Milling Cutter Data

This page contains information on selecting milling cutters and cutting parameters for the CNC machines.

General Considerations

While milling, make sure you're producing small chips rather than fine dust. Increase the feed rate and reduce the spindle speed to prevent the cutter from annealing (losing its temper).

High Spindle Speeds

CNC spindles can operate at relatively high speeds (up to ~22.000 rpm). This can lead to heat problems, because the milling cutter keeps rubbing against the already-machined edges and can thus anneal due to friction heat. This is particularly problematic with cutters that have many flutes, since more edges create more friction and chips are evacuated slower trapping further heat. For some CNC machines (e.g. WorkBee and BlackBox) the spindle speed is fixed and cannot be changed in your gcode, only at the mounted router itself. The spindle speed of the Kress can also only be changed on the machine but there is a dedicated controller and it's not directly on the spindle.

Caution with Large Cutter Diameters

Larger diameters result in a higher cutting speed at the outer edge. This increases friction between the cutter and the workpiece, which generates more heat. The cutting speed is the speed at which the cutting edge of the cutter slides through the workpiece.

Machine-specific Considerations

WorkBee

Use the WorkBee only for wood and plastics, don't use any kind of metal for your workpiece. If you use plastics like acrylic glass you need to consider cooling using ethanol (in a little spray bottle, doing it yourself while milling).

For woodworking with the WorkBee, 1/8" (3.175 mm) cutters with 2 flutes have proven to be a good choice. Alternatively larger cutters can be used. These run hotter, but don't break immediately under aggressive cuts or misuse.

The cheapest source for cutters is AliExpress, but quality varies greatly there. High-quality 6 mm cutters can be sourced from Sorotec: 1201UN.0600.XX (replace XX with 12 for material up to 12 mm thick, and 22 for up to 22 mm).

Material	cutter diameter	feed rate horizontal	feed rate vertical	Depths
chipboard, MDF, birch multiplex	2mm	600 mm/min	120 mm/min	2mm
Chipboard, MDF, birch multiplex	5mm	600 mm/min	120 mm/min	2mm

BlackBox

The BlackBox CNC should be able to handle wood, plastics, aluminum and other soft metals.

Kress Portal Mill

The Kress Portal Mill is able to handle wood, plastics and aluminum. This CNC mill allows to adjust the rotation speed of the spindle, check the general considerations above for some notes. In addition it allows automatic cooling if you use metal materials. For this you nedd to connect the air compressor to the big blue tube and a bottle of ethanol to the smaller white/clear tube. The amount of coolant is controlled manually by the two wheels.

Material	cutter diameter	feed rate horizontal	feed rate vertical	spindle speed	Depths
chipboard, MDF, birch multiplex	2mm, 3mm	1000 mm/min	120 mm/min	12000 rpm	diameter of endmill
Aluminum (cooled with ethanol)	2mm	720 mm/min	100 mm/min	12000 rpm	0,5 mm