[xknacx]

Hey, I am still pretty new to this and while I was milling over the weekend I was having some problems. When I did cuts the aluminum was sticking to the side of the cut. It was also sticking to the mill bit, jamming it up and wont let it cut anymore. Am I doing something wrong or is it cheap aluminum? I dont know what grade since I got it from a scrap yard. If so how do I tell what grade it is?????

thanks!!!
mike

[cncadmin]

I don't know about how tell the grade, but you must use some lube and use a cutting speed that keep the chips flying, loading the bit may lead to breaking it.

[xknacx]

I tried wd40 and was using the max speed on the hf mini mill. I was using a 3/8 2 flute going through 1/4 aluminum.

[mvaughn]

I wouldn't consider WD40 a lubricant.

I'm not a machinist, however, but I would try anything besides WD.

[JFettig]

I had those kind of problems before, If I remember right the chips werent clearing and being pushed around a lot. Another factor is heat, when the end mill gets hot the chips start melting to the EM.

You probably need a good lubricant or something like that. If you have some water based stuff, mix some up in a spray bottle and give it a squirt from time to time.

Another factor is that the chip load might not be large enough, its hard to give it the right chipload and not break the end mill when milling manually, its too easy to push too hard when trying to push hard enough.

Jon

[xknacx]

JFETTING that sounds like whats happening. When the bit and aluminum is cool it cuts pretty decent. then it all goes to hell. trying to get the aluminum tidbits out of the bit SUCKS!!! I did break one too!!!! I was thinking maybe the bit was too small for the job and not clearing away the aluminum?? What lube do you guys suggest? Can I use motor oil? whats the easiest to clean up?

[thielert]

>"using the max speed on the hf mini mill."

Use a much slower spindle speed for AL, you have to form a chip that will eject, not a dust that will clog and "gal".

Cutting fluid is also a must with AL, not just for cooling, and anti-gal, but also for good surface finish.

TT

[fpworks]

I recommend a cooling system of some sort...flood, dry, or near dry.(latter two are mist systems). Applying cutting fluid alone isn't good enough, because it doesn't remove the chips or heat.

I use a mist system...cleanup is very easy (chips are dry), you don't have to dispose of old coolant, and runs off of compressed air...no pumps. However, you must fully enclose the mill and ventilate the enclosure to the outside, or you will be dealing with atomized coolant in your work area. You should also consider ONLY "operator safe, biodegradable" coolants even with proper enclosure and ventilation.

Flood cooling is another option, with it's own set of pros/cons.

After saying this, I run 45 minute long mill programs on aluminum, from cheap and soft 6061 to very hard 7075-T6 without any of the problems you mentioned. Part and endmill is actually cold after milling, excellent finish (with 4 flute endmills), toolife is excellent.

[JFettig]

motor oil lubricates but makes a huge mess. having the rpm at max is ok if you give it enough feed.
Also, 2 flute end mills might be the key too, they can take a larger chipload and work better in gummy metals, with coolant I think maybe a 4flute end mill will work better, I have nothing to back that up but it will cut faster.

Jon

[Ken_Shea]

xknacx, I did not see what type cutter you are using HSS, Carbide ?, what is the Max RPM on the HF Mini Mill, your depth of cut, plunging, ramping ?, Feed?, chip load you are using?

Kinda all guess work with out more info.

[JRoque]

Here's what I do to cut 7075 aluminum: Use a 2 flute mill (like this one), spin it anywhere between 25K and 40K RPM and use WD40 and water as lube/coolant when I remember. Ok, ready for the flames....
IMHO, if you're clogging the tool you have either too many flutes, too slow/fast spindle and/or feed for a soft alloy.

Later,
Julio

[JFettig]

Jrogue, this info hardly applies to what he is doing because your spindle spins 25-40k and his spins 2k.

water and wd40 arent the greatest for cutting fluids

Jon

[xknacx]

I ran it at 2500 thats the max. I am cutting thru 1/4 aluminum with a 3/8 2 flute hss bit. Not sure on feed rate since I am doing it by hand, but it looks about 2ipm when I run that speed cnc.

[xknacx]

jrogue, wouldnt the wd40 and water evaprorate on contact at those speeds? Man, I thought I was new at this.

[mvaughn]

WD40 and water don't mix well either.

What about using a tapping/cutting fluid like you would use on a drill press? You could manually give it a few squirts once in a while.

[Ken_Shea]

xknacx, a conservative chip load on a HSS .375 end mill would run in the .002 range, 2500RPM is not out of line, IPM 10, DOC .030 for a light machine.

It has already been said that your material type is unknown except that it is aluminum, soft does not necessarily mean cheap, it could be high quality but in a 0 or untempered state. That is the risk you always run when you purchase at scrap yards, sometimes it works out sometimes it does not.


I have had similar experience and it was remedied by me doing the following.
Switched to carbide, I have never used any of the high-end HSS cutters but carbide made a night and day difference. Used flood cooling, you have to get those chips out of the way, some people use a small stream of air that seems to work.
Purchase material that is of a known temper. 6061-T6 is very common on EBAY, this cuts very nice.

[JRoque]

jrogue, wouldnt the wd40 and water evaprorate on contact at those speeds? Man, I thought I was new at this.

Hello xknacx,

Yes, I'm very new to this too. I'm not suggesting water and WD40 is THE solution (no pun intended) but simply that it has worked for me. In fact, I only mentioned it to encourage and show you that you don't need complex flooding systems to make successful cuts. I don't get material clogging my tools so there might be a slight merit in how I do it.

Cheers,
Julio

[BarnBurner]

WD-40 is probably the best for aluminum, except for the residue it leaves. If you are going to paint or anodize it needs to be thoroughly washed off.

Varsol is another good coolant for machining aluminum; biggest problem is that it will wash the oil off the ways.

One thing I sometimes use, especially when machining deep pockets, is using a wet/dry vac to pull the chips away; it's alot less messy than coolant or blowing the chips all over the place with air.

It sounds to me like you are feeding too slow; what ipm are you using?

Also, see if you can get Carbide tools for AL, they work ALOT better than plain HSS. Prolly 2 - 3 times as much, but will last 10 times longer!

[JFettig]

BarnBurner, have you used anything but wd40? like regular waterbased coolant mixed correctly?

Jon

[BarnBurner]

Yes, I have. I used it on my manual lathe for parting, and after about 6 months and 2,000 parts, the cross slide was so gummed up I had the pretty much strip the apron and clean it with a cold chisel. It was emulsifiable oil.

The advantage to WD-40 is it doesn't leave a residue like that; when the coolant dries the water evaporates and just leaves the oil, which turns thick and gets worse with way-lube. Also chips stick to and cause abrasion.

Using a small squirt bottle of coolant will work, but coolant works better in large quantities, with WD-40 you could give it a shot every inch or two of travel. And it works excellent for power tapping small holes.

But this is all just my opinion from a decade and a half of machining; I would suggest xknacx tries whichever he thinks sounds better, and sticks with the one he prefers.