Hi.

Suppose you have a 20 mm wide cutter.
And you want to cut 20 mm deep horizontally in steel.
How much force would there be on the cutter at a hobby router speed ?

I understand this force will vary a lot with the speed.
But i would like to have some idea how much the frame and bearings should be able to endure.

I think you'd need frame and bearings on the order of at least a bridgport milling machine. As far as "hobby router speed" I'm assuming You mean one ment to cut wood? That would be most likly too fast to cut steel, aluminium O.K. but not steel.

Cutting forces are highly dependant on the cutter geometry. You best bet is to contact the manufacturer of the cutting tool you are considering.

As for your machine's cutting limit, my concern would be the rigidity and vibration dampening rather than cutting forces.

cutting steel you would end up with a spindle speed of only 1000rpm or less and a standard router would have almost no torque at this speed. Steppers or servos have their greatest torque at the lower speeds (usually). This is why most people use mills for metal work and not routers.

I think your probably looking at a 3mm cutter with no more than 0.5mm doc and many many repetitive passes with a very slow feed rate. Assuming your router table doesn't vibrate itself to death first.

Thanks all.

It gave me a bit of a impression what to expect.
I realize now my expectation where to high :-)