Feed or Speed?

For a given production rate of metal removal, better tool life is obtained by using heavy feed and low speed.

Sorry, Flash.

Less horsepower per cubic inch of metal removal is required for heavier feeds (see the diagonal lines on the chart below.)

This also means fewer revolutions of the work (or tool) to get the job done.

This reduces wear on the tool.

Slower speeds results in less friction, less heat.

Surface finish declines as feed rate increases, but it is usually acceptable until a critical rate is reached (see the numbers along the curves above - they are the values for surface finish in RMS).

In steels, grades that are rephosphorized and renitrogenized can take heavier feeds than steels that are not. (That's why I'm showing C1213 at 0.07-0.012 phosphorous compared to C1215 at 0.04-0.09 Phos.)

Here is another graph to illustrate the effect of feed rate and surface finish.

As feed rate increases bottom (horizontal) axis so does surface roughness (vertical) axis measured in RMS.

The contract shop industry remains seduced by the siren song of speed to reduce cycle time.

Perhaps the proper use of the feed approach can make you some new friends among your customers.

These data are based on HSS tools. Obviously using carbide one needs to have sufficient speed to take advantage of the carbide.

Bottom Line: Increased feed rather than speed can result in longer tool life and less problems than increasing speed and dealing with the heat that results.

What is your approach? Speed for cycle time? Or feed for minimizing HP for removal and longer tool life and fewer problems?

Feed or speed? What's it gonna be?

Photo credits:

The Flash: http://www.ramasscreen.com/wp-content/uploads/2009/07/Flash-Adam-Strange-Aquaman.JPG

The Incredible Hulk: http://keneller.typepad.com/photos/uncategorized/2008/06/14/lou_ferrigno_as_incredible_hulk.jpg

Editor's Note: CR4 would like to thank Milo for sharing this blog entry, which originally appeared here.