I just installed a dust colletor and will be piping to different tools. I would like to make some custom collector hoods at the tools out of sheet metal. Never worked with it before. Any sites on forming and bending it?
I have had great luck bending sheet metal with a long piece of angle iron and a rubber hammer. Make a pattern from cardboard that you have fitted to the use. Then transfer that to the metal with a sharpie pen and "break" it over the angle with the rubber hammer. I set the angle on a saw horse and lay the metal over that one and another one. A clamp or two will hold it in place until you get the break going. I finally bought a harbor fright metal brake but I still use my rubber hammer most of the time.
Lots of sites out there. Google "bending sheet metal" or even ask in rec.crafts.metalworking newsgroup.
Go to a HVAC shop. They make better hoods than you can without rolling gear, and the prices are quite reasonable.
Don't make it, modify it. Most of my workshop ducting is cast-offs from factory ducting. It's a lot easier to take an existing hood and modify the shape than it is to make it from scratch. Even if you just keep the pipe mounting flange and replace all the "hood" itself.
Make protoypes in cardboard. For everything. You may even hook them up to the extractor and test that the shape works for effectiveness and for visibility.
Smoke matches (from a home repair shop, as sold to gas fitters) are useful for visualising airflow. Failing that, _natural_ jute or cotton string smoulders well enough to use.
I use 1950's school or apprentice-level metalworking textbooks. Once you understand how to draw a "development" (the flat plan of a complex curved shape) then the rest is just donkeywork.
The basic development technique is to lay out out the major edge as a baseline. Straight for a straight edge or a cylinder, curved for a cone. Then use dividers to lay out measurements along this edge and up from it, according to the shape you need. The way to work out the radius of the curved edge for a cone is to imagine the cone extended all the way to a single point, then measure the radius from this virtual point. Practice with cardboard first!
The tools vary somewhat, depending on what materials you use. The hardest part is cutting it out to shape - I use a few grand worth of plasma cutter, which is just about the most fun you can have in a workshop. A set of "aviation snips" will do much of it, but they're a bit of a chore to use. Roller shears, nibblers, notchers all help, but they're nothing like plasma. A bench guillotine (HF grade) is cheap and useful, but won't do curves. If you ever see a "Beverley shear", then snap it up - you can always sell it to armour makers later.
The best material for rolled or folded ducting is thin steel, hot-dip galvanised. You can't shape this into a compound curve though (which you rarely need for ducting). The easiest material to work with using limited tools is thin aluminium. Caravans / trailers / aircraft are clad with thin aluminium sheet. Use that scrapyard !
To form, bend and roll it, you use a press brake and a rolling mill, maybe even a swage roller. These are expensive, so you're not going to buy them just to make some ducting (why having it made is a good idea
- they have tools you don't, so they can just do it more quickly).
For folding, you _need_ a folding machine. These can be bought affordably, or you can make your own. The simplest version is two lengths of heavy gauge L-section angle iron a few feet long, clamped by a bolt at each end and held in a bench vice. The complicated version (bought for
I have made several DC shoots, hoods, cyclone, etc from sheet metal. I built my own planer hood because the manufacturer one was $70. The
4" connection is a small coffee can soldered and metal taped to the hood. No plans or sites needed.If you get good at creating custom hoods, I'd like one with a mini blast gate to connect my old Boston pencil sharpener to the DC. Everything else that makes shavings in my shop is "online" except that, and it's the one i never remember to empty until it's so packed full and a PITA to empty! ;) --dave
On Sun, 23 Jan 2005 20:59:47 -0600, the inscrutable "Rich" spake:
CAUTION: Buy some aramid gloves before you even START to work with sheetmetal. It's sharp and WILL cut you to the bone if you give it half a chance.
I just returned Audel's "Millwright's & Mechanic's Guide" to my library. It has formulae and info on sheetmetal for hoods. See if your library has a copy. Also look for books by Tim Remus and Ron Fournier while you're there.
Harbor Freight has sheet metal benders and fabrication machines.
"Dave Jackson" wrote in news:7yfJd.9144$ snipped-for-privacy@newsread3.news.atl.earthlink.net:
With a triac or a relay?
Patriarch
These are called Riv-nuts. Very handy.
Handy, hell... they're grrrrreat!
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