Shars 0 adjust 3 reversible jaws

COMachinist

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Sep 10, 2013
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Hi All
Well I finally got the the 6” Shars zero adjust chuck mounted and adjusted. I am really suprized with it. I have it down to .0002 TIR with .0008 repeatabily on ground drill rod 6” from the chuck. I used my 2” Sterrett .0001 dial indicator with my Noga large base which is rock solid. I could hardly believe it. My old Bernhardt 6” has .007” TIR with that same drill rod. I also have a 4 jaw self centering scroll chuck that I was able to get down 2-3 TIR. I turned the adjuster stub on the backing plate -.005” smaller than the d1 chuck dia. to allow 2.5 thou. adjustment. They spec it at .0002 but I figured 1-2 thou. boy was I wrong. I plan to get another Shars as money allows. That’s great for a hobby lathe. I have the lathe leveled side to side and front to back with my Sterrett Preston level. I can’t believe how much fun it is to have to not fight them old chucks. Will post some picks when it warms up a bit.
VBG
CH
 
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To check the runout of a three jaw chuck requires installing a reasonably long rod, checking it for runout at several distances from the chuck, then installing smaller and larger diameters and repeating the tests. Also note the clock positions of the runout test high point measurements. With just a single diameter test at a single distance from the chuck, several issues could be present that might show the chuck at its worst or at its best. Testing at multiple lengths and diameters shows how true the jaws are and also shows the accuracy of the jaw slots and gearing as well as how well the scroll is made at different diameters. The idea is to map the accuracy of the chuck so you can understand what you have and what any issues may be caused by, not just for trying to make you feel good about your purchase.
 
Ok. What is a reasonalbly long? Be specific please. I used a 12” rod measured at the jaw which was unmeasureable, 2 tenths at 6” and about 4 tenths at the 10” from the jaws, which more than good for a hobby machine. I’m very happy with it like i said the old Bernhard 6” chuck was like 7 thou.
VBG
CH
 
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Excellent! Glad to hear! I have always said the chuck is the heart of the lathe and only get a chuck with the set-true feature. Life is good now isn’t it!
 
Excellent! Glad to hear! I have always said the chuck is the heart of the lathe and only get a chuck with the set-true feature. Life is good now isn’t it!
Chips you got that right. Now i can zero the tail stock and do some good projects, like cuting good threads, boring straight holes. I”m planning on a regulator tester for PCP air rifles. I need good threads to seal 4500 psi air.
Keep making chips
CH
 
FYI - on a lot of the import chucks with 2-piece jaws, the removable jaws are final ground when mounted on the chuck to meet their claimed run out specifications so be sure to mark each jaw if you remove them or reverse them. Usually not a problem if they get mixed but I have seen a few that were different enough that the error exceeded the available adjustment range of the chuck. Also run out can vary depending on the diameter due to variation on the scroll so if dialed in on a 1/2" rod it may not run as true at 2". Always good to double check when cutting different diameter stock.
 
They came marked 1, 2, and 3 allready. When i cleaned and lubed the chuck befor mouning. They were marked.
Thanks for the tip though.
CH
 
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