Cutter Comp Issue on Dovetail Cutter with corner radius

[ryankheather]

I am using a 8 mm, 7 degree dovetail cutter with a 0.5mm rad on the corner to machine these pockets, but I am having some trouble with the cam.

When I select the edge of the pocket as below, the simulation seems to gouge into the part. I can correct this by modeling the 0.5mm radius in the corner and selecting the inside edge but once on the machine the cutter comp is surely going to make this incorrect?

I am yet to run this yet but is just a simulation issue and my original choice of contour will work correctly? Or am I doing something wrong here? (I probably am!)  Maybe something to do with the theoretical endpoint of the cutter and how its trying to account for that?   
Any help would much appreciated! 

[LibertyMachine]

No, you aren't doing anything wrong, and yes, it will gouge unless you fudge the cutter comp. Short on time, but I had a thread sometime ago where I was asking about this. I'll try to dig it up when I get back from my customer visit

[Steinwerks]

IIRC you have to add twice the corner radius to get the correct diameter when a dovetail mill has a radius.

[ryankheather]

Awesome thank you, that'd be great to have a look through !

[ryankheather]

Ok so as this is 8mm dia I would have to offset in the cutter comp as if it were 9mm? 

Thanks for the Info 🙂 

[chris_IgniteDigi]

A picture is worth a 1000 words .....

The offset amount for a dovetail cutter with a tip radius is the distance from the theoretical tip, to a vertical line tangent to the tip radius.

The diagram above shows the offset amount of 1.078mm for a 45deg (90deg included) dovetail cutter with a 0.762mm  (0.03") tip radius.

Hope that helps