Old chuck jaw refreshing

[ErichKeane]

Yep. Got that covered. This is just kind of a curiosity. Something to try. Maybe an alternative for the TP grinderless. I've never done any machine lapping. It seemed like a kind of effortless idea. Just turn it on and let it run, check on it every twenty minutes or so...But if we're talking days, maybe not so great.

Well, the big part about lapping is that the compound 'wears out' really quickly. You end up having to replace it pretty often (so more than every 20 minutes or so, particularly at RPM). But this is probably at least a long day's project. I know the handful of times I've done lapping (even with some pretty harsh valve compound), any amount of visible surface deformation took a LONG time.

One thing you might think about... I wonder if you could get a diamond coated 'burr' of a large enough size, and use that? It should accomplish the same thing as a tool post grinder, without having to use a motor (since it should 'wear out' more slowly).

You MIGHT have a hard time finding something like this though, my first quick googling just resulted in dremel tooling.

 

[jwmay]

Ah ok. Well I can put this plan on the "waste of effort" list, before it ends up on the "wasted effort" list. Thanks very much!

 

[Shotgun]

I don't see how lapping compound is going to be any better than the use of a grinder. You're going to be throwing grit all over the place either way.

What I did, year ago, was to clamp my dremel tool the the tool post. I put a grinding ball in the dremel, opened the jaws to about 1.5". With the dremel on medium speed, I fed it into the middle of the spinning chuck, then brought the crossfeed in until I could just hear it scraping. Feed it all the way into the chuck, then all the way out a few times. The move the crossfeed a thou and repeat. Oily rag down to protect the ways.

Haven't had a problem since.

 

[jwmay]

I don't see how lapping compound is going to be any better than the use of a grinder. You're going to be throwing grit all over the place either way.

Well I don't know that it would be better. But I imagined that abrasive paste wouldn't create an abrasive dust floating in the air. While I know for certain that dry grinding creates a lot of that type of dust. But it might be no different. Thanks for sharing your experience!

 

[graham-xrf]

I have trawled a lot of videos on the various ways folk use to turn a chuck from a doorstop into something useful. They all involve some scheme to clamp the jaws onto something circular, using some part of the jaws away from the belled out bit. Generally not-so-good are those involving expanding the jaws outwards to clamp into a metal ring. More accurate are the ones where the jaws are clamped down into a circular disc placed way back just beyond the part of the jaws that would ever grip, or using spacers onto the jaws.

The more popular one seems to be cutting three chunks from a flat bar, often aluminum, brass, or copper, and placing them 120°apart against the chuck face, and then clamping onto them. Then use a boring bar to cut them out. The carbide boring bar is then used to straighten the jaws.

Winky's Workshop --> Correcting 3-Jaw Chuck Runout the easy way
He shows how he gets it wrong first time around, and ends up changing 0.020" run-out to 0.002".

Batch 562 does the same trick --> 3 Jaw Chuck True-up, Amazing!
He used brass spacers placed up the jaws longitudinally ends up going from +0.006" to 0.001".
It must be said that he annealed the jaws - so not such an attractive option.
That said, a carbide boring bar might manage something.

Mateusz Turek does his version --> Szlifowanie szczęk twardych uchwytu tokarskiego
That is Polish for "Grinding the jaws of the Turning Holder "
He fixes a Dremel-style die grinder to the toolpost using a woodwork clamp.
I have seen a different version of this where the die grinder was crudely strapped to a piece of wood using fat cable ties!

These are all searchable on YouTube from the names and titles. There are more on this theme.

I think my point is that if the chuck is so far gone you don't have much to lose, you can have a last little go at it using one of these methods, or dream up some variation of your own.

 

[Tozguy]

The chuck has other issues

Unless fixing this old chuck is an excuse to try some new operation or process for you, why bother to fix it if you will never have confidence in it? A good reliable chuck is the foundation of most operations on a lathe. Glad you have other chucks to use.

 

[talvare]

A while back I had a 4 jaw chuck with bell mouthed jaws and as with you, didn't care to invest in a tool post grinder, so I just fabricated a mount for my pneumatic die grinder from some scrap material I had on hand and mounted it in the tool post. It actually worked out very well and that chuck went from being a door stop to my now favorite chuck.
Just some food for thought.
Ted

 

[jwmay]

why bother to fix it if you will never have confidence in it?

Just curiosity. If the run out was fixed, it would go in the drawer as a back up for those times when I've failed to plan appropriately, and need to turn a different part before I can remove the current one from the chuck it's mounted in. This happens more often than I care to admit.

 

[jwmay]

I have trawled a lot of videos on the various ways folk use to turn a chuck from a doorstop into something useful.

Me too. I like Winky. Although I'm often frustrated, as he seems to be somewhat flying by the seat of his pants, and always comes out smelling like a rose. I can't say that's been my experience. Lol

Just some food for thought.

I'll chew on it Ted. I have a Dremel tool with a grinding wheel. But the need being nonexistent, and the best outcome being a damaged, hideous, mildly useful chuck and some invisible grit eating on my 90 year old bearings and ways...I don't know.
Interesting side note: I thought I thought of this all on my own. But this morning I was rereading Basic Lathework by Stan Bray. He suggests this exact method as a suitable alternative to buying or using a grinder. So there's at least one guy out there who did it.

 

[graham-xrf]

@jwmay
I know I have explored this right down to the weeds, and I have a bunch of various size chucks of my own to check out. Rigging up an old router, or going for a die grinder, however one goes at it, is not the main aspect of this. If you tackle it at all, you know you need some kind of grinder spinning at the same height as the axis, and you always know to bring out enough plastic and covers to keep the grindings off the ways. At the end, a total clean-up of the chuck internals, and other sensible stuff is taken for granted.

We have diametrically opposed views from respected contributors, such as Suburban Tool Inc, and Joe Piecznsky. In my view, Joe Pieczensky has the most complete explanation on what to do.

Suburban Tool version ->> How to improve the accuracy of your 3 jaw chuck.

Best version Joe Pie's --> Jaw movement you probably weren't aware of.
You end up keeping in mind that, if you clamped onto something round set deep beyond the end of the jaws when doing the grind, then most starting out material bar would best be long enough to occupy the whole jaw length, and you try to keep it clamped until most of the part is finished.

I get it that you probably want to dodge any grinding scenario. I think that if the jaws are hardened, grinding is likely the only good way. You might end up with a chuck you won't want to dump, whatever it's age.