Side Milling with a 3" Shell

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IronSupremacy88

Plastic

Joined

Apr 6, 2021

• Apr 6, 2021

• #1

New to the site, hope to find some help. Im new to side milling with a shell mill. I bought a Sumitomo 3" 5 flute shell mill with 90 degree inserts. My current cutting specs are,600sfm 763rpm 0.006fpt 25ipm .04stepover .3depthofcut on 3"thick A36 plate that has been burned out. Im getting a surface finish that looks good, but i can see each step every .3 down. It is cutting like the inserts are not a true 90 but they are. The rake on the inserts is somewhat aggressive. I originally thought it was my depth of cut, but I ruled that out by taking smaller cuts.

Sumitomo Shell mill part #WEZ33000R05
Sumitomo Inserts part #A0MT170508PEER-G

I hope I have explained this well enough to not cause confusion. I've only been programming for a few years now.

Thanks

-Alex

 

Mtndew

Diamond

Joined

Jun 7, 2012

Location

Michigan

• Apr 6, 2021

• #2

That's just the nature of the beast.
I'm curious as to why only a .04" stepover?

 

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IronSupremacy88

Plastic

Joined

Apr 6, 2021

• Apr 6, 2021

• #3

Im not confident with it yet. Do you think I could go the full .12"? I also just tried running a light .005 finish pass to see if it would clean up. But it did not. I can still visibly see the ridges and feel them. Any help or suggestions would greatly be appreciated.

 

Mtndew

Diamond

Joined

Jun 7, 2012

Location

Michigan

• Apr 6, 2021

• #4

Has the A36 been annealed? Or does the burned edge have a hard crust?
With that shell mill you should be able to bury it in A36 or even 4150PHT for that matter.
IF your machine is capable of it.

The ridges are typical of a 90 deg mill, it's almost impossible to not have blend lines.
Slap an indicator on the outer edge of the inserts and rotate the cutter, what is the runout from insert to insert?

 

Mike1974

Diamond

Joined

Nov 5, 2014

Location

Tampa area

• Apr 6, 2021

• #5

Are you sure your inserts are true 90dg? I'm not up to speed on new tech for inserted tools, but they (at least what I remember) they have a slight back taper, like a drill. And if your pockets aren't perfect they will shift as they are cutting, ever slightly if the pocket isn't trash, but maybe enough to see/feel the steps between passes. easy check, indicator on table or vise and spin the tool by hand to check insert runout, then up and down in Z to see if there is any taper.

 

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AARONT

Stainless

Joined

Feb 19, 2013

Location

Madison, WI

• Apr 6, 2021

• #6

As already stated. It's the nature of an indexable cutter to leave steps when side milling.

With that cutter, you should easily be able to go .300" deep with a stepover of .12". For a frame of reference. In 4140 I can full slot .32" deep with my 2" Iscar HM390 shell mill. Now granted it's probably a different geometry than what you're using, but the fact remains. For a cutter of that size you should be able to take a much bigger cut ASSuming you have the horsepower to drive it and rigidity to hold it.

 

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IronSupremacy88

Plastic

Joined

Apr 6, 2021

• Apr 6, 2021

• #7

UPDATE

Mtndew suggested that I put an indicator on my inserts. I did. From the top of the 17mm insert to the bottom was .004 of protrusion. I contacted my dealer who i bought it from a few weeks ago, he will be sending me another one. Thanks for all the help!

 

C

CORONA VIRUS

Banned

Joined

Feb 25, 2020

• Apr 6, 2021

• #8

Your cutter diameter is much bigger than you need. You would have benefitted more with a 1-1/2 insert mill. But, even that will not remove your side steps. Leave .01" on the wall and finish with a 3/4" carbide 5 flute endmill.
As for your feeds and doc, they are way too low. With a 1.5dia cutter I would start out at 40% rdoc, .25adoc and .005"ipt feed to start.

 

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CarbideBob

Diamond

Joined

Jan 14, 2007

Location

Flushing/Flint, Michigan

• Apr 6, 2021

• #9

IronSupremacy88 said:

... It is cutting like the inserts are not a true 90 but they are.
-Alex

Click to expand...

They are not true 90. Looks like it but not and never will be.
It is almost impossible to design a true 90 indexable cutter if any rake in the lenghtwise axis.
The only off the shelf ones that can be true 90 are those terrible TPG things with no axial rake and they work not so good.
Everything else a design tradeoff except for really special cutter bodies and custom inserts to fit.

The big places can buy anything they want custom made for costs at or below catalog standard prices.
Most of the real world has to live with the tradeoff in a family.
Bob

 

G

Garwood

Diamond

Joined

Oct 10, 2009

Location

Oregon

• Apr 6, 2021

• #10

I can't believe the vendor took it back.

I wouldn't call it a finishing tool unless you're OK with steps.