I wouldn't get rid of that chuck. It's not that it's bad, its just a limitation of the design. The only thing 3 scroll chucks have going for them is convenience.
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Why can't I indicate my part?
- Thread starter Pat of TN
- Start date
I wouldn't get rid of that chuck. It's not that it's bad, its just a limitation of the design. The only thing 3 scroll chucks have going for them is convenience.
G
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The three jaw on my pre 1930 sidney lathe has only been off 3 times in 30 years.If I was to hazard a guess how much money that machine made in that time I know I could't come close.It don't help much that the 4 jaw weights a easy 100 lbs. and I ain't that young no more.Even back then I used to roll it across the shop floor and pick it up with the cherry picker to put it on.
It's not the machine or tool that matters it's the skill of the operator that makes it work.{Old school , no CNC or Dro in my shop,Hell the battery in my digital vernier calipers died and I never missed them.}
As far as repeatabilty goes if you mark your work to a jaw {1,2 or 3} and put it back to the same spot you should be close enough. Unless its going to the moon.
*******Just Saying**********G*********
It's not the machine or tool that matters it's the skill of the operator that makes it work.{Old school , no CNC or Dro in my shop,Hell the battery in my digital vernier calipers died and I never missed them.}
As far as repeatabilty goes if you mark your work to a jaw {1,2 or 3} and put it back to the same spot you should be close enough. Unless its going to the moon.
*******Just Saying**********G*********
i agree with your comment about the spindle bearings. it sounds like the spindle is moving. i had an old atlas that had babbit bearings in the headstock. try putting a prybar under the chuck with the indicator on your chuck or workpiece an see if you can get any spindle movement. timken bearings should show almost no movement ,babbit bearings will usually show a couple of thou. these can be adjusted by the shimpac under the bearing caps to compensate for normal wear. larryr
- Joined
- Mar 27, 2014
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Hi,
I have found on a small Jet (13x40" lathe) with 3-jaw chuck that I can get much better concentricity (prior to indicating anything) by tightening the chuck gradually. Tighten a bit, rotate, tighten a bit more, rotate, etc. Don't crank it all the way tight in one go on one worm screw.
Jon
I have found on a small Jet (13x40" lathe) with 3-jaw chuck that I can get much better concentricity (prior to indicating anything) by tightening the chuck gradually. Tighten a bit, rotate, tighten a bit more, rotate, etc. Don't crank it all the way tight in one go on one worm screw.
Jon
- Joined
- Sep 13, 2011
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- 271
Does your chuck have a master screw marked by a "0" on the chuck? Most do and it will give you the best results.
- Joined
- Mar 30, 2014
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- 115
Everyone is talking about the 3 jaw scroll chucks and not being that repeatable. I have a 4 jaw independant chuck but have yet to use it yet. But I have however seen 4 jaw scroll chucks. Whats the general idea on those? They any better than3 jaw?
- Joined
- Nov 16, 2012
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- 5,596
The main purpose of a scroll chuck is speed. If you're working from fresh stock, it's not entirely necessary to have it "perfectly" centered as once you start cutting, the natural center is found and all is good. Problems arise when you need to remove and later re-chuck it. Sometimes you can get it centered pretty well but, it takes an independent 4 jaw to nail it dead on.
Regardless of scroll chuck or independent type, 3 vs 4 jaws comes to your aid when holding irregular shaped pieces such as triangle or square stock. You can't hold a square in a 3 jaw nor a triangle in a 4 jaw.
Also, a 4 jaw chuck distributes the clamping pressure more evenly and if you have tubing, this is desirable. When parting a piece (which puts a lot of side pressure on the work) the 4 jaw chuck shines because smaller diameter shafts are less likely to get pushed in-between two of the jaws -and if that happens (and it's happened to me) things get ugly.
And finally, with an independent chuck, you can mount pieces at an offset to make a cam-shaped piece.
Ray
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- Dec 21, 2013
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- 186
I watched a video on Youtube today about disassembling a three-jaw chuck; I'm gonna take mine into school and clean it. I don't know if it's ever been done. That by itself may help.
I also tightened the screws for the spindle bearings. Not much, but a little on the snug side. I think that will help as well.
Flutedchamber - My chuck only has one key hole, so I don't have much of a choice! I have heard and read that though.
JeepsAndGuns - I don't know about a four-jaw scroll for holding round stock, good bad or indifferent. Their clearest purpose is of course for square stock, and it would have to be pretty much exactly the same size and actually square... but for round, I dunno.
I also tightened the screws for the spindle bearings. Not much, but a little on the snug side. I think that will help as well.
Flutedchamber - My chuck only has one key hole, so I don't have much of a choice! I have heard and read that though.
JeepsAndGuns - I don't know about a four-jaw scroll for holding round stock, good bad or indifferent. Their clearest purpose is of course for square stock, and it would have to be pretty much exactly the same size and actually square... but for round, I dunno.