Replies

1. 
   Jimma | Oct 15, 2004 04:10am | #1

   You know -- I'm not sure there's a practical answer for the "average" woodworker. My son-in-law, who is a consulting scientist, says the instrumentation needed for a really true reading of moisturer content is quite expensive and unavailable outside of laboratory sources. That's one opinion, but from a guy with a lot of field experience. For myself, I use a $100 Lignomat pin-type meter, but I don't make a lot out of the specific readings. I'm more concerned with whether it's OK to work the wood than to know precisely what the MC is. Soooo, what I do is take a measurement when I first get the wood in the shop and watch it for a while until the MC stabilizes. If it's green wood -- as in what's left after a hurricane -- I know it's going to be a year or so before it's suitable to use and just watch the readings over time. Maybe I'll cut across the grain someplace and see how the center compares to the end or surface. If it's quite different, it ain't ready. Most of the stock I use is kiln dried, but I generally season it in the shop anyway and just compare meter readings until they don't change much before using it. Practical answer -- it's good to have a reference or trend line, but accuracy isn't really of interest. You'll get used to what works and forget the science. (My opinion, of course.)

1. 
   forestgirl | Oct 15, 2004 07:19am | #2

   Well, I totally agree with your overall approach, Jim.  Otherwise, I'd not be bottom-fishing for a $35 moisture meter, LOL!!  I was just surprised to see how tiny the pins were on the mini-Ligno that I took a look at this afternoon.  Look to be about half the length of the pins on other <=$100 meters.  Am wondering if it makes any difference.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the  "I Rocked With ToolDoc Club" .... :>) 

1. 
   Jimma | Oct 15, 2004 04:47pm | #3

   My understanding is that the technology is one of essentially measuring the electrical resistance between the pins (similar to the way lie detectors work) so that the longer the pins -- that is, the deeper into the wood they can go -- the more they can measure and the "better" they are. However, if you're mostly using one-inch stock that has been acclimated to your shop, it isn't necessary to measure deeply into the wood since the wood, for all practical purposes, will have the same MC. The pinless meters do measure deeper than the pin types, but you would have to spend big bucks to get a device that would give you a "true" reading. I find the Lignomat to be a satisfactory shop tool for how I work, but maybe longer pins would provide a slightly deeper reading. Maybe Jon or Stanley could amplify on this.

2. 
   mlbfreestyle | Oct 15, 2004 04:50pm | #4

   I think it all comes down to whether or not there is a moisture gradient through the cross-section of the board.  That is, increasing or decreasing moisture as you move into the board.  The surface is more likely to change at a faster rate than the inside.  If you need to know the MC with a greater degree of confidence; do what I do.  Take an interior measurement by cutting off a chunk of the end.  I have checked moisture after having cross-cut a board and was satisfied that my meter was giving me good info.  I have the "Timber Check" variety.

2. 
   JohnWW | Oct 15, 2004 05:41pm | #5

   In practice the length of the pins probably makes no difference since the pins, under hand pressure only, will probably only go an eighth of an inch or so into the wood.  Some industrial weight meters have an accessory slide hammer with pins on the head that enables the user to drive the pins deeply into the wood.

   John W. 

1. 
   forestgirl | Oct 15, 2004 09:03pm | #6

   Thanks everyone, appreciate your input!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the  "I Rocked With ToolDoc Club" .... :>)