Here's a little report to kind of close the loop on all this.
Since I already had a nice fit between the first piston and its cylinder, I went ahead and bored out the inside. I couldn't see that the outside changed at all after the boring operation, so that one was keeper.
For the second one, I roughed the OD to within 0.030 or so of the intended dimension, then did all the internal boring. Then I somehow managed to take too much off the outside, so that one went in the trash. The second attempt at the second piston was successful using the same approach but without the bonehead mistake.
I never got any chatter or ringing through any of this, so I didn't mess with the mandrel idea. I just did all the machining on the end of a long piece of stock, parted off the piston after finishing up the OD, and then flipped it around in a collet to clean up and chamfer the bottom.
Instead of toothpaste and TV, I lapped the pistons together with the cylinders while the piston was still in the lathe. I used some of the magic TimeSaver lapping compound that RussN mentioned earlier in the other thread.
-- Russell Mac
Order of Operations Question
Re: Order of Operations Question
Your Timesaver solution was the best.
RussN
RussN
Re: Order of Operations Question
I usually find a piece of vacuum hose or fuel line that I can coil up and shove in the part to reduce ringing. Usually works some of the time!