How Fast Can I Machine?
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How Fast Can I Machine?

This is not an easy question to answer. The first step is to determine how much coolant pressure and flow are available to make the proposed cut. Enter that information in the calculator below and press the calculate button to see your available horsepowerkilowatts.

Once the horsepowerkilowatts has been determined we can apply the following rule of thumb to estimate a maximum metal removal rate. In mild steel we can remove about 1 cubic inch of material per horsepower per minute22000 cubic milimeters of material per minute per Kw.

About 3 times that much in aluminum and half that in heat treated 4140 or stainless steel. If your material is not included in our calculator or you wish to be more precise you can use the machinability rating from a source like the Machinery Handbook where B1112 steel has a machinability of 1.0. The calculator will allow you to type in a specific machinability number.

Machinability considers a lot of factors besides the power required to remove material. Things like abrasiveness and surface finish. But the accepted method of calculating a material removal rate per unit of power would be to multiply the available power by the machinability factor of the material. To do otherwise can get extremely complicated. We could consider cutter rake angles and lead angles, coolant lubricity and a laundry list of other factors but as this is not intended to be a machining course we will keep things as simple as possible. This should provide us with an acceptable starting point.

Just because we have enough horsepower to run an 1/8" a 3 mm End mill 5000 inches100 meters per minute does not mean the cutter would not break. Nor does it mean we can ignore all the machining rules we normally follow such as surface speed, chip load per tooth, part rigidity, surface finish etc. At the same time, if we have limited power we may not be able to machine at the maximum capability of the cutter without stalling the head.

Online Sources with Machinability Charts:
Engineers Edge

Milling Calculator

Drilling Calculator

View coolant pressure calculator

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