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Moisture Meters and buying lumber

#258836 by RFGuy » Sat Apr 13, 2019 7:51 am

A lot of my early woodworking was all 3/4" S4S lumber purchased from a big box store. No problems with doing this, other than the wood being more expensive (and limited quality sometimes). Once I got the Shopsmith planer many years back, I have migrated to working more with 8/4 lumber that I surface and thin myself. I have tried to research this a bit, but I can't seem to find an answer online. Recently for a project I bought a good amount of 8/4 cherry (8-10" wide and 6'-10' long). I won't name the local wood supply that I used, but it was a reputable place with a good sized warehouse with excellent wood options. I hand picked every board making sure in the store that they were as straight as possible with no cupping or warping, etc. I get them home and in a short time, some of the boards have cupped quite a bit and one or two have warped (twisted) as well. This dilemma seems obvious to me...the wood wasn't sufficiently dried sitting in the wood supply store. By the way, I stack my lumber flat with spacers when I get it home. So my solution for next time is to go into the store with a moisture meter and measure the wood in addition to doing my usual visual checks. Idea being that if the board is not sufficiently dry that I skip it and move on (how dry does the board need to be?). Am I on the right path here? Are there any other tips or suggestions that anyone has for keeping wood as straight as possible from the time it goes from store to shop before being cut?

Also, I am new to moisture meters. I was planning on getting a pinless one and was thinking of this one (Lignomat BW Dual-depth Pinless Moisture Meter), so if anyone has recommendations on moisture meters as well it would be appreciated.

https://www.amazon.com/Lignomat-BW-Dual-depth-Moisture-Capabilities/dp/B072BXHNN3/ref=sr_1_1?s=industrial&ie=UTF8&qid=1549383737&sr=1-1&keywords=ligno+duotec

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Re: Moisture Meters and buying lumber

#258839 by wa2crk » Sat Apr 13, 2019 11:27 am

Moisture meters have been known to give misleading results. I think that all they do is measure the resistance between two points on the wood at a specific distance. An ohmmeter calibrated in moisture rather than in resistance.
Bill V
Last edited by wa2crk on Sat Apr 13, 2019 12:22 pm, edited 1 time in total.

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Re: Moisture Meters and buying lumber

#258840 by Hobbyman2 » Sat Apr 13, 2019 11:47 am

My .02
Using your moisture meter check the moisture in a few boards at the store and then go back a few days later and check to see if they change .

I hardly ever buy anything other then from the mill so most all lumber I buy is well over 20%
I have had a similar experience buying 2x4 2x8 and 2x10 at the big box store ,I have hand picked premium studs and with in week they are twisted , crooked and look like ,, well they look like crap and others are still ok. the warping might be caused by the way the lumber is cut , flat saw'n, 1/4 saw'n ,rift saw'n etc. old growth v/s young trees also how much shake /twist / fuzzy grain knots are`in the board ,

is it possible the lumber you bought absorbed moisture after you bought it ? that can happen any time conditions change ?

I have had lumber stacked and it never moved , I have had lumber stacked and it twisted warped and bent ,had boards that were straight until I cut them and then they twisted , the way it was cut seems to make a difference in internal stress , this is just my observation .
If you use a moisture meter at the store and then check it a few days later in your storage my guess is the results wont be the same , unless you check the moisture in the air in the store and match that to the moisture in your transport and storage there will be a change in the moisture in the lumber .
If the boards are very wide you might think about cutting them and glue them back together to eliminate some internal stress

JMO
Last edited by Hobbyman2 on Sat Apr 13, 2019 12:02 pm, edited 1 time in total.

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Hobbyman2 Favorite Quote: "If a man does his best, what else is there?"
- General George S. Patton (1885-1945)

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Re: Moisture Meters and buying lumber

#258841 by Hobbyman2 » Sat Apr 13, 2019 11:49 am

wa2crk wrote:Moisture meters have been known to give misleading results. I think that all they do is measure the resistance between two pints on the wood at a specific distance. An ohmmeter calibrated in moisture rather than in resistance.
Bill V


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I agree , especially in long boards . the center will take longer to dry .

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Hobbyman2 Favorite Quote: "If a man does his best, what else is there?"
- General George S. Patton (1885-1945)

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Re: Moisture Meters and buying lumber

#258842 by Hobbyman2 » Sat Apr 13, 2019 11:55 am

how lumber dries,lumber dries from the ends more so then the sides , want to see for your self put a piece of green wood in a microwave for a few minutes , you will see the moisture boil out the ends , it moves moisture the same way it transfered the moisture from the roots to the tree top and back the roots ..

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Hobbyman2 Favorite Quote: "If a man does his best, what else is there?"
- General George S. Patton (1885-1945)

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Re: Moisture Meters and buying lumber

#258844 by RFGuy » Sat Apr 13, 2019 12:20 pm

Hobbyman2 wrote:is it possible the lumber you bought absorbed moisture after you bought it ? that can happen any time conditions change ?


Thanks. Yeah, I debated this and don't know the answer. I live in the Phoenix, AZ area so it is relatively dry here. Since the lumber is all in a good size warehouse, I would assume that the humidity level is higher there than at my shop. So, I assumed the lumber dried more when I got it home, but it could be the other way around.

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Re: Moisture Meters and buying lumber

#258845 by RFGuy » Sat Apr 13, 2019 12:27 pm

wa2crk wrote:Moisture meters have been known to give misleading results. I think that all they do is measure the resistance between two pints on the wood at a specific distance. An ohmmeter calibrated in moisture rather than in resistance.
Bill V

Thanks Bill. I tried one of the pin based moisture meters (a cheap one) and had problems with it so I returned it. In reading a bit about them and checking reviews is what led me to the Lignomat model that I put the link for. It uses electromagnetic waves instead of resistance to measure the moisture deeper in the board. These are supposed to be better, but are more expensive of course. Again I don't know how well any of these brands/models work. For me, $300 is a lot to spend on a moisture meter, but IF it works and IF I could use it to better select boards at the lumberyard then it could be worth it. Maybe some baords are going to cup and warp on me no matter what?

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Re: Moisture Meters and buying lumber

#258846 by Hobbyman2 » Sat Apr 13, 2019 1:16 pm

RFGuy wrote:
Hobbyman2 wrote:is it possible the lumber you bought absorbed moisture after you bought it ? that can happen any time conditions change ?


Thanks. Yeah, I debated this and don't know the answer. I live in the Phoenix, AZ area so it is relatively dry here. Since the lumber is all in a good size warehouse, I would assume that the humidity level is higher there than at my shop. So, I assumed the lumber dried more when I got it home, but it could be the other way around.



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You are suggesting taking a reading at the store and another a few days later at your shop?
I think you found your answer .

As far as meters go my'n is used as a reference because moisture will change no mater what until the lumber is and remains in a stable environment for a period of time ..
I know a contractor that puts their trim boards in the house for a week before he cuts and installs them , but here in ohio our humidity changes like the wind .

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Hobbyman2 Favorite Quote: "If a man does his best, what else is there?"
- General George S. Patton (1885-1945)

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Re: Moisture Meters and buying lumber

#258847 by RFGuy » Sat Apr 13, 2019 1:43 pm

Hobbyman2 wrote:You are suggesting taking a reading at the store and another a few days later at your shop?
I think you found your answer .


No, I was thinking of taking a moisture reading in the store. Hopefully in the <5% range. If so, then buy the board if it looks good. Then bring it home and hopefully is stays straight. This of course assumes that my shop humidity is stable and dry (good assumption here in Phoenix).

The other question is whether my shop humidity is higher than the lumber store. Besides using a hygrometer in both places, an alternative would be to use moisture meter on lumber in store before purchase, then re-measure lumber after it has stabilized in the shop. If moisture reading goes up after bringing it home, then my shop is the problem.

My assumption is the lumber in the store is much higher moisture content than I realize (maybe 20% or more). I still think this is the case, but I can't know for sure unless I test it.

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Re: Moisture Meters and buying lumber

#258848 by Hobbyman2 » Sat Apr 13, 2019 2:19 pm

Copy that . in that case the better the meter the more accurate the results will be .

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Hobbyman2 Favorite Quote: "If a man does his best, what else is there?"
- General George S. Patton (1885-1945)

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