Replacing a Lathe Chuck

[David2011]

. . . 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.

Is this the back plate that you used? https://www.shars.com/lathe-chuck-adapter-plate-8-d1-4-finished-machined-for-zero-set-lathe-chuck

I can see a couple of advantages to using an adjustable 8" 3 jaw chuck. One is the additional through hole diameter for working on pieces bigger than the spindle bore of the lathe. Anything up to as big as 10" or so long x 2.5" OD wouldn't need additional support. The other is that the only time I would have to change to a 4 jaw is for irregularly shaped pieces. One disadvantage is the substantial weight increase over a 6" chuck.

 

[RickKr]

After my last post I called CME. Doug answered the phone. He said Robert Wei is the owner and is in the Far East at some machinery expos. He also said that the don't import an extra thick D1-4 back plate for the adjustable 3 jaw chuck. L00, L0 and threaded back plates are available; just not D1s in the recommended 1-1/2" thickness. Doug said that some people just add an additional plate of steel to add the required thickness. guess I could do that; it's just extra time machining.

Well, maybe you'll just have to do that extra machining. Really isn't that difficult and is exactly what I did, as shown in post #19 above. In that case, there were NO backplates available ANYWHERE to fit that Rivett spindle - proprientary - L00 taper but with non-standard 4 tpi threads. We machined 10 backplates from 4140 and 8620 steel bar stock, some for my friend Brett's Rivett and some for mine. (first photo, showning 7 of 10 threaded)

(Edited) Got my chucks mixed up. The one requiring the extra machining of adding the boss/shoulder was for the Bison 5", 6-jaw Set-Tru (photos 2-4). We had made an extra thick one (top on stack in right rear of photo 1), which was used to directly machine the boss for the Buck 6", 6-jaw Adjust-Tru (photos 5 & 6).

 

[Advil]

My lathe from CNC Masters that I got last year came with Sanou 3 and 4 jaw chucks. Wasnt familiar with that chuck name until then. I have mainly used the 3 jaw but they are both fine. Runout roughly around .001... Close enough for all 3 jaw work. Holds great even on the bigger cuts. They are definitely not junk. They're no Bison, but Id say a good value probably as low a price as you can go and get some kind of usable quality.

 

[David2011]

Well, maybe you'll just have to do that extra machining. Really isn't that difficult and is exactly what I did, as shown in post #19 above. In that case, there were NO backplates available ANYWHERE to fit that Rivett spindle - proprientary - L00 taper but with non-standard 4 tpi threads. We machined 10 backplates from 4140 and 8620 steel bar stock, some for my friend Brett's Rivett and some for mine. (first photo, showning 7 of 10 threaded)

(Edited) Got my chucks mixed up. The one requiring the extra machining of adding the boss/shoulder was for the Bison 5", 6-jaw Set-Tru (photos 2-4). We had made an extra thick one, which was used to directly machine the boss for the Buck 6", 6-jaw Adjust-Tru (photos 5 & 6).

You did some very nice work on those backplates. Making parts for unusual things can be stressful and lots of fun at the same time. I encounter that every week as a volunteer on the the battleship Texas restoration.

The problem is that they don’t have the D1-4 back plate to machine. They recommend a blank that’s 1-1/2” thick and I haven’t found one that thick in D1-4. An additional hitch is that their 6” adjustable 3 jaw is not 6”. It’s 6.57” so the bolt circle could be precariously close to the edge of a 6” back plate. I’ve machined back plates and you’re right; it’s not hard. It just takes patience and attention to detail.

 

[David2011]

My lathe from CNC Masters that I got last year came with Sanou 3 and 4 jaw chucks. Wasnt familiar with that chuck name until then. I have mainly used the 3 jaw but they are both fine. Runout roughly around .001... Close enough for all 3 jaw work. Holds great even on the bigger cuts. They are definitely not junk. They're no Bison, but Id say a good value probably as low a price as you can go and get some kind of usable quality.

Thanks for the input. I used small lathe a few days ago that had a San Ou chuck on it. No issues at all. I still ended up bringing the work home to put it in a 4 jaw, try to recover a bushing that’s stuck in a larger piece.

 

[RickKr]

You did some very nice work on those backplates. Making parts for unusual things can be stressful and lots of fun at the same time. I encounter that every week as a volunteer on the the battleship Texas restoration.

The problem is that they don’t have the D1-4 back plate to machine. They recommend a blank that’s 1-1/2” thick and I haven’t found one that thick in D1-4. An additional hitch is that their 6” adjustable 3 jaw is not 6”. It’s 6.57” so the bolt circle could be precariously close to the edge of a 6” back plate. I’ve machined back plates and you’re right; it’s not hard. It just takes patience and attention to detail.

Yes, making specialty stuff is a big part of the fun, but sometimes ya just want to grab something and go.

Ah, yeah, that is a problem. I've not re-read the whole discussion, but would it not work to get an 8" D1-4 and machine it down to the diameter you need be a staring point for adding the set-tru shoulder? I looked and found a couple 8", although the photos don't give me a lot of comfort.

PENN Tool Co.

Shars

 

[G-ManBart]

Is this the back plate that you used? https://www.shars.com/lathe-chuck-adapter-plate-8-d1-4-finished-machined-for-zero-set-lathe-chuck

I can see a couple of advantages to using an adjustable 8" 3 jaw chuck. One is the additional through hole diameter for working on pieces bigger than the spindle bore of the lathe. Anything up to as big as 10" or so long x 2.5" OD wouldn't need additional support. The other is that the only time I would have to change to a 4 jaw is for irregularly shaped pieces. One disadvantage is the substantial weight increase over a 6" chuck.

I was putting it on a lathe with a 2-1/4-8 threaded spindle, so I didn't use that exact Shars adapter plate, but it has the same specs for bolt hole spacing and registration boss diameter so it would work just fine.

Both of my larger lathes are 14" swing and most often they've got an 8" 3J adjustable structure chuck on them...pretty versatile. Having said that, today I plan to finish up fitting one of CME's 6" 3J adjustable chucks (really 6.5") to my 14" Logan as sort of an experiment. Everything seems a bit quieter and calmer when using a smaller chuck (maybe my imagination), it's probably a touch safer since it doesn't reach out quite as far and sometimes a smaller chuck makes it easier to get close to the work.

I actually bought the 6" CME chuck for a SB 10L that I'm fixing up to sell and it took up more space than I wanted on a short lathe. The body is fairly large and the jaws are on the tall side to it extends farther towards the headstock than I like. The farther the chuck sticks out, the more likely you are to get chatter, and that's not a good thing on a small lathe. A buddy found a vintage 6" Buck 3J adjustable chuck for me for $50 and that takes up a lot less space. I got a new adapter plate for that one and plan to finish fitting it today.

 

[G-ManBart]

You did some very nice work on those backplates. Making parts for unusual things can be stressful and lots of fun at the same time. I encounter that every week as a volunteer on the the battleship Texas restoration.

The problem is that they don’t have the D1-4 back plate to machine. They recommend a blank that’s 1-1/2” thick and I haven’t found one that thick in D1-4. An additional hitch is that their 6” adjustable 3 jaw is not 6”. It’s 6.57” so the bolt circle could be precariously close to the edge of a 6” back plate. I’ve machined back plates and you’re right; it’s not hard. It just takes patience and attention to detail.

True. In my last post I mentioned working with one of CME's 6" 3J adjustable chucks this week. It definitely is 6.5" and absolutely will not work with a true 6" adapter plate. I thought their 2-1/4-8 threaded extra thick 6" adapter plate was just big enough, but they showed me it really wasn't. They do list the 6" AT chuck with a D1-4 adapter plate (not sure whether the website or eBay has the better price).

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

 

[David2011]

True. In my last post I mentioned working with one of CME's 6" 3J adjustable chucks this week. It definitely is 6.5" and absolutely will not work with a true 6" adapter plate. I thought their 2-1/4-8 threaded extra thick 6" adapter plate was just big enough, but they showed me it really wasn't. They do list the 6" AT chuck with a D1-4 adapter plate (not sure whether the website or eBay has the better price).

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

Doug told me that they were supposed to take that eBay listing down because the back plate doesn't work with the adjustable chuck.

 

[G-ManBart]

Doug told me that they were supposed to take that eBay listing down because the back plate doesn't work with the adjustable chuck.

Oh man...they'd better take it down quick. If someone buys one they're going to have to eat the shipping to return it, and that won't be cheap.