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Grinding the jaws on my three jaw chuck
Auskart:
Grinding the Jaws will not help if the Scroll is to badly worn. :clap:
mattinker:
--- Quote from: Auskart on January 20, 2018, 06:49:11 PM ---Grinding the Jaws will not help if the Scroll is to badly worn. :clap:
--- End quote ---
Thank you, but I don't think any body said anything different! No miracles, just some improvement!
vtsteam:
I agree with Matt -- and "badly worn scroll" is one of those blanket statements that doesn't really explain much in a how-to
A chuck with a worn scroll certainly can be improved if the jaws are also unevenly worn or scarred. Grinding will remove one part of the centering error. Improvement doesn't necessarily mean perfection. It just means better.
Also grinding will improve centering if the scroll is relatively evenly worn. In that case centering across all diameters will be better than it was.
Also grinding will improve it if the scroll is worn over the diameters of primary interest in repetitive use in a similar sized gripping range.
If 90% of what a chuck is used for is say 1" diameter stock, grinding at that diameter can eliminate run out at that diameter, even though the scroll is worn, and will not center as well at other diameters. At least 90% of the work will center well, rather than all work needing variable adjustment.
Grinding can't work miracles with a worn scroll, but it may improve matters, depending on where the wear is, what the various causes of the grip eccentricity is, what the use is, and other factors.
awemawson:
Most styles of three jaw chuck can be converted to a 'Grip-Tru' type with a bit of ingenuity to allow precis centring. The chuck is made a deliberate sloppy fit on the register and four grub screws are placed to be able to move the chuck relative to the register using tolerance introduced by enlarging the mounting holes. When the workpiece is satisfactorily centred the backplate bolts are finally tightened.
Personally I wouldn't want to use this approach on a good chuck, but it's a rescue plan for an older worn one.
mattinker:
--- Quote from: awemawson on January 21, 2018, 09:35:09 AM ---Most styles of three jaw chuck can be converted to a 'Grip-Tru' type with a bit of ingenuity to allow precis centring. The chuck is made a deliberate sloppy fit on the register and four grub screws are placed to be able to move the chuck relative to the register using tolerance introduced by enlarging the mounting holes. When the workpiece if satisfactorily centred the backplate bolts are finally tightened.
Personally I wouldn't want to use this approach on a good chuck, but it's a rescue plan for an older worn one.
--- End quote ---
Andrew, that's a useful idea, although in my view, it's a solution if you haven't got a four jaw. If you're going to dial it in with adjuster screws, it's probably easier to use a four jaw.
cheers, matthew
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