Due to my clausing mill have a mt2 spindle, which type of steel should i use make a mt2 solid holder out of? I am also looking to make a ER20 collet for my SB 9A as well. Should i harden the solid holder as well?
Ease of machining and availability would be: steels: 1215, 12L14, 11L17 and 1144(stressproof), SS:303, . for hardening:O-1.
There are many other choices but may be hard to find and expensive.
If you get into hardening you have to worry about distortion after the hardening process.
It's not that easy. You ought to be able to find it annealed. 4140 is not like carbon steel, it needs to soak (be held at temp) for specific times (possibly hours) for each operation, and case hardening needs the same temps as any other hardening. I bought some 4140 flame cut drops, they were diamond hard (so to speak) I couldn't hack saw them. I built a charcoal fire in my grill, put the two pieces (3/4 by 3/4 by 12 ") in and let it burn out. cooled overnight. I could then cut it with high speed steel but it wore the cutter pretty quickly. Once it's annealed (Half Hard) its still RC 30 or so.
Good, sharp HHS tools are all you need.
My lathe is a combo Grizz with only 3/4 Hp and it cuts rifle barrels, etc with little effort. I don't go crazy with feed or depth-of-cut.
4140 actually is easier to machine than 1018, in my experience.
Here's a coincidence- look at the date you joined here. then look at my date.....
My first job with my last employer was making ETD 150 into piston rods, form turn each end then thread them. One thread about 1 1/2 long the other about 4. I musta made hundreds, from 3/4 diameter up to about 2". They wanted to see if I could chase threads. I showed 'em.