Occasionally I have to surface grind aluminum and it usually isn't to big of a problem but I wish I could figure out the optimal way to do it.
Currently I tend to use whatever alum. oxide wheel I already have on the machine which is usually a 46H, 46I, or 46J (Norton 32A). It seems to make very little difference which one because all are so much harder than the aluminum.
I spray the parts with WD40 or LPS while grinding to keep the wheel from loading. This generally works fine.
I would like to improve in three main areas:
1) Optimal choice of wheel
2) Optimal dress of wheel
3) A way to use regular flood coolant so I don't have the mess of WD40 which then contaminates the coolant tank. I would like to find a coolant which works for both steel and aluminum.
Any advice would be appreciated! Thanks!
A long time ago I ground some aluminum and as I recall I loaded the wheel with beeswax to keep it from loading. I still have the beeswax in my toolbox but the grinding happened almost 20 years ago. So my memory might be a little foggy. It may have been some copper alloy that I ground. Either way the beeswax did the trick.
You should never use grinding wheels that are not rated for soft metals. When the wheel clogs it heats up and can explode.
I saw pics of a large grinder that exploded from grinding brass. The guy survived but the large wheel was in pieces!
I've heard stories of wheels exploding but the truth is you have to be completely ignoring what is happening to get a wheel so clogged that it explodes. It doesn't happen instantly (at least not with aluminum, I don't know about brass), it takes awhile to clog and it starts grinding like crap way before then. I have no problem keeping the wheel clog free with either WD or LPS but it makes a mess, and if I don't use a lot of it, it will start to clog. If there's a wheel that doesn't require a lubricant like WD or LPS or if there's a coolant that works as good as WD or LPS for aluminum I'd like to know what it is.
Water soluble coolants will work well on aluminum if you make the mix richer than normal. A 46 grit wheel is going to work as well as anything. I have been told by guys over the years that green wheels work better. Ive done a lot of grinding(jig,OD,ID,surface) and my routine with aluminum is to use the wheel that is mounted. They all seem to work about the same. I am sure that you had a bazillion peices to run you could home in on a wheel and coolant combo that paid off ,but,most my stuff is short run,1 or 2 peices. As far as the exploding wheel ,its true that if the wheel loads up it continues to pick up aluminum and "gets bigger" but you would have to be a nit-wit to let this condition blow a wheel up.
The textbook "correct way" to grind aluminum is to not use an aluminum oxide wheel. Silicon carbide springs to mind.
David Boyer : I use a 32A Norton 32A46-GVBEP .
I occasionally grind aluminum plate, not often enough to research it well. I use Norton 32A 46H or I, fairly porous (guessing 8?) cause that is what is usually mounted anyway. Cimtech 95 fairly rich, 'cause that is what is in the tank. Never had a loading problem, and the finish is usually "mirror bright". I use infeed grinding method. Have also used ruby, 46H, if that was on the spindle at the time.
My understanding is that oil is better for Al. Certainly an alkali like the Cimtech 95 is not good to leave on aluminum, but seems to work fine for grinding it.
Would not be surprised if mentioned "wheel explosion" had to do with poorly mounted/blocked work? remember, the magnet itself will not hold down Al But as others said, pay attention, you'll hear if a problem is developing.
One caveat, this grinder has through the wheel coolant, don't know how much if any that may help as far as preventing clogging on Al?
I haven't tried grinding Al since I'm a noob to grinding. How does the finish compare to face milling? I've gotten mirror finishes using the face mill, and it's obviously a hell of a lot faster.
Zumba you make a good point. It's definitely better to mill aluminum to size if you can do it, but we are having problems with parts that are large and thin enough to be next to impossible to mill flat. The customer is asking for flat and parallel .0005 so I have been float grinding them 3 times (twice on one side and once on the other) and then screwing them down to steel rails for the final grind. It's still tough to hit but I can do it. If I had the most optimal wheel and coolant it might be easier. Imagine wiping that WD40 off the table and part and then spottlessly cleaning things for each side. It's a royal pain.
Maybe we sholud send them out for lapping? I just don't like to admit defeat!
The coolant in the tank is Cimtek 100 full synthetic. Great stuff for just about anything else. It is usually mixed overy thick due to the fact that I use a CBN wheel often too. The wheel will clog if I use just this coolant. I have tried it.
Speaking of CBN I have heard that if the grinder had variable speed and I could crank it up to like 7500 SFM I could actually use CBN on aluminum!
By the way Zumba the grind finish is pretty sweet.
Water soluble coolants will work well on aluminum if you make the mix richer than normal
I grind aluminum using water soluable coolant straight no water at all! I Just brush it on with a small acid brush works well. I'll use a coarse wheel. How thin are these parts? Too thin for a magnetic hold down ?
I like your lapping idea,
customer is asking for flat and parallel .0005
Won't be as pretty though.
How big are the parts ?
Pardon my ignorance but I am relatively NEW to grinding as I just bought my first surface grinder.
Why would you grind aluminum anyway?
I know so many methods of reducing material on aluminum, why go through the headache of loading up a grinding wheel?
What are the applications needed for grinding aluminum? I need to learn about this?
Guys, I'm going to say it again - silicon carbide wheels are meant for nonferrous materials.
We grind aluminum all day long at work, and have no problems with wheel loading. The choice of abrasive in the first place, rather than specific bond strength or porosity, is what holds folks back grinding aluminum.
Just like you cannot grind steels with diamond, you cannot grind aluminum with aluminum oxide. It's the same type of problem.
Get a silicon carbide wheel, or other non-Al2O3 wheel.
Earlier today I was given a tour of a company nearby that builds aluminium super-yachts, we noticed one of the (4"?) air-powered angle grinders had a carbide-tipped cutter. This looked like a minature skill saw blade with finely pitched brazed-on carbide teeth. Pitch of maybe 8-10mm. Looked like quite a beast, didn't see it in use though.
Mind-boggling boats BTW!
I dont do precision grinding on alum, but do some hand & pedestal grinding. & if you dont want to change wheels for short runs, Just spin a cheap candle into it as it will fill the pores in the wheel to help prevent clogging.
You have convinced me that silicon carbide is the way to go. Can you give me some specifics on the wheel (grit, hardness,etc).
Unfortunately, I'm not in the grinder department at work, so I don't know what specific wheel parameters they use. I do know that you can call up Norton, and they'll give you a specific wheel to try if you can describe your process. This is the path I would take.
Interesting that you should mention that Peter S.
angle grinders had a carbide-tipped cutter.
I have a brochure from a surface grinding machine manufacturer that shows a vertical spindle grinder equipped with 8" dia. face milling cutter w/ many inserts. 1800 RPM. If I remember correctly it says it is used on AL or non ferrous metals.
These guys are into aluminium fabrication in a big way, where I saw the carbide tipped angle grinder was under the hull of a 170 ft yacht (the first one on the web page below, see "Under Construction"). On the bottom of the keel is a huge bulb about 20 feet long, 6-8 feet wide, beautifully shaped. They were welding in the last pieces of aluminium plate to close it up, plate about 16mm thick (5/8"). The hull itself is a bit thinner though. Huge aluminium ribs etc, in fact every part of the boats are aluminium, hence the companies name.