Making A Woodruff Cutter

 

As some of you know I live in the middle of nowhere, and there is no such thing as the End-Mill store near by, so when I snapped off the cutter of my 1/4 Woodruff I came up with this.  Just so you can laugh a little, I snapped my Woodruff the first time I used it, the CNC job finished and I was amazed to see the cutter still there (I crossed my fingers the entire run).  When I did a manual rapid to bring the work to me so I can see the little grove I clipped a clamp and knocked the little end off.  $20 bucks gone, that hurt.

A Woodruff cutter is used to cut little groves inside a circle.  In those little groves you can put an O’ring, an internal snap ring, or what ever needs an internal ring.

Finally, there are a few benefits to making your own.  First of all they’re cheap to make from an old cutter.  Second, you can make one the exact width you need.  Wider ones for O’rings and thinner for snap rings. 

If you look up O’ring manufactures on the web they often have handy charts that tell you the width and depth you’ll need the standard types of rings.

Here we're making a 1/4" (pretty small) and using the other side of the cutter that had the first one I made.  The first one lasted about 50 groves, so I feel like I got pretty good mileage out of it.  (When using one this small we use 2000RPM / 2 IPM)

 

 
Chuck up you least favorite cutter.  Warn-out cutters are great because you can grind off the first 1/8" or so.
Mount your angle grinder in the tool post.

I got this grinder from a discount store for $5 and it is seriously cheap, so I mounted a bar on the back and it now mounts like a regular tool.

Grind off the end of the mill.  Make sure you get rid of the center cutting area and any worn areas.
The end is flat.
Come in about "yo far" and grind down about "so much", but not too much.
Next, get out your handy dandy Dremel and clean up the top section.  The trick is to thin down ever so gently and make the top concave, without cutting the end off,  making it too thin, or nicking the remaining cutting surfaces.
Nice and thin.
Make the bottom ever so slightly concave as well.
0.100 (that's what I wanted)
Ready for action.

Finial Thoughts:

All the actual cuts were made with the lathe running at about 700RPM.  Use plenty of coolant (or something) to keep the cutter cool during the entire operation.

Wash down the lathe when you’re done to get the residual abrasives off the ways of your lathe.

Dremel cuts were made free hand.

Be VERY careful when doing this tip and practice a lot of common sense.