More stuff, this time the big ends for the conrods. I'm really enjoying this build, it's at a level where I can make rapid progress, but still throws out trials from left field. These bits were at that kind of sweet spot, where it wasn't frustrating but still challenging.
Here's some brass flat I had on hand.
It's the hard, no lead, I'll mess with you kind
More seriously, for this job who cares, it's small and easy to machine.
So I cut a piece off, which was too long in the long direction. A little milling and it's like this
Then into the lathe and turning a spigot on the end. Here it is with the spigot partially turned, the thread tapped, and the rest of the conrod screwed in. I've faced off the end such that the thread locks up with the required rotational alignment.
I put the 8BA thread in using my custom made tapping chuck type thingy. It spins and slides freely on a 3/8" shank which fits in the MT2 shank in the tailstock.
Then got rid of the excess with a parting tool and faced her off to leave a reference surface
At this point I still need to split it in half. Oh the drawing is wrong here, hence my doodling on the side, I'm going to make the gudgen pins a 1/16" higher in the pistons to compensate.
Next I drilled some holes, and tapped 8BA. I don't have a height gauge, I just use the digital vernier's height measuring face at the top end. I find that if I add two thou for the thickness of my scriber this gives excellent results. Hope you get what I mean. This works super well. That's how I do near all my marking out. The reason I don't have other stuff (a height gauge) is this works so well I can't be bothered. (Actualy I have a surface gauge that I don't use
). I drilled the first half to the major thread diameter which served to guide the tap.
Then tapped the threads. I got this pin chuck from Jaycar at a good price (info relevant to fellow Aussies only)
I had left an 1/8" to play with before sawing in half. Then I faced the half that went on the conrod down to size.
The other end had a flat reference face, so was an easy milling job.
Then drilled and reamed for the crank
So here's the result. They're small but took a couple of evenings work all the same
Even posting this was more involved than I anticipated, but they're done, and I'm happy
That's all that counts of course
Steve