Saturday, June 30, 2018

Small Parts

No, not bit parts in a movie.  Small parts for my flame eater.  Also known as the fiddly bits.

I spent a couple of days making the piston rod.  It's small in every dimension except length, but could be done comfortably on my micro milling machine.  Since the drawings are copyrighted and in a book I bought, I probably shouldn't give all the dimensions here, so this drawing doesn't give you enough info to make the part, but will show you the critical sizes. 

At it's thickest, it's 0.187, which is 3/16", but that's only on the right end.  Everywhere else it's 1/8" thick.  It started out as 1/4" thick aluminum, about a quarter inch wide and got progressively smaller.  Every cut required a different setup and I spent a lot of time trying to ensure the part was parallel to the table so that I'd cut off the same thickness on both ends.  I went back to the OEM jaws on the vise which are about 7/8 tall, and had to put the work piece on a shim on top of my 3/4" tall parallels.  The next size parallel in the set is too tall.  I wasn't holding on to much more than I was cutting off, which is precarious and high pucker factor. 

I thought I was done Thursday and then realized that I also left the little square tab on the left end 5/16" square - which meant that long central part of the rod was too wide.  I finished it yesterday, and made one tiny, minor, glaring, huge mistake.  I cut off the bottom of that quarter inch wide tab on the left.

I know I've said that if your motto in life is "close enough", machining might not be the hobby for you, but in this case, "close enough" is probably true. 

Today I started concentrating on parts that attach to this.  On that small end, it gets a yoke that rotates around a pin in that hole.  The part was that pin, which ends up as a piece of 1/8" diameter steel rod, with a 3/32 hole down its axis.  That leaves a tube that has walls about 1/64" - about .015 thick.  That took a couple of minutes on my Sherline manual lathe, and I moved onto the yoke.  It's also small, 5/16" diameter aluminum round bar, finished length is 21/32.  It has one end that's turned down and threaded 6-32 by 3/16" long.  Didn't quite get that finished today, so more pictures in a day or three or whatever. 

1 comment:

  1. Wouldn't it be easier to just make all the parts double size?