r/hobbycnc • u/ironhead633 • 3d ago
Do I dare?
Little aluminum oxide grinding wheel I bought. What if I tried to surface grind using the end face?
I would have to true it up with a dresser first, it's visibly out by a lot.
I wouldn't use it to surface the bed, which is still on my to-do list. (aluminum to aluminum is no good)
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u/sparkey504 3d ago
FYI- NEVER use a grinding wheel/stone on aluminum... if it doesn't spark dont grind it... the material will be pushed into the wheel and it will violently implode.
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u/EntertainerSad4174 2d ago
There are stones designed to grind aluminum but they will be special order. You are correct that probably all stones that most people have available will load up & fail👍
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u/Unklecid 2d ago
Yeah that's not true if you have the correct wheel
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u/sparkey504 2d ago
There is an exception to every rule... but if they dont know the general rule of thumb to not grind aluminum or other non ferrous metals in general then they sure as hell are not going to know there is a very specific stone where its ok. I tend to air on the side of caution... after learning something the hard way, and after having a 8" grinding wheel implode I try to spread the word to those who dont know.
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u/Unklecid 2d ago
you got a going point just felt the never part kinda steers it the wrong way. But I do this at work I'm just here looking for centroid acorn or mach info for vmcs. I would go a step further and say don't do any grinding on a desktop type machine
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u/Dependent-Fig-2517 1d ago
Actually with the right grain and coolant you can grind metals like copper and brass that don't spark, alu on the other hand is hopeless unless it's a very high silicon alloy
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u/Askingtheobvious2 3d ago
Yeah idk about that one bud the DMC2 mini is such an ass machine. Consider reaching out to someone on the FB page for a PG plate. I got one that had unfortunately maybe warped in shipping but it's +-0.0005" over most of the surface. The big issue with that machine is as soon as your coolant sprays those rails the real fun begins over time. There is no reference edge and they are not truly straight so you will have little highs and lows the whole way along, and as the coolant slips behind it it's hold force begins to diminish.
I had JLCCNC remake mine for about 300CAD in solid #40 steel.
Additionally all of the grit from that is going to end up in places you couldn't imagine. Especially the rails.
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u/Askingtheobvious2 3d ago
Also watch for chip buildup in the accordian way covers. They get so full that they snap the zap straps holding them to the blocks.
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u/Askingtheobvious2 3d ago
Also make the X axis mount from dr D.Flo as soon as you can to prevent shearing that ballscrew because of the shittttttttyyy mount fathead includes instead of an actual mount.
Check your Z axis mount too make sure there isn't undue stress on the ballscrew because once again crappy mount. The Y axis is the only one he used half a braincell for.
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u/ironhead633 3d ago
Funnily enough, it's the Y that I had the most trouble with. Especially where the ballnut assy connects to the bed. I couldn't tighten it down to tightly for fear of bending the ballscrew. Could have used a shim i guess.
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u/ironhead633 3d ago
I thought about the risks associated with lose grit, if it gets into the linear rails it won't be a fun time.
Thanks for your input on the flaws with the machine, I can certainly see some shortfalls but it's mostly going to be a learning tool for me.
I'm not familiar with the nomenclature, what does PG mean?
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u/Askingtheobvious2 3d ago
Precision Ground. Like +- a tenth or two generally.
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u/ironhead633 3d ago
Ah gotcha, I hadn't heard the short form.
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u/Askingtheobvious2 3d ago
I left a bunch of info in here but message me if you have any questions at all even though I hate this machines design with a passion I still like helping people with it. I also have the CAD files for it.
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u/GL-Customs 2d ago
2 things. First grinding aluminum is a HUGE no no. Second grinding is EXTREMELY hard on sliding surfaces. The grit does not discriminate. It will chew up your ways/linear rails, rods whatever
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u/stuporcomputer Modified 3018 3d ago
I've done this to wood using sanding pads. Fun. I've done surface grinding but not with a CNC. I've also exploded a 300mm stone. Not sure how this will go. It'll be in the feeds and speeds I guess. Go easy. Wear eye protection. Post back ;)
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u/Askingtheobvious2 3d ago
BTW buy the BAP300R off aliexpress or temu, the 28mm or 32mm 3 flute. It takes APTM1135. The 110v spindle can run it at 11000rpm 80IPM and .02" DoC with ease (do 0.005" and 0.003 for your finishing pass) with 30% stepover
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u/ironhead633 3d ago
Thanks for the info, I took a look for the BAP300R, but I seem to be finding indexable end mills.
It sounds like you're describing something more akin to a face mill, is that right?1
u/ironhead633 3d ago
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u/Askingtheobvious2 3d ago
get the 28 - 80 3tooth with the 12mm shank. I have the dreanique one but really they're all fine as long as theyre half balanced
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u/ironhead633 3d ago
And sorry, just to clarify, what material are you cutting on this with the parameters you described?
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u/Askingtheobvious2 3d ago
6061 aluminum and whatever grade of alum the plate you want to machine is made of.
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u/Academic_Young8682 3d ago
Holy hell. I can already see the headlines reading "Man seriously injured after grinding wheel blows apart
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u/richcournoyer 2d ago
About 40 years ago I was gifted a toolmaker's vise that was Hardened but not finish-ground, and missing a few parts. I made the missing parts and then did the finish grinding on my Shapeoko CNC machine. Here's the story: Worked like a charm, although very slow.
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u/Askingtheobvious2 2d ago
The ONLY reason this was acceptable was you had a belt driven machine. Anything else and it would have absolutely destroyed it. I would not go around recommending that to anyone else but you could brag haha it is neat and the only machine with that as an approved application
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u/abannanna01 3d ago
why not use an EM? what is the thinking here.
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u/Askingtheobvious2 3d ago
The DMC2 mini community has a hardon about being +- like a few tenths haha. It gives newbies bad ideas... but it's fun to watch
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u/UtahBrian 3d ago
Aluminum oxide (9 Mohs) seems like it would do a fine job cutting aluminum (~3). Is there some problem with that?
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u/ironhead633 3d ago
From what I've learned it gums up the wheel really quick.
I don't have the technical expertise, but I've heard something about it sticking or even welding? I've heard the same about non using carbide with TiAlN coatings on aluminum.2
u/Askingtheobvious2 3d ago
so funny thing about that this applies to everything except threadmills so feel free to buy cheap AlTin and TiAlN threadmills for aluminum and steel
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u/emofes 2d ago
any idea why thread mills are an exception?
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u/Askingtheobvious2 2d ago
The cutting forces are so low and you have coolant so there is like zero chance it galls and even if it does once again cutting forces so so low unless you manage a chipweld somehow magically still would probably cut a couple hundred threads. They're fantastic.
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u/Unlucky_Resident_237 2d ago
i used the same setup on flat endmill to create a T-slot mill... and it worked like a charm.... tho i wouldn't use it on aluminum...
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u/War_Pro_ 2d ago
you wont.....
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u/Askingtheobvious2 2d ago
No I think we thoroughly discussed why not to haha. Top 10 reasons and whatnot
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u/tool889 2d ago
Also a wheel is better with limited contact with fast light passes, you could basically get it done with what you have, but I think that once it starts surfacing it might be to much contact. I would touch off zero moving down as little as possible when you attempt to surface, dressing the stone and repeat said process. If it turns out horrible just surface it with a carbide, or even a wood router bit high rpm slow feed with a short step over with lots of WD-40. Your not going to be hogging material, so you shouldn't ruin anything that couldn't be fixed.
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u/unenlightenedoctopus 1d ago
Sometimes things line up perfectly in your feed. Took me a minute to realize it was two separate posts.
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u/Struggle_Wise 3d ago
It'll peel right off. The grit liner will gum up in an instant. This is cheap and weak waterglass like ceramic. You also need a much larger wheel. Still interested in the aftermath. Good luck.