# Thread: aluminium and steel machining

1. ## aluminium and steel machining

What is the optimum spindle speed for machining steel and aluminium? Need to figure out what size pulleys to go on my home made milling machine with a 1720rpm motor. Machining ops would include flycutting, endmilling, facing, etc. (don't know if that makes any difference)

2. Hobbiest I can sure relate to your question as I have been fighting that since the get go (about 8 months ).

I have come to think it is some form of witchcraft, with endless variables that only a great deal of experience seems to be able to make any sense out of.

I do know this, there is no optimal speed that is not adjusted for specific material types, size of cutter, # flutes, tool material, coatings, machine rigidity, horse power and condition and a host of other factors.

I will be keeping an eye on this thread in hopes of gleaning some helpful information.

Ken

3. This software will give you feed rates- http://www.shopfloorautomations.com/...t_tool_box.php

4. There is no one optimum speed, as Ken pointed out. There are so many variables, that it is safe to say that you need the entire speed range from 0 to as fast as you dare run your spindle and tooling.

Machinists sometimes think in terms of "unit horsepower" for a given material. This formula tells you that it takes so and so much horsepower to remove a given volume of material in one minute. So when you know this, then you look at what horsepower your spindle motor has, and that is the basic limitation on how fast you can theoretically remove material.

There are certain rules about toolbit materials and workpiece materials. With modern day cutting with carbide, there is no practical speed limit in machining aluminum, but the unit horsepower factor will be your machine's limit, nonetheless.

In steel, heavy cuts are typically taken at slower speeds to attain some practical tool life. 350 to 400 feet per minute (with carbide) would be the typical maximum speed range of the largest radius of whatever cutter you are planning to use. For finish cuts you can boost this up to 600 feet per minute perhaps.

If you want to machine steel with HSS tools, then 80 to 100 feet per minute is the max cutter circumferential speed, but you must machine wet, because the temperature is still too high in the cutting zone for the tool to last very long.