Feed rates / spindle speeds for HF spindle

Hi,

I know that there are books with feed rate and spindle speed data for large milling machines with "slow" spindles, however I'm not sure if there's much information about higher speed spindles like these Chinese HF Spindles which are showing up on Ebay. I'm also not sure about how the formulas for calculating them scale as the speeds get much higher.

In terms of rigidity, the machine I have is this from Marchant Dice:
http://www.worldofcnc.com/images/main_image.JPG
I'm no engineer, but the machine seems to be pretty ridged to me. Having said that it is aluminium and has unsupported linear bearings - It's no Bridgeport. The work area is around 200x300mm for size reference.

I was thinking about buying two Chinese spindles - A 1.5KW (2HP) version and later on a 3KW (4HP) version. (26,000RPM)
I was thinking of using them as motors for my own spindles and gearing the 2HP spindle up to 52,000RPM (2:1) and gearing the 4HP spindle down to 13,000RPM.

This would allow me to use the smaller one for PCB routing, drilling and small milling tasks while using the larger one for larger milling tasks, boring and surfacing.

I'd like to know about spindle speeds, feed rates and depth of cuts which should be used with these set-ups, both with and without cooling / lubrication. I'd also like to know if there's more ideal ratios to use on the spindles.

1mm Carbide Drillbit - PCB. (Copper and fibreglass.)
V-point Carbide engraving toolbit - PCB. (Copper.)
3mm Carbide Endmill - Delrin.
3mm Carbide Endmill - Aluminium.
3mm Carbide Endmill - Copper.
6mm Carbide Endmill - Delrin.
6mm Carbide Endmill - Aluminium.
6mm Carbide Endmill - Copper.
Boring - Delrin.
Boring - Aluminium.
Boring - Copper.
50mm Fly Cutter - Delrin.
50mm Fly Cutter - Aluminium.
50mm Fly Cutter - Copper.

Thank you for any advice.

Hi,

An 800w spindle is probably all the power this machine could handle.

Take the manufactures chip load data and reduce by at least a third.

Get as close to the surface feet per minute recommender for the material as you can with your limited rpm's and reduce your feed rate to suit the chip load.

Set your depth of cut to suit the rigidity of your machine.

I would not use a fly cutter on this machine, use the largest end mill that will fit into the collet.

The supplied 20mm spindle mount is a clue to the limitations of this machine :)

John

Hi John,

Thank you very much for your advice on this, I'll request the chip load data now.

I think I'll just stick to the 1.5KW spindle without any gearing and will limit it with the VFD if required.