Hello,

Newbie here. I am looking for basic information on milling. I recently purchased an old but very hefty Mill/Drill and i need some basics to get started. I am interested in making aluminum parts for audio projects i build.

I found information on cutting speed. but how do i calculate spindle rpm for a given bit diameter and material?

For example, if i am milling 1/4" thick aluminum with a 1/2" 4 flute end mill. what RPM should i set the machine up for?

I will be milling slowly by hand at first and adding PC Based CNC later. Quality of work is more important then speed. etc.

Thanks

Zc

Every material has a "cutting speed"

Its up to you to know what that is for the material you are machining.

Cutting speed is not RPM... cutting speed is the speed in linear feet per minute that a given tooth on the cutter will be moving when it slices through the material

Cutting speed is feet per minute or "FPM" for short

All materials have a documented cutting speed or "CS" for short

As a general rule the CS for Aluminum is close to 200 FPM

For mild steel, about 100 FPM

To find RPM then you need to follow this formula: RPM=(CSx4)/D

Where CS is the cutting speed in feet per minute, 4 is a constant, and D is the diameter of the cutter

Saying it a different way, multiply the cs by 4 and then divide the result by D

Ron