A Batch of R8 Milling Arbors
© Frank Ford 2008; Photos by FF

I thnk that one of the coolest things about working with machine tools is the ability to make my own tooling. Last year I made a slitting saw arbor for the mill, and since then I've been thinking of other projects, including some special fly cutters, that might be good to have in my growing arsenal of shop made tools.

So, today's effort was to make some R8 blanks I could use for future projects.

First, I posted the drawing with R8 collet dimensions (posted on the Web courtesy John Stevenson) on the light support over my lathe:

I find that with the drawing right in my face, there's a slightly lower probability that I'll forget what the heck I'm doing.


I Grabbed pieces of 1.25" cold rolled steel in the chuck, and carefully turned the shaft sections down to the appropriate diameter (.09490" - .09495").

I believe I got eight of the ten in that range, and the other two came out just a hair small, but they seem quite usable.


Each one got drilled:


And tapped to 7/16 - 20 for the drawbar:


Reading the taper (included angle 16 degrees, 51 minutes) from the drawing I set up the angle on my compound using my shop-made lathe sine bar fixture.


With the tool set precisely on center and the shank held in a collet I was able to turn the taper using the lathe compound:


Since there was no keway milled in the shaft of the collet blank I couldn't test its fit in the mill spindle, so I used the gauge I'd made before when I did a previous R8 project:


Now, the majority of the shaft will eventually be turned down for clearance, leaving only the last inch and a quarter at precise diameter for alignment in the spindle. But, since I would later want to chuck these blank arbors for additional machining, I figured I'd do each one after it was configured for its final use.  So, I milled the keway slot in each blank as a final operation.



Here's the batch.  They have arbitrarily different lengths because I was working with short cutoff pieces of 12L14 stock I'd gotten off eBay in one of those USPS flat rate boxes:

Here's one of the blanks being made into a fly cutter.


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