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I re sawed a piece of 8/4 rosewood into fretboards. They all bowed quite a bit. I did what I could with a drum sander but it's getting to the point where they are all close to the .25"-.28" range and some as thin as .22".

Question... Would using the heating blanket I use for bending sides be able to straighten these boards? I mean wrapping theme up the same way with a spritz or two of water and clamping them to my bench for a couple days after applying 250-300 degrees for 15-20 minutes. Anyone ever done this?

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"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

At these dimensions if the bow is length wise with no twist I don't think you will have much of a problem after fret slots are cut. You will most likely be able to easily hold it in place on the neck with finger pressure.
Tom

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A person who has never made a mistake has never made anything!!!

Excellent point! I suppose I'm just being overly cautious. It's for a neck I'm building for somebody.The first one turned out to have a problem with the truss rod channel so I decided to make it again. Just trying to alleviate any possible future issues.

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"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

I've used heating blankets to flatten backs and sides that had warped a bit. I sprayed them lightly with water and clamped the wood and the blanket between 2 pieces of thick plywood. I would heat the wood to 250-300 and leave the heat on for 5 minutes or a little longer. Let the wood fully cool before removing it from the clamps. Leave it overnight if you have the time.

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Josh House

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I must have gotten some funky wood. All of it is bowing and twisting in every direction. I made another neck, ended up having to take it apart, clean it up and and reglue it because it was back-bowed about .011"-.012". I guess the fretboard was cupped badly because after running it through the drum sander, it ended up being narrow compared to the neck's core. Basically it was too small. Also, when I glued it back up, I purposely put a shim under the caul at the midpoint of the fretboard in a effort to counteract the back bow that was happening. After I took the clamps off, it was still back-bowed about .010". It's getting to be a bit maddening.

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"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

.010 back ow is a non issue IMO. A 2 way rod should take of that.

I have clamped between steel plates in the oven. The heated wood becomes pliable and, after cooling between the clamped plates, it sets flat and stays that way. Do not heat wood if there is any wax on the ends.

Aaron:
Just reread your post and see your cutting fingerboards from 2" stock. I would be inclined to wait a while before using especially if you don't have a way to measure the moisture in the boards. Also do you measure and control the RH in your shop?
Tom

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A person who has never made a mistake has never made anything!!!

I hear ya. I'm using a one way rod though. The issue is that the one way rod is very specific as far as depth and the core is only a hair above its final thickness. Not enough wood to straighten it out.


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"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

How hot and for how long?


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"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

I did wait some time but they are all bowed to some extent. At a point, you only have so much thickness left. I suppose my mistake was trying to get that extra fretboard out of the stock. I hate to waste wood but sometimes it gives you no choice.


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"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

I just laid out a few pieces of hard maple about 1" thick after planing, drum sanding, etc. to get them straight and square. No we wait...


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"I'm not going to say that perfection has never been achieved. However, if it has, it probably went unnoticed due to it's lack of character."

I do not recall exactly how hot or how long. I am sure that I do this hotter and longer than necessary. I think any temperature that would be hot enough to bend sides would be hot enough, as long as you leave it in the oven long enough to completely penetrate. I think anything below charring temperature is safe. Although I did spritz the surface, I do not know if that is necessary. I also wrapped the wood loosely with a layer of aluminum foil (ends open) just to protect the steel plates from sap building up on them. I recall that at least some of the time I preheated the steel plates in the oven, which requires appropriate gloves. I used large C-clamps. The heat may accelerate rusting. So, I am guessing I heated to about 350F. let them cook a few hours, then turned the oven off and waited until the next day to remove--but, as I said, I think this was longer and hotter than necessary.