Figuring out kerf for precision parts

Knowing how much material a laser cutter takes away can be a tricky problem for precision parts, but James Williamson has an answer.

It’s easy to tell when most tools take away material from a cut. A bandsaw cuts a slot the width of its teeth. A table saw cuts a slot the width of its blade. There’s lots of swarf, and powder, and sawdust around telling you things have been cut away. Laser cutters are a bit more subtle.

The amount of material a laser cutter will take away, or kerf, will depend on the speed of the laser cutting, the material, its thickness, and the power of the laser.

James Williamson has come up with a pattern (see above) that he’s cut in a variety of materials on a 40 watt laser cutter. By sliding all the cut pieces to one side of the frame and inserting a shim he’s able to determine the total material lost. Divide that by the number of cuts and you have the material removed by each cut. Clever, nes pas?

Here’s his table of the materials he’s tested:

Material	Thickness	Cut Speed (/400)	Cut Power (/100)	Go (mm)	No go (mm)	Average Kerf (mm)
Acrylic	3mm	6.5	98	1.25	1.30	0.125
Acrylic	5mm	3.5	98	1.30	1.35	0.130
Acrylic	6mm	3	98	1.40	1.45	0.140
Ply	3mm	7	98	2.00	2.05	0.20
Hardboard	3mm	3	98	1.90	1.95	0.19
Mount Board	1.25mm	12	98	2.00	2.05	0.20

For more brilliant laser projects, check out James’ site.