wrist alternative method

[Cody Deegan]

For those who want to bypass the acquisition of those huge odd-sized drill bits and also add some stability to the homebuilt wrists, this method might be helpful.  Instead of using square tube, you'll need to get solid aluminum that is close in size to the original dimensions in the plans.

Mark your two holes for the bearings and drill through with a bit that is just larger than the inner race of the bearings.  This ensures the bolt will not rub on the aluminum.

Now use a bit that is the same size as the OD of the bearing.  It should be centered over the hole that was just cut.  Set your depth stop so that the drill will only go down the same amount as the height of the bearing.  Once drilled, the bearing will have a nice secure seat.

I would suggest building the elbow and shoulder in this manner as well.