Mastercam Gotcha: Two Same Contour Toolpaths / Different Bit Sizes Ruins Verify

If you have two contour toolpaths using the exact same drive chain and the verify is showing a ledge when it shouldn’t, it’s because the tolerances in the verify settings and not an actual deviation in the real toolpath.

0.01 tolerance on a .1 bit will render a slightly different verify than 0.01 tolerance on a 1.0 bit resulting in a ledge if you only have the smaller bit cutting deeper.

This can be reproduced: create 1 line anywhere.

Run a contour toolpath with your larger bit with any settings to any depth.

Right click-drag to copy the toolpath, and only change the tool to a new bit .1 SMALLER than the previous operation, and change the depth to go DEEPER.

.5 bit, -.25 depth for Contour1
.4 bit, -.5 depth for Contour2

Verify will show a ledge, when the real machine path will have none, as you might expect.

Tightening the tolerances will make the ledge smaller and smaller, but it’s still there.

I feel like relying on verify like it represents reality exactly has caused me the most trouble.

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