[Goemon]

Now that I finally got my (3 axis) CNC machine up and running, I want to make some aluminum molds but I need a little help choosing end mills. I need to be able to mill a reasonable quality flat bottom surface (without deep tool marks that can not be easily polished out).

I can see from my early test cuts that the finish quality (of flat bottom surfaces) depends a lot on the choice of end mill but I am not sure what is best for my set-up and purpose. I am using a 24,000rpm 7.5hp electric fan cooled spindle with a range of 2000rpm up to 24,000.

So.... for those with aluminum milling experience (with high speed spindles), what end mills would you buy to mill (for example) a 1" wide x 1" deep x 30" long flat bottom pocket in a slab of mic6 or 6061?

[QuinnSjoblom]

Now that I finally got my (3 axis) CNC machine up and running, I want to make some aluminum molds but I need a little help choosing end mills. I need to be able to mill a reasonable quality flat bottom surface (without deep tool marks that can not be easily polished out).

I can see from my early test cuts that the finish quality (of flat bottom surfaces) depends a lot on the choice of end mill but I am not sure what is best for my set-up and purpose. I am using a 24,000rpm 7.5hp electric fan cooled spindle with a range of 2000rpm up to 24,000.

So.... for those with aluminum milling experience (with high speed spindles), what end mills would you buy to mill (for example) a 1" wide x 1" deep x 30" long flat bottom pocket in a slab of mic6 or 6061?

My workhorse for aluminum is a 1/4 3 flute high helix zrn coated endmill from maritool. I run it at 13k rpm with koolmist coolant. Great finish. I prefer a slight radius, like 3 thou. Sharp corner endmills chip much quicker.

You mentioned you're doing molds and need a good finish on the bottom surface. Is it a square channel like you mentioned? Or is there 3d contouring? One thing I've learned is that with 3d surfaces that blend into flat surfaces, a radiused endmill with a partial flat bottom is better than a ball mill. Ball mills do a terrible job when they pass over flat surfaces since the very center of the endmill has zero surface speed. Something like a 5/16 or 3/8 endmill with 1/8 radiuses will do much better when doing 3d that also has flat or shallow surfaces.

[ToolHIT]

Quinn is right on! With a 7.5HP High Speed Spindle I'd go with a 1/4" o Diameter 3 Flute End Mill with either 40-45 degree helix. The best floor finish I have seen is with Helical's new H40 Variable Pitch End Mills that have a wiper flat. The Wiper Flats at the end of the tool have given us single digit Ra finishes if you slow the feed rate down and increase the RPM They would offer a 1/4" Diameter x 1" LOC Tool in their ZPLUS Coating:
https://www.toolhit.com/products/48136hel

Or if you don't need the wiper flats then the YG Alu-Power is tough to beat, they have the sharpest cutting edges on their 3 flute End Mills. Here is their 1/4" Dia x 1-1/4" LOC Tool:
https://www.toolhit.com/products/36573

You can run either tool at 13,000-23,000 RPM and .001"-.002" CLPT.

Hopefully this helps!

Mike

[Goemon]

My workhorse for aluminum is a 1/4 3 flute high helix zrn coated endmill from maritool. I run it at 13k rpm with koolmist coolant. Great finish. I prefer a slight radius, like 3 thou. Sharp corner endmills chip much quicker.

You mentioned you're doing molds and need a good finish on the bottom surface. Is it a square channel like you mentioned? Or is there 3d contouring? One thing I've learned is that with 3d surfaces that blend into flat surfaces, a radiused endmill with a partial flat bottom is better than a ball mill. Ball mills do a terrible job when they pass over flat surfaces since the very center of the endmill has zero surface speed. Something like a 5/16 or 3/8 endmill with 1/8 radiuses will do much better when doing 3d that also has flat or shallow surfaces.

My molds have both flat bottom channels and curved. I make rifle stocks so they come in various shapes and sizes.

Do you find that you get better results with 3 flute end mills than 2 flute or just with the Maritool end mills? I am going to buy some to try. Thanks for the recommendation.

I have been looking for a new coolant to try. The one I use now leaves a horrible residue that seems to stain aluminum. I read that Datron machines use ethanol coolant that leaves parts dry and clean. Have you ever tried an alcohol based coolant and do you know where I could buy some?

I assume that ethanol coolant is not just pure ethanol as that sounds dangerous on a mill....

[Goemon]

Quinn is right on! With a 7.5HP High Speed Spindle I'd go with a 1/4" o Diameter 3 Flute End Mill with either 40-45 degree helix. The best floor finish I have seen is with Helical's new H40 Variable Pitch End Mills that have a wiper flat. The Wiper Flats at the end of the tool have given us single digit Ra finishes if you slow the feed rate down and increase the RPM They would offer a 1/4" Diameter x 1" LOC Tool in their ZPLUS Coating:
https://www.toolhit.com/products/48136hel




When you talk
Or if you don't need the wiper flats then the YG Alu-Power is tough to beat, they have the sharpest cutting edges on their 3 flute End Mills. Here is their 1/4" Dia x 1-1/4" LOC Tool:
https://www.toolhit.com/products/36573

You can run either tool at 13,000-23,000 RPM and .001"-.002" CLPT.

Hopefully this helps!

Mike

It does help a lot. I hadn't seen those wiper flats before. I am going to give them a try. Thank you.

Can I ask, what sort of spindle do you use them with and, have you tried any sort of face mill with aluminum at high speeds? The only face mill I can find that is made for high speed spindles (for aluminum) is the Amana Tool RC3400 but it's too large for my needs. If someone made a 20mm face mill with a 1/2" straight shank, it would fill a gap...

[mactec54]

It does help a lot. I hadn't seen those wiper flats before. I am going to give them a try. Thank you.

Can I ask, what sort of spindle do you use them with and, have you tried any sort of face mill with aluminum at high speeds? The only face mill I can find that is made for high speed spindles (for aluminum) is the Amana Tool RC3400 but it's too large for my needs. If someone made a 20mm face mill with a 1/2" straight shank, it would fill a gap...

Shear Hog make some around 20mm diameter https://abtoolsinc.com/prod/shear-hogs/

[Goemon]

Shear Hog make some around 20mm diameter https://abtoolsinc.com/prod/shear-hogs/

It looks like the smallest shank diameter they offer is 3/4" which is too big for my ER25 spindle.

So far, I have only found two face mill options with 1/2" straight shanks. One is to buy a Shars 1/2" x 3/4" shell mill arbor. This would allow me to attach any face or shell mill cutter designed for a 3/4" arbor.

The other is the Amana tool RC-3400 - a 2.5" face mill with a 1/2" shank. This is the only one I have been able to find that is specifically designed for facing aluminum on a cnc router (instead of a mill). It has a suggested spindle speed of 8000 rpm which is fine for my spindle. I would still have 2.5hp at that speed but.... it costs $215... and it would only be useful to me for stock squaring.

I am trying to find one that is like the Datron face mill except with a straight 1/2" or 5/8" shank instead of the HSK holder. The Datron tool has a 20mm cutting face and is designed for use at higher speeds. Either there is a large gap in this market or I am not looking in the right places...

[mactec54]

It looks like the smallest shank diameter they offer is 3/4" which is too big for my ER25 spindle.

So far, I have only found two face mill options with 1/2" straight shanks. One is to buy a Shars 1/2" x 3/4" shell mill arbor. This would allow me to attach any face or shell mill cutter designed for a 3/4" arbor.

The other is the Amana tool RC-3400 - a 2.5" face mill with a 1/2" shank. This is the only one I have been able to find that is specifically designed for facing aluminum on a cnc router (instead of a mill). It has a suggested spindle speed of 8000 rpm which is fine for my spindle. I would still have 2.5hp at that speed but.... it costs $215... and it would only be useful to me for stock squaring.

I am trying to find one that is like the Datron face mill except with a straight 1/2" or 5/8" shank instead of the HSK holder. The Datron tool has a 20mm cutting face and is designed for use at higher speeds. Either there is a large gap in this market or I am not looking in the right places...

They will make it any size you want ER25 can do .625" I have some that I machined at .375 shank single insert Shear Hog

[Goemon]

They will make it any size you want ER25 can do .625" I have some that I machined at .375 shank single insert Shear Hog

I didn't realize that they made custom sizes. In theory they could make me a 5/8" shank x 7/8" cut diameter end mill.

I have a 1/2" shank x 3/4" cut diameter end mill here but it's just a HSS one so it's not much use to me. It would be great if I could get the same but made from carbide. I could use it to remove tool marks in a final finishing pass.