Drilling aluminum

[Magura]

Originally posted by ashok
Thanks chipco3434 .
As we are on the topic of machining aluminum I have a couple of other questions.
1. Is it better to use a lubricant when brush finishing aluminum or is it better to do it dry ? Lubricant would take away particles that could spoil the surface (?).
2. Is it better to use a rotary wire brush ( or rotary pack of emery type sheets ) or a belt sander ?
Thanks.

A coarse scotchbrite pad will work just by hand, and gives consistency you your work. As far as I remember it, it's the brown version (they're colour coded) that gives some of the best results.


Magura

[mantisory]

thanks a lot you guys - awesome load of info here!
I think i will try the gloveless, clamped, (cheap) forstner bit method with some lube - have some tapping oil around somewhere...
the finish is another thing...i am also going to try some home anodizing at some point but am trying to source out a cheaper alternative to the 500$ power supplies at Caswell plating...maybe i will go with that frosted look with the orbital sander first...looks real nice!
Byron

[jol50]

If you use fine paper at high speed it will shine, but leaves a pattern. I used a DA locked with about 320 or 400 grit paper at high speed very lightly. Did an aluminum finned cover on an engine so pattern did not show. I put base color on it then sanded/polished or whatever you call it, then cleared it all and it looked very nice. You can sand it fine and buff it if you want to work it down that far. It will look like chrome, then clear it to keep the finish...just like machined car wheels. I used automotive urethane clear. You can even use the gray scotch pad(2000 grit) and clear will cover it, after you have shined it up. The red pad is for paint, it is 600 I think. They are perfect for doing edges and contours.

[Peter Daniel]

The coarse Scotch Brite pad has a tan color and works OK, IF the surface is in reasonable shape, no deep scratches.

It is rather hard to remove scratches with a pad and after a while you will get corner rounding which may affect final look of the panel.

I smooth out all the scratches first with fine sandpaper (150-300 grit), use coarse pad and after that general purpose pad which is maroon color.

However, to get truly professional finish a belt sander is recommended. So far, I was using 6x48 belts with good results. Such short belts need a lubricant and Varsol is my first choice http://www.recochem.com/english/products/faqs.html
I used WD40 few times but it's messy, sticky, dissolves glue in belts and as such is not recommended.

80 grit paper usually worked fine and I didn't dare to go lower.

I recently acquired heavy duty oscillating sander which works with 6x99 belts and here I found that no lubrication, 60 grit belts perform best.

After belt sander I usually smooth out the finish with Scotch Brite pad: http://cc.msnscache.com/cache.aspx?q...957&FORM=CVRE5