Galvanized dryer vent for DIY side bending iron?

I've been using an old piece of 2 1/2" black iron pipe clamped in a pipe vise, heated by a hand-held torch for bending, and it works pretty well. But I've been hankering for a larger-diameter (or even teardrop or oval) shaped bending iron to get some curves smoother. I was in HD yesterday, and picked up the hardware to make another bending iron using a light bulb as the heat source (picked up 150 and 200 Watt incandescent bulbs at the same time). As the actual iron, I picked up a length of galvanized dryer vent and a cap.

I know that galvanized iron can cause zinc poisoning if it's heated to above 700F or so, which is why you need to be really careful welding it. I don't expect a bending iron to get anywhere near that, though it could easily get to above 200F, even using a bulb as a heat source. (After I'd bought a regular light switch, it occurred to me that I could have bought a dimmer switch instead, but for now, my "thermostat" will just be putting in stronger or weaker light bulbs, as I practice with it...)

Googling shows a number of examples of DIY bending irons that people put together from galvanized pipe, and I've never heard of anyone suffering from zinc poisoning from using one. But I thought I'd ask here:

Has anyone had experience with using galvanized as a side bending iron? Have you heard of anyone getting sick from doing that?

Thanks!

4" dryer vent also comes in aluminum where you wouldn't have the worry about zinc poisoning.

Thanks, Lee. I'm going to make the 5" one this weekend, using the galvanized. I've googled and YouTubed, and there are loads of guys using galvanized for bending irons, boiling troughs, etc. So I'll give it a shot. I'll report back re: whether it makes me sick or not. But I'm not expecting any problems.

The bigger problem is that it is pretty flexible stuff where pipe is not. You will be putting some pressure on it when you bend... It will probably cave in.

Temperature wise - a pipe type side bender runs over 400 degrees to get the wood hot in a reasonable amount of time.

My worry with black pipe is that the iron can stain a lot of types of tannin rich wood....

The most common solution is to go beg a 1' piece of muffler pipe off a muffler shop.

I'd want a stiffer pipe. 3-6" cast iron pipe is common, most plumbers can probably give you a piece of each out of their scrap pile. The iron will also retain and disperse heat to help avoid hot spots and burning--more forgiving when heating with a torch.

for i know galvanized iron in bending there is no poisoning problem.. our carpenter also doin it so far.

I'm an electrician and I grabbed a foot long offcut of 3" rigid aluminum conduit. So electrical shops could be another source. That pipe is expensive though so they might be stingy with it. If you do decide to go, try to find a place that does industrial construction. You don't use pipe like that very often in residential or commercial electrical.

An update: I finished the project over the weekend, using the 5" diameter dryer vent. Here's a picture, along with a piece of Aspen that I tested it with:

Attachment 356994

The total length of the pipe is about 7 1/2" or so. The heat source right now is a 150W incandescent bulb, controlled by a dimmer switch. The pipe was completely rigid, though I applied enough force to bend that piece of not-very-good-for-bending wood. I addressed the rigidity issue by making a circular MDF base that exactly fit the bottom of the pipe section, and by using a cap. Over this length, there are no rigidity issues.

Re: zinc poisoning ... I'm alive and well.

I have the materials to make a 4" version of this next - I'll also keep hunting around for scraps of other pipe...

Thanks for the responses!

EDIT: Hot spots and burning: There aren't any. The heat source is constant and is at the center of the cylinder, not bearing on the inner surface. With the 150W bulb, it takes a little longer to bend the wood compared to bending with the pipe+torch combination that I was using, but there's no danger of scorching. And, as far as taking longer is concerned, I'm talking about maybe twice as long. I figure I get that time back by not having to deal with scorched wood.

Regarding black iron and tannin-rich woods. Good point. I've never bent oak. I've used it for rosewood and maple with no discoloration.

Looks nice!

Not sure on the use of MDF, but good clean work.

Quote:

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Originally Posted by Matt Lau

Looks nice!

Not sure on the use of MDF, but good clean work.

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Thanks! Is your objection to the MDF philosophical? I've been using it a lot lately, to make forms and other stuff in preparation for getting started on the real part of the build. It's not any kind of a pleasure to work with - I hate it. But, for what it's good for, it's good. And cheap. Really cheap.

Over the weekend, I found myself saying to myself, "I can't wait until I can start actually working with wood again!" Almost there...

Great news on the bender. Sounds like a success.

Aspen is generally pretty straightforward to bend. Most northen USA hardwoods bend pretty easy.

Ironically - mahogany (and its African cousins) can give you more hang than you would believe. It seems to be mostly related to runout in the wood - but the only wood I have severely burned in the bender and *Still* couldnt get it to do anything until I hit 0.065" thick was Mahogany. But another set bent just fine.. Go figure.

This was an old piece of "hobby" aspen from HD. Plenty of knots and runout. I just grabbed something that was already pretty thin from the pile to test the bender out without having to plane it much.