[Busch_dk]

So I built a CNC machine from a kit a couple of months back and fittet it with a Kress 1050 FME-1 spindle (Milling motor 1050 FME-1 - Precision milling motors ?made in Germany?). So far I have been very conservative with the feedrate but I can tell that this practice takes a heavy toll on the router bits. Researching optimum feedrates on the web I can see they are way higher than I have been going.

This led me to speculate about what is the maximum feedrate the spindle can handle before not being powerful enough? I work with birch, hardwood and pine plywood using 6mm(1 flute) or 8mm(2 flutes) bits. Each pass is usually at the same depth as the bit diameter. I know it is hard to give a definite answer but even a ballpark estimate would be good as I literally have no idea what the spindle can handle.

-Søren

[JerryBurks]

I suspect you might rather break the smaller bit before stalling the spindle. But why not just increase the feed rate until the overload protection kicks in? Then you know the limit and can back down from there. If you really want to know you can hook up an amp meter and see at which speed the motor takes up the nominal current.

In any case you should easily be running the 6mm bit at 2500-3500 mm/min and 12-15krpm.

[widgitmaster]

I agree with Jerry, I have three Kress 800-FME spindles! When running at MAX RPM, the brushes wear out really fast! So I just swap spindles and keep cutting, while I replace the brushes in the other spindle!

As for speeds & feeds, charts are conservative to say the least! Every machine has its strengths & weaknesses, so I usually push it to the limit and back it off at the optimal point! This is a good practice if you are producing more than one part, as you can make adjustment to get the run perfect! But one-off parts require a little more patience and feel for how the machine is vibrating and sounding while cutting!
Widgit