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

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...

Well I did notice the hinged cover over the across feed screw, but that was intimated with the "etc, etc". Brilliant idea, but I'll look again just in case that's not it.

-frank
 
Good eye, Frank. Yeah, that hinged cover is longer, protects more of the screw and way, and makes it easy to lube the screw. But, that's not it. The mod is very visible, but not obvious...
 
Ok now you're just toying with me. It's the wider carriage itself, right? The back wings (if that's what one could call them) look about 1-1/4" wider to each side, and there's something not quite Atlas about the shape. I'd expect the carriage has less potential to cock to the side when you change travel direction. Brazed on?

-frank
 
Good eye, Frank. Yeah, that hinged cover is longer, protects more of the screw and way, and makes it easy to lube the screw. But, that's not it. The mod is very visible, but not obvious...


Hey Frank, check out the power feed on the compound.

Steve, tell us about that.
 
Haha, Frank, you got it! Yes, a wider carriage, longer gib, and 2 more gib screws. Really stabilizes it.
 
Hey, Rangemaster1. Welcome to the forum! That powered compound is disclosed in this thread:

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

I see you're into gunsmithing. A noble trade.
Now I'm wondering if I should post up some amateur acccuracy mods done on this lathe, in the gunsmithing section.


Thanks for for the welcome, and thanks for the info on the compound feed. I use my compound to turn tapers on muzzle brakes. I taper the rear of the brake down to the barrel diameter for appearance, and I seem to do a lot of them, mostly on the target rifles I build. It gets tedious at best. A power feed would certainly make life easier. I can get a near polish on the brake by hand, but it's a pain. I'm book marking your thread so I can find it when I get home. Thanks again,

Ron
 
Finished grinding the ER32 3/4" collet, made with a few very light passes.
The little grinding wheel settled-in and now has a proper cutting edge.
ER32-Grind03.jpg


Changed over to a medium Craytex wheel to polish-out the grinding.
ER32-Grind04.jpg


Test fitted this collet into the collet holder, got no sloppy feel.
Slipped a 3/4" bar into it, and found that tightening from finger snug to full tight was less than a 1/10 turn of the collet nut.
Much better.

ER32-Grind03.jpg ER32-Grind04.jpg
 
While doing the next collets, came across something that may be of interest.

First, the 5/8" collet had a few small burrs where the ID exits the backside of the collet. These burrs would catch the edge of a test shaft as it was slid thru, and could cause accuracy problems, plus scratch the shaft. The burrs had to be dressed out with a craytex point. Here, you can see the thin, shiny corner edge where one of the burrs was removed.
ER32-ColletBurr.jpg

The second issue is the collet taper. As measured earlier, the 5/8" collet showed a 15.85° total angle. But, when fitted to the 0.627" mandrel, its angle was rechecked using the compound and DTI, and found to be very close to 8.00°.

What this means is that an ER series collet may not present a precise 16° taper while in its relaxed, unsprung state (especially the budget ones). Some ER collet chuck projects that I've read involve using the collet as a master gauge when cutting the chuck inner taper, using layout blue markings as an indicator to adjust or confirm the compound angle. I've noticed, in those project pictures, that this 'master' collet is empty, relaxed, unsprung.

As such, for those folks that choose this 'master-collet / layout-blue' method of cutting the taper, I would humbly recommend fitting a slightly oversized (0.002" - 0.003") shaft into any collet that would be used as a master angle checker .

ER32-ColletBurr.jpg
 
Been grinding the other ER32 collets, have some observations about them.

None of them (so far) have the correct taper, don't have straight sides, and are eccentric (by up to 0.003")
What's worse, is that they looked so nice and shiny, until I took a closer look. It seems that they were rather roughly cut, then someone spent considerable time at the buffing wheel to make them pretty. So, this is what to expect from import tooling, pretty junk. Oh, well. After grinding, they're better than they were.

Now I'm ready to work on my high-dollar, high-precision SYIC Techniks 8mm collet.
It appears to be much better quality, smoother bore finish, proper chamfering of bore edges, no sign of buffing wheel cover-up funny business.
But, under the magnifying glass I found numerous nano-sized metal hairs emerging from the slits. They're stuck there and don't wash away with cleaner. Had to meticulously scrape them out with a fine dental pick.

The mandrel has been turned dead true, then collet fitted and painted. Checked its taper with the dial gauge, looks very close.
ER32-Grind8mm01.jpg


Started with a light 0.0005" cut, and let the powered compound make several passes until spark-out.
There is a very slight wasp-waist shape here, and it's very slightly eccentric, revealed by the residual paint in the circled area.
But, we're only talking a few microns here.
ER32-Grind8mm02.jpg


Advanced the cross slide another 0.0005", and let the powered compound make numerous passes until spark-out.
The collet cleaned-up nicely, no more indicator paint left.

Changed over to a medium Craytex wheel to polish-out the grinding.
ER32-Grind8mm03.jpg


Finished, oiled, put back into its wrapper for later testing.
ER32-Grind8mm04.jpg

ER32-Grind8mm01.jpg ER32-Grind8mm02.jpg ER32-Grind8mm03.jpg ER32-Grind8mm04.jpg
 
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