Optimizing CNC Pockets for Hex Nuts

For the closed end wrench handles I made in a previous post I needed a pocket for the hex nuts on the vise shafts.  These are the steps I used to make an optimum vector outline for the CNC cut pockets.  

1. Start by carefully measuring the size of the hex nut.  A digital caliper is preferred for that task. 

Hex Outline

2. Draw a hexagon that size.   My CNC software has a nice polygon drawing tool that makes drawing hexagons easy. 

3/16" Bit Used

3.  Choose the smallest diameter end mill that has enough length to cut a pocket as deep as the nut is thick.   Draw a circle that diameter centered on each corner of the hexagon.  

Corner to Opposite Corner

4. Now draw lines from corner to opposite corner. 

Inner bit outlines

5. Draw another circle the size of the bit centered where the initial circles cross the diagonal lines .

Almost Done!

6. You can now delete the initial circles and diagonal vectors.  

Circles Snipped

Hex Snipped

7.  Hopefully your software has a snipping tool as you need to snip away the section of the new circles that is inside the hexagon, and then snip away the section of the hexagon that is inside what is left of the circle. 

What you are left with should be a closed vector outline of the optimum hex pocket shape. 

Room for Hex Nut Corners

Again, choose an end mill the smallest diameter that is long enough to cut the pocket for the hex nut.  The example above was a 15/16" tall hexagon and the bit used was a 3/16" downcut spiral end mill.  For 1/4-20 hex nuts I use a 1/8" bit.  For even smaller nuts a 1/16" bit can be used.  

Comments always welcomed!

4D