After a bit of searching here, I couldn't sort thru the various postings about cutting stainless steel, so I figured I'd ask to get a clearer answer.
I need to make a connecting rod/piston for small steam engine. Plans call for stainless - 316. It's about 1.1" long, 3/16" square head - 1/4" long on one end (w/hole to connect to crank disk) with the rest of the stock turned down to 0.172 (piston end)
Not having any experience with stainless till a few days ago on a full-sized lathe. I put the 3/16" sq 316 stainless bar stock into a collet, center drilled the other end, promptly broke off the end of the #1 center drill in the stock. No prob, left it plenty oversized, & attempted to part off the end to get past the embedded tip of the ctr drill. That didn't go too well either LOL .... what I'm assuming was a HSS cutoff blade, after it got part way thru the 3/16" stock, it flexed a bit and left a little nub on the end of the stock. Carbide lathe tool took that off with some trouble. Figured 1000 RPM with carbide & 3/16" would be ok, still got quite hot for what little there was to face off. Guess the 316 work hardens pretty easily. Oh well scrapped that part so got to practice with a bigger center drill and managed to center dril and then turn a decent dia on the remaining scrap. Practice practice.
OK, enough background. Went to the local metals shop, got some 1/4" 304 stainless bar stock. So now I need to mill it down to 3/16" and then turn the longer part down to 0.172 o.d.
Cutting speed of 50 sfm for 304 from a couple of places on the net ?
Using a mill, what speed is the best for say a generic 1/4" (HSS I'm guess) E.M. ? 800 according to (4 * 50)/0.25 ? How about feed (manually) ?
Then on the lathe - similarly, (4*50)/(3/16") = ~1000rpm. How about for a carbide bit - usually 2-4X faster ?
Do those number sound about right ?? Lots of cutting oil I take it to cut down on the heat ?
Thanks folks !