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Why are there no MRGN tool holders smaller than 3/4"? - Doug Ayen's Blacksmithing Blog [entries|archive|friends|userinfo]
Doug Ayen

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Why are there no MRGN tool holders smaller than 3/4"? [Apr. 7th, 2011|03:25 pm]
Doug Ayen
I've got the W2 disc in the lathe now, and have started the roughing out. The 3/8" drill bit I bought to drill out the arbor hole had to be sharpened 3 times during the drilling -- and I put the disc through as best of an annealing process as I could (heated to critical in a preheated forge, blocked off all the forge openings, and let it cool down overnight.) And this was the expensive "cobalt" drill, the best Home Depot had. Time to order some good drills in the sizes I need them I guess.

At any rate, the roughing out was going slow -- the disc turned out to be nearly 5" in diameter, which is right at the limit of what the lathe can handle, so it has to be running slow, but since it's a DC motor, at that speed it doesn't have a lot of power. I'm using indexable carbide tooling, which sorta works, but while taking a break I hit the books to see what would be the right tool for what I'm doing.

Turns out that what I should be using is a round carbide bit, type MRGN, in an appropriate holder. Searching around, however, all I see is .75" and thicker shanks on the holder, and my lathe takes .5" at the thickest. Looks like my options are to either make my own, or buy a .75" and cut it down if I want to do this right. Of course, there may well be a very good reason you need a studly shank on the tool holder, roughing is pretty hard on the tools no matter how you do it. Worth a try, though.

Before I proceed, though, I'm going to have to figure out what happened last night as I was finishing up -- I heard a clunk, and the headstock suddenly lost a bunch of ridgidity -- with it off, I can visibly move it with just hand pressure, something's allowed it to get loose.