Thank you for pitching in, Stew.
I managed to put in a few more hours into the build, so I started to work on piston and cross head assembly.
First on the order of business was to make a form tool. I didn't mean to make it ugly.
I had a CAD model where I drew several versions and decided on radius of 8 mm as pretty enough. I ground the HSS blank and while it was not the prettiest, I figured it's close enough. Unfortunately, once I turned the actual part it didn't match the intended geometry. I suppose it's not important, but is also just another reminder that I need more practice.
It's not nearly as rounded as I hoped for.
Anyway, I decided to carry on. I can always come back and redo the part from scratch, right?
I removed the bulk of material in the center on lathe, in preparation for the milling machine that will clean up everything else
A quick thread tap. I have tapping function on the milling machine, where it has reversing buttons on the feed levers, but I'm a bit anxious to use that on such small threads. I've stripped some threads with it in the past since I really don't have a good feel of how it's coming along. The machine is too powerful for such small taps, so hand threading it is. I promise, the hole is not that crooked, it's just the photo.
I also drilled out and reamed the cross holes.
You'll probably notice (as I did, but too late) that the cross holes are not centered. At first I thought that I made an error in finding the center, but it seems (as I will later find out) that my gibs are a bit too loose and I either bumped the wheel handle or it dropped on its own due to gravity and vibration. Tightening the gibs is on my to do list.
I'm not sure why I don't have the photos of the milling process, so you'll have to imagine a piece of metal in a vise on a milling machine. I also rounded it on the grinding wheel.
All this was done about two weeks ago, but I didn't get around to posting it, so now you get a double dose.
The following work is still warm from the lathe. I started with the piston rod, and perhaps the only interesting part about that is the threading. I have a nifty little thing for threading on lathe which sits on the tailstock and freely slides and rotates, keeping the axial alignment. I turned the chuck by hand, of course.
The piston itself, after parting, I reversed it and mounted it on the piston rod to clean up the parted side. This is where I discovered some wobble. I'm not sure where it came from, since the hole and the threads were done on the lathe and the piston rod is brand new piece of silver steel, and definitely not nearly as crooked as to cause that much wobble. In any case, somehow I managed to fiddle it to run true and clean it up.
This is where I had another one of those bright ideas. I was fiddling with the cross head and realized that I forgot to clean it up and break the edge, so I thought it would be fine to put it on the piston rod and chamfer it.
Of course, it caught and bent the piston rod, fortunately only slightly, and I was able to return it to the original shape. You wouldn't even know it if I hadn't told you. Admittedly, the cross head does look better now.
Everything together.
