I finally got the first chips cut on my first project in with my new to me tools. I chose as my first project the Poppin air-cooled vacuum engine by Dr. J. R. Sentf from Live Steam November 1980. The internet has hundreds of plans but I chose this for its well documented build steps and many fine examples on this board and the internet to use as references.
I bought a fine tool collection from a friend that was retiring for what I thought was a very good price and my wife thought would break the bank, so the better part of this build is going to be a ‘run what you brung’ project, so if you see weird compromises or steps away from the plans of Dr. Sentf that is what is going on. I am as far from an expert on machining as anyone I know so please feel free to give tips where you see this build going astray.
The plans call for Meehanite bar which I had no idea where to get or what it was, but in my introductory post I asked and was informed that it was basically grey iron available anywhere and so I went and got a 12” stick of 1” grey iron class 40 from Enco. So the rod came and I whacked off 2 inches in the band saw and went to work.
I have been practicing cutting fins on some old cold roll I had laying around while waiting for the grey iron to arrive and they all looked terrible fat and not the least bit like the stuff I saw being build to I Goggled ‘cutting cooling fins model engine’ and came up with this great tutorial http://modelenginenews.org/techniques/fins.html
. It gave me the two clues I needed to cut good fins; grind up a special cut off tool to the desired fin spacing, and then to move the combined distance between fins and you come out right in the end. I ground this down to .047 with as close to the following clearances suggested in the tutorial as I could without a tool grinder
I faced off the grey bar and center drilled.
This is cutting the fins. I decided to use the compound for these cuts as suggested in the tutorial above because my carriage does not have a measurement and I haven’t figured out a good place to stick my dial indicator yet on my old Atlas. As this is my first project, I checked the cross slide and compound against a dial indicator and was satisfied with the accuracy. For the first cut I touched the left side of my fin tool to the shoulder, then calculated the width of my tool and the desired first width and started cutting, plunging .125 for each cut. After the first cut I simply moved .080 each cut and ended up with perfect fins. I thought for sure that I would break some but all was well. Well, minus the fact that it all worked so well I forgot to count and ended up with an extra fin and a slightly longer cylinder than the plans.
I tried boring the cylinder but I have two problems the first is my excellent tool buy did not come with a boring bar and the second is I have no inside measuring devices. They are now on my list but will try to work around them for this go. I tried using a cutter that is labeled threading tool that looked like it would do the trick and it cut just fine, but when I unchucked the bore was larger by .005 on one end than the other. As I have no inside measuring tools but my tooling did come with a nice set of reamers I think I will finish the bore with a 5/8 hand reamer.
Not a bad first days work.