Why did my second toolpath cut twice as deep as I typed? (Start Depth vs Cut Depth)

Why this happens

Cut Depth is measured from the Start Depth, not from the material surface. This is one of the most commonly misunderstood fields in the toolpath forms.

If you pocket 0.5" deep, then add text inside the pocket with Start Depth 0.5" and type 0.75" as Cut Depth (thinking "I want the text to reach 0.75" total"), you actually get 0.5 + 0.75 = 1.25" total, or a snapped bit.

The same rule applies to V-carves placed inside pockets: the V-carve's geometric depth is added below the Start Depth.

The fix

Think "how much further from where the tool starts":

• Pocket floor at 0.5", want text bottoming at 0.75" total: Start Depth 0.5", Cut Depth 0.25".
• Setting Start Depth correctly also keeps the tool from wasting time air-cutting down to the floor.

Pro tips

• After calculating, run Preview Toolpaths and check the simulated depth against your material thickness before saving G-code.
• Start Depth greater than 0 also changes where ramps and lead-ins begin, so preview carefully when stacking toolpaths in a recess.