I actually started making these brake pad retainer pins for Neil on Friday, but hit a roadblock. Rare for me.

They are made out of a Ø 0.870" valve actuator shaft that's some form of 1704PH (precipitation hardening) stainless steel. While turning the long 0.184" diameter, I noticed right away that this stuff would work-harden in a flash, and it gave me fits. Neil had finished the 0.184" diameter on one while I ran an errand, and warned me that he was having trouble with it work-hardening. He was right. My carbide inserts weren't holding up all that well, so I switched to some cermet TPG inserts and got through it.



To turn the length of 2.125 without a center, the trick was to turn about .400" (10mm) of length at a time to finish size and then move further down the length another .400". That worked well. Neil had said we didn't need to mill the hex like the original, because it's something that just pull straight out and doesn't require turning with a wrench. I simply put a freehand form on them and polished, that's why they're on an exact match. However, the 1.5mm (0.0591") hole has to be there, and that was my undoing.

The parts were held in a 3/16" 5C collet and square collet block, faster to set up and use than my spindexer. I spotted the holes both sides with a 1/8" (3.18mm) 118º spot drill and set to drilling the holes with a new 1.5mm HSS-Co drill I had. And the second one. They dulled almost instantly, as did both No.53 drills I had. I found I had one 1/16" solid carbide twist drill with 1/8" shank. It drilled one hole and broke the second it drilled through the part. I was able to punch the broken tip out of the hole, but was now at a loss for drilling the second part. Here's the mass of dulled and broken drills it tool to drill but two 1.5mm holes through about 0.150" of material. The one in the lower right is one of the two Titex A1164TIN-1.5 solid carbide TiN-coated drills I'd ordered Monday morning.



As I went to pick up the drills from my distributor, it occurred to me the most of the reason that the one carbide drill I'd tried and broken had failed because the quill on my machine gets a bit stiff at the end of its 5" travel. I had little feel for how the tool was cutting and it grabbed and broke as it cut through the part into the opposite side's 118º spot. Stupid me, I have a nearly new, unused by me Albrecht No.1 drill chuck with sensitive drilling mount!

I set that in the machine and drilled the second hole successfully! Here's the drill I used:



Glad it got done! Neil will be picking up the pins tomorrow, and I can move on to Ed's lathe cross slide parts and let Neil make the handlebar end weights he needs.