Todays Project - What did you do today?

[PixMan]

I went to the shop and remade the blank for the 70T Mod 1.75 change gear I need for my lathe. I made one out of "scrapbinium" and it cut a lot like 1018CRS. The guy who's going to cut the teeth for me said it would not hob to a decent finish, so I went to a local steel supplier (Peterson Steel, Worcester MA) and got a Ø6" x 7/8" thick round of annealed 4150. I figured I might as well make a new one because I went .0012" oversize on the 20mm bore on the crappy material one.

Here's the stock as I faced off the sawn side. It was out of being parallel by almost .040" (1mm).


Here's the finished front side, it came out quite nice and the bore in now right at 20mm.


Now I've turned it around to finish the back side. Too thin to simply snug it up against the chuck jaw faces and the bore too small to get in there with an indicator. So what I did was use an indicator on the cross slide and "zero out" the DRO in Z axis. By retracting the cross slide just enough to velar the 6" diameter, I could move the carriage out to index between the jaws and then return the carriage to zero and run the cross slide back in. If anyone has a better way of doing it I'd like to hear it. The blank came out parallel within a "couple of tenths".


Finish turning done, now I need to figure out a good way to get the 6mm keyway in it before shipping to the gear hobber.