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Greetings!

I am completing the body of a tenor uke, and bent the bindings yesterday. When I removed them from the bender they were in pieces or deeply cracked in a number of (not surprising) locations. I would like to tell you the details of what I did and ask for any input before I try again.

The bender is home made (see attachement). My bending combo was: bender (which has a steel bending surface), the 4 ebony bindings spritzed with distilled water and wrapped in a single layer of aluminum foil, the blanket and the spring steel slat. I got this combination into the bender and placed the cauls with no pressure (just enough to hold it all in place). Brought the blanket up to 250 and steadily brought the waist half way down. I then worked steadily first on the upper bout then the lower. Finally brought the waist the rest of the way. It took about 5 minutes or less to get all the bending done once I started. The heat max was a bit above 350. I don't have a thermostat, so I unplugged at 350, let it cool to 200 and replugged back to 350, then unplugged and cooled. After about 45 min, I removed them and the pictures tell the story.

I am assuming it was a technique error, but am also wondering if ebony binding is harder to bend properly for some reason?

I appreciate any input I can get! Thanks, Beth

Guess my pictures didn't post. Will do them individually.

Well yes it is slightly more difficult than rosewood. The temperature can be a little bit higher and it must not be forced. I bend by hand and always make sure I do not push too far away from the tangent point creating leverage. I am sure others using a machine will have something to say. You could also search for "bending ebony", we already had several threads about it.

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Build log

Thanks Alexandru,
I am having trouble posting the pictures.

I did try to search for info on this before I posted but couldn't find the right combination of words to actually find a useful thread.

I will try to search "ebony binding" and ebony bending, but still appreciate the advise on any changes to my setup. I don't yet have a bending pipe, and can see where that might be a good way to bend binding, so you have a feel for how much heat and pressure is needed.

Ebony can be unpredictable. Some pieces bend fine. Others break. Sometimes from runout, sometimes not. Making them thin and using plenty of heat helps.

Or go with black fiber

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http://www.chassonguitars.com

I have just had a like problem with ebony binding on a tenor uke. Over heating seemed to be the problem at one point. Then they would break when I took them out as it was hard to control the metal sheets on the very tight bend.

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http://goatrockukulele.com

You can make one like this real cheep!

Supersoft II makes ebony behave much better, I would wait to start bending until the temperature is higher. I sometimes get a little cracking in a tight waist but a little thin CA with ebony dust and some sanding fills them. I always bend 3 pieces for the cutaway, but usually end up using the extra on the next build.

Fred

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Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

I also use SuperSoft II for Ebony bindings but I spray it on heavily several times with several hours between each spraying. As per instructions I let it sit overnight before bending on the form. For the Florentine cutaway I bend it by hand on a pipe. SSII will bleach some dark woods when used heavily but it does not seem to effect the Ebony binding. I bend Ebony at about 325 F.

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GEO
perpetual beginner

the machine out performs the pipe but learning to bend on a pipe is a big help . Ebony can be a pain . Ebony is hard to tell grain direction. You don't need the 2nd cycle that is a waist of time and energy, You need to allow a bit more heat to start the bend and be a bit faster.
Ebony likes to be a little hotter to start bending. Also think pressing more than bending. You don't want to have the see saw effect bending at the force at the fulcrum point can crack the wood. Heavy springs help to focus the pressing. What gauge slat do you use ?

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

John, I use the slat sold by StewMac, and only on the top of the blanket. So in light of what you're saying, it would be preferable to have a spring steel slat to go under the bindings (towards the machine) as well, to help support the bend. I was thinking of the slats as more to keep the heat and moisture in, so figured that the upper would suffice and that the strong steel support that makes up the top of my machine would be good enough. But now I'm thinking that a lower slat would support the actual bending process better.

Thanks to all who have weighed in. I am going to make another attempt incorporating your various observations and suggestions. Everything is a lesson!
I greatly appreciate the time all of you took to help. Beth

I use Ebony bindings a lot and here's my procedure. I thin the bindings to .070. I use a Fox style bender that I made and use 2 heating blankets and 2 spring steel slats - blanket, slat, wood in craft paper, slat, blanket. I wet the paper but I don't spray the wood directly. I heat to 230 degrees and then start the bend. I close the waist down completely, then do the lower bout and then the upper bout taking probably no more than 45 seconds to complete the entire bend. I stop the temprature at about 320 degrees and cook for about 5 to 10 minutes (I have a router speed control that I use for regulating the temprature). I let it cool maybe an hour or until I get back to that operation (there's always something else to do).

I usually tape at least 4 binding strips together and put them in along with the purflings and bend everything together.

I havent broken one in a long time, but now that I say that watch the next ones snap like twigs!

Good luck!

Chuck

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"To live a creative life, we must lose our fear of being wrong"
- Joseph Chilton Pearce

Hey Chuck,
Sounds a lot like what I tried to do...right down to the temps, but I wonder if your success vs my failure is in having that second blanket. Unfortunately, if I did that setup, I would need to buy a second blanket. What your story does tell me though, is that the temp I was measuring (at the level of the blanket) was probably not the true temperature of the wood. I appreciate the detail! Beth

you can try putting the blanket on the bottom and slat also I have used that technique with hi curl koa with success.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

So Todd, are you lightly wetting the binding? I'm assuming you wouldn't be talking about the steam stopping otherwise, but I just want to get all the right steps. Beth

Two blankets and two slats may be overkill, but the first I ever saw of using a Fox style bender was on John Mayes' video and that's what he did. Monkey see, monkey do. Since then I have learned that most folks only use one blanket, but my method works for me so I'm sticking with it. I think the wood actually gets hot more evenly this way, but I certainly couldn't prove it.

Chuck

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"To live a creative life, we must lose our fear of being wrong"
- Joseph Chilton Pearce

I have those videos too (love 'em) and although I do not have a Fox-style bender yet, the two blanket idea appeals to me, aside from the added cost of a second blanket.

It does raise a question for me, though. If using two blankets, or just using one but placing it under the side wood, do you need to account for the added thickness of the blanket when shaping the form? Or, is the difference in shape so minute that the bent sides fit into the mold just fine?

Bend hot. Avoid pieces with runout.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

I allow for the distance from the form to the wood. What's on top doesn't matter.

Chuck

_________________
"To live a creative life, we must lose our fear of being wrong"
- Joseph Chilton Pearce

Not all heat blankets are the same. Some are only 2 1/2 watts per inch . As a result ,they loose a lot of heat and don't work well. 5 watts per inch can carry that thermal load, I bend about 5 sets a week so I do my share. Wood is stupid and only knows it is hot. Once it reached its thermoplastic limit it will bend . using more than 1 blanket is overkill . Ebony is a hot bender as is paduck and maple. Not all wood bends in the same thermal range.
Runout is a killer on ebony and bloodwood. Some woods will accept a bend with runout but ebony isn't one of them. Be sure you have well quartered if you can get it .

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I am buying my ebony binding strips already cut from LMI. I find the grain difficult to read, but have assumed they would be cutting the strips properly.
Hope you all have a wonderful Thanksgiving.....I am thankful to all at the OLF who have been so generous with their time and talent!

Happy Thanksgiving,
Beth

I've gotten whole batches of ebony binding that refused to bend, usually because the grain wasn't aligned. In that case, grab another board and go back to the bandsaw. When I'm bending, I use lots of heat, not a lot of water, tape the strips together (it's possible that taping everything together gives me a better sense of the wood's resistance), and I usually bend an extra strip or two just because. Ebony's not that hard to bend, it's just hard to read the grain.