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Any suggestions for polishing aluminum castings where the metal is left bare rather than painted? I'm looking for a regimen of increasingly fine grades of abrasive, and then polish, to get the job done as quickly as possible, especially if starting with a casting that was not originally polished or that needs scratches taken out (my Firebird, was worked over by someone who thought that re-polishing it with a wire brush power attachment was a good idea, but which of course scores and scratches a soft metal like aluminum)

Also, given that I'm sure that doing it myself will be time-consuming if not a trial-and-error process, is there anyone good to send castings to for polishing? I don't know of a local polishing shop that I'd trust, and in my experience, especially with silverware, they often polish very heavily to get quick results and wear down the detail of the metal excessively.

Thanks,



JP

I use an 8 inch buffing wheel with 80 grit compound. I've made the following observations

1) Home Depot and Lowes brand compounds leave a lot of residue on the aluminum making it very difficult to gauge polishing progress
2) I buy my wheels and compounds from McMaster Car. They literally arrive the next day for regular ground shipping prices.
3) I use 80 grit compound on aluminum which cuts through the corrosion and scratches without the need for finer compounds. One grit polishes nicely.
4) Don't use Harbor Freight wheels, they throw threads and fabric all over you and the shop. Then disintegrate quickly.

Note the following link is a 2 1/2 pound block of compound! It's not the small packages sold at the hardware stores.
http://www.mcmaster.com/#4795a1/=wtjiw6

The following slot stand legs were polished using only 80 grit buffing compound from McMaster

You can see no detail was lost. If you want to have the work done by a company that specializes in slot machines email Dave Berten at http://mrslot1.com/




I hope this info helps! Good luck and be careful with those buffing wheels, never buff with the edge of the work facing up, always facing down. The wheel will grab the work and yank it right out of your hand.

Jerry

Truchaos, what type of buffing wheels do you recommend? I used the cloth type and it left a mess all over the garage. I haven't used a buffer before and I need help. I'm in the process of restoring a war eagle and it needs polishing. Can you please post the types of buffing wheels you recommend? Thanks in advance.

Here's what's in my shop. I have been using these 8 in. wheels, stacked two or three at a time:

http://www.mcmaster.com/#4819a13/=wujqof

on a Harbor Freight grinder/polisher:

http://www.harborfreight.com/8-inch-bench-grinder-buffer-94327.html

mounted on a low-rent stand:

http://www.harborfreight.com/catalogsearch/result?q=grinder+stand

Be forewarned, though. This stand is about as cheap as they get and you MUST bolt it to the floor, otherwise, it will walk its way right out of your shop like it were on ball bearings.

Here's a better alternative. It's base is cast iron, so it is more rigid, but still needs to be bolted to the floor:

http://www.harborfreight.com/heavy-duty-bench-grinder-pedestal-68321.html

Also, throw away the Harbor Freight grinding wheel (you can never balance it no matter what you do) and replace it with a decent wire brush wheel:

http://www.mcmaster.com/#4840a39/=wujtlu

Finally, if you REALLY want to be cool, one of these on the end of the motor shaft will cover all the curves:

http://www.mcmaster.com/#buffing-wheels-for-angle-polishers/=wuk3s4

Get a rubber bib and face mask then go at it. And put it in the corner of your shop where the debris can be contained.

For those who do not want to do their own polishing ( it really is a messy job!!), I use the same people who my plating.
they are the best I have found.
They are knowledgable, fast, and reasonably priced.
you won't be disappointed.
others on this site have used them, and been pleased.
take a look at their website.
http://spacecoast-plating.com/

^ What MidcoastVintage said. Per his recommendation, I recently sent several items to this company for plating, they did an excellent job, and had the parts back within about 2.5 weeks.

Truchaos wrote:I use an 8 inch buffing wheel with 80 grit compound. I've made the following observations

1) Home Depot and Lowes brand compounds leave a lot of residue on the aluminum making it very difficult to gauge polishing progress
2) I buy my wheels and compounds from McMaster Car. They literally arrive the next day for regular ground shipping prices.
3) I use 80 grit compound on aluminum which cuts through the corrosion and scratches without the need for finer compounds. One grit polishes nicely.
4) Don't use Harbor Freight wheels, they throw threads and fabric all over you and the shop. Then disintegrate quickly.

Note the following link is a 2 1/2 pound block of compound! It's not the small packages sold at the hardware stores.
http://www.mcmaster.com/#4795a1/=wtjiw6

The following slot stand legs were polished using only 80 grit buffing compound from McMaster

You can see no detail was lost. If you want to have the work done by a company that specializes in slot machines email Dave Berten at http://mrslot1.com/

IMG_0935.JPG

I hope this info helps! Good luck and be careful with those buffing wheels, never buff with the edge of the work facing up, always facing down. The wheel will grab the work and yank it right out of your hand.

Jerry

Thanks.

That would work for things like the ornate legs you show. I need to polish a casting that has flat surfaces, and that has some flaws like scratches that need to be taken out. Also, what you run into - and I may find under one of my projects - is that you have a casting that the factory painted rather than polished on that particular production run, and then you have areas that have a rough/pebbled casting finish that a buffing wheel will only smooth out a bit but not flatten, and you have to take it down flat with hard mounted abrasives first. What I'm familiar with in cases like that, is that you start with a hard backing pad or belt mount that is going to keep the flat of the surface, and use some rougher grit abrasive/sandpaper like 220, usually going one direction, then go the other direction with something finer like 3200 until you've taken out the scratches from the previous pass, and then do the same again with 400, until it's finally ready for a buffing wheel - and maybe working through a couple of increasingly finer abrasives on that - to get the final polish. The trick to making it go right, and quickly, is to know between the material and the conditions - both of the original casting, which may have some remaining roughness that needs to be worked out, and of any scratching or other surface damage - what grit to start out with and to finish up with, so that you're not working any harder or making any more passes than you need to. If you try to use a buffer for all of a job like that, in the process of taking enough material off you end up excessively rounding edges that should be kind of sharp, blurring details, and so on. Sometimes for individual dents or flaws you do need to work in to them with sandpaper and fingers, and then a small buffer, to try to make them disappear as much as possible, even if you're never going to actually get them flat.

Maybe the 80 grit you describe will suffice for a single-pass final polish, without even having to get too fine with the hard abrasives pass/es, but I know that I need to work with sandpaper or a hard wheel first, that's what I'm trying to figure out. For starting with a really rough casting, the traditional recipe is to take about half a dozen steps from around 40 grit to around 600, before the final polish, but I know that I can get away with fewer steps on a slot casting, I'm just trying to figure out how few and how to do it most quickly. From observing just a few examples, I don't think that even Mills necessarily did that great a job in the old days, and put out polished fronts that were still a bit rough and scratchy.

Mendozaco wrote:Truchaos, what type of buffing wheels do you recommend? I used the cloth type and it left a mess all over the garage. I haven't used a buffer before and I need help. I'm in the process of restoring a war eagle and it needs polishing. Can you please post the types of buffing wheels you recommend? Thanks in advance.

Not getting into a long-winded discussion over the different types of buffing wheels, as it would take a booklet
to explain everything. I have been doing all of my buffing for many years, except for the cast iron jobs for the
plating shop. But even then, I have at times, sanded and lightly buffed original castings, that sometimes have
raised lumps from the factory, so that they turn out better when plated.
First of all, don't use cheap buffing wheels, as they do have a tendency to shred faster than the good quality
brands, as you will have a pile of cloth on the floor, deeper than your shoes. All buffing wheels will tend to
throw more particles around, until they are broken in. Also, do not rely on a single wheel, as they are too
narrow. Build the wheels up. Usually 4 to 6, depending on their single width. I learned the 'buffing mess' issue
a long time ago, and remedied the situation, by having just my small buffer, with 4" wheels, in the shop, for
small parts. I have a large buffer, on a heavy duty cast iron stand, (that does not walk), that I use for large jobs,
that I wheel to the yard on a hand truck, so that all the residue can fly into the wind. Besides, my wife doesn't
bitch about the mess, because I think she is convinced that it makes good fertilizer for her flowers.
On another note: DO NOT use cheap wire wheels for cleaning parts either, as you will find wire pieces all over
the shop as well. And by all means, Wear Good Eye Protection, as I have at times, had a wire stick in my forehead.

[

Maybe the 80 grit you describe will suffice for a single-pass final polish, without even having to get too fine with the hard abrasives pass/es, but I know that I need to work with sandpaper or a hard wheel first, that's what I'm trying to figure out. For starting with a really rough casting, the traditional recipe is to take about half a dozen steps from around 40 grit to around 600, before the final polish, but I know that I can get away with fewer steps on a slot casting, I'm just trying to figure out how few and how to do it most quickly. From observing just a few examples, I don't think that even Mills necessarily did that great a job in the old days, and put out polished fronts that were still a bit rough and scratchy.

I think you'd be surprised at how well a hard felt wheel will take out scratches on flat surfaces using a medium or somewhat coarse grit.

There are also other tools for grinding and polishing flat surfaces. I inherited one of these. https://www.youtube.com/watch?v=xHoWoRQ-9kI

Take your time and of course there is never any shame in having professional do it. Just get quotes as there seems to be a lot price variation.

Truchaos wrote:[

Maybe the 80 grit you describe will suffice for a single-pass final polish, without even having to get too fine with the hard abrasives pass/es, but I know that I need to work with sandpaper or a hard wheel first, that's what I'm trying to figure out. For starting with a really rough casting, the traditional recipe is to take about half a dozen steps from around 40 grit to around 600, before the final polish, but I know that I can get away with fewer steps on a slot casting, I'm just trying to figure out how few and how to do it most quickly. From observing just a few examples, I don't think that even Mills necessarily did that great a job in the old days, and put out polished fronts that were still a bit rough and scratchy.

I think you'd be surprised at how well a hard felt wheel will take out scratches on flat surfaces using a medium or somewhat coarse grit.

There are also other tools for grinding and polishing flat surfaces. I inherited one of these. https://www.youtube.com/watch?v=xHoWoRQ-9kI

Take your time and of course there is never any shame in having professional do it. Just get quotes as there seems to be a lot price variation.

Thanks, I didn't notice you referring to a hard felt wheel before, so I was assuming a regular cloth wheel, but I can imagine that doing a lot to take out scratches while keeping the surface flatter, and will give what you described a try.

I think I am going to face more than just regular scratches, or some areas of rough original casting surface that I want polished, and so I'm going to have figure out the best way to do some surface removal with hard (or belt) mounted abrasives, and then polish.