Milling aluminum

[elewayne]

so I'm going to try to mill my first part out of aluminum. I don't think the aluminum is anything special, just ali bar stock.
About how fast do I want to set the machine for RPM? I'm very new to this.

[ERIE S-1 BERKSHIRES]

Well that all depends on the diameter of of the End Mill you're going to use, when I cut aluminum on the bandsaw , I use a metal cutting blade but it's on a wood bandsaw Delta Rockwell that is so I don't reduce the speed at all same RPM as wood Cuts like butter

[elewayne]

sorry, I meant to say more and got rushed.I'm using a 1/2' two flute end mill. I'm making new end caps for the 4" square tube bumper on my camp trailer. so I can carry a really cool ladder that folds up to 4" square inside the bumper. I'll make it fit then drill for a rod that I can clip to stay in place.
So I have to get the piece down to exact size, mill a flange around the outside, and remove at least some of the material from the inside so I don't have to drill a 4" hole all the way through it.

[Harold_V]

Knowing the alloy and hardness can make a difference, although there are no hard to machine aluminum alloys (that excludes aluminum bronze).
2024 T351 is a shear pleasure to machine. 7075-T6 and 6061-T6 are also quite nice to machine. Unless you have a high speed spindle, no need to worry about how fast, just throw all the machine has at it, assuming you can keep up with the cuts. It's always a good idea to have each flute remove a thou or more, and it should be able to handle ten thou per tooth without issue. It's very hard to run a cutter too fast in aluminum.

I highly recommend you lubricate the cut, especially if the alloy is 6061. If you don't, you're likely to get chip welding, and the overall finish will suffer, even if you don't get the welding I speak of. As it isn't necessary to flood the cut, you can lubricate with an acid brush, using kerosene, WD-40 (smells a lot better) or even some solvent that has seen a little use and contains some oil.

I use a small can with a piece of scrap steel in the bottom to keep the can from getting tipped over too easily. As I use air, it also prevents the can from being inadvertently blown away. A small diameter and tall can is better than a large diameter short can (like a tuna can), as it keeps the brush erect, and presents a smaller opening for chips to be collected. I favor something like a tomato paste can.

H

[elewayne]

All good things to consider, thanks, we'll see how it goes this morning.

[SteveM]

I use a small can with a piece of scrap steel in the bottom to keep the can from getting tipped over too easily. As I use air, it also prevents the can from being inadvertently blown away. A small diameter and tall can is better than a large diameter short can (like a tuna can), as it keeps the brush erect, and presents a smaller opening for chips to be collected. I favor something like a tomato paste can.

I love my spillmaster:


Only costs $9.99, keeps the brush standing, has only a small opening.

If you are worried about it getting blown over by air, you can put Harold's chunk of metal in it.

You have it correct to use a 2-flute, as it has more clearance for the chips.



Steve

[elewayne]

I'll have to do one of those.
Just about had one of my parts completed and had to take a break for a while, went back to it, and threw the switch and got the briefest hum from the motor and then nothing. motor's warm, but not that hot. Quill is spinning freely, but no go now.
I knew something would happen, it never fails.

[BadDog]

I prefer to use the laboratory type wash down bottles. They sit upright with no seams below fluid line, so no worry about leaks. They have a bent straw coming out the top with a tiny tip for very precise application of small amounts of lube. I've got them for various cutting and lubricating oils. And if the tip is too small, you cut it back to get the size you want (like caulking)

I've only got 2 issues with them. First, they are almost impossible to mark on, so identification can be a problem if you don't tag them with contents. Second, if you don't crack the seal on top, you will get a "leak" as the barometric pressure drops, and the bottle makes like a makeshift barometer forcing the contents up, and potentially out) of the tube.

Other than that, they work fantastic. And they really shine when parting as you can easily apply drops of cutting lube right into the slot as you cut. Cant do that with a brush, and it won't even hurt the straw if it brushed the edge of the slot, the stuff is really tough.

[Harold_V]

I avoid both of those options for one good reason. When roughing with negative rake carbide, the chips are wicked hot. I have the burn scarred neckline to prove that point. The hot chips make short work of plastics.

H

[BadDog]

I expected so. But surprisingly enough, my wash down bottles sit right on the mill table by the vise, and right on the flat cross slide of my lathe. Neither bear any appreciable scars, though they have undoubtedly been hit by blue hot chips may times. It seems that unlike other surfaces (top of my shoe right behind the tongue, my bed shroud made from neoprene remnants when I forget to put them away after finishing cast iron and switching to steel, the rubber mats I stand on at the machines, etc) the chips fall away before doing any damage. Well, I shouldn't say "no scars" as the nozzles have had close encounters with hot stringy chips a few times, and do bear the scars, though none resulting any impact on effective use. In any case, I'm certainly not a full time machinist and it might go differently when running machines constantly, but I switched to these before Enco went out, and have yet to replace a single one from any type of failure. And I've become very cavalier with regard to their protection. All I can really say is, "works for me"...