Replacing a Lathe Chuck

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David2011

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H-M Supporter Gold Member
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The chuck on the lathe I purchased recently seems pretty much worn out. One time I chuck up the shank of a 3/4" end mill I get .007" runout, the next time I tightened very carefully and got .0045 and usually get about .020 runout, measured with a Fowler Verdict DTI. The spindle itself has .0002 or less runout and the OD of the chuck has under .002" runout. The jaws are very loose in the chuck body. It's probably a cheap Chinese chuck anyway so not worth spending money on it.

The items I've purchased from Shars seem to be decent for the money. Has anyone had experience with their chucks? Thinking about this one. https://www.shars.com/6-3-jaw-self-centering-scroll-lathe-chucks-d1-4-reversible-jaws

For precision work I will use collets or a 4 jaw chuck.
 
I have a couple Shars 4jaw small chucks, a 3" and 6" they are reasonable chucks for imported. Most of the Shars things I have bought have good quality, better than other imports. I can't speak for the 3 or 6 jaw, as I rarely ever use one, but if they are like the 4 jaw they should be OK.
Ben
 
Your chuck accuracy experience mirrors mine. Some will say that 3 jaw chucks are never accurate, nor are they intended to be. Regarding that Shars chuck, it looks like a good value.
 
The relatively cheap “H” brand on my Grizzly has a reliable .003” - .004” runout when checked with an end mill but repeatability even when the jaw and workpiece are marked for orientation isn’t great. Even so, I would like to start out close to concentric.
 
After using one, I can't imagine buying a 3-jaw chuck that wasn't an adjust-true style. Even the inexpensive kind will get you down to about .001" runout pretty easily.
 
G-ManBart said:
After using one, I can't imagine buying a 3-jaw chuck that wasn't an adjust-true style. Even the inexpensive kind will get you down to about .001" runout pretty easily.
Click to expand...
You’re right. Any recommendations for a reasonably priced one?
 
I can’t comment on the chuck itself but getting a chuck like shown with reversible jaws will give you options down the road by being able to make/buy soft jaws
 
This is a trick that I don't see mentioned about 3-jaws. Put the stock in the chuck, lightly snug and indicate. Using a soft hammer, tap the jaw with the high reading to bring it down, then snug a little tighter. Repeat until tight. We did this all the time at my shop. It's surprising how close you can get this way.
 
David2011 said:
You’re right. Any recommendations for a reasonably priced one?
Click to expand...
I've had really good luck with San Ou chucks from CME Tools. CME is based here in Madison Heights, MI and is the importer for the San Ou chucks that get sold by many other retailers. I've been to their place multiple times and they've let me walk around in back to see the massive pallets of stuff...it's pretty amazing. The guy who I've dealt with the most says the big boss started importing machine tools from China 30+ years ago and they've just bought a much larger warehouse because they've run out of room. They told me the San Ou chucks come from the largest chuck manufacturing company in China who makes chucks for some of the big names.

I have their 8" 3-jaw adjustable structure on one of my lathes and it was no problem getting it down to half a tenth runout on a 1" carbide end mill I used to check. I'm sure it won't stay at half a tenth if I change diameter stock, but even if it's a couple of tenths it's fine for what I do...if I need better it's time for the 4-jaw anyway. I'm getting ready to buy one of their 6" 3-jaw adjustable structure chucks for a lathe I'm refurbishing.

I did a mix and match with the 8" by using a fully machined Shars backplate so I didn't have to deal with drilling the bolt holes...worth the slight difference in price. That's actually my only "complaint" with CME is that the backing plates for the adjustable structure chucks are only semi-machined meaning very thick and no bolt holes. That gives you options, but makes it a bit messier, slower job to fit one. Here's the 6" CME chuck on eBay...it's worth checking both the CME website and their eBay store as sometimes the price will be better on one or the other.

www.ebay.com

6"/167mm 3-JAW Adjustable Structure CHUCK #0603AJ, K31-167A & D1-4, D4 adapter | eBay

6" - 3 JAWS Self-Centering precision adjustable structure chuck, 6"/167mm w. D1-4, D4 semi-finished adapter plate. TWO PCS TONGUE AND GROOVE REVERSIBLE HARDENED top & bottom JAWS. Back mounting recess dia: 80mm.
www.ebay.com
 
MrWhoopee said:
This is a trick that I don't see mentioned about 3-jaws. Put the stock in the chuck, lightly snug and indicate. Using a soft hammer, tap the jaw with the high reading to bring it down, then snug a little tighter. Repeat until tight. We did this all the time at my shop. It's surprising how close you can get this way.
Click to expand...
Old timer showed me this and he is always the guy who says , gotta make good with what you got.
That said I have a bison 3 jaw that works , feels and looks better thsn the factory chuck. I am not a machinist
 
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