First time milling aluminum

[John TenEyck]

I needed to mill a couple of slots with beveled edges in a 1/8" piece of aluminum bar stock for a project. I've milled some thin brass before on my CNC but never aluminum. I didn't want to use my nice 0-flute bit so I tried a downcut 1/8" bit to mill the slot. Big mistake. It cut OK for a little bit, but then started making a mess of things and then broke. OK, gotta use the 0-flute. Wow, what a difference. Nice, clean cuts, with the correct dimensions. The 90 deg V-bit cut OK, not perfect, but plenty good enough for my needs. I bought the CNC primarily for woodworking purposes, but it's nice that it can cut other materials, too. The 0-flute bit is dynamite in UHMW plastic and acrylic. Very versatile.

John

[Jim Becker]

It's always best to use tooling designed for the material and in general both plastics and non-ferrous metals cut well with O-flutes made for the purpose. I have not figured out the difference between the O-Flutes made for plastic vs those made for metal cutting, however, but then again, I haven't looked at it that much. I do want to do some more of this kind of thing now that I'm fully moved into the new shop, including a "nearly zero clearance" insert for my slider out of aluminum. That requires the obvious cut outs, drilling/chamfering plus chamfering the back edge and relieving some material on the bottom so it fits in at proper height. It will definitely be a "skill building" exercise! I used my o-flute tooling to cut brass a couple years ago for a pet urn project I was working on and it did great.

[Mel Fulks]

Denatured alcohol sprayed on aluminum makes for crisp non-gummy cutting.

[Michael Burnside]

Denatured alcohol sprayed on aluminum makes for crisp non-gummy cutting.

No kidding? I wondered. I've tried that trick on the drill press, just never thought to do it on the CNC.

To the OP, I've never cut aluminum with an up/down cut bit before, so I don't know if you did something wrong with feeds/speeds or if it was just the wrong bit. The o-flute is the go-to for aluminum and brass from what I've experienced, but your picture looks great.

[Mel Fulks]

Yep, makes gummy aluminum crispy !

[Jim Becker]

I guess if you use green alcohol it also makes the aluminum minty fresh? (Interesting tip about the alcohol. Thanks!)

[Mel Fulks]

I think I first saw the alcohol tip in an old “Popular” magazine . It dang sure would never had occurred to me !

[richard newman]

WD-40 is also good for cutting aluminum. Isopropyl might be safer than denatured to be breathing

The type of aluminum you are cutting makes a HUGE difference. Soft gummy stuff from the big box stores is going to be the worst. You want something like 6061 T-6 or T-651, very commonly used, easy to find, relatively inexpensive. The T refers to temper (hardness)

Aluminum is pretty easy to machine with woodworking tools - I've bandsawn, tablesawn, and routed it with good results.

Metal machining is much more sophisticated and well researched than woodworking, and just as much fun. For friendly advice check out the Home Shop Machinist - https://bbs.homeshopmachinist.net/

[John TenEyck]

Thanks for the link. Bookmarked for future exploration.

I plan to use anodized 6061 T-6 next time. This stuff was from the big box store but it cut fine once I used the proper bit.

John

[Carl Beckett]

Thanks for the link. Bookmarked for future exploration.

I plan to use anodized 6061 T-6 next time. This stuff was from the big box store but it cut fine once I used the proper bit.

John

'Hard' anodize is a harder top surface which will wear tools. 'Decorative' anodize doesnt have that. If hard anodize take a bit more depth on the initial pass so you are cutting all the way through the top layer at once (.005" ish min). It also makes the surface a bit 'porous' but that usually doesnt matter

As I recall, 6061 T6 has higher tensile than mild steel. A 'go to' in the engineering world.

'Soft' aluminum is gummy.

Another lubricant that works great is Tap Magic cutting fluid. Plenty of others to choose from.

[Jim Becker]

The one thing about using lubricants with the kinds of CNC machines that many folks here might use...the lubricants are not a good thing for the typically MDF machine bed/spoil boards. So to help with that and also to help contain the chips, making a fixture out of something like Melamine with raised sides can help keep that stuff off the machine bed/spoilboard. If one is using the superglue/tape method for workpiece holding, the surface can be quite conducive to a "good stick"...as long as there is no residual lubricant on it, of course.

[David Buchhauser]

I needed to mill a couple of slots with beveled edges in a 1/8" piece of aluminum bar stock for a project. I've milled some thin brass before on my CNC but never aluminum. I didn't want to use my nice 0-flute bit so I tried a downcut 1/8" bit to mill the slot. Big mistake. It cut OK for a little bit, but then started making a mess of things and then broke. OK, gotta use the 0-flute. Wow, what a difference. Nice, clean cuts, with the correct dimensions. The 90 deg V-bit cut OK, not perfect, but plenty good enough for my needs. I bought the CNC primarily for woodworking purposes, but it's nice that it can cut other materials, too. The 0-flute bit is dynamite in UHMW plastic and acrylic. Very versatile.

John

John - try spraying some WD-40 on your bit while it is cutting. This works for me.
David

[John TenEyck]

Thanks, David. As Jim said, I'd have to make some sort of containment tray out of Melamine or similar to keep any kind of lubricant from getting slung off onto the MDF spoilboard. I typically use the blue tape and CA glue method to attach workpieces to the MDF or secondary board, as shown here, and wouldn't want anything to interfere with that, or to stain the next workpiece. So far, alcohol sounds like the first thing to try although, to be honest, I saw no aluminum sticking to the 0-flute end mill.

Maybe your and some other recommendations are targeted more at reducing wear on the bit. If so, that's probably not a major concern for me at this point as I don't need to mill aluminum on a regular basis, or many square inches when I do. But if I do, I have some recommendations on what to try.

Why do I use tape and CA glue? Yes, it takes time and costs money to do it. The advantage for me is I can use parts precut to all or a subset of final dimensions and do the milling w/o worry of cutting into clamps, etc. A vacuum hold down system would be the better approach, but that's not likely to happen unless someone has an economical design that uses something no larger than my 3 cfm vacuum bag pump, can accommodate parts of varying sizes, and holds them securely during milling. Anyone have something like that?

John

[Jim Becker]

The alcohol is the better choice for this if cooling/lubrication is needed, John, simply because it doesn't leave a problematic residue when it evaporates. Your hold down method is one of the best for this kind of material, too. It eliminates the need for tabs and doesn't cause interference. It's easier to release than the really good and really sticky double sided carpet tape, too. If you have any kind of pocketing or other non-through cutting that has to have precise depth, you can calculate an allowance to account for the thickness of the tape if you measure from the spoilboard like I do rather than top of material. That's not necessary with top of material. (I don't use TOM simply because I don't want to be switching back and forth and suddenly forget how something was drawn and destroy the workpiece or burry tooling in the machine as my normal mode is top of spoilboard on my machine)

[Michael Burnside]

On using CA glue and tape, if it works for you, don't worry about it. It's not my favorite for some reasons Jim pointed out (I z-zero to the spoilboard 99% of the time) and the time it takes to do, but nothing wrong with it in general. I personally setup my spoilboard with MFT spacing so I use dogs as stops to prevent shifting (this is generally the problem we have on CNCs) and a couple low-profile clamps as needed to hold it down, especially when using an up-cut bit. I have a vacuum, bed, but it's more work on non-sheet type projects, so you're not missing out and your solution is better anyway.