Witness Marks on Adjustable Scroll Chucks?

[Chips O'Toole]

I'm putting my shop back together after a long time away from my tools. Yesterday I decided to adjust my 3-jaw chuck, even though I had done this years ago. I was surprised to see it was way out of adjustment.

The first time I adjusted it, I put a piece of tape on the lathe spindle so I could remember how the chuck was clocked with regard to it. Of course, I forgot what the tape corresponded to on the chuck, so when I reinstalled the chuck, it may or may not have been lined up the same way.

I'm wondering if other people put witness marks on chucks so they'll be aligned as well as possible after being taken off and reinstalled.

 

[Tim9]

I’ve never paid any attention to mounting my lathe chucks. Of course my South Bend is 1-1/2-8tpi threaded and Clausing has L-00 taper mount. The L-00 has a key way.
So it’s a non issue for me. I’ve never used a D mount. If I had a lathe where it mattered....I’d probably first mount a 1/2” precision rod and mic it.... then remove and check at different positions to see if iT even matters.

 

[Chips O'Toole]

My lathe has a D1-6 spindle. The adjustable chuck is nice to have. You can get the runout down to nearly nothing, and if you want, you can change the adjustment for individual parts. By doing this, you can fix it so you can turn a part from both ends and have a finished product with almost no line where the cuts meet.

I used to have a Clausing with an L00 spindle. I still have an unused South Bend 13" back plate for it. I really need to put it on Ebay.

 

[darkzero]

I put a center punch mark on my D1-4 spindle. I don't center punch all my chucks though but I do mark them all. On some of them I just put red paint in the center drill hole for the cam lock pin I choose that had the lowest runout when clocking.

 

[mikey]

Higher end chucks, especially scroll chucks, will have run out specs. Those specs are accurate when tightening only one pinion and that pinion will be marked. Usually, that level of chuck will also have a witness mark on the back rim of the chuck that aligns with the fixture they used when checking accuracy. I have found that aligning those marks with the one marked by the factory on my spindle gives me the lowest run out for that chuck.

 

[Chips O'Toole]

My chuck is a Gator. Not CDCO, but not a Buck, either.

 

[benmychree]

Higher end chucks, especially scroll chucks, will have run out specs. Those specs are accurate when tightening only one pinion and that pinion will be marked. Usually, that level of chuck will also have a witness mark on the back rim of the chuck that aligns with the fixture they used when checking accuracy. I have found that aligning those marks with the one marked by the factory on my spindle gives me the lowest run out for that chuck.

My Buck 8" 3 jaw chuck has only one pinion, no problem to know which one to use!

 

[mmcmdl]

I used to have a Clausing with an L00 spindle. I still have an unused South Bend 13" back plate for it. I really need to put it on Ebay.

If it's a L00 , I may just be interested in it .

 

[NortonDommi]

D1-5 camlock and chucks + faceplate stamped with a small cold chisel so they always mount to the spindle the same way. Jaws are marked as well and the corresponding slots stamped with that number. Makes life simple.

 

[Superburban]

My shopfox came with witness marks already done on the scroll chuck and spindle. I was happy, as I swapped to the 4 jaw, without first checking for a witness mark. One of these days when I get board enough, I may try it in other positions, and see how the runout changes.