Hi,

I make some small aluminum parts and sometimes the surface has imperfections, either extrusion lines or scratches and such. I was looking at surface grinders and thought maybe this would be an effective way of getting rid of the imperfections. From what I can tell, most people use magnets to hold down the parts during surface grinding. This obviously wouldn't work for aluminum. Then I thought maybe I could use a vacuum plate. Would this work? How else can you hold down an aluminum part for surface grinding?

I've attached a picture of the parts I'm trying to surface grind if that is any help.

http://www.laptimerholders.com/images/lth/LapTimersAno.jpg

Thanks,

Craig

what you want to do is called grainning or sanding. Grainning is when you sand in the direction of the materail grain.Sanding welll you know what that is.Try a little finish or orbiting sander. It is possible to surface grind Alum but your dealing with finish not flatness. Also those specail Alum. magnetic table cost a lot of money and you may have trouble finding a maker of one.

Hi Mike,

Thanks for the quick reply. Sanding might be an alternative, can you recommend a particular grit of sandpaper? I have the wet tumbler and the dry tumbler to finish the parts so they come out looking like a mirror but it's the little scratches and such that then ruin the parts and the wet tumbler can't remove those.

Thanks again,

Craig

after tumbling use 280-600 grit. If your surface is unlformally scratched by sanding part it will look a lot better.A finish sander works the best where it keeps the scratches going in the same direction.A piece of carpet pad makes for a good mat on table to sand on.

If the quantity justifies buying a machine you could consider using a drum sander made for finishing wood. I think this is the name; it has a larger roller covered with sanding material that can be adjusted above a table. The wood is pushed through with feed rollers or maybe there is a feed roller sunk in the table directly below the sanding roller.

For your parts I suggest machining matching pockets in a length of wood, plastic or aluminum, put the parts in the pockets to get carried through the sander. Something like 180 grit would give a good finish if the marks are not too deep.

Or if the surface doesn't have to be mirror, use a small sandblast cabinet with some fine glass beads in it. This gives a nice even matte finish to aluminum. Could do this first and then if still desired run through the tumblers.

JP

Or, just use two sided tape and mount them on the grinder table with a stop bar to prevent them taking off in the opposite direction

If you're not specific about mirror finish, you can use Wire brushing for your parts. Alternatively you can also consider using Sand Blasting.

Alum can be surface ground,its easy to do with rich water soluble as coolant. Not sure what the stock looks like before you cut these out but,that may be the time to deal with scratches etc. 180 or so wet or dry used wet with soapy water will blend things well. The soapy water makes a big difference in appearance and life of the paper. Use rubber cement to hold it down to a flat plate for lapping. Grinding may be overdoing it.