Cutting question - rake

Dec 23, 2005 2 Replies
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When you cut something, how does a zero or negative rake work?



Zero rake I can understand - flat work surface, blade downward pressure distorts the surface, the surface which is then immediately presented to the edge is "higher" than the edge, and thus gets cut.


Is negative rake just the same? Or ar we talking about scraping the surface off?



How does that work?


Ta,


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Have a peek here:

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The relevant stuff is at the bottom of the page.

Regards,

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  1. In order to get any cut at all, you must have a "Clearance Angle" underneath the tool, otherwise the tool will just slide over the surface and polish the work. It is the Clearance Angle that enables the cut, by allowing the tool to get down below the surface of the metal.

  1. The Rake, or top angle deals with the metal after it has been sheared away by the action of the clearance angle. The difficulty with Brass and other soft metals is that once the tool has got under the skin, it may dig in and try to dive deep with a positive Rake.

With a negative Rake, the sheared-off metal is broken into numerous small flakes so that there is not a continuous swarf tending to drive the tool down.

You are right > When you cut something, how does a zero or negative rake work?

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