I just glued on my 3 jaw chuck...

[Batmanacw]

Yep, this is going to be the key. Even a $1000 3-jaw chuck isn't consistent more than ~2-3 thou throughout its holding range.

Last time I tried it I had nearly perfect results. I even mentioned it in the original post.

 

[aliva]

Hopefully the repeatability will stay.
A lot of effort but if its works over the long run, good for you.

 

[Batmanacw]

Hopefully the repeatability will stay.
A lot of effort but if its works over the long run, good for you.

I couldn't find my jb weld and acetone so I have $18 invested.... the worst part is waiting for for epoxy to cure. I'm dying to pull it off and see how it repeats.

 

[Tozguy]

So why not have a dead accurate 3 jaw? I didn't get rid of my 4 jaw. Do you know what glass bedding a rifle is? The wax is a release agent. The epoxy won't stick to it. I should end up with a very accurate removable fit.

Sounds like a good idea to me. I am sure that reducing one variable like that can only help.

 

[ErichKeane]

Last time I tried it I had nearly perfect results. I even mentioned it in the original post.

I only saw you say you used a single gauge pin, so I didn't see if you tried it with a 5" pin and a 1/4" pin, etc. As 3 jaws are tightened over time, they get 'grooves' or worn spots in the scroll that throws them off. You can see it in any well-used 3 jaw when you take them apart.

From my perspective, it doesn't really matter how good my scroll-chuck is, if I want to do a 2nd operation concentrically, I use a collet chuck or a 4 jaw.

 

[Batmanacw]

I only saw you say you used a single gauge pin, so I didn't see if you tried it with a 5" pin and a 1/4" pin, etc. As 3 jaws are tightened over time, they get 'grooves' or worn spots in the scroll that throws them off. You can see it in any well-used 3 jaw when you take them apart.

From my perspective, it doesn't really matter how good my scroll-chuck is, if I want to do a 2nd operation concentrically, I use a collet chuck or a 4 jaw.

The last time I checked a second diameter I used a piece of turned material around 1" but it has been a while.

I can be absolutely certain the accuracy will degrade over time. This is a fun little experiment to see how good it can be with very little invested other than a little time and less than $20

 

[erikmannie]

I have a PM-1030V, & I leave the 4J installed. As easy as it is to install the 3J, I strongly prefer a 4J.

Same with my larger lathe: 4J in there, face plate on standby, 3J in a box that may never be opened as long as I live.

I know that many machinists get a lot of use out of their self-scrolling chucks. I guess I prefer repeatability over speed. I like having the option to remove a part & then chuck it up again as true as I want.

I would only use a 3J either if I were (1) sure that I would not need to remove and rechuck the part, or (2) in a big hurry.

I would be worried about abusing my spindle bearings ever so slightly using a soft hammer to tap (and thus center) stock in a 3J.

 

[silence dogood]

Penn Industries offers a 6 jaw chuck that is repeatable to .0005". It's a BTC Zero-Set precision. With that you don't need a collet chuck. It costs $3,847.00. Hm. I think I'll pass and stick with my 4jaw and collet chucks.

 

[Batmanacw]

Penn Industries offers a 6 jaw chuck that is repeatable to .0005". It's a BTC Zero-Set precision. With that you don't need a collet chuck. It costs $3,847.00. Hm. I think I'll pass and stick with my 4jaw and collet chucks.

Me too.....

 

[erikmannie]

Penn Industries offers a 6 jaw chuck that is repeatable to .0005". It's a BTC Zero-Set precision. With that you don't need a collet chuck. It costs $3,847.00. Hm. I think I'll pass and stick with my 4jaw and collet chucks.

I am glad that the manufacturer’s offer the “Set-Tru” self scrolling chucks. I would never buy a self scrolling chuck that isn’t a Set-Tru or the like.

From https://en.m.wikipedia.org/wiki/Chuck_(engineering)