HELP!! Side Bending

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HELP!! Side Bending

Postby Seth Wojciechowski » Tue Mar 13, 2018 3:47 pm

I am an amateur guitar builder, and am having trouble bending my guitar sides. I am using straight grain indian rosewood which I hear is relatively easy, I have tried dry bending the sides on a homemade bending iron that I made out by attaching a heat gun to one end of a metal 1 inch diameter pipe. I am sure that the pipe is hot enough but for some reason my sides dont want to bend, have tried dry bending and soaking the sides in water for about 10 minutes before bending, but they dont easily bend like I see others on youtube do. My sides are about .10-.11 in thickness so they should be thin enough, is there something im doing wrong, I cant get them to bend very easily and it seems to take about 3 hours for me to get a slight curve in the wood. Im getting desperate so any help is greaty appreciated.
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Re: HELP!! Side Bending

Postby Brian Evans » Tue Mar 13, 2018 3:56 pm

The pipe should be hot enough to instantly dry water sprayed on it, around 250 degrees. The sides should be .080" - .090" thick, or less. I think a 1" diameter pipe is very small, I use a pipe with variable radius (not diameter) between 5" and around .75" that started as a 3" diameter pipe that I squashed oval.
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Re: HELP!! Side Bending

Postby Bryan Bear » Tue Mar 13, 2018 4:04 pm

A few thoughts and questions in no particular order:

Is your pipe hot enough that water droplets dance on the surface like a pancake griddle?

How long are you heating the sides on the pipe before trying to bend? You need to keep the wood rocking on the pipe to get a length of side heated enough before you bend. The small contact patch of the pipe will not spread the heat well enough on its own. Keep rocking and warming a section of the wood while applying some pressure, when it gets hot enough to bend, you will feel it start to relax under your pressure and you can then bend that section. It takes a little while to get the feel for it but once you do you'll be off to the races.

0.1" is a bit thick. Go down to around 0.85" and it will be MUCH easier to bend. You can go thinner but that creates its own issues if you end up needing to sand a lot to get the sides perfect after bending. Better to leave a bit more material until you have made a few.
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Re: HELP!! Side Bending

Postby Seth Wojciechowski » Tue Mar 13, 2018 4:16 pm

Okay, I have planed the sides down a little bit more, now they are at around .8-.9 (I went a little thin in one area and went down to .75) I will try a to get it hotter and see if I can find a bigger pipe.
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Re: HELP!! Side Bending

Postby Seth Wojciechowski » Tue Mar 13, 2018 4:19 pm

Now that I think about it more, i was getting the pipe hot enough for the water to sizzle as I threw it on the bender, I guess ill try some patience and see how it goes
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Re: HELP!! Side Bending

Postby Barry Daniels » Tue Mar 13, 2018 4:47 pm

You need the pipe hotter. A sizzle is not enough. As Bryan said, the drops need to jump and dance around when they hit the pipe. You should hear popping sounds when you place the damp wood against the pipe.
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Re: HELP!! Side Bending

Postby Bob Gramann » Tue Mar 13, 2018 5:41 pm

To save your rosewood, you may wish to slice up any wood you might have to .080" and play with that for a while on the pipe until you get a feel for how it works. Once you find the skill, bending on the pipe is a joy.
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Re: HELP!! Side Bending

Postby Tim Allen » Tue Mar 13, 2018 7:41 pm

All of the above advice is excellent.

I would also suggest that you search the MIMF archives for previous discussions. This is a good one, for example:
viewtopic.php?f=3&t=2002&p=29224&hilit=bending+iron#p18631

You could also benefit from taking a look at typical home-made benders. Just do an image search on something like

home-made guitar side bending iron

I made a bender using an electric charcoal starter and some aluminum pipe, controlled with an electronic router speed control, and it works well, but there are many other approaches.

Good luck!
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Re: HELP!! Side Bending

Postby Mark Swanson » Wed Mar 14, 2018 10:19 am

All good advice here. but I will say that you need a bigger pipe, too. A pipe that small will not spread the heat over a larger area of the wood, you need to get a decent sized area of the side hot. Even if you move it back and forth it'll take forever to heat a large enough area to easily bend.
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Re: HELP!! Side Bending

Postby Bryan Bear » Wed Mar 14, 2018 11:45 am

Mark is right. I originally missed that the pipe is only 1" D. That will make it even harder to heat enough of an area and I'm wondering if it is getting hot enough with a heat gun. I was originally picturing the heat gun blowing into the pipe but that would seem to be impossible without hot air also streaming along the outside of the pipe and burning your hands. Do you have the heat gun aimed at the side of the pipe? What type of metal is the pipe? Iron is not a great conductor, you may not be getting the whole pipe hot enough. A cool spot (below the 375ish needed to bend will keep the side from relaxing properly.

Can you show us a picture of the setup?
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Re: HELP!! Side Bending

Postby Alan Carruth » Wed Mar 14, 2018 12:23 pm

Good advice so far.

I tend to bend at about 300F.

It might help to have some idea of what's going on. Wood is a composite of cellulose fibers in a matrix on about equal parts of hemicellulose filler and lignin glue. Neither the cellulose or the hemicellulose is much affected by heat, but lignin usually starts to soften at about 180F. From what I can tell water helps lower the softening temperature, but it also weakens the bond: the more water you use the more likely you are to have split outs on the outside of the bend. There is normally enough water in the wood to bend it so long as you don't heat it too much and drive the water off. Most woods can start to scorch at around 300F, although that varies. As you drive off the water the temperature required to soften the lignin rises, and eventually reaches the scorching temperature, at which point you're done for the day with that piece of wood, since it won't bend without scorching.

SO, the idea is to use an iron that's close to the scorching temperature so that you can heat the wood up fast before all the water goes away. Putting a little bit of water on the inside of the bend can help: it flashes to steam and works its way through the wood, helping it to soften. Water on the outside just makes trouble. Using a 'back strap' of something like soft aluminum on the outside really helps to hold in the moisture and distribute the heat, as well as helping to resist splits on the outside of the bend.

Ideally what you do is get one spot hot enough to bend, bend it, and then move the wood to chase that hot spot along. The slower you move the wood the more bend you'll get.

It's important to remember that the lignin stays soft for a while, even after it has pretty much cooled off. The shape that the wood is in when it cools is the shape you'll get, so don't let it relax until it's cool.

It's more important to bend to a smooth curve than the right one. Corners and flats spots can be hard to correct, but it's usually pretty easy to touch up a smooth bend. I always try to over bend things a fair amount if possible; they're more than likely to spring back anyway, and it's always easier to straighten them out than to get in more bend.

Start with the hardest part, the waist or the cutaway. Bend that, over bent if possible, and allow it to cool off for a while before you do the rest of the side. That helps avoid spring back in the hard bends. It's also the most likely place for you to break a side, so if that happens you haven't spent all the time on other stuff.

Walnut, straight grained maple, and cherry all bend well, and are cheaper than rosewood to practice one.
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Re: HELP!! Side Bending

Postby Mario Proulx » Wed Mar 14, 2018 1:38 pm

You need to have a 2" pipe, minimum, and it needs to be heavy-walled steel. A thin pipe will cool instantly when you present the damp wood to it.

Practice on scrap until you get a feel for bending wood. Get the pipe hot enough to scorch the wood, then back-off on the temp a bit... I don't think a heat gun will get a heavy, 2" pipe hot enough...
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Re: HELP!! Side Bending

Postby Barry Daniels » Wed Mar 14, 2018 1:53 pm

On the first few guitars I used a thin walled aluminum 3" pipe as shown in Irving Sloane's book. I had the same issue of the pipe not holding sufficient heat. It made bending quite difficult.
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Re: HELP!! Side Bending

Postby John Clifford » Wed Mar 14, 2018 5:18 pm

I like a hotter pipe than Alan. I usually set mine around 400-450F, and keep the wood moving so it doesn't scorch. I agree that less water is better. I use a spray bottle with distilled water in it, and just "spritz" the wood from time to time, mostly on the inside. No soaking.

Keep in mind that you don't have to bend it all the way on the first pass. Sometimes it's easier to bend a wider curve, then go back and slowly tighten it up. This can help avoid kinks.

Most importantly, don't give up! Once you learn how to do free form bending on a hot pipe, it becomes a real pleasure, and you can bend any shape you want, without having to bother with bending machine forms and all that.
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Re: HELP!! Side Bending

Postby Chris Reed » Thu Mar 15, 2018 6:26 am

I use a heat gun with a 3 inch/75mm steel pipe and it gets hot enough, but I still have to rock the wood on the pipe to heat a wide enough portion to bend. If I don't rock it, I scorch a narrow strip and also produce a sharp kink rather than a nice bend.

A damp rag on the pipe and aluminium strip on the outside helps a lot.

If you hold the wood with both hands fairly close to the pipe (too close and you burn your fingers!) you can feel the wood heating up. Apply gentle pressure and you feel it start to give, but don't force it, just ease it into the bend and keep heating until you've got the bend you want.

Alan's point about chasing the bend along the side is a useful one, because the wood next to the point you're bending is already getting hot. I try to complete each bend in a single go.
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Re: HELP!! Side Bending

Postby Bob Howell » Fri Mar 16, 2018 9:38 pm

I learned this skill 18 months ago and found locating a pipe big enough the first hurdle. Made 3 before I got there. Finally found a 3" steel pipe in my basement from original construction 60 yrs ago. cut off 10" and flattened it to oval . Started with propane but then Heated it with charcoal starter. Got a voltage controller but found I keep it wide open all the time, controlling heat by moving to cooler spots that develop.

Find bigger pipe.

Good luck.
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Re: HELP!! Side Bending

Postby Ryan Mazzocco » Sat Mar 17, 2018 12:15 am

Get a bigger pipe. that's good advice. But don't trash the one you've already made. I have a 1" pipe that I use for bending my headstock binding. I have some really tight radii that I'd never get with a bigger one. In fact the 1" is a little too big for some places. My point being, even though a bigger pipe may be better for general purposes, don't feel like you've wasted your time making the smaller one. There may still be some use for it. As for your heating method, I'm not sure why you're not getting hot enough. I also use a heat gun and believe me, it gets plenty hot. I have to turn it down to the lower setting.
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Re: HELP!! Side Bending

Postby Bob Howell » Mon Mar 19, 2018 9:53 pm

My original 2" pipe is still used sometimes and I am about to set up a 6" pipe some one brought me. All have uses.
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