Replacing a Lathe Chuck

[MrWhoopee]

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.

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

I'm quite happy with my San Ou 4-jaw chuck. My only "complaint" is that the jaws were consistently too tight in their slots. So tight that it took 2 hands to turn the chuck wrench. I spent some time lapping them down to a more reasonably snug fit. If I had a surface grinder it would have taken no time at all.

 

[benmychree]

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.

When I was an apprentice, I saw one of the top journeymen doing that trick frequently, if the shop is not buying a new chuck, you have to make do with what you have, in addition, I note that he had one of the best, newest chucks in the shop, it was a steep downward journey from there with respect to worn out chucks from there, still, acceptable work was done, a lot of it inspected by QC.

 

[David2011]

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.

Been doing that for years but the chuck in question is really worn. The jaws all have .005” of movement in the direction of the centerline at their noses. That may not sound like much but they rock in their grooves. To see them move I would have guessed that they have 1/32” of slop. They’re as sloppy as a WWI G.I. 1911 pistol slide or worse.

 

[David2011]

When I was an apprentice, I saw one of the top journeymen doing that trick frequently, if the shop is not buying a new chuck, you have to make do with what you have, in addition, I note that he had one of the best, newest chucks in the shop, it was a steep downward journey from there with respect to worn out chucks from there, still, acceptable work was done, a lot of it inspected by QC.

Any chuck that will hold the workpiece tight enough can produce excellent results as long as the OD of the piece has to be reduced and the piece is never removed until finished. I’ve been working on 1910 vintage US Navy guns. Most of the time the parts were/are made from standard diameter stock so close concentricity is required. Within .003-.004“ is usually adequate but .010 off isn’t going to fit. The machine work on the guns is quite good. I have had a lot of trouble achieving parts fits as good as the original parts on my Chinese 11x26 lathe. They’re certainly useful for a static restoration display but achieving the very close slip fits has been difficult. We’re finished with the 1910 era guns but still have 7 of the 3” antiaircraft guns and 7 of the 40mm Bofors Quads remaining to restore.

 

[David2011]

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.

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

That looks very interesting and it’s about $200 less than the Shars. For $200 I can machine the backplate and make threaded holes. Oops! I looked again. The Shars 6” 3 jaw adjustable is over $600 without the backplate. Guess I was thinking of the fixed 3 jaw.

 

[kenh3497]

Kind of a new guy here but I purchased a Vevor 7X14 as a box of parts. EVERYTHING was apart including the chuck. I just recently re-disassembled to the chuck to give it a proper cleaning as I hurriedly threw it together to see if I had a viable lathe. Anyway, after cleaning and re-indexing the chuck to the lathe I'm down to .0015" run out on a 5/8" bar from .0045" run out. I'm happy with that.

Ken

 

[G-ManBart]

That looks very interesting and it’s about $200 less than the Shars. For $200 I can machine the backplate and make threaded holes. Oops! I looked again. The Shars 6” 3 jaw adjustable is over $600 without the backplate. Guess I was thinking of the fixed 3 jaw.

Yeah, the price difference is pretty hard to argue with really. I don't expect it would equal a new Bison, Kalamazoo, Gator, etc but for most 3-jaw work I think they're more than acceptable.

 

[RickKr]

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.

You’re right. Any recommendations for a reasonably priced one?

Don't know about reasonably priced adjust-true type chucks. I have one Buck and two Bison, but these on on the spendy side.

But... if interested and willing to do the design and machining work, it is possible to turn a non-adjustable scroll chuck into one that is adjustable. I did this with a 4" 3-jaw about 20 years ago and am about to do so with a 4" 6-jaw chuck. from Little Machine Shop The latter is most reasonably priced are around $270. (My memory tells me the 3-jaw was a Bison, but my photo notes tell me it was also from LMS.)

Get a copy of this article, from Metalworking, The Best of Projects in Metal, Book One:

"Greater Precision for Scroll Chucks by Richard Torgerson"

It amounts to machining an intermediate backplate that adds the adjustment screws into the sandwich. The 3-jaw Bison went on the 7x12 minilathe, bolt-on spindle, I had at the time. Still have the chuck and backplate, but sold the minilathe a long time ago. I was routinely able to get well under 0.001" TIR with it. The LMS 6-jaw is for my recently acquired Crafstman 6" (MK2) lathe that is currently mounted on a threaded plain backplate.

 

[RickKr]

In another instance, where I had to to turn a standard non-adjustable backplate into an adjustable one, I machined an insert to bolt onto the face of the standard backplate to serve as the adjusting screw boss. This was to mount the 5" 6-jaw Bison Set-Tru chuck on the pre-WWII Rivett 1020 that I restored (my avatar image), where I had to machine all of the backplates because it was a non-standard L00 taper with 4 tpi spindle threads.

First image shows what I started with, an original Bison threaded backplate for this chuck and a blank L00 backplate I made for the Rivett. Second image shows that backplate turned with a recess to receive the boss insert, with the original Bison backplate next to it. Third image shows the boss insert screwed in plade (extra holes were from a machining mistake). Fourth image shows the Bison 5" 6-jaw chuck mounted on the Rivett 1020 using the newly made set-tru backplate.

A few years later when I came into a 6", 6-jaw Buck Adjust-Tru chuck from my father's shop, I machined one of the blank Rivett backplates for mounting of the that chuck on the Rivett. It was possible to use just the backplate, without the additional insert, because the boss for the adjust-tru screws didn't need to be as tall. (last two photo).

It is clear I love adjustable chucks. With the Bison and Buck chucks, I have gotten the TIR down to 0.0001". Don't really need it, but I like it.

Rick

 

[G-ManBart]

Don't know about reasonably priced adjust-true type chucks. I have one Buck and two Bison, but these on on the spendy side.

But... if interested and willing to do the design and machining work, it is possible to turn a non-adjustable scroll chuck into one that is adjustable. I did this with a 4" 3-jaw about 20 years ago and am about to do so with a 4" 6-jaw chuck. from Little Machine Shop The latter is most reasonably priced are around $270.

I have three Buck AT chucks in 3 and 6-jaw varieties, so I'm comparing to known quantities. My Buck chucks are all made in the U.S. before they went overseas.

The San Ou chuck I linked is $299 (free shipping) and comes with a D1-4 back plate. No need for engineering and design, simply fit the back plate, drill/tap three holes and you're set. That seems like a bargain to me. I put the 8" version on my 14" Logan and it's been great. The San Ou actually replaced a Buck 8" AT chuck that had worn jaws. It was cheaper to buy a new chuck than get the Buck properly fixed....still might have Kalamazoo fix it, but that's really just not wanting to trash something that can be saved rather than a smart money decision.