VBits feeds and speed

[JonathanBaltodano]

I’m new to the CNC world and I figured out feeds and speeds for milling but how do you figure out 60,90 degree and fine detail bits

[SethCNC]

Personally, I watch and listen to my machine adjusting accordingly until I just know the sweet spot for each bit on my machine.

Some bit manufacturers (amana) provide setting recommendations

[Ken4]

Approximation[edit]

The exact RPM is not always needed, a close approximation will work (using 3 for the value of {\displaystyle {\pi }}).

{\displaystyle RPM={CuttingSpeed\times 12 \over \pi \times Diameter}}

e.g. for a cutting speed of 100 ft/min (a plain HSS steel cutter on mild steel) and diameter of 10 inches (the cutter or the work piece)

{\displaystyle RPM={CuttingSpeed\times 12 \over \pi \times Diameter}={12\times 100ft/min \over 3\times 10inches}={40revs/min}}

and, for an example using metric values, where the cutting speed is 30 m/min and a diameter of 10 mm (0.01 m),

{\displaystyle RPM={Speed \over \pi \times Diameter}={1000\times 30m/min \over 3\times 10mm}={1000revs/min}}

Accuracy[edit]

However, for more accurate calculations, and at the expense of simplicity, this formula can be used:

{\displaystyle RPM={Speed \over Circumference}={Speed \over \pi \times Diameter}}

and using the same example

{\displaystyle RPM={100ft/min \over \pi \times 10,inches\left({\frac {1ft}{12,inches}}\right)}={100 \over 2.62}=38.2revs/min}

and using the same example as above

{\displaystyle RPM={30m/min \over \pi \times 10,mm\left({\frac {1m}{1000,mm}}\right)}={1000*30 \over \pi *10}=955revs/min}

where:

• RPM is the rotational speed of the cutter or workpiece.
• Speed is the recommended cutting speed of the material in meters/minute or feet/min
• Diameter in millimeters or inches.

[JonathanBaltodano]

Wow that’s some good info from you guys