Quote Originally Posted by HankMcSpank View Post

Oh yeah...one last question, Two sided milling - how can I flip a part over to mill the other side, yet still have it lined up ok ...so that the tool ends up in the right place on the board vs the other (original) side - presumably some form of keying comes into play?

Make a sacrificial plate up, MDF or alloy and put a hole in at 0,0 say 3mm [ up to you.] Now put two holes in on the Y 1.5mm to the left of the 0,0 point about 30 to 50 mm apart [ depends on size of board ]
Do same in X with the holes 1.5mm lower than 0,0
You now have 4 contact points that are on Y 0 and X 0 you can butt your board up against.

If you program everything from 0,0 it will be in the correct relation, now if you program the other side again from 0,0 remembering to take mirroring into account [ don't ask ] just flipping the board will allow you to pick position up again.

Next time you use the jig, square it up on the bed, drop a 3mm peg into the 0,0 hole, zero your controller and you can re run pre programmed codes again with no trouble.

You could do the same with a corner machined out to form an L but they are prone to getting dust and crap in the edges that hold the board off.
using pins gives an edge contact that's easy to keep clean and free from obstructions.

Often on a simple one off job I'll code the drilling of the 5 holes then the part.
Fit the sacrificial plate, drill the holes and before the part code starts bale out of the program with e-stop.
Edit the 5 holes out of the program then run the program for the part.

Hope this helps.

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