I bought 2 new high helix, center cutting, 2 flute, HSS mills from Niagara (D201's) and both of them are grabbing the workpiece. This is a simple circle pocket with conventional milling. I'm down to shaving .002 per pass at 4 ipm! When I put in a 45 degree carbide from Niagara (A245) it doesn't grab until I get all the way up to .003 at 6 ipm. The head is rock solid until the plunge then it hops and ruins the z location (inexpensive servos). It is just a mini mill head but it is very tight and not moving under other circumstances. Anyone doing any better with different tooling?

Hi,

are you sure its the head moving?

It sounds more like its the backlash in the table when it changes direction.

Graham.

I agree with Graham.When I first got my machine(sherline 2000) I was having the same problem.I rechecked and I hadn't tightened the head's arm as much as I thought I did and it was jumping when it caught some resistance.

I'm pretty sure it's not the head moving. This is a moving gantry type mill. The x axis is a double nut thomson ballscrew and the y axis is a brand new daedal slide. I tested for backlash to .001 and there is none. The workpiece is a flat piece of 6061 and the grabbing takes place at different portions of the circle at different depths. I have not taken the 45 degree carbide to the grabbing stage yet.  

The only thing that can cause gouging is movement.

Something is loose or flexing.

Graham.

Try to run a Helical Ramp with the tool.. If you need some test code I can post some for you... Plunging with an endmill sucks! I run 1.000 Carb mills in 304SS all the time and with a helical ramp you can't tell that I am cutting.

These are good american made end mills. I found the error though. Thanks to all for the help. I took your advice of slowing the rpms and climb milling and a long ramp up and it did help, but I found the flexing was in the gantry itself (good call Graham). After a base plate replacement, both mills are performing well. The mini mill head still makes me take .005 at a pass at 10 ipm. Does roughing end mills speed up the process much? What other tooling have you mini mill guys used to speed up "hogging" large amounts of aluminum?

Set over 40%  of the tool Dia and bring the tool down to depth... this is plung milling and should be nice and fast...
BTW I run mills with 2-30HP spindles and I know very little about mini mills