Problems cutting a oblon tappered hole in a hammer head

[num1bryanp]

Hello chip makers,

What started out as a simple hammer is getting the better of me. I am trying to cut an oblong handle hole in some 2" round C1018 steel. The oblong hole is causing me to get a path that seems to cause inconstant cutting and lots of chatter. I used a loft to create the model. But not sure how to fix the cutter path. I have included a shared link:  https://a360.co/2MBKPgf

I am not a trained machinist, so it is very possible I am approaching this the wrong way, maybe I should be using a bull nose cutter instead of the sharp corner end mill.

The tool used: HSS 5/8" 2 flute end mill on a Bridgeport 720 interact mill.

Based speeds and feeds on 100 ft/min  Spindle speed 611 rpm speeds max 25 in/min

When running I had to reduce feed speed 50%,to control grabbing/chatter then the cutter sounded like it was rubbing part of the time.

Link:  https://a360.co/2MBKPgf

Any Ideas will be appreciated,

Bryan

[zwelsh91 · Accepted solution]

After a fairly quick look at your shared link, there a few things that stand out. First you will probably be able to do what you are trying to with a 2 flute cutter but in common practice a 4 flute would work best in steel. Second the pocket tool path may not be the best option for what you are trying to accomplish. Have you tried using a contour with ramping turned on then going in after and doing a finish pass at depth or a couple depths?  by looking at the shape, my inclination would be to use a 1/2 or 3/8 diameter tool 4 or 5 flute and ramp down to the bottom and finish afterward. I would suggest in 1018 to run between 100 and 250 sfm and a chip load of .0015 to .003 ipt  (these are conservative numbers) using ramp, set the ramp pitch to .03-.04 depth per pass. if you have coolant flood it or if you have air blast down into the slot to evacuate the chips. In the ideal situation you could drill a series of holes inside the slot with a diameter just under the width of the slot to remove most of the material then come in and ramp to the bottom so your cutter is not having to make all of those chips.