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View Full Version : How to allocate this wedge angle to rake and relief



Elninio
05-23-2013, 03:00 AM
I have some triangle inserts (11 degree relief, 0 rake), I have to divide this wedge angle of 79 between rake and relief to make general turning of steels as efficient as possible. Otherwise, I can grind top rake. I would also like to allocate this wedge angle differently (if it is required) for some of these inserts that I will reserve for finishing. What's the ratio?
http://www.mfg.mtu.edu/cyberman/machining/trad/turning/geom.jpg

becksmachine
05-23-2013, 04:43 AM
Hmm, a bit confusing. The N designates no relief (ERA?) in the insert itself.

Are you saying you want to build a holder for the TNG inserts?

Dave

Elninio
05-23-2013, 05:13 AM
Hmm, a bit confusing. The N designates no relief (ERA?) in the insert itself.

Are you saying you want to build a holder for the TNG inserts?

Dave

You are correct. It's the wedge angle that matters, since holders can be used to introduce the negative rake. I'm just not sure how much to allocate for rake and how much to allocate for relief in the tool holder.

becksmachine
05-23-2013, 10:27 AM
Ok, if they are actually TNG inserts the angle on the insert itself is 90, not 79.

To achieve side clearance (SRA) and end clearance (ERA) the entire insert is tipped forward and sideways which then results in a back rake angle (BRA) that is negative, as opposed to the positive angle as shown in the diagram.

A 79 wedge angle could only be achieved by grinding the end relief angle on the insert.

Hope this helps, Dave