Perplexing milling cutter tip breakage
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Perplexing milling cutter tip breakage
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Topic: Perplexing milling cutter tip breakage (Read 1540 times))
KnifeMaker
GTA Senior Contributor
Posts: 8224
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Real Name: Michael
Re: Perplexing milling cutter tip breakage
«
Reply #20 on:
November 29, 2019, 10:33:33 PM »
Since I mostly worked in steels. Usually aerospace after burner rated alloys,I used carbied almos exclusively. As that is what i have, it is what I use. I hve never broken an quality carbide.
Issue here may be the flut number. Two flute is for soft alu. Not 6061m adb bever fir 7075. A 4 flute will handle the cut much cleaner and smoother.
Save the two flute end mills for soft alu, plastics, and if needed, wood routing.
I switched to auto feeds years ago. Carbide doesn't like interrupted cuts. Hard to be precise in the wheel turning by hand. Not that expensive, and very clean work.
Knife
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Marksman
Posts: 429
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Real Name: Troy Adams
Re: Perplexing milling cutter tip breakage
«
Reply #21 on:
November 29, 2019, 11:25:21 PM »
Where you running the cutter in reverse in stead of forward low speed high speed.
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Ga Conyers
MJP
Member 4400+Fpe Club
GTA Senior Contributor
Posts: 2136
I'll make it real. For me.
Real Name: Marko
Re: Perplexing milling cutter tip breakage
«
Reply #22 on:
November 30, 2019, 02:55:48 AM »
I disagree with you Mike on the two flute cutters. They are intended for aluminum, disregarding the alloy. We ran two flutes on all alloys including 7075 T6 you just need to have a right machine that is intended for production and not some manual mill.
Feeds and speeds matter, tool manufacturers don't test those just for the fun of it.
Tools need to be run on high rpm to get the surface speed right, 250-450m/min on aluminum and high enough feed to clear the chips so that they don't weld on the cutter.
Marko
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Finland
Impossible just takes a little bit longer to achieve.
If an engineer is not presented with a suitable problem, they will create their own!
KnifeMaker
GTA Senior Contributor
Posts: 8224
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Real Name: Michael
Re: Perplexing milling cutter tip breakage
«
Reply #23 on:
December 02, 2019, 08:55:16 PM »
I bought and sold machine tools tgo different NASA companies Based at the Marshall Space Flight Center-Huntsville Ala.center where they built the Space Shuttles. learned there observing and studying finishes and loads that it does make a difference. For Alu in 7075 T-6 for instance, it is harder than any file steel. Well over RC-70 surface finish. The higher the rpm, the lower the edge shock. More flutes, less load shock. Simple
And exactly why exotic CNC's, can push tooling in the many 40-50,000 rpm and higher range. They would snap like twigs at tool steel speeds. Better off Forgetting alu. designed tooling for it and Ti.
I don't talk about my experience Here Ric. I'm retired, But I have extensive in Metallurgy and its applications Exotic Coatings and heat treats.
I didn't become one of top Craftsmen in the world by not leaning Researching, and eventually knowing what I was doing. My work is collected World Wide.
Aerospace and NASA are the pinnacle. Most of it is in NO Machinist Handbook. Much is fully Classified.
Other than for wood, I don't so much as own a HHs Tool Steel End mill. Useless for me. Haven't used one in over 30 years. Ever!
For what it is worth. 7075 does not weld on end mills. . Hint, never use gold Titanium Nitride Coated Bitts on any Alu. On any soft grade of alu, it causes welding. The sales staff at the Big Hardware stores should be horsewhipped for selling it for siding and home projects without telling people it will not work well in alu. I've had many a home builder tell me that coatings were a scam. Well, they are not. Just like anything else, proper tools, (and coatings) for the job.
Now, no more talk about my paste. LOL I hate it!
Mike
«
Last Edit: December 02, 2019, 09:34:06 PM by KnifeMaker
»
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MJP
Member 4400+Fpe Club
GTA Senior Contributor
Posts: 2136
I'll make it real. For me.
Real Name: Marko
Re: Perplexing milling cutter tip breakage
«
Reply #24 on:
December 03, 2019, 12:49:40 AM »
Those TiN coatings are just for home gamer shop marketing wank.
I have not seen much in a real production shop for some reason, those coatings are more of a dull grey, greyish purple in nature. And if it is golden it's most likely sandvik carbide and that is not just TiN on the coating.
Dormer makes excellent 2 flute for 7075, very good material removal rate, better than any 4 flute, and tool life is very good.
Time goes on and tools evolve, that's all I'm saying.
Marko
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Finland
Impossible just takes a little bit longer to achieve.
If an engineer is not presented with a suitable problem, they will create their own!
luge007
"What ever, just crash it!" (kid from 1980's Toyota Cienna crash testing commercial)
Plinker
Posts: 293
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Real Name: Matt
Re: Perplexing milling cutter tip breakage
«
Reply #25 on:
December 03, 2019, 12:23:08 PM »
Well, it appears there is quite a difference of opinion, as well as a lot of life experience here. I can clearly see I have a LOT more to learn. In the mean time I will enjoy my hobby of machining my own parts and hopefully learn from my mistakes so I do not repeat them.
I do agree that 'coatings' are useless for most tooling used by hobbyists. For a CNC machine shop that pushes the tooling to it's maximum the coatings (when properly selected) work as advertised. For my friends machine shop, he prefers 'polished carbide' for cutting aluminum, no coatings. Not saying it is 100% correct for every application, but it works for him and his jobs.
I also agree that carbide does not work well with an interrupted cutting as it doesn't handle shock well. (found that out the hard way my first week with my lathe;) Also the cutting tool needs to be precisely on center line of the material when facing or parting off on the lathe, or you will end up with broken inserts.
I disagree with the statement of "For Alu in 7075 T-6 for instance, it is harder than any file steel. Well over RC-70 surface finish." I believe it was stated with good intent, but incorrect, possibly crossing specs of materials?. I can easily cut 7075-T6 aluminum with a file, HSS tools, heck, can even score it with a pocket knife. Also found these highly detailed specs online.
https://www.engineeringclicks.com/7075-t6-aluminium/
7075-T6 has a Brinell hardness of 150, magnum bullet lead is about Brinell (BHN) 24 just barely marked with a fingernail. So aprox. 6x the hardness of hard lead....
"RC surface finish" Rockwell C surface hardness? Hmmm maybe an anodized coating? That would be much harder than the raw material, but usually the finished part gets anodized after all the machining is done.? I doubt it would be harder than a file though. A link I found to Rockwell A,B,C to Brinell conversion just for reference.
https://www.engineersedge.com/hardness_conversion.htm
2 flute cutters are recommended for aluminum by many machine tool suppliers for rapid cutting and maximum chip removal. (from my limited experience and talks with a tool salesman of a big supplier) 3 flute high helix cutters are recommended for aluminum also, providing a shearing action, reducing tool load and providing a cleaner cut. This seems accurate from the 3fl endmills I have used. 4 flute cutters seem to be best utilized for harder materials like steels, and 5 flute endmills are recommended for titanium and other difficult to machine materials. (from what I've researched, no experience with Ti)
Having now researched "surface speed" (thanks MJP) as it applies to the tool cutting tip speed, I now don't have to guess any more.
BTW, I also picked up a Machinists Handbook to review the gospel of "the bible of machining". I probably should have started by reading it but like most, I jumped to the good stuff without 'reading the directions'.
Cheers,
M
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USA, RI, SK
KnifeMaker
GTA Senior Contributor
Posts: 8224
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Real Name: Michael
Re: Perplexing milling cutter tip breakage
«
Reply #26 on:
December 03, 2019, 03:32:34 PM »
the T-6 I use is military Armor plate 7075-t6, so as you guessed, it is hard anodized. A new Nicolson file will only scate across it, and it's teath flattned. So very high B scale.
I use mostly high helix 3 flutes as yl guessed as well. Bear micro grain carbide, that I diamond hone the end flutes with. 2200 grit, well worn sharpening surface. This only after they dull a bit.
I fully admit, I have been out of the AeroSpace arena ever since moving to Ft. Hood. World's largest Military base in the Free world. I mistakenly believed it would be hi-tech similar to RedStone Arsenal and Marshall Space Flight Center. Boy was I WRONG. More third world than Modern high tech. LOL!!!
Mike
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Central Texas
luge007
"What ever, just crash it!" (kid from 1980's Toyota Cienna crash testing commercial)
Plinker
Posts: 293
yes
Real Name: Matt
Re: Perplexing milling cutter tip breakage
«
Reply #27 on:
December 03, 2019, 06:37:21 PM »
I would love to see an example of that super hard 7075-T6 used for armor plate! I am only familiar with AR500/550 steel plate, the aluminum sounds much lighter. Hard to believe it is hard enough to shed a file stroke, that is totally amazing (to me).
Woah, sharpening 3 flute endmills with 2200 diamond hone? Can it still be done with the little 3/16 endmills I seem to use so often? Probably not the right place to ask, but how the heck is that done accurately (hopefully not years of experience)? I'd love to know because endmills are expensive and resharpening them myself would make them much more cost effective.
Cheers,
M
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USA, RI, SK
luge007
"What ever, just crash it!" (kid from 1980's Toyota Cienna crash testing commercial)
Plinker
Posts: 293
yes
Real Name: Matt
Re: Perplexing milling cutter tip breakage
«
Reply #28 on:
December 17, 2019, 11:55:57 AM »
"Kinfemaker"- Actually I was serious about the resharpening of endmills with a diamond hone. If you could post pics of the process here or start a new thread of the process and link it, it would be greatly appreciated. I'm mostly focused on HOW one precisely lines up the cutting edges for honing because it seems like an impossible task by hand.
Cheers,
M
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USA, RI, SK
MJP
Member 4400+Fpe Club
GTA Senior Contributor
Posts: 2136
I'll make it real. For me.
Real Name: Marko
Re: Perplexing milling cutter tip breakage
«
Reply #29 on:
December 17, 2019, 04:34:38 PM »
Not too complicated, you need suitable canted sharpening fixture for the endmill and surface grinder with diamond hone. Search YouTube for endmill sharpening.
Marko
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Finland
Impossible just takes a little bit longer to achieve.
If an engineer is not presented with a suitable problem, they will create their own!
luge007
"What ever, just crash it!" (kid from 1980's Toyota Cienna crash testing commercial)
Plinker
Posts: 293
yes
Real Name: Matt
Re: Perplexing milling cutter tip breakage
«
Reply #30 on:
December 18, 2019, 09:18:29 AM »
Darn! I was under the impression that the "diamond hone" was a hand lapping hone and the job was done by hand, hence my piqued interest. By the time I invest in a proper jig and an expensive surface grinder with a diamond wheel, I could have purchased an entire cabinet of cutters. So much for the 'hobby machinist' resharpening endmills cost effectively at home.
I did look into sending my carbide cutters out for resharpening but the cost is almost half of a new cutter and the about cost as HSS. So, for now I will just stick with HSS and buy new carbide for specific jobs that would benefit from it like cutting Stainless. (though I will keep my eye out for a used, small surface grinder)
Peace,
M
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USA, RI, SK
MJP
Member 4400+Fpe Club
GTA Senior Contributor
Posts: 2136
I'll make it real. For me.
Real Name: Marko
Re: Perplexing milling cutter tip breakage
«
Reply #31 on:
December 18, 2019, 02:23:15 PM »
If you have enough interest and a steady hand you can use angle grinder and tile cutting disk. Thats how I make custom inserts for lathe and dress some corners on bigger endmills.
Marko
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Finland
Impossible just takes a little bit longer to achieve.
If an engineer is not presented with a suitable problem, they will create their own!
luge007
"What ever, just crash it!" (kid from 1980's Toyota Cienna crash testing commercial)
Plinker
Posts: 293
yes
Real Name: Matt
Re: Perplexing milling cutter tip breakage
«
Reply #32 on:
December 18, 2019, 04:54:14 PM »
Woah, brilliant! The tile saw blade/grinder idea never occurred to me, but it makes total sense with a diamond blade. Hmmmm. Well IF I don't have a double espresso shot in the morning I have a steady hand........perhaps I'll invest in a tile saw blade for my angle grinder and give it a shot. Do you run the blade wet or dry for diamond on carbide?
Thanks for the direction to try, worst case dull bits get ruined.
Cheers,
M
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USA, RI, SK
MJP
Member 4400+Fpe Club
GTA Senior Contributor
Posts: 2136
I'll make it real. For me.
Real Name: Marko
Re: Perplexing milling cutter tip breakage
«
Reply #33 on:
December 19, 2019, 01:35:53 AM »
Dry, and wear a very good quality respirator as the tungsten is a heavy metal it will stay in your lungs.
You can make a stand for the grinder and a 90deg angle iron guide for the endmill to make things easier. Just take what relief angle you want and adjust the guide to that.
Marko
«
Last Edit: December 19, 2019, 01:39:30 AM by MJP
»
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Finland
Impossible just takes a little bit longer to achieve.
If an engineer is not presented with a suitable problem, they will create their own!
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Perplexing milling cutter tip breakage