Retrofit ER-32 collet chuck to an Atlas/Craftsman 618

SG51Buss

Active User
Registered
Joined
May 20, 2014
Messages
191
I've wanted an accurate collet system for my Atlas/Craftsman 618 lathe for a long time. Acquired an MT2 drawbar collet set several years ago, but wasn't impressed. Too much runout, plus limited depth. Looked into the 5C collet system, but wanted to avoid the expensive/complicated/heavy chuck, and the long protrusion. Decided to look into the ER collet system. Accurate, simple, compact system, which allows through-passage of workpiece. Inexpensive collet chucks of numerous types everywhere. Except for the older Atlas/Craftsman 618 type 1"-8tpi sleeve-bearing spindle.

Yes, there's collet chuck plans out there, and I was heading in that direction, until I found this PSI woodworking ER32 collet kit, on sale for $68 on Amazon. So, let's see if we can make this thing work. Warning: Even though it's possible to cruise thru this post in a few minutes, the actual project took me two months. I must be out of my mind.

Squaring-up on the collet nut threads (because I wanted the collet nut to run true), I shortened and re-registered the 1"-8 mount end. Mounted it on the spindle, and the collet nut threads ran true.

Tried a 1/2" reference rod, it took almost 3/4 turn to snug the collet (something wrong here), and the runout was horrible. Checked runout of the tapered bore, 0.006" TIR. Well, that is to be expected. So, made a 16.0° gauge plate and checked the collet holder opening. Sure enuff, wrong taper, quite a bit less than 16°. Decided to check the included collets, and found 2 of the 5 collets were a bit off taper, 15.85° and 16.35°.

My near-term project will be using 5/16" and 8mm stock, so ordered precision collets in those sizes. Their tapers measured right at 16°.

ER32-Collet-01.jpg

So, now the challege is to cut a precise 16.0° taper, using the compound slide set at an even more precise 8.00° +/- .01° angle (relative to the spindle centerline). Using the 4-jaw, chucked-up, centered and trued a 1/2" reference bar. Then set the compound slide angle using a dial gauge against that reference bar to get within 0.0005" of 0.240" of forward travel on 1.725" of compound slide travel (1.725" times sin(8°) is 0.240"). Max travel on this compound is about 1.8", so this is as good as it gets.

While cranking the compound, noticed significant operator-induced wobble during the compound travel. Even with the gibs snugged, carriage and crossfeed clamped, it still wobbled too much. Then realized that I'd have to carefully and slowly hand feed that thing for 1.3" worth of cut.

So, this project had to be put on hold until implementation of another bucket-list project, a powered compound feed system, which was done in this thread:

http://www.hobby-machinist.com/showthread.php?t=24766

With that done, repeated the arduous 8.00° compound slide setup. Now, we're ready for some cutting on that ER32 collet chuck.

ER32-Collet-02.jpg

Now, this is some strange metal. You can hear the cutting in this short video:

https://youtu.be/qxwERYLQFmA

Yes, there's cutting oil in there. Never cut anything like this before. Noticed its strange behaviour during the cutting of the mount base. With very sharp and honed bits, both carbide and HSS, using various face and rake angles, this stuff takes a bit more pressure to start a cut, and it doesn't cut clean. More like a tearing. Imagine trying to carve a matress with a shovel. What you get are tears and micro-gouges. It doesn't flake/chip/powder like cast, doesn't curl or string like steels. With 0.001" depth of cut, the chips are various micro-sized C-shaped chiplets. It's not that hard, you can file it, but even the file marks are rough. Very odd.

So, figured that toolpost grinding would have to be used. I have a couple of dremel toolpost mounts, but decided to use a Foredom-type cable drive with a long/slim handle to reach into that tapered bore. Doing only 0.001" finish passes, my various fine-grit stones didn't much care for that mystery metal. It just chewed them up. The surface finish looked more like a skin disease than the normal finely-ground surface.

So, next up was my Craytex wheels:

ER32-Collet-03.jpg

After several passes, the coarse Craytex finally gave an acceptable finish. Strangely, I never got sparks with the stones, but the Craytex would occasionally throw a short/tiny yellow spark. Sounds like maybe low-carbon? Exotic chinese rare/precious smelted battleship pig-iron, alloyed with carefully-selected Pabst beer cans and IBM disc drive platters?

After full cleanup, it was time for a test fitting. With the spindle turning, slowly ran a dial test indicator down the bore, and got zero deviation and runout. Chucked-up the 1/2" reference bar (only took 1/8 turn to tighten the collet this time), spun it up slowly, and ran the indicator along the bar using the carriage leadscrew feed.

ER32-Collet-04.jpg

Got 0.0002" TIR at the chuck, 0.0004" TIR at the 6" distance. I can live with that...

ER32-Collet-05.jpg

ER32-Collet-01.jpg ER32-Collet-02.jpg ER32-Collet-03.jpg ER32-Collet-04.jpg ER32-Collet-05.jpg
 
Sometimes you buy a tool, sometimes it is a kit. Nice rework. I never have done anything to mine as I only use it on my wood lathe.
 
I've wanted an accurate collet system for my Atlas/Craftsman 618 lathe for a long time. Acquired an MT2 drawbar collet set several years ago, but wasn't impressed. Too much runout, plus limited depth. Looked into the 5C collet system, but wanted to avoid the expensive/complicated/heavy chuck, and the long protrusion. Decided to look into the ER collet system. Accurate, simple, compact system, which allows through-passage of workpiece. Inexpensive collet chucks of numerous types everywhere. Except for the older Atlas/Craftsman 618 type 1"-8tpi sleeve-bearing spindle.

Yes, there's collet chuck plans out there, and I was heading in that direction, until I found this PSI woodworking ER32 collet kit, on sale for $68 on Amazon. So, let's see if we can make this thing work. Warning: Even though it's possible to cruise thru this post in a few minutes, the actual project took me two months. I must be out of my mind.

Squaring-up on the collet nut threads (because I wanted the collet nut to run true), I shortened and re-registered the 1"-8 mount end. Mounted it on the spindle, and the collet nut threads ran true.

Tried a 1/2" reference rod, it took almost 3/4 turn to snug the collet (something wrong here), and the runout was horrible. Checked runout of the tapered bore, 0.006" TIR. Well, that is to be expected. So, made a 16.0° gauge plate and checked the collet holder opening. Sure enuff, wrong taper, quite a bit less than 16°. Decided to check the included collets, and found 2 of the 5 collets were a bit off taper, 15.85° and 16.35°.

My near-term project will be using 5/16" and 8mm stock, so ordered precision collets in those sizes. Their tapers measured right at 16°.

View attachment 82919

So, now the challege is to cut a precise 16.0° taper, using the compound slide set at an even more precise 8.00° +/- .01° angle (relative to the spindle centerline). Using the 4-jaw, chucked-up, centered and trued a 1/2" reference bar. Then set the compound slide angle using a dial gauge against that reference bar to get within 0.0005" of 0.240" of forward travel on 1.725" of compound slide travel (1.725" times sin(8°) is 0.240"). Max travel on this compound is about 1.8", so this is as good as it gets.

While cranking the compound, noticed significant operator-induced wobble during the compound travel. Even with the gibs snugged, carriage and crossfeed clamped, it still wobbled too much. Then realized that I'd have to carefully and slowly hand feed that thing for 1.3" worth of cut.

So, this project had to be put on hold until implementation of another bucket-list project, a powered compound feed system, which was done in this thread:

http://www.hobby-machinist.com/showthread.php?t=24766

With that done, repeated the arduous 8.00° compound slide setup. Now, we're ready for some cutting on that ER32 collet chuck.

View attachment 82920

Now, this is some strange metal. You can hear the cutting in this short video:

https://youtu.be/qxwERYLQFmA

Yes, there's cutting oil in there. Never cut anything like this before. Noticed its strange behaviour during the cutting of the mount base. With very sharp and honed bits, both carbide and HSS, using various face and rake angles, this stuff takes a bit more pressure to start a cut, and it doesn't cut clean. More like a tearing. Imagine trying to carve a matress with a shovel. What you get are tears and micro-gouges. It doesn't flake/chip/powder like cast, doesn't curl or string like steels. With 0.001" depth of cut, the chips are various micro-sized C-shaped chiplets. It's not that hard, you can file it, but even the file marks are rough. Very odd.

So, figured that toolpost grinding would have to be used. I have a couple of dremel toolpost mounts, but decided to use a Foredom-type cable drive with a long/slim handle to reach into that tapered bore. Doing only 0.001" finish passes, my various fine-grit stones didn't much care for that mystery metal. It just chewed them up. The surface finish looked more like a skin disease than the normal finely-ground surface.

So, next up was my Craytex wheels:

View attachment 82921

After several passes, the coarse Craytex finally gave an acceptable finish. Strangely, I never got sparks with the stones, but the Craytex would occasionally throw a short/tiny yellow spark. Sounds like maybe low-carbon? Exotic chinese rare/precious smelted battleship pig-iron, alloyed with carefully-selected Pabst beer cans and IBM disc drive platters?

After full cleanup, it was time for a test fitting. With the spindle turning, slowly ran a dial test indicator down the bore, and got zero deviation and runout. Chucked-up the 1/2" reference bar (only took 1/8 turn to tighten the collet this time), spun it up slowly, and ran the indicator along the bar using the carriage leadscrew feed.

View attachment 82922

Got 0.0002" TIR at the chuck, 0.0004" TIR at the 6" distance. I can live with that...

View attachment 82923

Okay I know my hearing is not perfect working with lathes over the years. Doesn't sound bad to me. Some metals just squeal. The only thing might be the boring bar is a little small in diameter. If the finish looks good without a lot of chatter marks then it is fine. I like to grinder approach to finish the taper. Very nice job. I am glad you were able to convert it to your lathe.
 
Okay I know my hearing is not perfect working with lathes over the years. Doesn't sound bad to me. Some metals just squeal. The only thing might be the boring bar is a little small in diameter. If the finish looks good without a lot of chatter marks then it is fine. I like to grinder approach to finish the taper. Very nice job. I am glad you were able to convert it to your lathe.

Thanx, Bill. Yeah, my tinnitus doesn't help me much, either. And stupidphone audio has it's shortcomings. Wish you had been here to experience cutting that stuff. Outer cuts, facing, were all very strange. Agree on the grinder, so I'm now looking for better stones...
 
Following up on this project, I decided that after all the effort to get the compound to the precise 8° angle (actually, within 1 MOA), I wanted to grind the collets to match the collet holder and be centered to the lathe spindle. So, the compound angle has been left undisturbed since the machining of the collet holder.

The plan is to cut a mandrel, in progressively smaller diameters, to fit the collets in the set, one at a time. Each successive diameter will be a couple thou oversize so that the collet will press-fit onto the mandrel. This will ensure that the collet is unsprung and true, plus withstand the mild grinding forces.

The first collet is 3/4", so I turned a mandrel down to 0.752", 0.0000" TIR, for a nice press fit. I really don't expect to use this collet. Something this large, for this lathe, is probably better off being setup in the 4-jaw. So, this one is sort of a proof-of-concept, and will act as a sort of sacrificial piece to get the little 22mm grindstone settled and true.

I fitted the 3/4" collet, and ran the DTI down its 8° surface, and found that it was indeed a wider angle, about 8.15° (for a total angle of 16.3°), about what I was expecting. Then I painted the whole 8° surface with a sharpie (poor man's layout blue), setup the toolpost grinder, and made a few very light passes.

ER32-Grind01.jpg

The little grinding wheel is still settling in, but you may be able to see that the collet's taper is indeed off. And sure 'nuff, the sides weren't perfectly straight and it's slightly out-of-round (probably can't see that here, gotta turn the chuck to see the varying pattern).

ER32-Grind02.jpg

ER32-Grind01.jpg ER32-Grind02.jpg
 
Very nice Steve. As a fellow 618 owner I am also intrigued with all the little custom trinkets you've added to the machine -- carriage stop (very discreet), large cross feed dial, nifty little cover to stop chips from getting into that stupid spot under the headstock, etc etc. Too cool! Now I just have to figure how you did them all.

Thanks for posting, very interesting.

- frank
 
... As a fellow 618 owner I am also intrigued with all the little custom trinkets you've added to the machine -- carriage stop (very discreet), large cross feed dial, nifty little cover to stop chips from getting into that stupid spot under the headstock, etc etc. Too cool! Now I just have to figure how you did them all...

Hey, Frank, thanx for your interest! Yeah, your wandering eyeballs caught some of those things. Well, I plan to do some more threads on those 'trinkets'. Most of them were done by dear 'ol dad back in the '50s and '60s, when I was just a kid, so they'll be more of a post-mortem expose' than an active project. Since they're Atlas/Craftsman specific, they'll go into that sub-forum. I think you'll be interested in that large-dial crossfeed, it has a special feature. And, to pique your interest, ask yourself what appears different about the far side of the carriage...
 
Back
Top