PDA

View Full Version : OT: Metal Finishing..



3 Phase Lightbulb
05-01-2005, 10:50 AM
[O]n [T]opic: Metal Finishing

I've been playing with aluminum and was wondering what the proper finishing techniques are? I remove machine marks with a disk sander, then remove the disk sander marks by hand sanding..

What do real metal finishing folks do?

What kinds of finishing tool(s) are used?

-Adrian

snowman
05-01-2005, 11:00 AM
Good question.

Lets add another variable. Initial state it cast.

Needs to be polished shiny by the time it is ready to ship.

What would your most efficient process be?

-Jacob

topct
05-01-2005, 11:31 AM
Just tried to put a link to this subject in the search function but it didn't seem to work?

Try typing in Aluminum polishing in there.

One tool I like to recomend is one or two of those old Black and Decker vibrating sanders. I have two. One with 220 and one with 400 or 600 wet or dry paper and some Wd40 or aluminum cutting oil.

Wear some rubber gloves this is real dirty work.

------------------
Gene

[This message has been edited by topct (edited 05-01-2005).]

WJHartson
05-01-2005, 11:38 AM
Surface finish on large flat pieces and full sheet can be done on large drum sanders with scotch brite rolls. Smaller parts can be burnished, polished and deburred using a tumbler with a varity of media and cleaning compounds.

For cast parts tumbling with different media can go from rough surface to polish over time. Depending on the as cast surface some hand work may be required prior to tumbling.

Joe

plm
05-01-2005, 11:56 AM
3 Phase, Snowman,

In general, here is what I do for aluminum and brass:

Using a flow-thru vibratory tumbler filled with medium or fine plastic media, I will tumble for 18 to 36 hours. This will deburr and get rid of the machining marks.

To get a mirror-like polish, I will tumble in walnut shells treated with rouge powder for about 12 to 24 hours.

Time consuming, yes; but, no elbow grease involved.

You can experiment with different types of media and times. Sometimes I might use a more aggressive media, like ceramic, for a short amount of time and then go to the less aggressive plastic.

I bought Ron Newman’s manual on home anodizing that covers making tumblers, finishing and, of course, anodizing – I think it is about $25, here’s the link:

http://www.focuser.com/atm/anodize/anodize.html

It helps if you have more than one tumbler or, at least multiple bowls containing the different media you might be using.

Hope this helps.

plm



[This message has been edited by plm (edited 05-01-2005).]

plm
05-01-2005, 11:57 AM
[This message has been edited by plm (edited 05-01-2005).]

[This message has been edited by plm (edited 05-01-2005).]

plm
05-01-2005, 11:58 AM
Oops again. I must of spilled a Pepsi in my keboard or hit a wron button.

[This message has been edited by plm (edited 05-01-2005).]

ibewgypsie
05-01-2005, 12:20 PM
Purchase a velcro pad for a 4" grinder, stickback scotchbrite pads work. If you need to abrade down evenly start out with sticky sanding discs.

Kinda expensive but once you get the backing pad it is relatively cheap. I saw a similar product at (*choke) HF. Much cheaper than the welding shops.

Stainless is my love. Slick, shiny, hard and frustrating to work with.

David

Joel
05-01-2005, 03:41 PM
Belt sanders work pretty well with aluminum. A long belt tends to self clean and run cool.

As you already know, you just have to work through the grits, removing the sanding scratches from the previous coarser grit to get a smooth finish. I use a brushed finish whenever possible to save time and effort. I probably use a ‘Scotchbrite finish’ most of the time. It looks quite nice and is reasonably easy to achieve.

My most used belt sander usually has a well worn, fine belt on it. This works well for getting small, low tolerance parts smoothed out. You can keep a medium grit on the disk side for roughing and smoothing. 2 belt/disc sanders really helps to cut down on the abrasive changes.

A flat flap disk on an angle grinder is invaluable for many roughing jobs (especially welds). Carbide burrs, wire brushes, and rotary abrasive wheels also see a lot of use.

For many parts, a woodworkers DA sander does the fastest job of working your way down through the grits. The hook and loop disks make for quick disc changes (the fact that you can reuse them is very handy). I then switch to Scotchbrite, getting the tighter corners by hand or with other power tools, then hitting the flat surfaces with the DA. I then switch to buffs and compounds if a mirror finish is necessary. A grey or maroon Scotchbrite finish is usually plenty good, and holds up well to handling. It is also easy to do a quick buff and bring the finish back. 3M Roloc disks are useful at times.

Fine grits (320-2,000) of wet/dry sandpaper, wire brushes, Craytex rubberized abrasives, felt buffs, and other various items are also sometimes used. It just depends on the part’s shape, size, and finish I need. I have been meaning to try 3M’s Trizac abrasives ($$).

I have 5 or 6 wheel grinders, maybe 7 die grinders, a host of power hand sanders, and 3 belt sanders loaded with various abrasives, wire wheels, buffs, and such. I don’t like to change wheels and belts any more frequently than I must. I also have foam pads for the drill and DA that work great for buffing with automotive compounds. I sometimes start off with a 3M rubbing compound, then switch to Imperial Microfinish (my most used), then finish up with FinesseIt for that ‘mirror’ finish.

Stainless is the biggest pain to get from a fabricated finish to a mirror finish, aluminum is the easiest.
BTW, I am not a “real” metal finisher, but I have done everything from production parts to automotive paint jobs with good success.

-Cross posted at bbssystem.com-