Sunday, August 5, 2018

More Small Parts

I really only made two more parts for the flame eater engine this week, a non-standard screw that becomes the Cam Roller Shaft, and a part called the Cam Roller Fork.  It will eventually hold the Cam Roller, pictured last Saturday next to the cam.  

The screw, the Cam Roller Shaft, is a small part, just 11/32" long (0.343).  The screw head is 1/4" diameter and 1/32" thick, and the screw threads are 4-40.  Yes, I had to cut that slot for the screwdriver - using the Sherline CNC mill and the fixtures that were in place on it.  The fork is enormous by comparison, 1-1/8" long by 1/2" wide and 11/32 tall in that thick section.  There are three holes visible on the thick section: a 1/8" reamed hole for the valve push rod, and two at right angles to that hole that are threaded 4-40.  

The holdup this week was that screw.  I chose to make this little part on my little, manual, Sherline lathe.  Unlike most lathes which come either with a gear box or changeable gears (like my big lathe), the Sherline doesn't cut threads when stock from the factory.  They sell a threading accessory kit, but their method has the user remove the motor and a fair number of users had decided that was too much hassle.  If the handwheel is mounted on an extension tube, the handwheel will clear the motor and there's no need to remove it. 

When I went to set up the threading kit, it had been long enough since I used it that I needed to relearn how to do everything.  I couldn't quite get it set so that the last gear meshed.  It took a full afternoon and walking away from it for a while for me to get the method straight in my head and start cutting threads.  After a few practice pieces, I was able to cut the real piece.  Before I put the kit away, I took lots of pictures and wrote myself a paper on how to set it up next time. 

There are only two parts left on the page of "fiddly bits" I've been working at for a while, and neither of them looks as hard as some of what I've done already.  I think there are two other parts after that.  A die is on the way to cut some 5-40 threads I mentioned, and I need to spend a little time with the list of necessary nuts and screws and make sure I have everything. 


  1. About half of my "Project Book" for the Supra is pictures, and HOWTOs.

    Same with the project books for my Ham Radio stuff.

  2. I smiled for a second at "enormous by comparison" and then I realized you were exactly right.

    Looking forward to more.

  3. Very nice work. 4-40 and 5-40 screws are pretty dang small, what my Dad used to call Needle Dick Bug Fucker small.

  4. What type of steel are you using for stock?

    1. The screw and the cam roller I showed off before are both 4130, which is a decent steel. I didn't attempt to harden them.

    2. Hardened or annealed? I have had some problems getting a decent finish on 4140 annealed- sort of gummy or sticky under the cutter.

    3. Online Metals says "cold rolled, normalized". I don't think I got a nice finish at all. Lots of tool marks.

      It has been a while since I ordered this, so I'm not sure the memory is right, but I think I started out looking for 1018 and ended up with this 4130 for some reason.

      The book's author, Duclos, is very nonspecific about alloys to use. I remember for one part (I think the piston), he said use "CRS, bronze or cast iron". That's not just three different materials, it's three different families of materials.