What tolerance in dimensions should allow from the manufacture?

[Jparis1138]

I am about to send my design to a manufacturer, but I’m not sure what tolerance I can allow in my design . I’m especially worried about the screw holes as I’m not sure how precise the dimensions need to be for the screws to fit. If anyone can help I’d be really thankful.

[nevin]

Ask that manufacturer your planning on sending it to.

[xudongz]

It depends on what you're getting manufactured (PCB, CNC, laser cutting, etc). If the manufacturer needs to tap screw threads for CNC, you'll likely need to provide them with a technical drawing with details on what/where to tap.

If you don't need threads but only need the screw to fit through, you can do something like 3.1mm holes for M3 screws based on the manufacturer's specified tolerance.

[Leslieann]

Laser and water also have kerf to deal with (beam spread).

There are charts that tell you the proper dimension for screw holes prior to tapping.