I leaned something new about my old chuck today

[darkzero]

I always wondered why nobody does this on a lathe as it is so simple .

You know, I thought about that before. My theory was that for big lathes, under heavy cuts or interrupted cuts, without a backplate register supporting the chuck, the chuck could get knocked out of alignment. I'm not sure how easy that could happen with just the chuck mounting screws providing the clamping force. But they designed chucks to sit on a register for a reason right?

For grinders & small hobby lathes, I assume there wouldn't be enough force to knock a Tap-Tru out of alignment. Maybe a crash or heavy interrupted cut may? I've never had it happen to me but then again the chuck I turned into a Tap-Tru doesn't get used that much.

However, I could of sworn that I once read instructions for a certain brand adjustable chuck that said after you are finished adjusting TIR & tighten down the mounting screws, you then back off the adjustment screws. I've never done it that way on my Set-Tru chucks, I leave the adjustment screws tight. Now if that is indeed the recommended way, then no need to worry about a Tap-Tru getting knocked out of alignment?

 

[mmcmdl]

Yes , we also used the flat backs on the mag chucks . I remember you have them . The larger chucks bolted onto the ground faceplates and never moved after tightening , and we had some big arse parts in them .

 

[Ironman2]

You know, I thought about that before. My theory was that for big lathes, under heavy cuts or interrupted cuts, without a backplate register supporting the chuck, the chuck could get knocked out of alignment. I'm not sure how easy that could happen with just the chuck mounting screws providing the clamping force. But they designed chucks to sit on a register for a reason right?

For grinders & small hobby lathes, I assume there wouldn't be enough force to knock a Tap-Tru out of alignment. Maybe a crash or heavy interrupted cut may? I've never had it happen to me but then again the chuck I turned into a Tap-Tru doesn't get used that much.

However, I could of sworn that I once read instructions for a certain brand adjustable chuck that said after you are finished adjusting TIR & tighten down the mounting screws, you then back off the adjustment screws. I've never done it that way on my Set-Tru chucks, I leave the adjustment screws tight. Now if that is indeed the recommended way, then no need to worry about a Tap-Tru getting knocked out of alignment?

Tightening chuck perimeter screws will not hold it true, as soon as it is loaded it will go off. I posted a pdf up above on post 5 about doing one and Yes, you do have to drill and tap 4 setscrews. You don't beat with a hammer to adjust. Every chuck backing plate on a flat back chuck has a register that is usually a snug fit to the backing plate which has a step for the chuck register. You have to machine about 50 thou off the register to allow the setscrews room to move the chuck on the backing plate. I also recessed my backing plate to use the full depth of the register, more area for the setscrews to bear on. Then it is just like using a 4 jaw to set it to zero, and it will stay there within a range. You leave the setscrews tight where they are.
I have found my 8" chuck seems to stay where I set it for ever, until I readjust for a larger size if needed.

 

[darkzero]

Tightening chuck perimeter screws will not hold it true, as soon as it is loaded it will go off. I posted a pdf up above on post 5 about doing one and Yes, you do have to drill and tap 4 setscrews. You don't beat with a hammer to adjust. Every chuck backing plate on a flat back chuck has a register that is usually a snug fit to the backing plate which has a step for the chuck register. You have to machine about 50 thou off the register to allow the setscrews room to move the chuck on the backing plate. I also recessed my backing plate to use the full depth of the register, more area for the setscrews to bear on. Then it is just like using a 4 jaw to set it to zero, and it will stay there within a range. You leave the setscrews tight where they are.
I have found my 8" chuck seems to stay where I set it for ever, until I readjust for a larger size if needed.

I don't think you are quite following what we are discussing. Yes it will hold but to what extent. I have a total of 4 chucks (one a collet chuck) that are modified to be tap-tru, none of them have ever moved on me, but they don't get used a lot.

I did not DL your pdf but I'm well aware of the method. Modifying a plain back chuck & making a back plate to use adjusting screws is a nice mod but unnecessary for me. I have 2 Bison Set-Tru chucks that are my primary use chucks. The "tap-tru" method has been around for decades. No one here is beating the chuck with a hammer, hence "tap-tru".

 

[pontiac428]

Any time two parts are aligned, they should be tapped true. Every assembly has play (well, maybe not taper pins) and can be aligned. That's a principle from the old school of mechanics, where a mechanic kept systems running with experience and expertise, he was not a car repair guy.

Sent from my Pixel 6 using Tapatalk