Aluminum Grinding

Who else grinds aluminum on a regular basis. I work for a tool and blow mold company and for being such a sizeable industry, I can find much info on it at all. Though I've been doing it for about four years, there's still more to learn! Any threads already started? Or if not I'm up for answering questions, we do anything from 20x50 manifolds to .225 shims.

I have tried unsuccessfully several times to grind AL. Just scrap pieces to see what was needed. General points would help what wheel is first?

I've ground the surface of AL blocks a couple of times when I had no other means of ensuring precision greater than a BP could offer. It was 6061 and I had several AO wheels to choose from as well as a SC wheel. Nothing I tried worked very well, the wheels loaded up rather quickly and required frequent dressing. Heat and thermal expansion was another issue as well. I ended the experiment using flood coolant, a coarse SC (green) wheel, and only taking about .0005 total for finishing to dimension. Although doable it was not much of a success in my opinion. I'd enjoy reading about methods others have tried with better/worse results as I still have other projects in mind that would allow me the option when needed.

Regular surface grinder or..? I've ground a fair bit of aluminum in a Blanchard grinder, but that was some years ago. We used 36 grit wheel sections, not sure of bond or anything, but it required frequent dressing, but was very doable.

Mike1974 said:

Regular surface grinder or..? I've ground a fair bit of aluminum in a Blanchard grinder, but that was some years ago. We used 36 grit wheel sections, not sure of bond or anything, but it required frequent dressing, but was very doable.

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Mike- Was that OA, carborundum, silicone carbide, or something else wheel sections?

AD Design said:

Mike- Was that OA, carborundum, silicone carbide, or something else wheel sections?

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Couldn't tell you
This would have been like 2006-2008. I remember the 36 grit was pink and we had one other grit (not sure) that were white sections....

Liberal use of grinding wax and 7075 if at all possible

Grinding aluminium

Toms Wheels said:

I have tried unsuccessfully several times to grind AL. Just scrap pieces to see what was needed. General points would help what wheel is first?

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The wheel we use is an open structure or very poreous glass bonded aluminum oxide wheel. And assuming your flat grinding and not off hand ie that you have a magnetic chuck. Precision blocking and flooding coolant are the real dictators of flat aluminum parts and finish. Also knowing the behavior of the wheel cutting at a reasonable infeed is going to save you from scrapping a 2000 dollar manifold. So we cut around 2 to 4 tenths indeed, usually 5 to 20 thousands stock and we hold flatness tolerances no worse than .0003.Feel free to ask more questions, I've been at this for 4 years

AD Design said:

I've ground the surface of AL blocks a couple of times when I had no other means of ensuring precision greater than a BP could offer. It was 6061 and I had several AO wheels to choose from as well as a SC wheel. Nothing I tried worked very well, the wheels loaded up rather quickly and required frequent dressing. Heat and thermal expansion was another issue as well. I ended the experiment using flood coolant, a coarse SC (green) wheel, and only taking about .0005 total for finishing to dimension. Although doable it was not much of a success in my opinion. I'd enjoy reading about methods others have tried with better/worse results as I still have other projects in mind that would allow me the option when needed.

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Hey, so an Ao wheel glass bonded and 46 grit size is what we use and we have a minor problem with the grit size. We produce blow molds and as a company rule the parts need to look pretty when they leave the shop, so when we have a coarse dress it looks bad but I like it because the wheel behaves predictably.
So, when we cut it's an infeed of 2 to 4 tenths, for precision grinding, we have to learn the behavior of our particular wheel. For example we get a good finish with a fine dress and with a single point, I can remove stock regularly at a 1:1 ratio with a .0002 infeed no problem, meaning what I program it to remove is what it takes.
Now when I step it up to .0004 infeed, the wheel has a harder time cutting, so when I tell it to remove four tenths at a time with a medium to fine dress on my wheel I know it's bound to disappoint. It's going to take less in the beginning of a run and by the end, it's going to dull and cut more.
So say in the beginning I tell it to remove .004, well when I indicate it, its reading .0037. Then at the end of a run, I will find, it will take .0035. so when I compensate the .0005 the damn thing takes the original .004 plus the .0005. wtf! Well what happens is the wheel gets dull and does something called burnishing. It won't cut small numbers like a tenth. it will apply a lot of wheel pressure to your part and polish it until the pressure causes it to break and redresses the wheel.
So to counter the problem we are getting a finer grit wheel, so we can dress the wheel at a fast pace, make me happy, and keep a smooth finish, making management happy. So that was a bit of rambling but it's a challenge we are facing.

Your Reply

sjzona- I'm certainly no grinding expert but I've ground a fair bit of ferrous and non-ferrous material in a former life as a tool and die maker. My attempts at grinding AL over the years have been experimentation and for personal projects at home. My last serious attempt was for a shuttle and I wanted a few .0001's flat/perpendicular/parallel on bearing blocks. Wheel loading and burnishing were the obvious problems so I tried various dressing speeds and step-over grinding feed rates, trying to create enough pressure to fracture the grains that would reveal new edges. The best technique I could manage was to grind a thou or two (total) in roughing and go for a few .0001's to size/finish after dressing again. I was never able to achieve what I considered satisfactory results but perhaps I simply needed to accept that AL just has to have different methods/results than grinding ferrous material. I've never met anybody that could claim/admit to obtaining good results on AL with anything other than a belt sander. Perhaps I need to experiment more with dressing speed and/or reduce the step-over while grinding. Posting your results are confirmation that it may be possible and I look forward to attempting this again with similar results as yours. Thanks for posting.

As an apprentice we had an aerospace job that required .0002: flat and parallel. It was a casting so somewhat harder than 6061. we fixtured on a steel fixture and against all recommendations for Al we used a Norton 38A46H wheel. We sprayed the part with WD40 and fed down at .0002 to .0003. The wheel would go for 2-3 hours with a dress until the burnishing took over. Never a problem with loading, just the finish went to shit and size became unpredictable.

I have ground a lot of Al over the years and this works for all soft metals. After blocking in your part or putting it on a fixture, coat it well with Crisco vegetable shorting. It will keep the wheel from loading and give you the finish you are looking for. The best part is a large can is cheep.

Norton 32A46H grey wheel, lots of coolant and a sharp diamond to dress the wheel and an aggressive dress (several passes at .002" and a quick motion). Don't take light passes for a finish dress. I find proper dressing is critical when grinding aluminium.

I used to occasionally jig grind aluminum. Not often enough to research wheels but I did manage to get the job done. Wound up waxing the hell out of the wheel, redress and rewax when the finish or sound became "off".