Tuesday, May 29, 2018

Rev 2 is Mostly Ready

Revision 2 of the cylinder for my Duclos flame eater engine, to replace the one I destroyed Friday, will most likely be ready to put back on the mill tomorrow.  I expected to get this one in a small fraction of the time spent on the first, since most of the time spent on the first one came from trying to figure out how to do certain things with tools I have (instead of immediately buying more new tools) and it did.  I spent about a week of "4 hour days" working on the first one, and about three of them on the second. 

It's not quite done.  The narrow diameter on the right needs to be reduced a little to press fit the pedestal onto this, and it needs to be cut off the extra rough stock that you can see in the lathe chuck on the left (wrapped in thin cardboard).  The same tool that made the fins on the cylinder will be used for that.  Most likely.

The truly detail-obsessed* among you will notice this one is different from the other, which is to say I also learned from my mistakes.  If you count, you'll see this one has nine fins; the other had seven and a smidgen of an eighth.  The print I'm building-to shows the slots and fins both being 3/32 wide (.0938").  On the first one, I just advanced the cutting tool by twice that and expected it to turn out.  I ended up with tolerance buildup - most of the fins and spaces ended up 7/64 wide.  This time, I had the idea to use the blue layout fluid (you can see a little remnant of it in the pic) and layout where edges should be.  Then I marked the edge of a space (between fins) by cutting a couple of thousandths deep; it allowed me to measure how wide the fin would end up and I could move the edge to make sure the fin was really .094 wide.

There are other small differences that I won't get into.  Think of it as a challenge.

I expect to spend more time agonizing over the setup with a dial indicator, verifying that it's the same height everywhere, and maybe putting a foot long pipe on the vise handle to clamp it tighter.  Basically, all the little tricks I've come across will get used, unless they contradict each other or something else.

( * "detail-obsessed" sounds better than "anal-retentive" doesn't it?)


  1. Excellent! Yes, you do learn little things about your project as you go along, and you make adjustments "As Required".

    It took me over two weeks to rebuild the driver's side suspension on the Supra, and a little over 4 days on the other side.

    Your hobby of machining your own examples of little-known engines is fascinating. The only 'motor' I made from scratch that way was in College, and it ran on compressed air.

    1. Yes, you do learn little things about your project as you go along, and you make adjustments "As Required".

      I think I spent a career designing radios and every single time I got to the end of project, I could think of better ways to do it.

      To think, I got started intending to mill out enclosures for electronics projects, like my CNC control box with cutout panels on the front and back.

  2. Cutting work off stock seems to be a bit of a problem, especially with smaller lathes. One solution I saw on utube is to invert the cutoff tool and run the spindle in reverse. This way, the tool will flex away from the work instead of digging in. The same method is useful for threading, since the tool moves toward the tailstock, and presumably, the open end of the work. Precautions are needed if your chuck threads onto the spindle. And off. Joe Pieczynski knows lots of neat stuff.

    1. I have my cutoff blade setup that way on my micro lathe, the Sherline. That has about 1/10 HP motor. This one has a 1-1/3HP motor and it has handled the cutoffs well from the front of the piece the few times I've done it.

      HOWEVER ... at the moment, the blade is only extending a little under 1/2" out of the tool holder. I'll need to extend it to about 1-1/4" and I might switch back to the thinner blade I have (1/16 instead of 3/32).

  3. SiG

    Does your vise open far enough to clamp the cylinder lengthwise? You would get more clamping force on two flat ends than trying to clamp at the circumference. You would have to change your program to use the other longitudinal axis, but the rigidity of the set up will offset the time lost re-coding the cuts. Just run an indicator along the OD to make sure you are parallel with the axis.
    Good luck.

    Whitehall, NY

    1. I'm pretty sure it can, and I want to look at that. The problem is that it needs to be held the way it is for another operation and it just delays the issue of the tool wanting to throw the work.

      Irish suggested milling a little flat into the soft jaws to make a little channel. It doubles the surface area that's contacting the cylinder to hold it. Some playing with a 3D model shows that a half inch channel 1/32 deep is just about perfect.

  4. A row of perfect machined and equally spaced identical fins.
    It looks so simple to accomplish, but like most machine shop work there is a large amount of skill, time, and brain work involved in making those simple projects. (and yes, a scrap bin with ever increasing occupants)

    So this phase is finished. (giggle)

    Well done.

  5. It's about time for Florida Flicker and Flash to hit you with a power surge right in the middle of the most critical machining operation...