Need help with strategy for machining inside of radius pocket

[jgaertner]

I need some advice on a machining strategy for the pocketing of a concave nut interior I am machining. I am limited to the HP of my Tormach machine and the fact that it only can machine 4140 steel very slowly and with modest WOCs. I had no problem machining out the upper 2/3 of the pocket but now I need to machine the lower 1/3 and it has a curved bottom to it and a big 5/8" hole drilled through it. The result is two shelves that have to machined away. 

I have tried programming Scallop but I think its trying to cut too much material in a single pass, even with the step down set to around 0.005". So I need some help. I would like to use a .50" 4 flute ball mill if possible. None of my 3/8" carbide end mills are long enough to reach any further into the pocket than I have already milled 1.5".

Thanks, 

[HughesTooling · Accepted solution]

Think I'd make a copy of the body and remove the cross hole and use that for finishing the bottom. Could do with pocketing deeper, in the attached I used the ball nose cutter you might want to use a flat bottom though. Then finish with 3d contour and the ball nose. If you look at the attached file You'll see I selected the copy under Model in the ops.

Mark

[jgaertner]

Hello Mark, Thank! that is exactly what I needed. A new set of eyes on the problem. It never occurred to me to reverse the machining and take the hole out of the model. I can do that. Appreciate your time and consideration. Will post the results in a couple days. I ordered a new, longer 3/8" ball end mill and it will have to arrive in order to do the last step.  Regards, 

Jgaertner 

[jgaertner]

I just wanted to share the results of the help Mark gave me. I was able to get the interior of my deep acorn nut machined with a smooth interior radius. I have to make some more of these and I an stuck on the challenge of swath removal verses the lower portion of the pocket machining with the long .375" ball mill. I had to go really slow and with small DOCs because of the limitations of my CNC Mill and the depth of the pocket. If the pocket did no have the perpendicular hole drilled in it, before I machine the deep pocket all the swath would just settle to the bottom and cause major problems. But if you machine the cross hole, then the lower pocketing operation has interrupted cuts as the tool ramps down, into the steel. I have 3 jets of flood but there is no way they are going to flush the swath out if the cross holes are not there!  Anyway, here is a picture of part #1.