Time for an update on the real meat of this thread, although both concrete and using horse urine to color copper roofs were both interesting sidelines
I had the stitches taken out Friday (October 1) and have been working toward setting up to resume work on the crankshaft since last weekend. The finger is really ugly but mostly functional. I'm very likely to have full use of it.
Back in
post 39, I mentioned that I was going to round up the parts to make the cutter
@Eccentric showed in
his post and called it the Terry Thomas cutter. I ordered a couple of 1/4" shaft brazed carbide cutters from MEC, planning to cut the notch. Out of nowhere, I received an email from a friend of a friend recommending
a video by YouTube machinist Joe Pieczynski. It's a 18 minute video, but he makes a cutting bit like what I was considering except with a wider gap in the middle. Not a slot but a rounded area. That video led to this cutting tool.
It's a little raggedy looking, but not much more ragged looking than Joe P.'s cutter. The relieved area was made using a Foredom Flex Shaft grinder with a diamond dentist's bit. The background in this image, by the way, is the gray cast iron bar that's going to become my cylinder. It's a 2" square bar (almost 2-1/16 on a side) that needs to cut down to 1.750" on a side.
After this, I positioned the cutter in a tool holder so that it was touching the metal at the same machine zero as the other tools I was going to use. Because it's a 1/4" shank and the cutter is almost exactly 0.250, I relieved the shank on both left and right sides, so that the shank of the cutter absolutely won't touch the side of the bar before the cutter does. I did that on a benchtop belt sander. Since it's a 1/4" tall shank in a tool holder set for a 3/8" tool, I put a small piece of 1/8" thick aluminum under it, visible at the very bottom of the picture along the left side of the tool.
I used Joe P's method, using my 3/32 wide parting tool to take deeper cuts in the stock, which makes it look like our typical cylinder heat sinking fins, and then used the cutter I modified to sweep back and forth reducing those fins to the desired constant diameter. After that it just needed some final size tweaking of both the length and diameter of that round section.
After a two week interruption, this step is just about finished. The width is right (0.438) but the diameter is about .0015 over.
@Eccentric showed some grinding stones that he uses, which I don't have as a ready option. I have sand paper (AlOx paper) in grits that will work and I have needle files. I've just come in from testing a couple of those and while they're small, they don't get my hands too close to that rotating bar that started the whole delay. I need to do a look at some of my wife's nail abrasives. She has some nail buffers with four grades of abrasives and they do produce a very smooth finish on metals. The ones I can think of are too wide to put in that 7/16" wide slot. If I need to use sandpaper, I'd prefer a tool to hold strips with than using my fingers. Maybe I can find something to print on the 3D printer.