Aluminum Roughing End Mill: Recommendations?

Chris- that all seems like good information, but can you qualify the statement below with any documentation?

"Is this for a manual 2-3hp milling machine? If so, I think you'd be better off spending $17 on a good HSS end mill"

Why is that a true statement? From my (admittedly limited) experience, as well as what I read when looking into coatings, the fact is that ZrN coating adds lubricity that bright finish end mills simply don't have. On top of that, the coating increases tool life due to the increased hardness as well as temp resistance. I can't find the lubricity rating for bright finish micrograin carbide tooling, but I did find it for the ZrN coating (at 0.5). I think it's easy to make the case that high speed machining DOES require much faster and more efficient chip evacuation than slower spindle speeds, but I don't see why that eliminates specialty coatings from being effective for manual machines. With the increase in temp resistance and hardness, it seems like a big win to me. Am I missing something obvious?
 
First off: This is all based on cutting aluminum. If you're cutting steel that's a different conversation.

When I first got into CNC I was buying 3/8" 2F carbide end mills for aluminum. Someone on CNC Zone talked me into trying a "good" HSS end mill. He was using them on a larger machine than mine. I gave them an honest try and I've been using them ever since. There are a few arguments for them on a HP limited machine:

1. HSS is cheaper than carbide. In my case $12 vs. $20 for my most common end mill (1.6X). In your case it's $17 vs. $55 (3.2X).
2. Carbide is brittle and chips easier than HSS. Chip one corner on that $55 end mill and it's scrap.
3. Since you're running a manual machine you're more likely to stall or crash the machine. The HSS is more likely to survive.
4. Carbide is brittle and can't hold as sharp of an edge as HSS so it takes more HP to remove the same amount of metal. Your machine is HP limited so using HSS will allow you to sustain a higher MRR than carbide. The HSS end mill isn't the limiting factor on your machine, it's the low spindle speed and limited feed rates that the average human can produce.

Like I said, if you're trying to cool and lubricate the end mill you're better off setting up a mist/fogless coolant system.

BTW: I do use carbide end mills under 1/4" as they can handle a higher MRR in carbide than HSS.
 
I agree completely with Chris. Coated tools are like inserts in that they are efficiency enhancers for maximum production. Even when I did work in a production shop, we did all of our aluminum work in the mill department with HSS and steel with cobalt, nothing more. Tapping titanium is one place where ZrN would be used, but never on Al. Coatings have come a long way, but for those of us turning handwheels, there isn't any justification for the added cost. Tool life and finish quality has more inputs than coating, inputs that can be eliminated with better bearings in the quill, good tool holders, correctly adjusted gibs, proper cuts, and mist coolant. I'd rather buy HSS and spend the money saved on improving my setup. In a rigid machine, an HSS end mill can run 24/7 for weeks in aluminum before sharpening or replacement.
 
ZrN or any coating isn't going to do you any good if you do not have a system to get rid of the chips. On aluminum I have tried both uncoated polished and ZRN coated, to be honest I will do something stupid that will break a tip on a carbide end mill before it wears out from use. I have been using Hanita carbide 3Fl high helix and Niagara HSCO TiCN coated, and they both last a year or more with 1/2" end mills in aluminum. I also pick them up on eBay, the last batch of 1/2" carbides were $25 a piece. The major downside of carbide is that they are very brittle, bounce a tip or tap anything and you will break a tip. I still continue to use them for roughing out material, the carbide is razor sharp. At $25 a pop they are not worth resharpening, and the price difference vs. HSCO is minimal vs. longevity. CNC is a different situation, were I typically see 2Fl 1/4 or 3/8" end mills used, and more continuous run with dedicated high flow coolant systems.

My experience is similar petertha. I like to use cobalt end mills and also the powdered metal cobalt ones by Minicut, the 3Fl wave type (930PM) does very well in aluminum for manual milling with fast metal removal. I do not do CNC, but for manual I prefer the 3Fl. If you want to remove a lot of aluminum quickly, i would recommend a 4 or 5Fl 3/4-7/8" rougher. They will shower you with a pile of chips very quickly, much faster than a 2 or 3 Fl end mill in my experience. You will need a more rigid mill with 2-3 Hp to use the larger rougher.

Milling 2500 RPM 0.20 x 0.60 DOC 10 IPM passes using a 7/8" HSCO TiCN 5 flute fine rougher
293365

I haven't found that the coatings make much of a difference at my level of milling in aluminum. If using carbide, you also will have better luck with a small corner radius on the flutes. I have worn out HSS end mills, but not my carbide ones in aluminum (I have only used HSCO and carbide). The biggest factor with milling aluminum (at my level) is chip evacuation, climb cutting and cutter profile in my experience. See attached article which discusses factors to get an optimal surface finish in aluminum.
 

Attachments

  • Effect of Machining Feed on Surface Roughness in Cutting 6061.pdf
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Well I'm hesitant to post this since I really don't know what I'm doing- so I made the video unlisted. But I did say I would so... enjoy? ha.

This is the Maritool 1/2" roughing end mill I linked to in the OP.
For profiling it is running at 327 SFM, 1.0" ADOC, 0.110" RDOC, and 4 IPM.
For slotting it is running at 327 SFM, 0.5" ADOC, and 2.4 IPM
1HP machine.

The Lakeshore Carbide rougher arrives tomorrow.

 
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At those feed rates the tool is just rubbing the material away. You need to increase your feed by 8-10x. Try taking a .25” deep x .125” wide cut and get used to how fast you can push the end mill. Then start increasing the DOC.
 
ChrisAttebery said:
At those feed rates the tool is just rubbing the material away. You need to increase your feed by 8-10x. Try taking a .25” deep x .125” wide cut and get used to how fast you can push the end mill. Then start increasing the DOC.
Click to expand...

I don't know man. Either I'm not being clear in my point, or you're not reading it. The feeds & speeds I used are literally direct from the manufacturer. The question isn't if it can be optimized more- of course it can. Even the manufacturer states as much. The question is if your uncoated end mill can keep up. Now I've proved that the coated end mill can handle a pretty fast feed given a very slow speed. The end mill handled a full feed of 4 IPM at 2D ADOC and .25D RDOC at only 40% of the recommended SFM without any chip welding or other issue. Can the bright end mill hang? That is the question.
 
3 flutes, 2500 rpm, 4 IPM is only .00055 IPT. Are you sure it isn’t 40 IPM?


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Wow! The Lakeshore Carbide one is night and day better. Insanely smooth performance and begs for more. I found a winner!
 
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