Wife wanted to get housework done before our anniversary dinner tonight so I spent much the day in the shop. The "sight leaf" part I'm making for dallen is almost done now. The only thing for tomorrow is to grind .003" off each edge and perhaps try scribing the graduations along one of the edges.

First order of business was to put the part on the mill and use the 2-axis CNC to mill 180º of the Ø 0.310" round shape. Once that was done I drilled and tapped the 1/4-40UNS thread through. Oddly, the print showed to use a .221" drill (No.2) for the tap drill size, but my Machinery's handbook showed min and max to be .224 to .229. A 5.7mm drill would have been ideal at .2244" but I don't have one so a parabolic flute No.1 at .228" had to do. His tapped worked fine with that and the thread looks nice.

Now the hard part, bringing the .310" round (.155" radius) around to the full sweep of 298º with sharp corners where it meets the blade thickness of .150". The only practical way was to make use of the radius/angle dresser I had bought off Craigslist for cheap money, never been used. I read the instruction book briefly and played with it a little bit. Set the diamond above center by .155" using the height gauge on the surface plate, dress the wheel.

Set the part on a pair of thin pass-through magnetic parallels (which I'd also never had occasion to use), set the part square with a 4" Starret solid square and engage the magnetic chuck. I used a 1/8" thick parallel behind it to back it up as there's not a lot of surface area on the workpiece to keep it from moving with the force of a 1" wide wheel. Here's a couple shots of the surface grinder set-up:




The wide, flat portion of the wheel was used to bring down the .150" (nominal) thickness, as I had left it at about .160" with the milling and wanted a nice finish. This A2 tool steel is remarkably stable, not a hint of bow in the part.

Here's a couple shots of the part now, and fitted to the mating part.




Very gratifying day that'll only get better. Today is one of those unusual days (here in the US anyhow with our date format), it's 12/13/14. This marks 34 years of wedded bliss for Donna and I, and I'm taking her to a new restaurant about 10 minutes away who is having their grand opening night, tonight! How appropriate!