Thread: Long Thin Spindles - pulling not pushing

Originally Posted by NeilS

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.

Attachment 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.

Attachment 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

Originally Posted by Nubsnstubs

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.

Neil
The nonrotating part of the mandril is greater diameter than the rotating part, therefore holding it while drilling is not an issue .
Ted

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.

1. 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.
2. 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.
3. 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.
4. 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?08032019 Tension spindle device.pdf08032019 Tension spindle device.pdf

Originally Posted by jmk89;2129813Any thoughts?[ATTACH

450423[/ATTACH]08032019 Tension spindle device.pdf

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.

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.

Originally Posted by Nubsnstubs

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....

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

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 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 at A$125 matched up with their 1" X 8 LIVE THREAD ADAPTOR 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 (not sure how well those jaws would hold under tension without adaption) or their 2" MINI 3-JAW CHUCK 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....

Originally Posted by turnerted

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

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

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=0A5Z...y57sGg1jy04_zQ .............. Jerry (in Tucson)USA

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

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=0A5Z...y57sGg1jy04_zQ .............. Jerry (in Tucson)USA

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

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

Originally Posted by Nubsnstubs

.....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?