Feel for you, Bro. My first class was in 1973, and only a semester (or maybe a quarter) long. Finally got desperate in 2008, and bought a Harbor Freight 93212 7x10 Mini-Lathe. Same one they carry in the stores now. Not a terrible machine, really, but I was a terrible machinist, and couldn't figure out why. Until my wife got tired of listening to whine, and told me to take another class. Started the class in February, 2015, finished in May of 2022. Should normally take 8-9 months, if you go full-time. Long story short, I was a crappy machinist because I could not accurately measure anything. There is a sense of touch you need to get the caliper or micrometer consistently tight enough to get the correct reading. I lost that sometime between 1973 & 2008. Only took a few hours sitting in class with a set of Jo-blocks and my mikes and calipers, and I had it. I've got more than one lathe, though the 7x10 is now gone, and the one I've spent the most time on lately is an Atlas TH42, which now sports and ER32 collet chuck on it's 1-1/2"x8tpi spindle. MT3 taper.? I traded the 7x10 for a couple of Unimats, an SL1000 and a DB200, which are essentially the same machine. They can be configured as either a lathe or milling machine with minimal accessories. I've made an ER25 collet chuck for one, of them, though I haven't gotten to test it. Also, I made it on the big machines at school. A Clausing Colchester 13, that being the closest thing they had to my smaller machines.?

As a restoration project, there is a 1941 South Bend Heavy 10L sitting in the back of the shop, too. 2-1/4"-8tpi spindle on it. They have a proprietary insert that adapts to, in the case of mine, an MT3, IIRC. Might be MT4.? I've heard it said that the insert is about a Morse 4.5, but can't swear it's accurate. If you can get measurements of the taper, you can make all the inserts you want! Those inserts are not held in by a drawbar, BTW. I guess they're a self-holding taper just as the normal Morse Tapers are.?

The tailstock is definitely an MT3, though. Steve Wells' site has a lot of the old catalogs and machine forms, so you might be able to find out more about your machine there. If you have the serial number, you can get a copy of the serial number card from Grizzly. It will at least tell you how it was originally equipped, and when it was shipped to the first owner. Gets you the correct model number, too. Can be useful looking at those forms and catalogs.?

I've not tried for an ER40 yet, as none of my functional machines can make full use of that size collet. But someday!

HTH!

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)