how to cut out the hole in a donut?

[jrlandau]

Beginner question:  I need to cut out a 1" x 1" hole through a slab of 3/4 inch mild steel. I'm thinking of using chain drilling to remove most of it and then a 2D contour to finish.  Is this the correct Fusion 360 solution, or does F360 offer a better way?  And does F360 offer a nice way to lay out that chain?

[etfrench]

I usually do large pockets by using a 2d contour with roughing.

To do chain drilling, simply create one hole, create the toolpath, then use a circular (machining) pattern to complete the chain.

[jrlandau]

I don't have the picture of how you would use 2D contour. Do you follow
the outline of the hole increasing depth until the hole falls out, or do
you go back and forth wasting the unwanted metal? Here is a picture of the
part--maybe I was a trifle inaccurate calling it a donut. Sorry if it was
misleading.
[image: image.png]

[etfrench · Accepted solution]

Yes, that is the way to use a 2d contour.  You need to make sure the toolpath is the inside the line.  Fusion 360 will usually pick the correct side, but verify by running the simulator.  This is essentially a slot cut, so you will want to use a roughing toolpath.  Here are the settings I usually use for plastic with an 1/8" bit on a not very rigid CNC router:

I usually use the two layers of masking tape and CA glue to hold the stock, so tabs aren't necessary.  The center of hole must not be allowed to just drop out as that can pinch the toolbit and destroy it.  Use tabs or clamps or the masking tape/CA glue.