High helix end mills keep gouging

[kdoney]

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). Anyone doing any better with different tooling?

[lakeside]

try droping rpm which will increase tool load or change path to climb mill

[DareBee]

High Helix cutters ar made for cutting aluminum.
You are cutting aluminum - right?

[kdoney]

Sorry, yes I am cutting aluminum. 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.

[ger21]

Sounds like the machine may not be rigid enough for what you're trying to do?

[lakeside]

1/4 end mill in alum. 1500 rpm maxs

[Dawson]

try droping rpm which will increase tool load or change path to climb mill

Conventional cutting is more than likely why it's grabbing. Switch the path to climb, and you should have no problems.

[ViperTX]

Good one Dawson....twas what I was going to recommend.

[dertsap]

how much stick out do you have on the tool , 1/4"' highspeed is like a wet noodle ,
try stumping it up the best you can ,and i agree with the climb milling ,especially with a high helix , the tool is most likely pulling the chips right back into the part

[DareBee]

I never use HSS cutters in diameters smaller than 3/8.
They simply have too much flex, carbide only baby.
1/4 carbide cutters are (cheap ones) are about the same money as HSS anyway and work better.
Although a high grade carbide with TiCn or TiAln coating will outlast the cheap carbide 100X and is well justified in cost (and my personal recomendation).

This does not take into consideration any deficencies that your machine may or may not have.

[kdoney]

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 it did help, but I found the flexing was in the gantry itself. 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?

[warpedmephisto]

What type of minimill is it? You should be able to remove a lot more material than that, even on a minimill. I'm running a stock Taig + flood coolant and am taking 1/4" HSS high helix 2 flute at 4300 RPM 0.100" deep 50% chip load at 20 IPM. For 100% chip load I slow it to 10 IPM.

The thing you have to worry about with the minimills is that the motor doesn't supply enough torque to power through a heavy cut. And the rigidity of a minimill is a lot less so your cuts will start to get sloppy if you go too fast or heavy. What RPM are you running?

Edit: fixed RPM speed mistake.