Tight Tolerance Builds on Sherline or Taig Lathe?

[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.
 

[Bear]

Thank you Crueby for the excellent response. By the way, what second lathe did you get for threading?

[crueby]

Thank you Crueby for the excellent response. By the way, what second lathe did you get for threading?

My main lathe is the long bed version. For threading I  got the short bed one. You can buy it a bit cheaper without the motor since the threading doesnt use it. I did get the motor since it wasnt much more as part of the package, and I  needed a spare one soon after so it was a good gamble. I put a LOT of time on my machines over the last 20 years, and wore one motor out. Had put in new brushes a couple times but finally wore out the commutator ring. The newer motors dont have replaceable  brushes, will find out in ten more years how long they last!

[Bear]

Thank you again Crueby. I missed the Sherline November 20% off sale on lathes. I am very tempted to try one. I remember they used to have discount codes a while back. Anyone aware of any for the lathes?

[RReid]

Cylinder is approximately 1.125 outside diameter with a .875 bore by 2.5 inches long (fin diameter not included in this dimension)?

I don't see any problem doing a cylinder like that on the Taig. I haven't done any quite that size, but have done several steel cylinders 0.75" bore by 2" that came off the lathe straight and smooth, several others slightly smaller. I like to make a close fitting plug gauge to check that the bore is straight, and if there is more than one cylinder, that they are consistent.

I've also turned 1.5" diameter locomotive driver wheels in steel, and flywheels up to 3.5" (that one was cast iron).

[Bear]

Thanks Ron. Very encouraging.

[paul gough]

A 2.5 inch bore is quite long but you could probably be able to use at least a 3/8 shank boring bar to assist reducing chatter. I have only made 9.5 bore 30mm stroke cylinders using a HSS boring bar I ground up from 1/4 inch rod. Very light fishing cuts! I was able to achieve comparable accuracy and finish on this cylinder as on the other which I drilled and then used a machine reamer on my Sherline mill for a test. I used the bore gauges to check for discrepancies and found none. Both my machines are metric with ER 16 headstocks with C5 bearing option. As Sherline make all their chucks with the 22x1.5 (ER 16) thread this was an ideal and versatile arrangement. Especially moving jobs/chucks between lathe and rotary table or angle plate. Sherline make an ER 16 adapter for the rotary table but don’t and will not make one for the angle plate, but it is easily made. I think Chris Rueby has given an excellent appraisal and he was my guide when I put together my miniature ‘tool room’. The length of bores you quote means you would need the long bed lathe and if you are contemplating a 5400 mill seriously consider the 15” option as you would probably need the extra height. Overall, satisfactory little machines for miniature modelling, though Chris’ might be a touch beyond miniature!!!!! Regards,Paul.

[Bear]

Thank you, Paul.

[paul gough]

I notice I said “Sherline make all their chucks with a 22x1.5mm thread….” What I meant was this is an option rather than the standard 3/4 inch thread. Sorry for any confusion. Regards, Paul.

[bent]

Originally bought my Taig lathe to do prototyping of "small" valve parts.  This is our work description, the valve in our case being 1-1/4 pipe size and smaller.  The parts I prototyped were of maximum 2.5" diameter.  Tightest tolerances were +/- 0.001", though I got tighter than that for some small model engine pistons and cylinders.  Most of getting that fine of tolerances is operating the lathe handles in one direction, to take up the slop in the feed threads.  Although outfitting your lathe with cheap DRO's makes hitting the same marks quite a bit simpler.

[Bear]

Originally bought my Taig lathe to do prototyping of "small" valve parts.  This is our work description, the valve in our case being 1-1/4 pipe size and smaller.  The parts I prototyped were of maximum 2.5" diameter.  Tightest tolerances were +/- 0.001", though I got tighter than that for some small model engine pistons and cylinders.  Most of getting that fine of tolerances is operating the lathe handles in one direction, to take up the slop in the feed threads.  Although outfitting your lathe with cheap DRO's makes hitting the same marks quite a bit simpler.

Thanks, Bent. Liking what you said about the Taig.