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.
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?????
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.
I wouldn't consider WD40 a lubricant.
I'm not a machinist, however, but I would try anything besides WD.
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.
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?
>"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.
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.
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.
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.
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.
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