How do we mold/ drill/ bend/ shape the materials?

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How do we mold/ drill/ bend/ shape the materials?

Post by gregzeng » Tue Dec 03, 2002 8:28 pm

I'm not a chemist - just an ignorant ex-handyman.

1) with solid plastics - shaping/ cutting/ drilling use a heat-controlled soldering iron. But beware not to breath in the "fumes". Clean the soldering iron whilst hot with tissue/ toilet paper.

2) thin sheet-aluminum - cut with sheet cutters, jigsaw, hacksaw, .... ?

3) thick aluminum - electric grinding wheel ?

Please ... how do I handle aluminum ?
Retired: PC Support (h/w, s/w), Ex-company-director (non-profit sector)

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Post by crisspy » Tue Dec 03, 2002 9:35 pm

I've done lots of work with aluminum and sheet metal. Here's what I found to work well:
  1. Solid Plastics: Drilling with normal drill bits is cleanest, or for large holes a sharp hole saw or jigsaw. Cut with sawblades, handles very much like wood. Shape by filing, grinding, or sanding, but watch out for everheating/smearing at high speeds. Bend with a heat-gun, or for acrylic see tips in Want to suspend, but cable too short.... Also for plexiglass see The Ice Cube, which is a fantastic article + how to.
  2. Thin Sheet Aluminum: Cut with tin snips / sheet metal cutters / nibbler tool. Anything too thick for that is thick aluminum. Drill with very sharp drill bits, special sheet metal drill bits are even better.
  3. Thick Aluminum: Cut with very sharp saws. Carbide blades on tablesaws, chop saws, skill saws, and radial-arm saws are all great. You can get special carbide aluminum blades that make an extra clean cut, very nice but a bit pricy. Also cut with hole saws, jig saws, hack saws, etc. Jig saws are especially versatile (large selection of blades) and very safe. Shaping can be done with care using carbide router bits, or angle grinders with course-grit sandpaper, or special aluminum grinding wheels. All of the above works very well for brass too. In general, people who do aluminum fabrication use saws for most cutting. Basically think 'kind of like very hard wood', but be careful and go extra slow, and with circular saw blades use carbide and try to use blades with high tooth count. Also a warning: aluminum smears and plugs up normal grinding wheels very badly, and this can actually cause grinding wheels to overheat and shatter/explode/fly-apart (think of angle grinders here - gives me the shivers).
Cheers to the handymen of the world :)

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Post by Bat » Sun Jan 19, 2003 3:13 pm

Any tips for working with copper? Same as aluminium but softer and even more of a problem with grinding? How difficult is drilling narrow holes in thick copper?

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Post by DanceMan » Fri Jan 24, 2003 1:37 pm

When drilling in plastic, use very sharp drills. I have a plastic case fascia with a pattern of amall dimples on the lower front and I wanted to drill these out into holes for better airflow to the intake fan behind. (I'd already opened up the intake at the bottom but was blocked from making it as large as I wanted by reinforcing ribs.)
For practise I took an old AT case fascia made by ASI that had a pattern of small holes, and drilled them out larger, using a pattern of large holes at the bottom progressing to small holes at the top. Looks really good.
But I was missing one of the drills I needed for the intermediate sizes, so I used one from an older set. Big mistake. It wasn't sharp and melted its way through, leaving an ugly hole with a visibly deformed edge. Tried sharpening the bit with a garage sale Craftsman drill bit sharpener. Same result. Either it isn't working or I'm not using it porperly.
Anyway, glad I tested first.[/i]

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Post by Gandalf » Fri Jan 24, 2003 1:39 pm

I use my dremel with cutoff wheels for pretty much everything. Except for large cut-out work .. I use a really heavy duty electrical jigsaw for that.
And yes, inhaling plastic fumes is very very very bad!

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Post by crisspy » Fri Jan 24, 2003 3:21 pm

I haven't done much work with copper, but I can make a pretty well educated guess from my experience. For drilling, you want to use a really sharp bit, and go slow. Copper is often harder / stronger than aluminum, so you should try to 'work with' the spirals as they get peeled out of the hole. If you go too fast they won't break off so easily, and if you are using a small bit it could easily break the bit. I repeat, small bits will break especially easily in a metal like copper, by going too fast for the bit to stay behind the spiral, without over torquing it. So low RPM's is best, and especially a drill press for consistant pressure (probably not high pressure either, just steadier). It would also help a lot if you can get very low cutting angle drill bits, ask for sheet metal bits for example. The low cutting angle helps a lot over 'steeper' bits because they travel less distance through the metal per turn, and will also help with cleaner rear side exits. The sheet metal bits are very good because they actually drill a hole through even quite thin sheet, instead of of pulling through at the middle and 'chewing out' the outside edges. They are also shorter, so they tend to get broken off far less often than longer normal hardware store type twist drills, a big problem especially with the smaller sizes.

For cutting with circular blades (table saw etc.) , copper should do well with a carbide blade, but as with brass, you don't want to use a blade with a steep angle on the teeth. You should use an aluminum cutting blade, or maybe a finishing blade. The more teeth the better. You can get away with almost any carbide blade for aluminum, but copper and brass are too much harder, and you could have a pretty bad time.

For cutting with other blades, you should be able to use a course pitch hacksaw, or a medium to fine pitch recip/jigsaw blade.

When cutting with any power tool (ie. high speed), when you get into thinner sheets you have to be careful that the blade is a finer pitch, or you risk having the blade grab/jam and warping/tearing the work, or worse.

Always, the magic word is...
Sharp Sharp Sharp Sharp Sharp Sharp Sharp Sharp Sharp Sharp Sharp Sharp Sharp Sharp Sharp

My buddy Jim says that copper does plug up grinding wheels, just like aluminum. So use aluminum grinding wheels for high speed work. Jim and I both prefer using sanding materials for brass aluminum and copper. Disk grinders are especially good for this (very high speed), and the thick laminated-layers-composite sanding disks are amazingly good since they wear down very slowly, and keep on sanding. For surface polishing I used a Makita orbital palm sander with aluminum oxide paper, starting at 150 grit and working down from there. I actually used the cheap black colored / paper backed drywall type stuff. Went through a few sheets of paper due to grit loss, but it's cheap. Works great.

I hope this is of some help. Good luck with your projects. And don't frget to post us a picture if you can.

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