Subtract

Use Subtract to remove one body from another. Select the body to cut first, then the bodies doing the cutting, and press B.

The first body you pick is the one that gets cut

The popover names the row "Minuend + subs". Minuend is the arithmetic word for it: the first body you picked is the one being reduced, and everything after it is removed from it.

That order is the only control. There is no field to change which body is the target. If the wrong one is being cut, re-pick starting with the one you want to keep.

Keep tools, and why you would

Keep tools is off by default, so the cutting bodies are consumed along with the result. Turn it on and they survive, sitting where they were, ready to cut something else.

This is the setting that makes a tool body pay for itself. Model a hex socket, a cable channel or a clearance volume for a bearing once, then subtract it from every part that needs it with Keep tools on. Each subtraction is its own feature, so changing the tool's size updates every part that used it.

Keep tools never spares the target. The body being cut is always consumed, and it becomes the result.

Subtract, or a cut extrude?

Both remove material, and they suit different situations.

An extrude set to Subtract draws the shape it removes, from a sketch, at the moment it removes it. Use it for a hole, a slot, a pocket, anything whose shape only exists to be taken away.

A Subtract boolean removes a body that already exists. Use it when the shape is a thing in its own right: a part that has to fit, a component you imported, a clearance volume you will use again. If you would want to look at the shape on its own, model it as a body.

When it fails

A subtract with a missing input reports it plainly. A subtract whose bodies do not overlap is not an error at all. It removes nothing, and the result is the target unchanged. If a subtraction appears to have done nothing, check that the tool body is actually inside the target rather than beside it, then move it and rebuild.

See also

• Union and Intersect: the other two answers about two bodies
• Clearance Cut: a pocket a part can actually enter
• Cut and Push Face: cutting a shape you draw instead