Limitation of a milling machine with low spindle RPM.

I am comparing the specifications of milling machines.

I notice that the gear head mills seem to have a limited top speed of spindle when compared with their electronically controlled equivalents.

For example the GH18 has a top spindle speed of 1420 rpm. The WM18 has a top speed of 2250 rpm.

Is this limitation regarded as a problem when using small cutters in aluminium and brass?

Small cutters will still cut at the lower speed it just means you can't feed as fast as you would be able to if the cutter were running at it's optimum speed so jobs take longer. You may get a slight drop in surface finish together with a bit more tool wear.

You need to think about what you will be doing the most as the slower belt drive machine will have more grunt a low speeds when using larger diameter cutters, boring heads, saws etc.

Edited By JasonB on 17/06/2019 13:17:57

The higher speed would be an advantage especially if using small solid carbide cutters. Reducing the feed rate would make up for the lack of speed if need be.

I am facing the opposite problem, The Tom Senior light vertical which I am working on has only 4 speeds, the slowest of which is over 500rpm. A bit fast for larger drills and cutters in steel.

While in theory it is possible to use small cutters at low rpm by reducing feedrate experience says it leads to broken cutters. The problem with manually feeding at a low rate is keeping the feed constant. It's only too easy to go a bit slow or a bit fast over a fraction of a turn. Too slow isn't serious but too fast can easily exceed the chip load for the cutter. Equals ping and a broken cutter. Been there done that.

Andrew

Re. Tom Senior speed, I have a Senior E that I believe is the same head as a light vertical. I changed the motor to three phase and a vfd, works very well and I seldom have to change the belt position.

That's still a low spindle speed, I have an Emco FB2 head which I run at up to 4000rpm and don't consider that as a particularly high speed.

Wow, I would not want to be using any decent sized slitting saw at 500rpm, for a start!

Thanks for replies.