Gotteswinter's Method

[Jammer Six]

More stupid questions.

Watching the thread on content creators, I found the name Gotteswinter.

Watching one of his videos, I found this method for tapping in a cylinder to dial it in:
https://www.youtube.com/watch?v=xH42L3WluPU

At about 6:40, he starts dialing in a cylinder he has reversed in his three jaw chuck.

I've never seen a method where one loosens the chuck mounting to dial it in. I thought one tapped on the work to move it relative to the chuck, as opposed to tapping on the chuck to move it relative to the lathe.

[Bob Engelhardt]

The "Bump True" chuck

[Jammer Six]

It looks a lot easier than bumping the work. But it looks like after the last bump, he tightens all three bolts down without checking.

Anyway, I think I'm going to try it.

[Bented]

One may move the scroll around by tapping the jaws in the appropriate direction, little is gained by this, I do it on nearly every setup when using a scroll chuck..

[Stu]

One may move the scroll around by tapping the jaws in the appropriate direction, little is gained by this, I do it on nearly every setup when using a scroll chuck..

Wouldn't that be bad for the scroll?

[RB211]

Wouldn't that be bad for the scroll?

I think tightening each key hole has similar results

[Bented]

I think tightening each key hole has similar results

Not all scroll chucks have 3 pinions, some have only one.

[Doc Nickel]

I didn't watch the video, but I get the gist. I suspect somebody has either "made" a "set tru" chuck by turning down the backplate register a bit, or it's a plain-back chuck on a plain backplate with NO register.

On any of my chucks, the backplate is pretty firmly keyed to the chuck body by a step register. Loosening the bolts and tapping would do nothing at all. (My six jaw, however, IS a "set tru", and I'll commonly use it 4-jaw style at times.)

Doc.

[Jammer Six]

Leads us directly to the next stupid question, what the hell is a "set-through chuck"?

[BCRider]

That's "Set-Tru" not "through". A 3 or 6 jaw scroll chuck where the body has screws that ride against a backing plate to permit zeroing the work.

The poor man's version is to make the body alignment step on the backplate about .02 to .03 smaller than the internal step size on the rear of the plain back chuck. Then loosen the chuck bolts and bump it like Stefan did or drill and tap for four set screws in from the outside so you can use those to move the slightly loosened chuck body with a little more finess. Just don't forget to re-tighten the chuck bolts.....

[Jammer Six]

Ah!

So this procedure isn't going to work if I just waddle down to the basement and try it without modifying my chuck!

Now, that was important information!

[BCRider]

Ah!

So this procedure isn't going to work if I just waddle down to the basement and try it without modifying my chuck!

Now, that was important information!

There IS a few thousandths of how the scroll tightens between the scroll and the body of the chuck and how the jaws seat against the scroll. So there's a slight amount of wiggle room. For that you need to tap on the jaws or part as you tighten it. And it may or may not be enough.

If you want to try the partial or whole "Set-Tru" modification here's the full meal deal.

He starts out with the idea of easing the step on the back plate to allow .02 or so of wiggle room and tap it into true like Stefan did. Then he goes on to describe and show how to drill and tap for four set screws so you can worth that wiggle room in a much more predictable manner similar to an independent four jaw.

(51) HOW TO MAKE YOUR CHUCK SUPER PRECISE BY ADAPTING IT INTO SET-TRU - YouTube

[Jammer Six]

That was interesting.

So tell me this: is tearing chucks apart and re-building them part of being a machinist?

[Randy]

So tell me this: is tearing chucks apart and re-building them part of being a machinist?

Absolutely. I think that modifying your tools to suit your needs is part of being a machinist. And even without modification (not everything needs mods) a chuck still needs a thorough cleaning occasionally.

[Doc Nickel]

So tell me this: is tearing chucks apart and re-building them part of being a machinist?

-Er, yes. The chuck, if used to any reasonable degree, will get chips and gunk in the scroll. For best accuracy and longevity, it's best to clean and re-lube it periodically.

Personally, the chuck on my most-used lathe, I tear down and clean about once a year, and it's always worth it.

Doc.