I'm trying to get the pitting out of cast aluminum intake manifolds I polish. I was going to go with a clean and strip wheel like 3M, but read it doesn't remove material - which is something I'm trying to do for sure. I use a dremel tool with 60 grit sanding tubes for the tight spots, but need something for the flatter spots that takes off material quick to get past the pitting. You guys know of a good grinder that can take aluminum down without durning or destroying it?
Much appreciated.

Try actually using the Scotch-Brite

I think this is what nett is referring to.
Harbor Freight Tools - Quality Tools at the Lowest Prices He beat me to it.

LDW, I was actually thinking industrial supply houses like Rutland Tool and Supply. Harbor Freight has disappointed me more times than I care to count. Rutland has the really GOOD stuff.

Rutland Tool - Abrasive Products - Category

Thanks for the quick responses guys. I was thinking a cup wheel, because although it's made out of the same material as the clean and strip discs it looks like it good take off some serious material. What does that attach to? I'm assuming i'll need a right angle grinder? Problem i see is it might be too wide to fit into most of the manifold's area therfore limiting its use - however effective.
I'm thinking a 4" dia 1/4" thick edge grinder, which will also use a angle grinder. Maybe use a softer one? I'll just drag it along the surface i guess.

Actually i dont see how i'd get this tool to access much of the manifold at all:

Edited January 8, 200917 yr by Cobra

I think this is what i'm going to do:
$35 craftsman angle grinder:
Craftsman 4-1/2 in. Angle Grinder - Model 11651 at Sears.com

and 24 grit 4" metal grinding wheel, because the grinder says it can take 4"-9" appearently, and smaller is better
Craftsman 4 in. Grinding Wheel, 24 grit Metal Work - Model 28440 at Sears.com

I wish it was wider than 1/4" as I don't actually want to cut the metal, just grind off the surface. But i dont see another option.

I'm going to buy some zirconia flap discs tomorrow too:
10 Zirconia Flap Disc 4" x 5/8" Grit 40,60,80,120- T29 - eBay (item 220339459824 end time Feb-03-09 10:11:24 PST)

7 40 grit, 2 60 grit, and 1 80 grit

Supposedly they hold up pretty well. Let me know what you guys think. Thanks!

Cobra,
If you have a small air compressor look at getting a die grinder. Some don't use much more than 4 cu ft of air to operate and you can get a variety of stones to use as well as various carbide or diamond burrs for real aggressive stock removal. There are several grades of stones that range from aggressive to polishing grits and with a diamond block you can shape the stone to fit the cavity you are trying to grind. They also come in a large variety of diameters and shapes to begin with and you can probably buy them to suit your purpose.

Cobra,
If you have a small air compressor look at getting a die grinder. Some don't use much more than 4 cu ft of air to operate and you can get a variety of stones to use as well as various carbide or diamond burrs for real aggressive stock removal. There are several grades of stones that range from aggressive to polishing grits and with a diamond block you can shape the stone to fit the cavity you are trying to grind. They also come in a large variety of diameters and shapes to begin with and you can probably buy them to suit your purpose.

I totally agree with TASMITH, as many nooks and crannies as you have this would be your best bet. IF you have air compressor.

I've used the different stones, because you can use them with a dremel, and the gunk up. It smoothe over with aluminum that fills up the "pores", plus it's load and the air compressor is loud. And i dont want to make any less friends around here as its a townhouse community, the angle grinder is loud but im not using it for very long.

Cobra,
I'm a professinal deburrer and I'll suggest a grinder (staight or angle) whit 1/4 shank whit flap wheel gr80, Scotch-Brite™ flap brush and for finishing the Hand pad.
The hand pad you can cut it in four parts and mount on a mandrel and use it like flap wheel.
If you want I can post tomorrow all 3m code, about the grinder you can find some electric grider whit 1/4" collet.

Can someone tell me if this shaft play is normal? This is the kind of thing when you know a supercharger is done, but dunno if it's normal in an angle grinder. The box was worn, i think someone brought it back. So im worry this play is a bad sign.
YouTube - Angle Grinder: This normal

BTw, these things are loud! I need to find another place to use it, this will xxxx of my neighbors. So much for more home projects with this manifold design.

Can someone tell me if this shaft play is normal? This is the kind of thing when you know a supercharger is done, but dunno if it's normal in an angle grinder. The box was worn, i think someone brought it back. So im worry this play is a bad sign.
YouTube - Angle Grinder: This normal

BTw, these things are loud! I need to find another place to use it, this will xxxx of my neighbors. So much for more home projects with this manifold design.

Cobra don't worry I saw the movie the angle grinder it's ok:D

Don't use that stone, its for ferrous materials, NOT aluminum. It will load up, stop cutting, start producing heat and run the risk of violently breaking apart. Use sanding discs. or 3M type abrasive deburring wheels.

deburring wheels - Google Image Search

I would go back to the foundry and ask them what they are using to degas the liquid aluminum. We made better castings than that in college! Tell them to try putting some potassim chloride on top of the metal in the ladle. You shouldn't have to put up with those gas pockets.

The pitting isn't throughout, just on top. Onece you get past the surface its gone. I'm mainly using zirconia flap discs right now and it seems to work. Although i havent been able to do much lately.

I don't do a lot of casting, and never Al. Having qualified my lack of experience , I have to say that those do look like gas bubbles. A better job of degassing should remove most of those from the cast. Also its possibly from too high a moisture content of the sand.

It's not bubbles, guys. I've seen a fully polished ones and it looks like chrome plating. I polish lots of Ford aluminum parts, and it's always crappy casting with good stuff underneath. Here is how it look after a 80grit zirconia disc (heavier scratches were from 40 grit which is too aggressive), i havent been able to use it long at all as i need to go over to a friends house where loudness isnt an issue.


The grinding wheel was just a bad idea, too heavy a method - it just cuts aluminum.

Edited January 13, 200917 yr by Cobra

Anyone know if there's a hard media blasting process that can take this down some? Like aluminum oxide or silicon carbide blasting? The small areas are really hard to get to.

Edited January 14, 200917 yr by Cobra