 2kg chuck hanging on the spindle end! A lighter chuck configuration on the spindle end would help overcome some of this. See tip below.

Observations

The concern leading up to these experiments was that the tailstock chuck would overrun on stopping (the oscillations previously reported), but the spindle failures that I experienced happened when starting up again after the spindles were down in the 3mm diameter range. They just twisted apart attempting to get the weight of the 2kg chuck at the tailstock end up to speed. There were no failures on ramping down, although at 3mm diameter over 2590mm the oscillations got up to about 120°of rotation (ie, twist, with this particular wood) if the following tip was not employed..

Tip from Tim Skilton: When stopping, turn the lathe off at the powerpoint when the speed has been dialled down to its slowest speed and then both chucks will coast down to a gentle stop, which avoids the VFD applying its stop brake.

Tip: If you must stop and start again, especially as the spindle becomes long a thin, pull the tailstock chuck towards you and give it a helping flick as you start up again. This reduces the severity of the twisting.

Tip: Once stopped, if you need to rotate the spindle (eg. to inspect 360°) hand rotate both chucks at the same time to avoid putting the spindle under unnecessary stress.

Tip: A lighter and smaller diameter chuck on the tailstock end, like a Jacobs chuck on a live centre (with drawbar), is expected to create less twist and oscillations.

Tip: Of course, use the VFD to slowly ramp the speed up and down.

Tip: Listen carefully to the vibrations coming from the spindle. As it gets thinner it starts to behave like a string on a musical instrument. I also thought I could see harmonics happening at different points along the spindle. These might be indicators for there needing to be more or less tension or a different speed.

*Note: The calculated tension used was about 3kg. This was calculated by measuring the force exerted on a set of scales placed between centres when the tailstock wheel was tightened with the same rotation (about 1/8th of a turn) as the reverse rotation used to get the required tension. Not precise, but at least an indication of how much tension I was using. I might try some other setups to see if I can get a reading that I’m more confident about.


Conclusion

I’m not likely to be turning spindles like these (I’m not a Trembleur (https://www.youtube.com/watch?v=4Ik-Dy1NC_8) type personality!) other than for the purpose of this experiment, but I’ve proven to myself that turning with tension is a more pleasant turning experience than the traditional way of holding the blank between centres. Your experience might be different!

The next time I do any straight spindle turning (multi-centre and eccentric pieces may be another matter) I will definitely be getting out this, or a similarly adapted, live tailstock centre, although I’m unlikely to be doing any more of the type of the spindle turning that I was doing 50 years ago. Yes, it has to be that long ago, as the spinner in the following photo is my wife, now in her 70s and grandmother of five… :U


451010

As always...

Skew ChiDAMN!!
19th March 2019, 07:42 PM
Interesting results! :2tsup:

(...and it always strikes me as odd how so many long-term turners' other halves are into spinning/weaving. :rolleyes:)

tony_A
19th March 2019, 09:37 PM
I admire your determination on this one Neil and an interesting result. Somewhat like you, pepper grinders and tool handles are about the extent of my spindle turning.

NeilS
31st March 2019, 07:24 PM
Following on from my earlier experiments with the Vermec Live Centre (see previous posts) I ordered a 2" mini chuck from McJing, plus their live centre adaptor to match the 1"x8 thread on the mini chuck.

The purpose for this was to see if a smaller chuck (and matching lighter adaptor) would make any difference to the oscillations experienced with the heavier chuck on the tailstock end. Those oscillations limited the thinness and length of the spindle that could be achieved despite slowly dialing down the speed and turning the power off to let the lathe coast down to gradual stop (ie, no electronic braking) as suggested by Tim Skilton. In my previous experiments I found that the twisting in thin section spindles caused a twist fracture when I got below about 3 to 4mm on the test wood I was using. Starting up, which is more abrupt, probably had a similar twist effect, at least in one direction, but this was not as observable like the oscillations on stopping.

The items ordered from McJing arrived promptly (as usual) and the mini chuck is certainly small and light.


451791 451792

451793


The mini chuck and the live component of its tailstock assembly weighs about one quarter of the Vermec with a 4" chuck attached (Nova and Vicmarc 4" chucks both weigh about 2kg). Here is a photo to show the relative sizes of the mini chuck assembly and the Vermec.



451794

As you can see the mini is a metal lathe chuck (for miniature engineering jobs), which I heavily fettled so that it wouldn't kill my fingers. I removed the jaws to do that. The only corners of the jaws I didn't round over were the inner holding faces that I intended to use to hold the spindle. I also eased back the first row of gear teeth that protruded beyond the chuck body when wound out that far.



451795

Next I drilled out the back of the Morse Taper ready for threading to take a draw bar. As advised by Turner Ted, I used the my 2" long nosed jaws to hold the MT, aligning it with a standard live centre to get some semblance of trueness. Unlike the Vermec live centre adaptor, which has an adaptor thread diameter (at least for a M30x3.5 thread) that is larger than the live centre housing, the McJing with the 1"x8 thread adaptor has a smaller diameter than the bearing housing and this allows the long nosed jaws to be used to hold the bearing housing on the MT shaft.



451796

I had to work up through small increments in drill sizes to get to 17/64ths, which is the bore needed for the M8x1.25mm thread I am using for my drawbars. The long nosed jaws held the bearing housing sufficiently to complete the drilling, but small drill size increments were necessary.

In use, the mini chuck ran true (at least sufficient for my purposes) on the McJing live threaded adaptor and with the tension I applied (probably about 2 to 3 kg) it didn't budge from its bearings.

I will report on the results from using this mini chuck attached to the McJing live threaded adapor in my next posting.

NeilS
31st March 2019, 07:45 PM
Using the mini chuck as described in my previous post and the same spindle that I was unsuccessful with in compression mode in my previous experiment; yes, the rough as guts effort that I only managed to get down to approximately 5 to 6mm diameter for part of its length, and without any success through its mid one-third.

First thing to report is that there was minimal oscillations with this mini chuck. So much so that I stepped up the belt position to max 3,000rpm, a better speed for thin spindles. I was also able to do less ramping the speed up and down until I got closer to my minimum thickness.

I turned away and turned away. It was almost pleasant, if spindle turning can ever be pleasant for a bowl turner!

Got down to below 2mm over a length of about 300mm. Yes, a useless exercise other than to prove a point. Here we are:


451799

The larger spindle (crossing the 2mm spindle) is the 3mm spindle achieved with the 4" chuck in tension mode during my previous experiment. Here are a few more photos as an indication of size.


451802 451801

For me that settles it on the advantages of using tension instead of compression, at least on long thin spindles, and probably with any spindle.

On the chucks, there is not much difference between the cost of the Vermec with drawbar thread if used with one of your existing chucks compared to the McJing mini chuck combined with their live thread adaptor, although you do have to add the thread yourself for the drawbar with that option.

For 6mm diameter spindles and above, the Vermec + your own chuck will probably work well in most cases. For sub-6mm the mini-chuck comes into its own.

Either way, you may find spindle turning a more pleasant experience when pulling it.

And, as far as I know, you won't go blind from doing this...:U

Anyway, it's back to bowl turning for me.


And, as always....