Locking a Screw - Any Suggestions?

[Anorak Bob]

I am trying to come up with a way of securing an 8mm screw. Here's the background....

I purchased a 30 Taper to 3 Morse adapter to enable the mounting of a Centricator in my mill spindle. The Centricator's 3M arbor is threaded to accommodate a 1/2" BSW drawbar. Most 30/3M adapters are machined to accept tanged arbors and the adapter is threaded to suit a drawbar. The one I purchased has no thread, the idea being that an extended drawbar, engaging the Morse arbor, is used.

I have made both a 1/2" BSW and a 1/2" UNC drawbar from 4140 and the original drawbar is M12. I wasn't keen on making yet another and while I have a few one metre lengths of 1/2" allthread, I've always viewed that stuff as a temporary fix. ( just me being anal )

Among the original accessories available for my mill were 1, 2 and 3 Morse to ISO 30 adapters. They were made to suit both tangs and drawbars and they utilised a removable rear section that was keyed into the taper. Attached is a photo of some accessories, not mine unfortunately, and the arbors can be seen with their separate ends at the centre bottom.

I thought something similar would be an easy alternative to an overlength drawbar. Seemed that way until I tackled slotting the case hardened adapter. Junked 3 slot drills. The end faces of the drills cut well enough, the hardened steel destroyed the flutes. I have a selection of small abrasive slips that came in real handy today, removing the burrs. The removable 4140 end piece is threaded M12 and counterbored to suit a cut down M8 cap screw. That screw then engages the thread on the 1/2" BSW extension, at present a cut down bolt. The M8 screw must be locked in placed without the possibility of unintentional unscrewing but it must allow rotation.

I could but I don't want to use Loctite. I would prefer some mechanical means. I had thought of a taper pin , I have some very small pins but whilst they are small they might be a bit fiddly/piddly. Maybe a purpose made 4140 lock nut, a standard nut is too large in diameter. I had thought of running the thread through the entire length of the 1/2""bolt" and screwing a set screw in from the opposite end as a lock screw. I'd need a pulley tap for the job though. Could be a M2 socket set screw in from the side....

Any bright ideas?

BT

[Sterob]

Why is everything so clean?.....:p

[Anorak Bob]

The photo I referred to in my initial post and somehow didn't attach.:doh: More relevant than swarf .

237852

[RayG]

Hi BT,

I'd keep it simple and just put a grub screw in, maybe 2..

Drill and tap for the grub screws, tighten the bolt up and mark the grub screw locations on the cap screw, then mill small flats on the threaded section where the grub screws come through,

Finally drill small locating holes in the flats for the grub screws to key into.

Regards
Ray

PS.. I didn't think it looked too clean...(even if there is such a thing as "too clean") I was going to suggest a cleanup could be in order... :)

[Stustoys]

Hi BT,
Why not notch the adaptor and cut a set of dogs on the 1/2" BSW bolt? It wont lock the M8 but there would no long be any torque trying to undo it.......... right?

Stuart

[azzrock]

hi bob have you seen 2 or 3 piece locking washer sets. there effective and are used instead of more transnational locking devices such as wiring.

[Steamwhisperer]

Hi Bob,
perhaps, room permitting, a small plug of nylon (or some kind of plastic) under the 2mm socket set screw. It wont damage the thread or were you thinking of the set screw landing on the shank of the M8, or have I completely misunderstood....again:-

Phil

[cba_melbourne]

hi bob have you seen 2 or 3 piece locking washer sets. there effective and are used instead of more transnational locking devices such as wiring.

These are called NORDLOCK washers. As used on aircraft. Made from stainless steel. The very best locking washer that I know of. Do a google search for "nordlock washer" pictures to see how they work. Chris

[Anorak Bob]

A whisker too big. The adapter bore is 13mm. Do you blokes reckon a lock nut would be up to the task? I haven't got any M2 set screws and I do have plenty of 1/2" 4140. A locknut would also make an M12 "bolt" version simple.

And Stu, the 1/2" bolt has to screw into the Centricator's arbor. Having it dogged into the end piece prevents rotation.

BT

[thorens]

The photo I referred to in my initial post and somehow didn't attach.:doh: More relevant than swarf .

237852


Bob.
you got some of the best gear .
which machine is it ? look like very high quality gear to me.

Cheers
Peter

[nearnexus]

Why don't you just use a double flap lock tab between the two parts ?

Pull it all up tight, mark the tab locations, unscrew, mill recesses, reassemble, bend tabs, job done.

Easily make your own custom lock tab.

Rob

[Anorak Bob]

Hi Peter,

That array is from a seller in Holland. He is chasing a bit under 22,000 Euro for the 1975 machine. More here - Machinehandel A.G.Bos#-#Freesmachines (http://www.machinehandelbos.nl/aanbod-machines/freesmachines)

Mine is 13 years older. Came with quite a few accessories but sadly no rotary table or the half round table and saddle shown in the photo. Did come with some other neat stuff. - http://www.woodworkforums.com/f65/schaublin-13-a-119340/#post1166884

Bob.

[azzrock]

These are called NORDLOCK washers. As used on aircraft. Made from stainless steel. The very best locking washer that I know of. Do a google search for "nordlock washer" pictures to see how they work. Chris


thanks chris now i know the name. they are good and well suited to counter board holes

[rogerbaker]

Hi Bob
I have seen some self locking bolts where they have drilled a hole into the thread and put a plug of teflon or similar plastic just proud of the thread. Maybe this would solve the problem?

Roger

[thorens]

Hi Peter,

That array is from a seller in Holland. He is chasing a bit under 22,000 Euro for the 1975 machine. More here - Machinehandel A.G.Bos#-#Freesmachines (http://www.machinehandelbos.nl/aanbod-machines/freesmachines)

Mine is 13 years older. Came with quite a few accessories but sadly no rotary table or the half round table and saddle shown in the photo. Did come with some other neat stuff. - http://www.woodworkforums.com/f65/schaublin-13-a-119340/#post1166884

Bob.

Hi Bob.
that is a great piece of machine .I wish I have spare cash :U

Cheers
Peter

[Stustoys]

And Stu, the 1/2" bolt has to screw into the Centricator's arbor. Having it dogged into the end piece prevents rotation.
But(if I understand what you are trying to do) you can wind the centrictor onto the 1/2" BSW bolt in the adaptor. get it almost tight then fit the adaptor to the mill, tighten the drawbar, that pulls the adaptors 30 taper into the spindle and the MT3 taper into the adaptor.
maybe ;)

Stuart

[Anorak Bob]

Stu,

I hadn't thought of screwing the 3M arbor into place. I slide them in. Based on your suggestion I assembled it by screwing. Worked well enough though removal of the arbor required the removal of the end piece and the screw then the reinstallation the M8 screw to enable the belting out of the arbor. With my intended set up the M8/1/2" bolt assembly is loosened and belted.


Anyway disaster struck this afternoon. I was going to use a simple roll pin to lock the bits together. My slack "centring" didn't pay off.:doh:



237918

[Steamwhisperer]

Bugga. That has certainly ended that end of the countersink Bob Luckily the job's not too badly damaged.

Phil

[Anorak Bob]

Cranking a 60 kilo table up doesn't really provide much sensitivity when drilling a 2.5mm hole Phil. The High Speed Head with it's quill feed was sitting a metre away. Laziness comes with a price.

BT

[Steamwhisperer]

:oo: Double bugga Bob. Agreed, a 2.5mm hole requires a much greater dose of 'feelage' to avoid catastrophe.

Phil

[Ueee]

That sux Bob, i am surprised you managed to drill the hole without having the same outcome. Or did you drill it on the drillpress? If it was me i would have thrown a larger drill in the cordless and "countersunk" the hole that way......but then my work would not hold up to BT quality control!

[Anorak Bob]

That sux Bob, i am surprised you managed to drill the hole without having the same outcome. Or did you drill it on the drillpress? If it was me i would have thrown a larger drill in the cordless and "countersunk" the hole that way......but then my work would not hold up to BT quality control!

Ewan,

Drilling the hole was simple enough. I should have exercised greater care when I centred the spindle. I just whacked a 12mm slot drill in the chuck, touched a flute up against the bar and and wound the Y the desired amount to centre the spindle over the bar. Obviously I cocked something up. With the bar rotated 180 degrees, the hole looks about half a mill out of alignment.

I'm wondering if this project is a dead loss. Here is a photo of a tanged adapter I was given this morning. It is 16 mm shorter than the thing I'm fooling around with. The stumpy version has seen better days but it is evidence that they exist. Maybe I should track one down and move on.

BT

[Stustoys]

Hi Bob,
Ok I think I wasnt fully getting your idea


I hadn't thought of screwing the 3M arbor into place. I slide them in. Based on your suggestion I assembled it by screwing. Worked well enough though removal of the arbor required the removal of the end piece and the screw then the reinstallation the M8 screw to enable the belting out of the arbor. With my intended set up the M8/1/2" bolt assembly is loosened and belted.
I'd thought of that but forgot to mention. If you leave the the MT3 taper half a turn or so loose it will still be pulled tight by the drawbar but have enough movement to be able to knock the taper loose.(though I'm not a huge fan of knocking a taper out that has a centrictor on the other end.....Would be easy enough to make something along the lines of a pulley puller to press them apart?)

Shame about the C/S, your picture doesnt help, it looks huge until you read that the pin is only 2.5mm

Stuart

[Anorak Bob]

Ray, Stu, Aaron, Phil, Chris, Peter, Rob, Roger and Ewan,

Thank you all for your suggestions.

And Steve, you only get to see half a square metre of my shed. Guess what the remaining 30 square metres looks like.:o

BT

[azzrock]

Ray, Stu, Aaron, Phil, Chris, Peter, Rob, Roger and Ewan,

Thank you all for your suggestions.

And Steve, you only get to see half a square metre of my shed. Guess what the remaining 30 square metres looks like.:o

BT

g'day bt
im having a guess that the rest of your shed is in pretty good order.
im hoping mine will be one day to.

[Anorak Bob]

g'day bt
im having a guess that the rest of your shed is in pretty good order.
im hoping mine will be one day to.

Wrong guess Azz! I'm waiting for that same day too.

[azzrock]

hi bob hope yout well. did you give up on this locking problem or gone down another path?

[Anorak Bob]

hi bob hope yout well. did you give up on this locking problem or gone down another path?

I am Aaron. Thank you.

The path has changed a bit. Alan "C-47", the giver of the other shorter adapter, managed to find another same short length adapter in fine condition, which he very kindly gave to me last Friday. It has the parallel extension for an M12 draw bar. The mill's original drawbar fits. Now I'm thinking of making up a screw in insert that will sit at the bottom of that extension and somehow engage the 1/2" BSW thread in the Centricator's arbor. Tricky to describe. The Centricator's arbor would require a reduction bushing threaded maybe M6 to provide suitable clearance.

I'm still thinking about this one.

Bob.

[Anorak Bob]

How's this for a simple solution? The purpose of the first ill fated modification was to prevent the accidental departure of the precious Centricator from the adapter. All I really need is something to arrest the fall. The bung might need to differ a bit from what I've suggested below.

Thank you Azz.

BT

[Steamwhisperer]

That's almost disgustingly simple Bob.

Phil

[azzrock]

was it my bad spelling that did it.
funny provoked isn't all ways a negative word

[Anorak Bob]

That's almost disgustingly simple Bob.

Phil

I had a look at the adapter last night and what's required is a tanged screw-in insert. The flats on the tang will serve for tightening and the safety pin can screw into the tang's exposed side.

Yes Phil, disgustingly simple.:U

Bob.

[Ueee]

Its is very simple, good thinking!

Do you have a supplier for the tanged insert or will you just make one? I'm sure i saw them on a website somewhere.....but can't remember where:?

[Anorak Bob]

Its is very simple, good thinking!

Do you have a supplier for the tanged insert or will you just make one? I'm sure i saw them on a website somewhere.....but can't remember where:?

I'll knock something up out of a bit of 4140 Ewan.

BT

[WCD]

Do you have a supplier for the tanged insert or will you just make one? I'm sure i saw them on a website somewhere.....but can't remember where:?

I was looking for these recently - see Arc Euro Trade - Search Results (http://www.arceurotrade.co.uk/catalogue/results.aspx?search=screw-in+tang)
Cheers,
Bill

[Anorak Bob]

Close Bill, very close, but the Centricator's draw bar thread is 1/2" BSW. Those things are cheaper than chips.

BT

[krisfarm]

Bob,
I made a similar set up to fit a 50mm face mill into a NT40 arbour, the arbor did not have a through hole so I machined up a 1/2"Whitworth threaded tang and loctited it into the face mill. I then seated the face mill into the arbor firmly,set it up in the mill drilled and taped the tang and made a loose fitting removable side tang extension that the allen screw fits into. I do intend to
make a much neater fitting side tang, but so far after using this cutter quite a bit it has not moved. Would your intended use have as much load/vibtation as my face mill? My idea was just to ensure that the face mill could not drop out. Photo to help understand the above description.
Bob

[Anorak Bob]

Bob,
I made a similar set up to fit a 50mm face mill into a NT40 arbour, the arbor did not have a through hole so I machined up a 1/2"Whitworth threaded tang and loctited it into the face mill. I then seated the face mill into the arbor firmly,set it up in the mill drilled and taped the tang and made a loose fitting removable side tang extension that the allen screw fits into. I do intend to
make a much neater fitting side tang, but so far after using this cutter quite a bit it has not moved. Would your intended use have as much load/vibtation as my face mill? My idea was just to ensure that the face mill could not drop out. Photo to help understand the above description.
Bob


The intended use of my setup would be less vigorous than cake decorating Bob. :U My side tang doen't need to be much more than a screw in stud. I'm heading up the shed now to start on it.

Bob.

[krisfarm]

Bob,
One point I forgot to mention is height of the location on the taper of your threaded hole. I made mine further up the taper to allow you to start the taper engagement and be able to see the hole so that you could rotate the two pieces to ensure correct alignment before the taper took up fully. Hope this makes sense for you. I will be looking for your finished work. You always set a high standard.
Bob

[Anorak Bob]

I had machined the tang with what I thought were nice coves at the flange end. When I mounted the assembly in the mill spindle I had an unbelievable 6 thou run out with the indicator stylus running on the 3M taper.

The 30 to 3 adapter has 0.00015" TIR at the outer end. Pretty bloody impressive. So something was wrong. Turned out the nice coves were in actual fact useless. They were preventing the proper seating of the taper in the socket.

So function before style, off they came.

The last photo shows the table in its lowest position. There is 50mm clearance between it and the centricator stylus. 50 is better than the 35mm I would have had with the other adapter.

BT

[Ueee]

As always, beautiful work Bob:2tsup:

Shame about the curves, i'm sure my tanged tapers have curves and not a square corner.....but then i don't really pay much attention to them. If you think of the table clearance being 143% more than the other option, its sounds like you have heaps more space:D

[Anorak Bob]

I like your maths Ewan.:U

The German arbor end is buried about 4mm deeper than the end of the taper on a tanged arbor hence buenos dias to the cove. I did like it but I came a bit unstuck when I used a 3/16" long series end mill to tighten the radius. Too long and too much flex milling the 4140. What you see is a lot of filing before I chopped it all off.

BT

[krisfarm]

Bob,
When I made my adaptor I ran into a similar problem I had to modify my adaptors by machining the curves further down, I see you did not have the space for this.I had to reduce the width of the top of the tang as well as it was making contact on the top of the internal tang slot and like you found not allowing the taper to mate correctly. I do not know if there is a standard set of dimensions for tangs. I also found after measuring all of the tang ends on my small range of tooling that no two were the same. Nice work as usual and your solution to the original problem should be solved. That sure is a fancy looking indicator.
Bob

[Stustoys]

Hi BT,
Did you give any thought to making an adaptor along the lines of this?
(sorry its late, its an attempt at drawing part of a 30 taper over the MT3 taper of the centricator. It should give you another 20mm(??) though you'll need a special drawbar.

Stuart

[Anorak Bob]

Bob,
When I made my adaptor I ran into a similar problem I had to modify my adaptors by machining the curves further down, I see you did not have the space for this.I had to reduce the width of the top of the tang as well as it was making contact on the top of the internal tang slot and like you found not allowing the taper to mate correctly. I do not know if there is a standard set of dimensions for tangs. I also found after measuring all of the tang ends on my small range of tooling that no two were the same. Nice work as usual and your solution to the original problem should be solved. That sure is a fancy looking indicator.
Bob

More on Mahrs here Bob. http://www.woodworkforums.com/f65/mahr-zentimess-oil-change-132563/#post1289149


Hi BT,
Did you give any thought to making an adaptor along the lines of this?
(sorry its late, its an attempt at drawing part of a 30 taper over the MT3 taper of the centricator. It should give you another 20mm(??) though you'll need a special drawbar.

Stuart

I had not considered alternatives to the precision ground conventional adapter Stu.
My concern is accuracy. Not much chance on me achieving the impressively low TIR of Alan's adapter with something home made. In fact there's no chance. But I will measure the two tapers and the spindle bore to see if it is feasible.
I do have the Dumore. It could probably cope with grinding a short 3M bore. Worth thinking about it a bit.

Bob.

[Stustoys]

My concern is accuracy. Not much chance on me achieving the impressively low TIR of Alan's adapter with something home made. In fact there's no chance. But I will measure the two tapers and the spindle bore to see if it is feasible.

Hi BT.
The way I see it, As these pieces of kit work by comparing the distance along a line that from the spindle axis that is fixed to a single point of contact on the work surface, TIR doesnt matter at all(though the axis of the spindle and the adaptor need to be parallel*). You could have 10mm run out and it would still work just fine, except that the indicator would move side to side.

Now while I wouldnt for a moment suggest that you try to only get within 10mm TIR, I'm just pointing out that you really dont have to worry to much as a few 1/10th's isnt going to matter..... I think :)

Stuart

*infact if the contact point was a sphere the axes wouldnt need to be parallel either.

[Anorak Bob]

Joe's translation reveals the manufacturer's viewpoint on run out. The accuracy of alignment comes into play when the centricator is used for measurement. Well that's my understanding. I could be miles off.
http://www.woodworkforums.com/f65/centricator-co-axial-indicator-munich-157591/#post1539943

[Ueee]

Surely if you chuck a piece of bar, set up and cut both tapers, grind the 30 if needed and then part it off the TIR should be as good as the lathes TIR.

[Stustoys]

"At delivery from the factory, the device may show a minute internal runout"I think. Thats the runout of the internals of the centricator itself.(which is a tricky little problem)
I think. You'd have the same runout if you turned the MT3 taper by hand.
I dont recall seeing a centricator used for absolute measurements, though at least you have a chance.
I'll test my idea with my co-axe in a boring head and get back to you.(some of us dont have Centricators laying around ;) )

Stuart

[Stustoys]

Hi BT,
Been out to the shed, video is uploading.
I measured my tapers.
Red arrow and red line are the max distance the MT3 and 30 tapers go into the spindles 30 taper.
Blue lines line up when then MT3 taper is in the adaptor. I'd say you'd be able to get another 40mm Z.
Though the adaptor wont look much like the one I drew last night.

Stuart

[Stustoys]

A couple of videos. The first is centering a bearing with the co-axe set up in a boring head with minium TIR, though as you can see its not exactly 0.00TIR lol. Not a big deal in a boring head.
min TIR - YouTube (http://www.youtube.com/watch?v=fMgiTwtDa-Y)

The second is the co-axe offset about 5mm so about 10mm TIR. Xand Y not moved at all
10mm TIR - YouTube (http://www.youtube.com/watch?v=fsS0CiLZZcw)

Sorry about the crap video.

Stuart

[Anorak Bob]

Hi BT,
Been out to the shed, video is uploading.
I measured my tapers.
Red arrow and red line are the max distance the MT3 and 30 tapers go into the spindles 30 taper.
Blue lines line up when then MT3 taper is in the adaptor. I'd say you'd be able to get another 40mm Z.
Though the adaptor wont look much like the one I drew last night.

Stuart

Stu, was there a drawing accompanying the vids? I would have thought an abbreviated adapter would end up with a wall thickness akin to a waffle cone.

I understand how spindle runout isn't effecting the centring of the work piece. We covered that extensively when the mounting of indicators used to check tail stock barrel alignment was discussed a while back.

BT

[Stustoys]

Stu, was there a drawing accompanying the vids? I would have thought an abbreviated adapter would end up with a wall thickness akin to a waffle cone.

No I was referring to the drawing I did last night.
You could be right about the waffle cone. serves me right for drawing something without actually measuring anything. :(



I understand how spindle runout isn't effecting the centring of the work piece. We covered that extensively when the mounting of indicators used to check tail stock barrel alignment was discussed a while back.
Oh yeah...... I'd forgotten about that:doh:.

Stuart

[Stustoys]

I would have thought an abbreviated adapter would end up with a wall thickness akin to a waffle cone.

Hi BT

The real thing would look some what different to my first imagenings.(though I wouldnt build anything to those dimensions ;) )

Stuart

[Anorak Bob]

Stu,
I eyeball aligned a 30 and a 3 after our discussion yesterday and if a sleeve was turned up, it would not offer a lot of support for the 3M taper. Be a bit like a steel cumberbund. :no:

BT

[Ueee]

Being only for the centricator surely it wouldn't need that much support.....just enough to ensure alignment?

[Stustoys]

Yes, one of my less brilliant ideas :D (I was telling some of the boys on the weekend I wasnt the best estimator)
Though I have another idea, who knows it may even work better than the last one lol

Next time you have it set up could you measure how far it is from the face of the spindle to the contact point of the Centricator?

Stuart

[Anorak Bob]

Being only for the centricator surely it wouldn't need that much support.....just enough to ensure alignment?

Bit of a tricky thing for me to machine Ewan. I guess there's more chance of achieving a reasonable finish if 1214 was used rather than the 4140 I've been using of late. Removing the sleeve from the 3M taper would require additional trickiness.


Yes, one of my less brilliant ideas :D (I was telling some of the boys on the weekend I wasnt the best estimator)
Though I have another idea, who knows it may even work better than the last one lol

Next time you have it set up could you measure how far it is from the face of the spindle to the contact point of the Centricator?

Stuart

Stu,

201mm from the taper side of the 30 flange to the nose of the shortest stylus.

Bob.

[Ueee]

I looked at the size of the 30 and 3 today Bob, they are closer in size than i thought. It would be a "mere wafer"......