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What does "Lead Angle" refer to and how do I find this out?


I’m trying to setup an indexable end mill (Tormach 25mm, 3 flt, PN 31255).  What does “Lead Angle” refer to and how do I find this out?  Tormach doesn’t give a lot of info w/ their tooling.  Also, what do you use for “Stickout”?  I was going to use the distance from the toolholder face, where the end mill screws in, to the insert tip.

Thanks for the help!


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For an indexable mill, the Lead Angle is the angle of the leading edge of the insert.  Looked at another way, if you cut a wall with the insert and the wall is vertical, you have a 90 degree lead angle.  

A Lead Angle of less than 90 degrees can result in a better surface finish and faster cutting speeds.  For more on that, see our article on choosing Face Mills by Lead Angle.  It is just as applicable to Indexable End Mills.

As for the Tromach, it’s a 90 degree lead angle.

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