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Tight Tolerance Builds on Sherline or Taig Lathe?

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Bear:
I know there are several Sherline or Taig users here. I am curious as to the largest I.C. engines you have made on these lathes. Actually, does not have to be I.C. engines. Could be anything that requires tight turning/boring tolerances. Looking forward to responses.

crueby:
I've built lots of steam engines on my Sherline lathe/mill, no IC engines. Largest steam cylinders were about 3" bore in brass and bronze, its not really suited to large bore in steel.


When you say tight tolerances, how tight? I like to bore the cylinders, then turn the pistons to match, lapping for final fit.

Bear:
Thank's Crueby. Yes, exactly what I am talking about. More specifically, is a cylinder with little to no taper (pre- lapping) for a Webster I.C. engine doable on your Sherline lathe? Cylinder is approximately 1.125 outside diameter with a .875 bore by 2.5 inches long (fin diameter not included in this dimension)?
 

Bear:
Note, I do have a Taig lathe and find it very useable; but was wondering if the cylinder the size of the one in the above thread could be made on the Taig. I know that the piston could easily be made to tight no taper tolerances.

I am kind of looking for an excuse to buy a Sherline lathe with the optional threading attachment to accompany my Taig.

crueby:
On the Sherline, the headstock angle to the bed is adjustable, plus they have a hey in that joint to keep it straight. The key gets it close, but not spot on, there is a slight amount of play still. It was fine for short cylinders, around an inch, but for longer ones I was getting a little taper till I took the time to true up the alignment using a test piece - made cuts down a bar the length of the cylinder, with the end of the bar supported by live center in the tailstock. Then made measurements with micrometer along the bar to check for taper, adjusting the alignment till it ran true. More recently, for doing some of my larger bore cylinders, around 3" diameter and 3 to 4 inch long, I also picked up a bore gauge so I could check for taper on the internal bore as it was being taken out to size to ensure nothing had moved. Made measurements when it was still short of final bore diameter so there was time to adjust if need be.
I've done most of my cylinders in brass or bronze, some also in steel. Its important on the sherline (probably same on Taig) to do some tests with the boring cutter to find the speed and feed rate, as well as height/angle of the cutter, to minimize chatter. Biggest thing I learned was to use the largest diameter boring bar cutter that would fit, and keep the overhang from the toolpost as short as possible, otherwise it would chatter. The Sherline is not as rigid as a larger lathe, so light cuts on final bore, and do some spring cuts at the end - passes without moving the cross slide in/out.

I also picked up a second lathe to use just for thread cutting - switching in and out of thread cutting mode on the sherline is a pain since you have to remove the motor, and the holders for the gears have a tendancy to slip so I added some supports down to the table to keep the gears meshed. The thread cutting on it does work, though its a lot of light cuts especially in steel. Well worth downloading the instruction sheets for the threading attachment from their website to see how it all works before committing to it.
 :cheers:

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