(04-15-2014, 02:15 AM)awemawson Wrote: 'Split Pins' surely ? A cotter pin is cylindrical with a tapered flat and often a thread to pull it tight into it's hole. Often used on bicycles as the pedal crank retainer.

Or is this a US / UK language thing ?

(04-16-2014, 07:44 PM)PixMan Wrote: I got about two hours in the shop after work today to try and knock out another little job for Neil. It's a pair of pistons for the front brake calipers on his Yamaha RD350 (or was that RZ350?) motorcycle rebuild project.

The original ones are made of some kind of fairly hard cast steel and are pitted badly from moisture getting into the system over the past 30 years. We discussed various stainless steels and almost went with a piece of 431ss he'd found. Fortunately it was too small and I'd thought of making them from the best, somewhat hard and extremely corrosion resistant material...17-4PH (precipitation hardened) stainless steel. I found a 4-1/4" long piece of 2" diameter, H900 condition, thinking that would be enough for one and have extra for when I screw up the first one. Then Neil reminded me he needs TWO of them! No room for error now.

The day before yesterday Neil came over and roughed out the bores with a carbide insert plunge mill/drill I have, a Valenite V520 (discontinued product.) He finished the bores to depth, and rough turned one of the O.D.'s. Today I finished the O.D. on both to EXACTLY 37.97mm (1.4949"), which is EXACTLY what the old sample is. I absolutely LOVE working with 17-4PH! It may be tough on the wrong tools, but I have all the right carbide tools for it and it's a joy. Best of all, it polishes easily to a very fine finish, a mirror if you want one.

I stopped at and 800 grit silicon carbide paper. Turned to 1.4954", polish the tool marks out with some 180 grit, hit it with a piece of ScotchBrite (about 320 grit), a few seconds with 600 grit silicon carbide paper, then final with the 800. If I wanted round mirrors I still have 1000, 1500, 2000 and 2500 grit, but the finish on the pistons need just a little surface texture to keep the rubber quad ring seals working.

One is done completely, the other just needs the end faced, radiused and recessed. Here's the one finished one:

(04-16-2014, 08:21 PM)Expat Wrote: WOW! Those look great! It's a pity they will live inside a brake caliper.
This bike is coming along and will look incredible when complete.
I will post some pics when it's a little further along, in the meant time, yet another huge thanks to Ken! His skills on the lathe and mill are a scarce commodity these days, a true craftsman.