working with rough aluminum castings?

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Actually, I was thinking of a 7" disc grinder, or a 4½" disc grinder or something like that. I do have a really coarse Pferd wheel I could try, and I could try beeswax or bandsaw stick lube. I'm not going to try for a superfine finish because these castings have imperfections and they're going to need a fair amount of Bondo already, so this job's going to be putty city. I just don't want to destroy a bunch of grinding wheels.

GWE

Roy wrote:

Don't do this. first of all you will load up the stone real quick, and then you are not grinding, you are burning. Worst case you will crack your wheel and send flying chunks of wheel at high speeds.

A sanding disk with an open coat is the right abrasive for this task. You can probably get one for your grinder.

I'm not going to try for a superfine

You will be able to get a pretty good finish with the sand paper and then only have to fill the voids.

Body file? Wood rasp? Gerry :-)} London, Canada

There are grinding wheels made for grinding non-ferrous metals, including aluminum, that don't load up. You should be able to get them at your local welding supply house.

Sanding discs at high speed -- NOT grinding wheels! Get a rotary pneumatic disc sander if you don't already have one. * Not* a dual action, just one that spins fast. They typically come with fiber backing discs for the abrasive disc. Imports are cheap and work well.

Here's one, though I don't know about the Jacobs chuck wrinkle:

This one is more like the one I use: I've been using my $29.95 import for 20 years, still works fine. A

40 grit disc will remove a lot of aluminum quite quickly without clogging, and will last a surprisingly long time. I don't use any wax or anything, just run it dry. You can find the discs at welding stores and places that sell supplies (paint etc) for autobody repair. They're heavy discs with no adhesive; they're held in place by the nut on the sander.

Grant Erwin wrote in news: snipped-for-privacy@corp.supernews.com:

Grant, You would be MUCH better off using a 80 or 100 grit flap wheel on the side grinder, not a regular grinding wheel.

Use a aluminum grinding wheel and it should work fine. Then a flapper wheel to finish it off.

Many DA orbital (dual-action) sanders had some mechanical means of setting the eccentric hub to a locked position, so the orbital action was stopped. Then a fine or medium coarse sandpaper disk could be used as either a disk grinder or polisher. Tip: if the glue heats up, the disk lets go, so stop and check the pad temperature once in a while. A flying paper disk won't take an arm off, but it's capable of causing a little damage if it hits and scratches a windshield or some other collateral damage.

Some 4-1/2" angle grinders come with a hub adapter and backer disk for using the flexible tough fabric-backed grinding disks with holes in them. The adapter, backup disk and a flush nut were included with my Skill grinder. I think those grinding disks are resin bonded abrasive (look like belts), and are best used starting at the edge, then gradually lowering the contact angle as the outer edge dulls (not gonna be a big problem with aluminum though).

Those high speed pistol grip air grinders are handy for rippng through finishing products, knocking down rust and even body filler. Messy, but fast at leveling fiberglass.

WB ............

Wood rasp sounds goofy, but I've used the really prickly type, the ones that the teeth actually stand up from the file, on aluminum, brass and cast iron. They also work great for roughing up a fiberglass repair area.. just zips thru gel coat and gets the repair area prepped for patching. I epoxied one to a length of flat aluminum stock, to cut on the pull stroke. A grinder works, but then you're in a cloud of glass dust. The teeth are in staggered rows on the one I've used, and it helps to guide it with a sideways slip/drift while advancing it along it's length. For a half-round, a little rotation in the stroke does the same thing.

The cheese grater type body filler files have fairly fragile cutting edges, and the edge exposure is limited. The Vixen type (deep parallel gullets) files used for leveling/shaping body lead are probably best saved for something that soft.

As for real metal files, I really enjoy finding the quality brands with really coarse-set teeth in like new condition at flea markets for .50 or a buck. Found one that looked as though it had paint spilled on it, and the exposed end was still very sharp, under the paint the like-new file had been well protected by the spillage.

WB ............

I have a pretty intensely coarse file intended only for soft metals, and I got all the "low hanging fruit" already. What's left, were I to file it off, would be backbreaking and very tedious, several hours.

I took Ernie's suggestion and spent a whole $6 on a 7" aluminum grinding wheel. I'll pop that sucker on the 7" Skil oilfield grinder Gunner furnished me with, wear really excellent eye and ear protection, clamp the work down firmly, and have at it. I'll post results. I never knew there were actual grinding wheels made for aluminum. Figures, but I just never knew.

Grant

Wild Bill wrote: