Hi Nick and Washout,

Thanks for the explanations and ideas. I entered various values into GWizard and selected 'Fine Finish'. Here are the final figures calculated:

1 flute 6mm carbide endmill
50mm stickout (Bottom of collet to tip of endmill). The block of Aluminium is 40mm thick.
1mm depth of cut
15671 rpms
2.76 mm/sec (165.5 mm/min)
Fine Finish

Any higher and the deflection is too much, so now to buy a good endmill :)

To use a 3 flute, I would need a spindle speed of 36,000rpm. My 6040's max is 24000rpm. I don't know the weight of my gantry. I didn't think to check that before assembly. I have purchased a 'clock micrometer' to check the alignment of the gantry to the bed.

"using something like adaptive clearing". OK, I need to read some tutorials.

Cheers

Gary