[techhelpbb]

Originally Posted by scottandme

I guess best case you're paying a decent amount of $$ over uncoated without an appreciable benefit compared to other coatings.

Not so sure about the $$ I paid < $10 for those 2 flute end mills including shipping and handing quite some time ago. In a production operation with various tool paths I can't say I consider that expensive.

I called both because I was curious if one would say the opposite of the other. I've never experienced the issue you have.

I did expressely mention that other people were telling me they were having issues with TiAlN in aluminum and they both stated it depends on a lot of factors like the feed rate, the coolant, the rigidity. So your mileage may well differ from mine.

I have never seen anyone sell an aluminum specific end mill with TiAlN on it - uncoated, TiCN, ZrN, TiB2, and DLC are the only ones I can remember seeing. I've also never seen aluminum as a recommended material for TiAlN or AlTiN.

I can't say that any of the TiAlN coated end mills I've used expressely stated that they were designed for aluminum. I don't necessarily use a rule of thumb for setting up for aluminum either. However I can't really say that router typically used for wood or a RotoZip was really designed for this purpose either. I don't use TiAlN coated end mills unless the RPM of the spindle is for some reason high and I can't adjust it down.

It doesn't really matter - you want to run carbide with smaller cutters. For one, the price difference is usually minimal compared to HSS. Carbide is significantly more rigid that HSS, which is especially helpful for small diameter cutters. And even uncoated carbide has almost no speed limit in aluminum. Cuts weld if the SFPM is too high, chip load is too low, or the chips aren't being ejected from the cut. So to fix the first you use carbide, to fix the second you use a single flute cutter so you can maintain proper chip load at lower feeds, and that also fixes #3 by giving room for chips to eject.

If it's on a mill and not a router, then you still want to use carbide if only for the rigidity benefits.

Most of all these bits with TiAlN coating are carbide inside anyway so I agree this is one of those little things.
The core advice is still the same.

Originally Posted by Cory

If you tried to run one of those end mills under aluminum specific parameters (1000+ SFM, .003"+ chip load) you will load it up and break it-guaranteed. This is as much because of the geometry being wrong as it is because of the coating, as the only tools that are ever coated with those are meant for ferrous materials.

Well if you try the calculator on the page I linked before:
1,000SFM with an 1/8" mill gets you a spindle RPM of around 30,500 RPM.
With a tooth load of 0.003 and 2 flutes you get: about 183 IPM feed rate.

I have a lot of people I've worked with that only dream about 183 IPM feed rates their systems could not achieve that.
They would be missing steps.

If you increase the diameter to 1/4" you'll get down to about 15k RPM and 91 IPM or so that's more practical for large steppers and closed loop servos.

Originally Posted by Cory

I'm not sure why they told you that you don't want to run the tool at elevated temperatures. I forget where it is exactly, but somewhere between 700-800C the coating dramatically increases in hardness. As previously mentioned this is why people don't cut ferrous metals with coolant when using those coatings.

There are many studies on TiAlN here is one that specifically mentions 800 degrees Celsius.
http://www.geocities.ws/sarangrh/report/seminar.pdf

TiAlN is the most recently developed coating with a hardness of 3300 HV and is
temperature resistant up to 800°C i.e. Excellent Stability at High Temperature and
Smooth Tool Surface, Balanced Wear Resistance and Fracture Resistance, allowing the
use of ultra high-speed machining operations. This multi-purpose coating is also suitable
for working cast-iron, High Speed Turning of Stainless Steel and Al alloys and reduces
friction and adhesion of plastics materials to the moulds. New applications are found
every day with this very efficient, high productivity tool.

Further we can ask a company that does coating what they recommend:
http://www.pvd-coatings.co.uk/coatin...tialn-coating/

TiAlN coating – Applications
The properties of the TiAlN coating make it suitable for high temperature cutting operations with minimum use of lubricant or dry machining. TiAlN is used successfully to machine titanium, aluminium and nickel alloys, stainless steels, alloy steels, Co-Cr-Mo and cast irons. TiAlN is also used to protect dies and moulds that are required to operate at high temperatures such as those in medium and hot forging and extrusion industries.

Though I never try to machine aluminum without coolant.
It does not specifically say you'd want to machine aluminum dry.

Originally Posted by scottandme

Either way - the proof is in the products that they sell. Duramill and Niagara don't put that coating on their aluminum-specific end mills.

Niagara Cutter 86002 Carbide Square Nose End Mill, Inch, TiAlN Finish, Roughing and Finishing Cut, 30 Degree Helix, 3 Flutes, 1.5" Overall Length, 0.125" Cutting Diameter, 0.125" Shank Diameter

Niagara Cutter A245 Carbide End Mill for Aluminum, TiAlN Coated, 2 Flutes, Square End, 4-1/8" Cutting Length, 1" Cutting Diameter

http://www.drillmex.com/img/PDF/NIAGARA/A245.pdf