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Old 21st July 2004, 01:25 PM   #1
Vikash is offline Vikash  United Kingdom
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Unhappy Case and metal working

I've recieved my aluminium pieces from a metal supermarket and I'm quite disappointed to the finish on the cuts. The cut sides look like a tile that as been scored and snapped.

Anyway, it looks like I'll have to triim them down and wanted to know the best way to do this as I've never done any metal work before. I've got a cheap router on a very crude diy table, and a table saw. Can I use a normal tct router bit or the standard blade that came with my table saw? Which would I get a better finish with?

Also, can anything be done about the scratches on the pannels?

Max pannel thickness is 6mm and material is aluminium or copper.
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Old 21st July 2004, 01:36 PM   #2
MWP is offline MWP  Australia
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Eeek, no dont use router bits... esp as i imagine they are for woodwork.
I dont quite know what would happen (i havnt tried it), but i dont think you would like the results.

Just use a simple hand file.
Copper and Aluminium are quite easy to file by hand.
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Old 21st July 2004, 01:38 PM   #3
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I would say get some sandpaper and alot of elbow grease. You can get rid of the scratches, and leave a nice finish starting with 220 grit paper and working up to 600 or so. Get the wet/dry stuff and sand the panels under running water to keep the sandpaper from clogging. It shouldn't take too long to get what you want.











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Old 21st July 2004, 03:07 PM   #4
widman is offline widman  United States
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I used a carbide tipped saw blade on my table saw to cut aluminum for an amp case. Generally I would make an rough cut, about 1/16" oversized, and then take a second pass to remove the final material. Light sanding cleaned up the tool marks left by the carbide.

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Old 21st July 2004, 10:28 PM   #5
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of course another option is to go to a local machine shop and ask them to cut for you... I had a similar problem last year when I ordered from onlinemetals.com. I had the panels cut and brushed for $20US and did the rest of the machining myself...

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Old 21st July 2004, 10:50 PM   #6
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Don't use table saw or router, if you don't have experience with working on metals, the finish won't be good anyway. Easiest way to finish edges is by using belt sander and 100-120 grid paper. If not available, use a wooden block, sanpaper and your hands. Sometimes additional board helps in guiding your block to achieve straight lines. Using soap as lubricant helps too.
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Old 22nd July 2004, 12:51 AM   #7
Vikash is offline Vikash  United Kingdom
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Quote:
Don't use table saw or router, if you don't have experience with working on metals, the finish won't be good anyway.
I feel like having a go at using the table saw and I've ordered an "80 tooth 250mm 6 degree negative rake non-ferrous tct cutter" from ebay. But now reading your post Peter, is it so much more difficult that you wouldn't recommend it to the novice?

I've recently invested in a myford lathe, pillar drill press, and scroll saw with full intent of learning to work with metal

I do have a belt sander, but I think there may be more than just sanding work required on this job as some of the pieces haven't even been cut square or perfectly straight. I've never purchased from a raw metal merchant before so I don't know if this typical.
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Old 22nd July 2004, 12:55 AM   #8
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You have a proper blade, so it's a first step. Cutting aluminum is not that much different than wood, so if you feel up to it, go for it. Just use safety glasses (they really neccessary) and make sure your hands are never close to work piece.

Here's how I do it: http://www.diyaudio.com/forums/showt...ht=#post376414
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Old 22nd July 2004, 01:05 AM   #9
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Before anyone tries power tools on metal, I really believe they should learn how the material reacts to hand tools. While the techniques are all similar, I have to say that when aluminum decides to resist, it is a different animal than wood or even steel.

IME, use a good 18 tooth hacksaw for most cutting, then use finer and finer cut files shape it down. Watch the "heat" or you end up with "melted" material on your files. If you have a band saw or scroll saw, even better. I've never tried a table saw on aluminum... the risks of "binding" seem too high. If you use the correct type of good quality blades and files with good bite, it shouldn't take much longer than power tools and there is much less risk of injury.

If the surfaces are scratched, there is probably nothing you can do to restore the original mill finish. But you can always give it a "brushed" look by sanding it in one direction only. Don't go back and forth. The aluminum will self-anodize after a time.

:)ensen.
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Old 22nd July 2004, 02:49 AM   #10
cjd is offline cjd  United States
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For rough finishing, a ******* mill file is my tool of choice. Where a different shape is needed (say, concave curves) a different shaped file is needed.

From there, I occasionally move to some light work with 120grit emery paper, lots of water. Normally, straight from the file to 220, 400, and 600. 600 gives a really nice satin finish, and can be buffed to a nifty sheen with scotch-brite - again, lots of water. You can go to a standard bobbing compound buff from 600 grit as well. If you want flat, get yourself a sheet of 1/4" or thicker glass and place the wet paper on it (grit side up, of course).

If you have experience working with very hard woods on your TS, you'll find it machines similarly to aluminum with one key difference - heat changes the size of metal. The key is to take your time. Heat is your enemy in a very big way, so taking the cut really slow is good (heat can cause it to bind faster than you know how to say aluminum through your stomach). Aside from shape, heat also makes aluminum gummy. I recommend wearing long pants and shirt. Gloves are quit useful if they fit close enough for you to be able to know what's going on. Full eye protection is a must (I use a full face shield) The metal shavings can do *severe* eye damage if one but gets caught in a corner.

FWIW, you can get results as good with hand tools as with power tools, and it only takes a little more time. I don't like working metal with a power sander at all.

edit: one comment - aluminum will NOT self-anodize. It will certainly patina, which can have a very similar result visually. (all metals do this btw - it actually provides a barrier, so constantly polishing the silver is technically NOT the best way to get it to last, but it sure looks purty).

C
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