Thursday, June 7, 2018

Finally Done With The Replacement

The replacement for the cylinder I ruined about two weeks ago is complete and ready to put aside for later (except for a little cleanup).  This is it immediately after the last cut completed; not cleaned up at all. 

The fins and slots in the end are matched to those on the diameter of the cylinder: 3/32 (.094") wide with 3/32 spaces.  Just as the slots on the diameter were cut to 3/32 wide with a cutoff blade in that width, for these I had to buy a slitting saw blade that width.  I had some trouble with the first slot and didn't realize what was wrong for an embarrassingly long while, (the spindle's R8 taper was loose) so the first one has varying widths - which you can see if you look at the right end of the cut (the bottom).  It's a little stepped.   

After the first one, I decided it would be smart to write a little G-Code to eliminate the possibility of entering the wrong commands.   I lowered the slitting saw the expected amount, just barely cut into the end about .003 or .004, then used calipers to verify the fin being started was the right thickness.  If it was off slightly (the second one was off because it referenced the first slot), I corrected it, then ran the code to cut the slot.  Each slot took almost exactly 6:00 minutes.  

Somewhat cleaner at this point, just not deburred, yet. 

There are some marks from being in the vise that I need to either address or live with, and it has a bit of oil residue on it.  A little cleanup is needed. 

The next part is probably going to be the flywheel.  At 3-1/2" diameter, it will be the largest thing I've ever put on a lathe.  I not only had to buy a larger chuck for my big lathe, I'll have to use the "outside jaws" on it.  Aside from size, though, it will be just like the one I drilled on the rotary table for my first engine. 


  1. How are you going to turn and finish the piston?

    What clearance are you shooting for?

    I know you'll post them, I just can't wait....!

    1. The piston is a way down the road, but the book said, "cast iron, bronze or cold rolled steel", so I bought a bar of 1" diameter CRS. (Notice how precisely he specifies the allow :-D ) It's a little undersized, so I made the cylinder ... (trying to remember) like 0.980. I'll turn the piston to fit the cylinder.

      Since then, I've come across a few guys who recommend using graphite instead of any of those metals. I might pick up a graphite rod.

      Like I say, that's a few parts away.

    2. Notice how precisely he specifies the allow That's alloy - not allow.

  2. Any good [easy] way to deburr the cylinder?

    Erik in Colo.

    1. I don't have one. I've been using a needle file manually.

      Slow. Tedious. OTOH, it's not terrifying.

    2. You could use a Scotch-Brite wheel mounted in a bench grinder. It gives a nice finish on metal.

      Whitehall, NY

    3. After taping off what you don't want affected, and research on the correct media, maybe a vibratory cartridge case cleaner, or a rock tumbler.
      Might be you have exactly the correct tool already from jewelry making.
      The part looks great.

    4. Leigh - I have Scotch Brite pads that I've held against parts rotating in the lathe but didn't know they were available for the bench grinder. Thanks!

      Time to hit the catalogs.

      John - the only polishing media have in the tumbler is corn cob. Never tried it on aluminum so I don't know if it works or not. Based on primer pockets, I will end up picking pieces of corn cob out from between the fins.

    5. That's what compressed air is for, SiG...

    6. If you search for Scotch-Brite Wheel you will find wheels like the EXL and such that are meant for deburring. They are expensive at roughly $55-$60.

      What you really want to try is the Standard Abrasives 860708 disc. 6” diameter, 1/2” hole, Very Fine. Much less expensive at $2.50-$3.00 each. They look use like a maroon scotch-bribe pad in a wheel shape.

      I use two of these discs mounted side by side on my bench grinder. The Airgas picture shows blue, but they are really maroon colored.

    7. Oops, looks like Airgas wants you to buy 10 at a time. And it is not clear to me if the discs would be available at your local Airgas or just online.

      I can send you a couple of these discs to try out if you are interested.

    8. I need to do some looking around, but not sure I can get to it this weekend. "Previous arrangements".

  3. Graphite, huh?

    I might be tempted to go that route. Self lubrication should allow a tighter fit, increasing efficiency.