Em throwing off a big burr

[Vern Smith]

After many years off I got back into some machining about a year ago. CNC was all new to me as well as carbide and high helix end mills. I have a close to new 1/2" carbide high helix Tin coated end mill with 3 flutes. I'm machining 6061, 6000 rpm and feeds 30 to 50 ipm. This particular em is raising a burr so pronounced that a deburring tool stalls out in it, I have to use a file.

Years ago with HSS this used to mean a dull EM. Is that still the case today? I have other similar end mills that raise some burr but nothing like this guy. I've heard they can be too sharp when new needing a penny scraped along the flutes.

Vern

[Geof]

Are you sure you are running the spindle forward?

Seems like a silly question but one time I actually did this; I have template programs that I use for different purposes and had been using a facing one with an M04 and a fly cutter running backwards. Then I called it up to do some facing with and end mill and forgot the M04. It actually did plough through the aluminum making quite a noise and leaving the most fantastic burr.

Another simple check; are you sure it is 6061? I have sometimes bought large chunks of aluminum alloy at a local scrap dealer and been assured they were 6061....no way, they were probably 5082 T1 or something which does even cut with a sharp tool and throws a big burr.

The flutes are not loading up are they? Shouldn't be at 6000 and 50 because that is not a heavy chip load but a 1/2" cutter does not have large amounts of room.

You are using coolant? Flood preferably.

TiN coated? A little niggle enters my brain that this is not recommended for Al? Alluminum sticks to this coating? I am not sure because I never use coated tools on aluminum.

[HuFlungDung]

"Close to new", is that like "I finished the race close to the winner", aka, I was a loser

[Vern Smith]

I've done the old backwards trick on a lathe but not on a mill, yet. The material is 6061 with certs. I checked the invoice for the cutter and I'm mistaken, it's is not Tin it's Zrn, whatever that is. It's listed on their web site as; VARIABLE HELIX MULTI INDEX END MILL WITH ZRCONIUM NITRIDE COATING FOR ALUMINUM.

Near new is about 4 hours of continuous use. It did the burr trick from the get go. I have two of these and put the second one in for comparison and got very similar results.

[Geof]

Are you climb or conventional milling?

Is it a reputable tool supplier? I have bought cheap tools in the past with simply no clearance to the cutting edge.

And that abouts end my ideas.

[Vern Smith]

I've been climb milling. The supplier's product has worked OK for me in the past. These could just be a pair that don't work. Thanks for your input.

Vern

[HuFlungDung]

There's got to be a reason why the tool behaves this way. Can you check the relief ground into the sides of the flute? By check, I mean just put an indicator slightly against the outer flute and rotate the tool by hand. As the indicator scribes the flute, it should show a bit of rise towards the sharp edge. Compare that to a twist drill which is basically just a section of a round cylinder along its flute.

[dapoling]

Vern the M4 may happen more the most suspect! However I would ensure you have good clean cutting edges along with ensuring the relief is relieved as I have seen those come back to the shop not being ground properly thus leaving a nasty burr.

[PBMW]

I was also going to say that near four hours of production is not near new. it's usually done.
I'd talk another three flute EM from another mfg and give that a shot. That will at least tell you if it's the cutter or the material.

And just because it's got certs, don't mean squat.
They just pulled em out a drawer and copied em. Match that to the heat lot number....

[Vern Smith]

I ran some tests this morning with a brand new EM from the same company that made the one that's throwing the big burr, and another brand (twice as expensive ). All were 1/2" dia. 1.25" LOC and 3" OL. It's the manufacturer, the results were rather startling. Not only was the burr almost non existent with the more expensive cutter but the finish was much better and it was much quieter during the cut.

I appreciate all the suggestions and advise. I guess you get what you pay for.

[duenow]

Originally Posted by Vern Smith I ran some tests this morning with a brand new EM from the same company that made the one that's throwing the big burr, and another brand (twice as expensive ). All were 1/2" dia. 1.25" LOC and 3" OL. It's the manufacturer, the results were rather startling. Not only was the burr almost non existent with the more expensive cutter but the finish was much better and it was much quieter during the cut. I appreciate all the suggestions and advise. I guess you get what you pay for.

I've been buying sounds like the same mill with ZN does the name start with a A?

[Vern Smith]

I called the manufacturer who is taking all three of the EM's back, one of them well used. They say they heard similar complaints around the time I purchased mine. They are sending me replacements from a new series that they say is "kicking butt", whatever that means.

I saved my test block and will run a new series of tests as soon as they arrive. I'll report then along with the name of the manufacturer if the results are good. There is no "A" in their name.

Vern