milling E4130

[rounsy222]

I need some advise on milling E4130. I am working on parts where the finish is critical as far as nicks and pits goes. I am doing a .007" finishing pass on a .711" finished sized square stock using a .875" 2 flute carbide insert. I am getting some shadowing and more importantly getting the occasional pit and that is where my issue lies. From the looks of things I am doing more pushing and tearing of the material than actually cutting it. I was thinking of a speed and feed issue or maybe just simply using the wrong tooling. What we have programed is a speed of 6000 rpm with a feed of 12"ipm. Any input would be great. Thanks, Marc

[HuFlungDung]

I'm imagining that you are conventional milling, thus accidentally pulling the odd chip into the cut (causing nicks), as well as scuffing up the surface and spoiling your cutter's keen edges.

Climb milling is highly recommended for metal work to avoid these problems.

[rounsy222]

Well actually I'm end milling( using the bottom of em). So normally I would agree, but not the case here. Maybe I should kind of restate what I am seeking advice on. By the way thank you for your response, I would assume the same thing because I wasn't very clear on what I am asking. If I understand 4130 correctly it is a chrome-molly and thus should be milled differently then say 1040 crs. With that said, do I need a insert that has more of a radius tip to reduce tool pressure or maybe adjust my speed and feed or ......????? It just seems to rip the material more than cut it thus causing my "pitting" issue, or is that a characteristic of this material, or something that I amover looking.

[Pres]

FWIW:
When cutting 4130, I ALWAYS do a light final pass while drizzling some Tap Magic cutting fluid on it.
Makes a world of difference on any material "tearing" during the final pass.
(almost fakes it into looking like a ground finish)

hth,
Pres

[rounsy222]

"light pass" meaning how little? My company doesn't have any tapping oils since this is one of only 3 different jobs that we do that is not aluminum so anything else might work like wd40 or lps or...?? I am gamed to try anything at this point, it's driving me crazy because 99% of the part is flawless and I am getting gigged on the 1% Thank you very much for your reply and any other input you might have for me.

[Pres]

"light pass" means anything over 0.001", or less.
(Without using TM the tear passes are sometimes deeper than 0.001")

About 50 years ago I "discovered" Tap Magic on finish passes machining 4130. Still true today (for me, at least

While the stuff helps a bit on other steels, it makes a major difference on 4130 finish.
I've tried a number of other cutting fluids but none matches TMs magic.
Whatever is in it does not seem like a regular cutting fluid since it is about the viscosity of water.
Perhaps somebody on this forum knows what this chemical is?

You just gotta try it to believe it. A small amount is all it takes.

hth,
Pres
p.s. I don't have any financial interest in Tap Magic (or the Steco Corp) - just my experience with it.
Check it out at: www.tapmagic.com

[CarbideBob]

Sounds like you're welding then tearing out pieces. At that RPM and feed you're burnishing the part not cutting it.
Smaller radii inserts will thicken the chip at the bottom of the cutter and reduce rubbing and tearing but will increase the feed per tooth ripple.
One word for fine finishes on 4130: Cermets
Bob

[rounsy222]

Thank you both Pres and CarbideBob, great input from both!!!!!! I work in a production shop where everything is done for you ahead of time so this has taken me a while to get to this point to make them realize that this is the wrong way of going about this job and your input greatly helps my cause. So I still have one more question about inserts on this material, is it better to have a shaper tip or more of a radius tip and if so what size would you recommend? Thanks again for your input!!