2 flute end mill cutter mark problem

[Manishpwn]

I am using 2 flute end mill on aluminum. Dia 9mm for plunging operation. But having cutter mark on the start of the hole.

End mill is uncoated 45 degree helix.
Please suggest some solution to resolve the issue

 

[Philabuster]

Is the endmill carbide or HSS? HSS endmills are way more flexible than carbide.

 

[TeachMePlease]

What machine are you doing this on? VMC? Drill press? PocketNC? SwissMAK?

 

[mhajicek]

When I want a butter smooth finish, I always take a finish pass of a few thou. Takes more time, but it's worth it when you need that finish.

 

[Mtndew]

What grade of aluminum?

 

[michiganbuck]

Not unlogical that a two-flute would do that on a plunge. likely one flute is high and catching and that would pull the EM off-center until both flutes are working.
I used to put more primary clearance on plunge use end mills, but that would not help your problem. A slower feed at the very start might help.

You might look at the end sharpening and see the tooth that may be high.
.oo2 would be enough to make the EM wonder at the start of a plunge.

Using the shortest EM the job will allow might help.