I need to reverse my lathe jaws!

[John Hill]

I have just bought an old lathe, it is a Milnes from the turn of the century before last!  1900 +/-

It came with a 4 jaw and with a very old 3 jaw.  The 3 jaw is quite bashed about and does not have the internal jaws just a set of external jaws.

I am thinking that I should be able to reverse the 3 jaw jaws somehow?  Maybe some surgery and welding?

Has anyone done something like this?

[Fergus OMore]

Obviously you cannot easily reverse the jaws unless you perhaps build up the scroll and re-machine it- cutting through the old scroll

However you can weld onto the existing jaws and do a sort of soft jaw thing. Again, you can make a set of collets or modify your faceplate( if you have one).

However, if your chuck is worn, there is really no easy way to restore its accuracy. Some say you can and I hold a different view.  However, you CAN do a lot of things to an old lathe which will definitely improve it. For the record, LBSC had one.

Any how, the 4 jaw and a faceplate are the things. Enjoy your new acquisition.


Norman

[John Hill]

The chuck scroll and fit of the jaws in the chuck body show very little wear. I just seems to have had a short and rather brutal life!  The front of the body is chewed up a bit and there are no internal jaws.  The external jaws are a little, not much, bell mouthed.

I am thinking of cutting the outer lug off the  external jaws and welding a chunk on the recreate the shape of the internal jaws.

Meanwhile I am wondering if anyone has ever done such surgery?

[awemawson]

It obviously CAN be done, the question is SHOULD it 

The welding will affect the hardening of the jaw. Many jaws are / were made to a standard specification, and there are firms that specialise in supplying after market jaws. Rotagrip in the UK is one such organisation - I appreciate that that's a long way from you !


http://www.rotagriponline.com/index.php?option=com_content&task=view&id=16&Itemid=33

[RussellT]

I don't think that's the difficult bit.  The teeth on the back of the jaws would need to be reshaped to fit the scroll, and if you're going to do that you might as well make some new jaws.  There was an article in MEW on how to do that.

Remember too that if you weld them they'll lose their hardness.

If you're intent on modifying the existing jaws then how about machining them flat and adding bolt on jaws - you'd presumably have to anneal them.

Russell

[vtsteam]

John I know you like to try the unusual, and often succeed despite the potential difficulties. And in any case, learn quite a bit in the process -- as do we while watching. So I'm going to say go for it, if it appeals to you.

There is no guarantee that the scroll will match the teeth and slide groove on the3 jaws afterward, true, and the hardening will be lost, also true.

But, there is also no guarantee that the working surfaces will be substantially altered after, no one knows for sure since it hasn't been triedby anyone here -- these are all guesses.

And parts can be hardened and tempered again. So there are possible complications and some risk, but it's up to you if you want to take them on.

If it was me, and I was inclined to try, I'd either try the anneal, saw off, bolt on method if there was enough meat for the bolt on jaws (and I think change jaws would actually be an advantage over fixed), or if not, anneal, saw off, and braze on new (rather than weld). I'd have first covered the teeth and slot with bar soap to reduce scale from the flame. After brazing I'd re-heat and plunge in oil for hardening, and then temper. The worst scenario would be cracking when hardening, which is why I'd try oil first, over water. If it failed to harden, I'd then try water.

Good luck, and looking forward to a blow-by-blow if you do, and no blame if you don't, too!

ps, it will be tricky maintaining the braze while heating to hardening temp -- silver braze may be too low melting temp, so maybe bronze braze, and maybe even plunge harden immediately after the braze flows and solidifies. Or, localized heating for hardening only the teeth and jaw surfaces might be an option -- you could maybe stay away from the braze joint with a small flame.

[Alan Haisley]

Has anyone done a homemade induction heater? You might be able to localize the heat before quenching that way.

[Fergus OMore]

Quelle Surprise! but I have repaired the wear to 'correct' the bell mouthing on an old 'Crown' 3 jaw on a Pools Major- which you have probably never heard of.  I used a small Mig welder with mild steel.  You don't have to have hard jaws but, it helps! Again, my father was a far better welder than I will ever be but he 'hard faced' worn cutting tools by has welding but I have read that it can be gas welded too.

You know this isn't rocket science or anything but if one pulls a decent old wood plane to bits, the good ones will have a blade which is actually two metals- one being wrought iron and the other carbon steel. There will be a black edge at the join.  Today, in the efforts to tidy  up, I found a electric planer blade which had a carbide edge. Mine was chipped- so you know!

Years and years before most were born, Dad tipped an old valve seating tool with carbide- it was brazed on. Again, digressing slightly but I have one or two silver soldered  carbide tips -CCMT on steel shanks as boring tools.

Romping away, I have an independent 3 jaw chuck which came off an old Enox baby lathe- probably never heard of that either( he said somewhat grumblingly)

Sorry fellas if I have messed up your theories but what the hell?

Norman
 

[trapper]

The theory that you cut the jaws flat and m/c inside/outside jaws to fit on sounds pretty decent -or could you just make a block with slot in drop over existing jaws and remachine it to what you want, no ideal but would be use able,or grip a smaller diameter chuck in the jaws available

[chipenter]

Just make some soft jaws http://www.homews.co.uk/page99a.html .

[John Hill]

Thanks for all the comments and information but this is what I had in mind!



I am wondering what pitfalls there might be in doing this?

[DavidA]

The three jaw chuck on my Denford has only the one set of jaws.  But each jaw consists of two parts. The (let's call it the base) that engages with the scrole,  and the part that grips the job.
This (gripper) part is held onto the base with  two capscrews,  and all one has to do to change from external to internal is remove this part and reverse it.

Very convenient.

Maybe you could adapt your chuck in this manner.
It makes the fitting of 'odd ball' jaws very easy.

Dave.

[SwarfnStuff]

Hi John and all,
       Just my two cents worth but in my limited experience, it seems the way to go if there is enough metal to do so, is to do as suggested by David A. Make a set of jaws that screw onto the base of the existing jaws will give you the option of holding from the inside or outside. A bit / lot, of work I guess but making machines do what we want is part of the fun and sometimes frustration of this hobby.
John B

[BaronJ]

Hi John,

Cromwells supply many types/styles of chuck jaws.  I got a set of soft jaws for my Myford for £20.  They fit perfectly.  PB wanted an arm and both legs for a set.  Although they did assure me that they would match with the serial No: on the chuck.

[vtsteam]

John, did you ever do the mod?

[John Hill]

Mod done and back on the lathe.

I ended up just cutting the jaws flat and adding blocks in the manner that are attached for soft jaws.  I eventually found someone who would sell me loose hard welding electrodes and I built up each jaw.

I used a brazed carbide lathe tool in a fly cutter to get the jaws back to shape and all is well.


This was just another time when I was too busy to stop and take pictures!