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aluminium sticking to end mill

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Eric Cox23/05/2022 11:09:02
544 forum posts
37 photos

I have been cutting some slots in aluminium using a 1/4" end mill running at 2800 rpm and hand fed with a depth of 30 thou. The aluminium is sticking to the end mill and closing up the flutes. How do I over come this

Ian Parkin23/05/2022 11:13:45
1021 forum posts
239 photos

Buy some wd40 in a 5litre container that comes with a hand sprayer..spray liberally on the cutter whilst machining..of course you can use the spray cans but the 5 litre route is cheap

John Hinkley23/05/2022 11:18:06
1332 forum posts
426 photos

If not already, use some WD40 or paraffin for lubrication/cooling. Use a 2- or 3- flute end mill, if you're using a 4-flute one. Others will no doubt suggest an alteration to speeds and feeds as well. I use a single flute carbide cutter at 10,000rpm with a depth of cut of 1mm, but that's on a 3d router table with aluminium, with no coolant.


Craig Brown 223/05/2022 11:21:39
63 forum posts
33 photos

When you say end mill are you using a 4 flute cutter? Slot drills (2 flute cutters) should be used for cutting slots. Along with a kerosene based lubricant as mentioned above

Hopper23/05/2022 11:27:45
6393 forum posts
334 photos

What sort of aluminium? The "lower" grades can be nasty sticky stuff to machine and tend to clog cutters pretty well. Something like 6061 T6 will machine very nicely usually.

Otherwise WD40 or kero as suggested. Maybe try dropping your rpm and see if that helps.

Dave Halford23/05/2022 11:28:02
2050 forum posts
23 photos

Try 1000 rpm, the slower speed should reduce the heat and therefore the welding. Unless you have one of the less machinable grades of aluminium.


beaten to it.angry

Edited By Dave Halford on 23/05/2022 11:28:35

Andrew Johnston23/05/2022 11:57:36
6601 forum posts
701 photos

I know the feeling:

clogged cutter.jpg

Can we assume that aluminium means an alloy? Pure aluminium is horrid to machine, bit like warm fudge. Summarising a few pointers:

* Use 2 or 3 flute cutters

* ideally use flood coolant or an occasional squirt of WD40

* If no coolant or WD40 can be used then a finish cut climb milling gives a much better finish

* Highly polished carbide cutters are available, specifically for aluminium

* Maximise depth of cut and minimise stepover, tends to give long thin swarf that is less likely to clog the flutes - Edit: for slotting one is stuck with full width cutting, flood coolant is the proper answer. Unless the swarf is continuously cleared not only will it tend to clog but will be recut which doesn't do the cutter any good

* On aluminium alloys I run fast, several thousand rpm and high feedrates so one gets thicker swarf rather than fine which is more likely to clog the flutes. For example slotting 22mm deep on 6082 with a 3-flute 6mm carbide cutter parameters were 2500rpm, feedrate 400mm/min and stepdown 5.5mm per pass. Of course I was using flood coolant, primarily to clear the swarf rather than provide cooling.


Andrew Entwistle23/05/2022 14:13:33
106 forum posts
200 photos

Since moving to cheap polished carbide 1/8" single flute cutters @3000rpm+ I have been able to leave the CNC unattended cutting soft aluminium to depths of 18mm, without the need for air jet/WD40/Paraffin/IPA to prevent clogging of cutters. I don't know if this success would scale up to 6mm/1/4" cutters though.


John Haine23/05/2022 14:40:14
4673 forum posts
273 photos

On the CNC I tend to use 5000+ rpm even with 6mm cutters on 6061 Ali. I believe that cutting action basically involves the metal softening at the tool edge, if run fast it gets softer and has a chance to flow off before sticking. This is using 2 or 3 flute mills, preferably the ones made for aluminium. I don't use coolant but do have an air jet to clear the chips away.

Howard Lewis23/05/2022 16:58:33
6104 forum posts
14 photos

Aluminium does tend to weld to the cutter.

As suggested, reduce the speed. That should reduce temperatures at the cutting edge. And for Aluminium, paraffin (kerosene) is the usual lubricant, with WD40 or its lookalikes as alternatives

For an end mill, the feed rate should be no more than 0.002"/ tooth, so at 1,000 rpm and a 4 flute cutter, so less than 8" per minute.

On then other hand, don't let the cutter idle over the work, to rub and generate heat.



Elliot Hirst23/05/2022 19:24:48
12 forum posts
8 photos

Our local tooling engineer was known in the factory as “Mr Pledge”. He sprayed cutters with furniture polish containing silicone. Cutting results were good and factory smelled pleasantly of lavender.

Eric Cox24/05/2022 09:59:44
544 forum posts
37 photos

I dropped the speed down to 1000 rpm.and it worked fine,

mark costello 124/05/2022 20:41:47
716 forum posts
12 photos

If You'all go to boot sales, buy up any cheap cans of spray on penetrant You can find. It all works on Aluminum.

Dennis Pataki24/05/2022 21:59:21
12 forum posts

One old time lubricant for machining aluminum was a 50/50 mixture of kerosene and lard oil.

Bill Pudney25/05/2022 00:40:03
611 forum posts
24 photos

I may as well contribute, I don't like using WD40 except for removing water , so I use kerosene (paraffin) and a really sharp cutter, polished if possible, and run it at as fast as I can on my little Sieg X2 , a max of about 3,000 rpm. I know a lot of people like WD40, but I found it leaves a waxy deposit all over everything. Some people may like that I suppose.



Bill Pudney25/05/2022 10:23:20
611 forum posts
24 photos

I mean't to add.....don't use cheap/soft al.alloy. Use only the harder grades like 6061, 6082, 2024, 2014, 7075 everything at T6 or better. The soft alloys, like those bought in a hardware shop are rubbish, it's just a waste of time.



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