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I'm beginning to see the need for one....I think. I started to research different types and brands of meters but I'm curious if any of you find it necessary, optional,....marginally helpful?

On the same subject...is there an optimal water content to build at or are we trying to simply achieve equilibrium within our shop environment...assuming a humidty controlled shop?

I was resawing some sapele body blanks from 8/4 down to 4/4. The blanks were 19" x 7". Right at the end of the cut the two halves "popped" apart under fairly high stress. The two halves cup apart almost .1" in the middle of the cup on almost every one of 12 pieces. These boards were kiln dried and sat in my shop almost eight months....stickered and waxed...42 percent relative humidity controlled carefully.

I suppose it's possible that humidity didn't play any role at all...and rather, the boards could have had internal stresses. It's just hard to imagine that they were not at equilibrium after eight months. A good moisture meter would eliminate that question....for $250. Is it worth it?

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Storage of wood can cause internal stresses. I like to resaw the wood asap . I don't like to let the wood I plan on resawing to stay thick. Once resawn I store it under a press between plywood and straps.

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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

Common lore tells us it takes about a year per inch for wood to go from 'wet' to 'dry' in air. Common lore doesn't tell us exactly what that means to go from say 'dry' to 'dry-er' in your shop or something like that.

If your boards cupped, i.e. the rings are trying to straighten our, then that does probably mean that the middle of the board is still wetter than the outsides. Don't give up hope though - let them sit like that for a while and see what happens. The truth is that all flatsawn wood is going to cup or warp in some fashion as it's drying. Once it's pretty dry you should be able to dimension it and it should hold dimensions pretty well from that point on.

I did buy a moisture meter because I decided to use a product called "compwood" that arrives wet, you bend it and then dry it to set its shape. For the first time I used it, I found it very useful but, with everything I learned in the drying process that very first time I don't really need it any more.

Since you're working with solid bodies, you might find more use for one than I have but it truly is a one trick pony. I think if you let your newly sawn slabs sit a few more months or even bake them in a kiln (which is as easy to make as a space heater in a five walled cube of styrofoam insulation) for up to 3 days, the moisture meter won't tell you anything you don't already know.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

I've been using an Electrophysics MT90 for my cabinetry business for many years, and just started using it to monitor my stash of guitar woods. It has a range of 6%-16% which is good for my purposes, but if you are buying green lumber, the next model goes to 40%. I bought mine from the designer at a trade show. They are made in Canada, as well. http://www.electrophysics.on.ca/e_index.htm
Equilibrium is just reaching an unchanging moisture content, not the same M.C. throughout. Regardless of how dry a piece of 8/4 is, the moisture content in the middle will be greater than the outside surfaces, resulting in the cupping. You can try letting the wood equilize by leaving it on a flat surface with the cut side exposed so that it will lose moisture at a faster rate than the other side. You may not get all of the cupping out, but you would likely have to re-surface the wood anyways. Hope this helps.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

If the wood popped apart while sawing (or at the end of the cut) it had internal stresses, case hardening, etc. in which case I don't think a moisture meter would have helped you.

Kevin Looker

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I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

Hi Stuart,

I use one. I have a pinless Wagner model (bought it from Woodcraft many years ago - around $200 IIRC). I bring it with me when I go digging through the wood piles at my local lumber stores looking for nice pieces that might do for b/s sets or bindings etc. Often, I'm suprised just how wet the stuff still is. If it's not too bad (say around 15%), I'll buy it and stack/dry it (to around 7 to 11% depending on the time of year) in my workshop. The wood needs to be about 3/4" thick for a reliable reading according to the Wagner manual, but I've found it to be quite reliable on stuff as thin as 1/4" if you hold it up in the air. I use it now and again in my workshop to see how dry/wet a piece is before using it, but not often. I should start writing dates/wetness/source/etc. on the wood itself (if only for Lacey reasons!).

I've had the same thing happen to me on a couple of mahogany neck billets from one supplier. They were dry, but had internal stresses (reaction wood most likely). Didn't use them in the end....put it down to experience....buy wood from a "better" source.

HTH,
Dave F.

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

I use one all the time. Mainly when I am buying rough sawn hardwoods. It gives me a good idea of how dry the wood is, and what I need to do. I will mark the date and moisture content on the end of the board (and species if not obvious) so I can monitor progess.
I also use it to monitor moisture content on logs that I cut and split into billets for resawing. You get the least amount of runout from your own wood.

Chuck

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I've really wondered about moisture meters too. I got a bunch of nice curly maple neck blanks from a major supplier that looked fantastic until I bandsawed them. At that point, they warped horribly--apparently case hardening during the drying process. I imagine these would have checked out fine with a moisture meter, but due to the way they were dried, they're fairly useless as necks. I've milled them into bindings and other trim pieces, so it wasn't a total loss. But even though I didn't check the moisture with a meter, I'd bet that it would have looked OK even though the wood had so much internal stress due to the way it was dried that it wouldn't have mattered.

Maybe what we need is a Lacey Act that deals with how the wood was processed along with where it came from....

Dave

Can someone define "case hardening" please. I've heard that term a few times now but I'm not certain what it means.

Also....Dave F....can you give me the model number on that Wagoner? I can get an L606 locally for $250. Is it that one?

Thanks all for the replies. I baked, flattened, and then planed two of these cut pieces but I'm going to watch them a few weeks before I proceed with the whole batch of them. I believe baking will permanently stress relieve these pieces. We'll see.

_________________
I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Stuart, I have a Delmhorst J-2000. It is a pinned meter and works great when working with billets. RH varies by area and season. Here in Michigan, stabilized RH seems to be around 7 to 9%. When I get new wood, I always check the moisture content. Thick lumber can take some time to adjust; however, resawn 3/16" panels will dry much more quickly. Checking moisture content of thinner stock may be easier with a pinless meter, but I have never used one.

I generally tend to resaw earlier as opposed to later.

Ken

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http://www.casperguitar.com

I use mine all the time, but then I tend to buy pretty close to the source (sometimes from the mill that cut from the actual rounds). I have set up my own drying operations (both DH and Vacuum kilns) when the deadlines didn't allow getting in the queue @ the mill.
Internal stress is a different animal, and is very real indeed. In very general terms if the wood moves as you cut it, it's stress. If after you've done your re-sawing it's likely to be moisture related.
-C

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Freeborn Guitars
and home of BeauGuard©

Case hardening usually happens when the wood is kiln dried too quickly or at too high a temperature. It causes the outside of the wood to dry faster than the middle. The outer wood cells collapse and prevent the internal moisture from releasing to the rest of the board. When you rip a case hardened board it can open like a blooming flower or pinch on the back of the blade causing a kickback.

Alex

By the way, I picked up a Delmhorst J-lite which can be found anywhere for around $150. It is a pin type but really, I don't find that to be a big deal as I stick the pins in the end grain.

I picked it because the minimum thickness is much smaller than the pinless types (though I didn't know at the time that you could use the pinless ones on thinner stock by holding the stock in air) and it's about $100 cheaper.

I just looked on e-bay and there's one on there at $29 right now.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

That's a good explanation of case hardening, thanks....but the result you describe is opposite of what occurred here. When I made these cuts, the middle of the boards popped away from each other. Doesn't that indicate that the inside was drier than the outside?

_________________
I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Can you describe the orientation of the grain with respect to the cut? I think it really can go either way and just remember that the thicker the wood, the worse the warpage is going to be and no matter what, it's going to warp. I just bought some 12/4 Hard Maple about 13" wide that I have to cut down to 4" wide billets for Bandura necks and I suspect that's going to be a bear to cut.

Thanks for reminding me that I have a moisture meter though!

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

It makes sense to me if the wood is case hardenened then the outside is going to be denser or more compressed causing the wood to cup to the outside while sawing and the opposite if the wood is drier in the middle which would pinch the blade.

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Hutch

Get the heck off the couch and go build a guitar!!!!

Unless wood is stored in a highly humid situation, the middle of a board is going to have a higher M.C. in the middle. When you measure the M.C. of a board, you want to get that measurment at the center of the board. With a pin type meter you push the pins into the wood parallel to the grain. If the wood is thicker, you can put two nails or screws into the wood the same distance apart as on the meter, and then connect it to the meter pins with alligator clips. This works well if you want to monitor the M.C. in any board over a longer period of time. You can chart the rise and fall of the M.C. and when it stays the same for a period of time, the wood has reached equilibrium, relative to its environment.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

Just to clarify - parallel means "long grain" right? I read that in the manual for my meter.

Perhaps this makes a bigger difference with a more accurate meter but, I just went into the basement and checked the moisture of 3 boards and got identical readings parallel, across, and in the end grain. Obviously though you do need longer probes for thicker material to get a reading deep in the wood.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Thats right, Andy. I think the reasoning for measuring along the grain is because the moisture across the grain can vary because of the distance between the pins. Measuring the M.C. parallel to the edge of the board should have pretty much the same amount of moisture, as wood will likely dry at the same rate along a boards length rather than across its width. The identical readings might mean that the boards have reached equilibrium.
Maybe I'll experiment next time I get some lumber by driving three nails equal distance from each other so that I can measure along the and across the grain with the center nail being a common axis point.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

One thing I just remembered that I read in the manual of my meter - they say for thick boards, you should use the insulated hammer in pins implying that uninsulated pins wouldn't give an accurate reading.

Edit: insulated shafts. The tip of the pin is bare.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

I guess an illustration would help.

To reiterate...this wood is kiln dried 8/4 Sapele cut to hunks 19" x 7". It is nearly perfectly quartersawn with the grain running from lower left to upper right in the illustration.

It sat in my shop 8 months stickered and waxed. Upon completion of this resaw cut the wood would "pop" open as illustrated.

Baking at 320F for three hours under serious pressure brings them back flat again so I think I'm ok on all this wood...but I would certainly like to understand this better.

_________________
I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Stuart - Were the outsides of the board slightly concave before you made the cut, or flat? If the center of the boards were thinner in the middle and thicker on the edges like an "I" shape it could be case hardening, otherwise I think we all know that wood can do some weird S&#t sometimes!
I would suggest in the future to select a thickness of wood that you won't need to resaw. I know that the thicker boards are usually the nicer ones, though. I'm glad the baking worked out. How did you weight the boards down? Did you do some potatoes on the side?

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

Stuart - it's a Wagner MMC220 - it's been solid and well worth the dough IMO.
Says $395 on the Wagner website, but I see them on theebay from $165.

Cheers,
Dave F.

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

The boards were straight as can be prior to resawing. It did the exact same thing on all 12 blanks I sawed even though they came from two seperate boards. I have about 36 more to cut......and now bake.

Troubling. It drives me nuts to fix a problem but not understand why it occurred. Ah well...at least it's controllable. In the oven the boards were clamped tight between two 1-1/4" thick aluminum plates. They seem totally stress relieved and stable after baking even though they were pretty well cupped to start. I'm still worried to build with them but time will tell. Sounds like a good idea to store them flat under pressure.

_________________
I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

This turned out to be a moisture issue which was discovered and resolved when I brought samples of the wood back to the distributor that sold it to me.

Putting a moisture meter on it we discovered the wood had a moisture content of 12%. Since I control the temperature and humidity of the shop...the man admitted that unit was pretty well fouled up in the drying process. Plus it was hard to argue with the resawn boards I also brought that were cupped like a potato chip. I told him that all the lumber had been processed into 19" billets and had been waxed.

He agreed to replace all 140 board feet at their expense. A very honorable company.

I bought a Wagner MMC205 moisture meter today. It's a little limited in the density range but the density of the sapele and maple I use is well within the range. I also read you can set it for half the density and double the reading...or something lke that. Doesn't really matter. It's probably a good idea to have a moisture meter on hand when sorting through piles of wood. That would haved saved me from this whole debacle.

_________________
I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic