Got off work a little early today and got into the shop at 3:30PM to help Neil make another 316 stainless steel shaft. This one was a Ø 10mm x 240mm long "hex head bolt" that would be the new rear swingarm pivot for his little Yamaha YSR50 mini bike. I didn't stop to take photos of me roughing out, finishing or threading the Ø 7/8" rod down to the 10mm with 25mm of M10x1.25 thread. Suffice to say that it went fairly quickly as far as getting it to 10mm went. The finishing to fit the bronze bushings we made the other day was a little more tedious. I turned it to 10mm, but the bushing we were using for sizing still didn't fit. I matched the diameter to the original steel part at Ø 0.390", still tight. It turned out that the 10mm drill he bought to size the holes in the bushings apparently cut a bit small. We polished it until it fit.

The lathe had to came apart a little bit to change the gears for metric single point threading, but we got the M10x1,25 thread done. now I faced the problem of milling the hex. I have a hexagonal 5C collet block and a good quality spindexer, but no 10mm nor 25/64" 5C collet and the 13/32" collet wouldn't close down enough to grip for milling. Now in the past I've just hit the lathe and made a slotted aluminum bushing to grip the oddball diameters. I didn't feel like shanging the gears on the lathe back, so a perfect excuse to employ my as-yet-unused-by-me Walter dividing head!

First, remove the vise from the machine to make room. Remind me to buy a small assortment of 1/2-13UNC hex head bolts from 3/4" to 2" long. Anyhow, got it secured on the mill, only to find I need to make a chuck key for the Rohm chuck that Neil and I struggled to get back on the head. I had taken it off to clean things up. What a PITA to get that back on! Ok so now to use the indexing feature of my dividing head. No dice using that for the hex, it's a 25 hole indexing plate.

So now to jog my memory back to trade school, the last time I had to figure numbers for a dividing head. 360 degrees/40 turns = 9 degrees per turn. 360 divided by 6 for the six flats = 60 degree increments. 60 degrees divided by 9 = 6.666666 turns per flat of the hex, or six and 2/3rds of a turn.

My only dividing plate for the unit has rows of holes numbering 63, 57, 49, 37, 36, 29, 24 and 22. Any number that can be divided by 3 is usable, so for 2/3rds of a turn, 42 holes on the 63 hole row or 24 holes on the 36 hole row. I chose the latter. Set the two adjustable arms for 24 holes and off we go. It came out perfect



What a pleasure to be able to use that thing which has been sitting in my stainless steel roll-around cabinet for the past few months! I will make a 9mm chuck key as soon as I get a chance though. Tightening the chuck with a wrench across a big screwdriver isn't a good long term solution. All cleaned up and out of the shop by 7:00PM.