Surfacing aluminum parts

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Forum topic by GregD posted 11-01-2011 03:37 AM 1225 views 0 times favorited 8 replies Add to Favorites Watch
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788 posts in 3341 days

11-01-2011 03:37 AM

Topic tags/keywords: question

Any suggestions for flattening the surface of an aluminum bracket? The surface is about 6” long and 2” wide. I would like to be able to take a straightedge to it and not see any slivers of light.

The bracket is too large for the sanding disk on my bench top disk/belt sander (6” disk I think). I suspect the belt sander would tend to grind the edges of the part more than the center section.

I was thinking about putting PSA sandpaper on my table saw table and try to sand out the imperfections that way. I might have to grind away a 0.002” give or take a factor of 2. Is this likely to work?

-- Greg D.

8 replies so far

View Loren's profile


10477 posts in 3853 days

#1 posted 11-01-2011 04:17 AM

Yes. A sheet of plate glass may be flatter than your table saw. You
can get abrasive dust, diamond dust or whatever, and grind the metal
against the glass with a slurry of abrasive and water in between.

View Sawkerf's profile


1730 posts in 3274 days

#2 posted 11-01-2011 04:37 AM

Depending on how non-flat your aluminum is, I would do it like you flatten a plane sole. A piece of glass, or other flat surface, some sandpaper, and a spray bottle of water.

I would probably start with a 120 grit and work my way up to whatever grit gives you the surface you want.

-- Adversity doesn't build reveals it.

View David Grimes's profile

David Grimes

2078 posts in 2845 days

#3 posted 11-01-2011 05:17 AM

+1×2 ^ ... the first like a lapmaster and the 2nd like a plane sole. Either will work and the aluminum will not take forever. You don’t state the gauge of the material, but if very thin (i.e flexible / easily deflected) ) then do not push down too hard or you’ll never get it flat.

-- If you're going to stir the pot, think BIG spoon or SMALL boat paddle. David Grimes, Georgia

View helluvawreck's profile


32087 posts in 3072 days

#4 posted 11-01-2011 03:14 PM

I have heard of people grinding aluminum with some hard and soft rubber wheels of some sort. I have heard that it is dangerous to grind aluminum on a grinder that you also use to grind steel with because of mixing aluminum with steel particles. It’s a safety hazard. However, I don’t have a lot of experience with machining aluminum because we use mostly steel and cast iron in our machine shop.

-- helluvawreck aka Charles,

View GregD's profile


788 posts in 3341 days

#5 posted 11-03-2011 03:32 AM

Thanks for the suggestions.

The parts are about 1/4” thick, so I don’t think they will flex significantly.

Will window glass work?

I know people flatten plane soles doing something like this, but I don’t know the details. Since Sawkerf suggests a spray bottle, do I need to get a particular type of sand paper? I was going to glue down some sandpaper and have at it.

-- Greg D.

View Grandpa's profile


3261 posts in 2881 days

#6 posted 11-03-2011 04:46 AM

Use wet and dry sand paper. I wouldn’t think you would need to use 120 if you are only taking off .002”. Maybe though….I am no expert in this area. Wet and dry cuts pretty quickly when you keep it wet.

View Sawkerf's profile


1730 posts in 3274 days

#7 posted 11-03-2011 05:18 AM

I use a piece of solid surface counter material and wet/dry sandpaper. I spritz the solid surface material to hold the sand paper, then spritz the sandpaper before I start lapping. I use this method to sharpen plane irons and chisels (with finer grits, of course) and have used it with coarser sandpaper to flatten 4-5 plane soles.

-- Adversity doesn't build reveals it.

View GregD's profile


788 posts in 3341 days

#8 posted 11-03-2011 02:43 PM

Great. Thanks for the help.

-- Greg D.

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