Using a metalworking chuck on a wood lathe

[graduate_owner]

Hi all,
If you happen to have a metalworking chuck that fits your wood lathe you probably know that it is not a good device for holding wood. However you can use it for:-
1 Holding sockets ( from a mechanic's socket set ) and then you can push it a square of wood instead of using a drive centre. Much more secure grip.
2. Holding a home made pin chuck - just a cylinder if metal with a flat filed on, or cut on with an angle grinder or abrasive wheel. The pin is just a nail with the head removed and cut to length.
3. Holding a home made screw chuck - again a cylinder with a hole bored centrally ( in the lathe), a countersunk hole for the screw head, and a hole drilled and tapped transversely to take a grub screw / locking bolt. Grind a flat on the screw to match up with the tapped hole. Countersinking the locking bolt so that the head does not protrude would be safer.
4. Holding an arbor ( i.e. a bolt with the head removed) onto which you can fit a grinding wheel ( but be careful to mount it properly - make up wooden flanges, use blotting paper washers, keep the seed down. Remember you have no guards, so no protection if the wheel shatters). You could also mount a leather strop wheel, or a felt wheel for polishing ( eye protection needed), or a wheel type wire brush ( eye protection most definitely needed - those wire bristles can break off and fly at speed).
If you need to turn something on a mandrel, then again a suitable sized bolt with nuts thghtened on either side of the work is a useful way of holding the work.


Finally, not wood turning, but I have found the ability to grip metal items forcleaning, de-rusting, polishing etc to be a great time saver.

I expect people will come along with more ideas, but I hope this is useful.

K

 

[TFrench]

I use mine to hold things I'm cleaning up quite often. I've also just picked up a pigtail mandrel for polishing mops that I can use in it.

 

[Paul Hannaby]

I think I would re-word the first statement about it being no good for holding wood. Engineering chucks (or even woodturning chucks with engineering jaws) will hold wood but generally smaller pieces or ones that are being subjected to low cutting forces. For example, I use the engineering jaws on an Axminster woodturning chuck to hold pen blanks when I drill them.

 

[graduate_owner]

I know what you mean Paul, and if it works for you then that's fine - I sometimes use a metalworking chuck myself when other work holding methods aren't available, but I have found the metal jaws tend to crush wood fibres. What's worse is the crushing is not symmetrical depending on where the jaws meet the varying grain of the wood. However they certainly do hold wood, or practically anything else, just not ideal for wood ( hence the plethora of jaw types for wood chucks).

What I was getting at really was to give people ideas if they happen to have a metalworking chuck, rather than just leave them in a drawer or sell them on, thinking that they might not be useful.

I think a CBN wheel on an arbor would be an excellent sharpening system because of the speed options on the lathe, and because you don't need any safety guards since a CBN wheel won't shatter. That's on my to-do list.

K

 

[J-G]

What you are both forgetting - or omitting to mention - is that you can get 'Soft' jaws for metalworking chucks and these can be machined to a much higher accuracy than any jaws available for wood-turning chucks.

Admittedly, you do also need a metalworking lathe to take up this option but if you have acquired a metalworking chuck, surely you have a metalworking lathe as well :?

Using soft jaws which have been bored to a specific diameter completely eliminates any issue of crushing wood fibres.

It is also possible to use soft jaws as 'carriers' for jaws made from wood, (beech, oak, ash; ... even leadwood!) aluminium, Tufnol, Acetal etc. which again can be machined to a specific size to very accurately mount and remount work.

 

[graduate_owner]

Good point - yet another use for metalworking chucks. I acquired one of mine when I bought a viceroy wood lathe and it has been really handy.
Just a quick question - how do you know what soft jaws to get? I have several metal chucks and the jaws are not interchangeable in either my two 5" chucks, or my 4" chucks. So how would I know what to buy? Is there a particular set of measurements I need to take? The chucks look quite old and I can't see a model number on them, just the maker's name ( Burnerd).

K

 

[J-G]

Just a quick question - how do you know what soft jaws to get? I have several metal chucks and the jaws are not interchangeable in either my two 5" chucks, or my 4" chucks. So how would I know what to buy? Is there a particular set of measurements I need to take? The chucks look quite old and I can't see a model number on them, just the maker's name ( Burnerd).

I've been very fortunate in-as-much-as I've acquired a number of sets of soft jaws with the three Pratt-Burnerd chucks that have come with the two Myford Lathes I've bought so I haven't had to source others.

A quick 'Google' using "soft jaws for Burnerd chucks" came up with Rotagrip Ltd. who seem to have a very wide range available and are happy to accept enquiries stating the full details of the Chuck make, diameter and existing jaw measurements.

The three important measurements are the width of the jaw, the width of the slot and the pitch of the scroll - personally, I would send them a drawing with as many dimensions as I could determine (taken from the existing hard jaws), even going as far as measuring the thickness of the scroll teeth in the centre and the edge.

In Rotagrip's list of what I assume are their 'standards', they don't mention the position of the slot with respect to the bottom of the scroll teeth but I would consider that critical.

To a certain extent, the height and length are a bit flexible so not critical.

Thinking back to my time as an apprentice, I seem to recall that fitting new soft jaws was very much a matter of filing the slots to match the chuck! Hopefully things have improved over the intervening 60 years :lol:

 

[graduate_owner]

Thanks JG. So am I correct in assuming that soft jaws are basically the same as normal jaws but not hardened - I know that sounds a bit obvious but what I was wondering is, if you were to heat up normal jaws to, say, red heat ( I'm not going to - just wondering) would that soften the jaws and thus create the same thing as bought soft jaws? Or would the heat distort the jaws and ruin accuracy?

K

 

[J-G]

Thanks JG. So am I correct in assuming that soft jaws are basically the same as normal jaws but not hardened -

Not quite - Standard 'Hardened' Jaws come in two types; External & Internal. Both are 'Stepped' to give some flexability as far as holding various diameter material, whereas Soft jaws are just rectangular blocks of steel (above the scroll & slot of course). The scroll & slot naturally must be identical to fit the same chuck.

I know that sounds a bit obvious but what I was wondering is, if you were to heat up normal jaws to, say, red heat ( I'm not going to - just wondering) would that soften the jaws and thus create the same thing as bought soft jaws? Or would the heat distort the jaws and ruin accuracy?

Aaaaarrrrgh!! It's some 60+ years since I spent time in a hardening shop - though I have many vivid memories of that time, I can't remember the intricate detail of the chemical processes involved. I do remember Cyanide baths and Nitride furnaces and the fact that some items were 'case hardened' whereas others were 'through hardened'.

What you are suggesting - and I would never countenance such action! - is 'Annealing' and you would need to heat the jaws to 1335-1355ºF depending upon the carbon content and then letting them cool naturally (no quenching).
Whether this would bring them to a state which could be machined using HSS, or even carbide, tools is debatable.

I would hazard a guess that the scroll teeth and slot(s) would suffer some distortion that would mean re-machining to make them fit the chuck again.

Hardening is seldom the last process in any manufacturing cycle since distortion is virtually guaranteed.

Heat Treatment of Steel is a very big subject and highly technical so my comments are only a very brief summary - and may well be inaccurate in some measure

 

[graduate_owner]

Brief summary perhaps, but very interesting all the same. I have never seen soft jaws, just heard the term mentioned occasionally.
Thanks for the explanation.

Keith

 

[J-G]

I have never seen soft jaws, just heard the term mentioned occasionally.

In that case the attached photo's will probably help your understanding.

The jaws mounted on the chuck have been used for holding both internally & externally. The middle photo shows some jaws I've drilled and tapped to use as 'carriers' for larger jaws made from Beech. The last photo shows further ingenuity, I needed to hold a larger diameter but thin disk so I drilled and tapped the outside ends then milled a slot in some steel blocks to fit the jaw width. Once screwed on, the 'extension' could be machined; on the outside to make sure they balanced and on the face to the required gripping diameter.

It just shows how versatile soft jaws are.

 

[graduate_owner]

Thanks JG, very informative.

K

 

[Robbo3]

In keeping with the original post of putting to use a chuck that tends to be stored in a drawer .....

Use the tailstock centre for support as much as possible.
As with woodturners chucks, use the jaws to hold morse taper drives or a Jacobs chuck mounted on a morse taper to save removing the chuck.