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Looking for different wood bending temperatures
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Author:  bill stewart [ Thu May 30, 2013 9:29 am ]
Post subject:  Looking for different wood bending temperatures
I recently purchased an electric blanket from LMI and built a new bender with temp. control, (a change over from light bulbs). But I'm not sure about temp. settings for the different species, such as: Cocobolo, EI Rosewood, Andaman Padauk, Ovangkol, American Black Walnut, English Walnut and Mahogany.

Bill S.
Author:  LarryH [ Thu May 30, 2013 9:40 am ]
Post subject:  Re: Looking for different wood bending temperatures
Would also like to learn of some basic guidelines. I've bent black walnut and mahogany and they were night and day temperature wise. The BW bent really easily with almost no spring back at 250 - 275 and the mahogany took some real baking at up to 350 to get the bend to really 'set'. I also used more water than I've seen recommended for the hog but it seemed to really help -with this particular set of wood anyway. I've also read that the rosewoods will bleed sap at too high a temp but I don't know what that might be.
Author:  Wes McMillian [ Thu May 30, 2013 10:32 am ]
Post subject:  Re: Looking for different wood bending temperatures
I've used this from John Mayes in the past:

http://www.13thfret.com/articles/sidebending.html
Author:  Wes McMillian [ Thu May 30, 2013 10:33 am ]
Post subject:  Re: Looking for different wood bending temperatures
Or to save a click.......

Bending Sides
by John Mayes



Ok so I get lots of questions e-mailed to me about bending sides and while I am always happy to answer the questions to save some repition here are my methods to bending sides that I learned/worked out in Maine working under Dana Bourgeois. Dana did all the hard part I just fine-tuned the temps and side thickness to the size I thought worked best. Ok so here it is.

For side thickness it will vary from model to model and for each species of wood as well. But as a general rule here are the thicknesses you should thin the sides to.

Dreadnaught .085-.090
Slope D .085-.090
OM .080-.085
SJ .080-.085
anything with a cutaway (unless it is a sharp cutaway) .075-.080

The best bending method I have used so far is to use TWO silicone heating blankets available from LMI/Watlow and other places too. Two blankets ensure that you get quick even heating across the whole piece of wood. One on top and one on bottom with the wood sandwiched between two pieces of spring steel .010 that is essential when bending to avoid cracks and reduce springback.

There are a couple different things to keep in mind while actually bending the wood. 1st is the point in which you can start the bend. There are a few ways to do this but I approach it this way. The boiling point of water is 212f so at about 225-240 you will start to see steam coming from the blankets. When you see steam you want to bend. Since the water is steaming the steam loosens the fibers in the wood and therefore makes it possible to bend the wood. As a steadfast rule you can start bending at 240f if you see steam or not. If you do not see steam it may be because you did not put extra water on it, and that is ok as long as you put enough on. Enough would be a thin coating over the whole side but not dripping off. You can know what temp you are bending at by buying as digital thermometer from wal-mart. The kind used for cooking. They have the long stem that would normally be put into a turkey or something like that. They read temps up past the highest we would use.

So at 240f you have started your bend. You move somewhat slowly..not so slow that by the time your almost done there is no water left in the fibers as that can run the risk of scorching, but slow enough so that you don't break the wood. On highly figured woods such as quilted mahogany use extra care as they can be very tough to bend. The process I use for bending is to bend the wasit first and then the lower bout and then the upper bout. Not the only way but the way that suits me best.

I regulate my temperatures via a potentiometer or a dimmer switch. I then can bring the temperature up the mark that I want and then keep it there for as long as I want with less plugging in and unplugging of the cords, but either way works.

So the waist press is down, and the sides are also curved. You will want to bring it up to a temperature and hold it there for around 5-7 minutes to really 'set in' the bend. Each wood has a different temperature to go to and some woods are less prone to scorch than other so here is a list of woods commonly used and what temperature to bring them up to:

Indian Rosewood: 300f
Mahogany: 310f
Maple (bigleaf): 290f
maple (European): 280f
Brazilian Rosewood: 305f
Cocobolo: 310f
Koa: 300f
Paduk: 310f
Walnut: 300f
Other Rosewoods: 300f

You will want to keep the wood at that temperature for about 5-7 minutes. Then unplug the wood or turn off your dimmer switch and wait for 30-45 minutes before taking the wood out.

With these methods I have bent hundreds of sides and using them should help you to feel confident in your bending and not afraid that you are going break a side.

Again these are just my findings. Above all be flexible and be prepared to find your own methods. I hope this helps!
Author:  bill stewart [ Thu May 30, 2013 10:59 am ]
Post subject:  Re: Looking for different wood bending temperatures
Thanks guys...the John Mayes method is exactly what I was looking for.

Bill S.
Author:  LarryH [ Thu May 30, 2013 11:44 am ]
Post subject:  Re: Looking for different wood bending temperatures
In my experience, with the Mahogany I bent, 310 was not hot enough and 5 -7 minutes was not long enough to prevent very noticeable spring back. I got it as hot as 350 and cooked at 300 for 15 - 20 minutes and the bend 'set' pretty well - not perfect but I think that might be the nature of the hog I have..

Hopefully others will elaborate a little if their experience differs from the John Mayes guidelines above. There's a video by Todd Stock on bending figured Mahogany that shows different times and temps as well.

Peak at about 330 degrees and cook for about 35 minutes at 300 degrees. Just sayin you'll probably have to experiment a bit to see what works for you and the particular wood you are bending.

http://www.youtube.com/watch?v=qhrHvfzfDLo
Author:  Fred Tellier [ Thu May 30, 2013 11:55 am ]
Post subject:  Re: Looking for different wood bending temperatures
I just set my PID at 300 and bend, turn back to 250 and cook for 15 minutes after cooling another 15 minutes or so seems to set the bends. A bit of spring back seems to creep in if I don't get the sides into the mold right away after I remove them from the bender. All the info on different woods seems to only vary 10 deg + or - which is a very small percentage of the total so I don't bother. I have bent the problem and easy woods without any breakage though only 24 sets of sides so far.

Fred
Author:  mkellyvrod [ Thu May 30, 2013 4:16 pm ]
Post subject:  Re: Looking for different wood bending temperatures
Fred, has much more experience than me with the bender, but like him I've seen very little difference between woods as far as the temperature needed to bend. I've only bent 5 sets of sides (Afr mahogany, leopard wood, spanish cedar, sycamore, and ambrosia maple) and some bloodwood and IRW bindings, but I've followed the same process each time. I follow Todd's utube video which uses wet kraft paper on either side of the wood followed by Al foil, and begin bending when I see steam rising (around 25O F) and by the time I'm done, the temperature has usually reached 300 to 310.
Author:  Joe Beaver [ Fri May 31, 2013 10:42 am ]
Post subject:  Re: Looking for different wood bending temperatures
I also am a One temperature does all kind of guy. I set mine for 307 degrees because that is what a successful builder told me once.

To me the variables for bending are water and time under heat. To much water on curly wood and it is probably going to cup. No little water on dry wood like mahogany or sapele and it will quickly get to dry and become brittle, etc.
Author:  Beth Mayer [ Fri May 31, 2013 11:54 pm ]
Post subject:  Re: Looking for different wood bending temperatures
I've used temps around the ones John gives in his guidelines, but what helped me the most was using a gloved hand to bend the bouts, and bringing the bending caul down as my hand is bringing the bending sandwich down. You can feel when the wood is ready to give. I got the idea from a YouTube video that I think is Mario bending some Cocobolo.
Author:  Dave Fifield [ Sun Jun 02, 2013 3:46 pm ]
Post subject:  Re: Looking for different wood bending temperatures
I've found the JM method above still leaves a bit too much spring back. Nowadays, I bend per JM, then after the side/s have cooled down to room temp, turn the heat back on and cook them for another 15minute cycle at around 230F. After the second cycle (usually leave the side in to cool overnight too) there is virtually no spring back.

Dave F.
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