EMC Calculator

June 7th, 2019

A few years ago I created an online calculator for predicting how much lumber will expand or contract based on its percent moisture content (MC). I personally use it quite a bit! The calculator requires a starting %MC and a final %MC in order to calculate how much wood movement will occur. Unfortunately, sometimes it can tricky to predict a final %MC based on where in the country the piece of furniture will live.

In order to help with deciding on a final %MC there are equations that one can use (the equations have been previously published link). In order to simplify the calculations, I created an online calculator which allows you to enter your ambient air temperature and the relative humidity; the calculator will provide the %EMC (equilibrium moisture content) from these values. You could, in theory, use a relative humidity and temperature that would represent the largest deviation based on where your piece of furniture will live.

So if you know your starting %MC via the use of a moisture meter, you could then use the EMC calculator to come up with a final %MC in order to calculate how much expansion or contraction the wood might incur.

If you have any questions please let me know below.

Un-sticky Glue

March 29th, 2019

Because the veneer on commercial grade plywood is pretty thin, I tend to be extra careful with glue around it. I don’t want to have to do any sanding because glue made its way onto the thin veneer. When edge banding strips of solid wood onto the edge of plywood it’s almost impossible to not get glue onto the veneer surface.

One way to deal with this problem is to quickly wipe away the glue squeeze-out with a damp rag and another is to prevent the glue from sticking and deal with it after it dries; I prefer the latter. Several years ago (~2008) I bought a can of Waxilit, which is a very soft wax. Applying the wax to the surface of wood prevents glue from sticking and after the glue has dried onto the wax surface it is easily scraped away with your fingernail or a piece of plastic. After all of the glue is scraped away, the wax can be removed by wiping the area with a rag dampened with mineral spirits.

A while back I ran out of Waxilit and recently I decided to try ordinary paste wax (I use Johnson’s paste wax) and the results were the same as with Waxilit. I apply the paste wax near the edge of the plywood where I will be gluing on the edge banding. After scraping away any dried glue, the paste wax is easily removed with a rag dampened with mineral spirits. And if you are using a wipe on oil-based finish, any residual wax that is not removed will dissolve into the finish as it’s applied. This is because wax, mineral spirits, and oil-based finishes are all nonpolar or lipophilic (lipid-like or literally oil loving) substances and if you remember from your high school chemistry class, ‘like dissolves like’. This means that nonpolar substances, like mineral spirits and oil-based finishes, will dissolve other nonpolar materials.

Give this technique a try on scrap wood and see if you’re happy with the results; I think you will be.

Table Saw Blade Alignment

November 2nd, 2018

Last Friday, I published a video describing how to make and use a dial indicator jig to align your table saw blade to 45 degrees.  The jig is incredibly easy to make, and if you made my 90 degree alignment jig, you might be able to use the same jig for 45 degrees as well.

I have been using a form of this type of dial indicator jig for close to 10-years and a few of the most popular criticisms I receive for using them goes something like this:

  1. “This is woodworking, not metal working. We are not building Space Shuttles, so this degree of accuracy isn’t required for woodworking!”
  2. “Because wood moves, you don’t need to machine wood to within a thousandths of an inch!”
  3. “We only need to align our tools to the accuracy that is required for the project we’re working on!”.

The first two arguments are meant to imply that I am using dial indicators to align my tools because I want to be able to machine wood to within a thousandths of an inch, which is fallacious.  I cannot stress enough that it is NOT my goal to use dial indicators so that I can machine wood to within a thousandths of an inch, but rather to use them so that I can align my tools quickly without making test cuts.  The high degree of accuracy that comes along with using dial indicators is just a side effect; it comes along for the ride as a freebie.

The third argument above I sort of agree with, but if you are going to align your table saw blade to 90 degrees why not align it to a degree of accuracy that would accommodate ALL of your projects (you might forget to re-align it)?  My point above regarding speed applies here nicely; that is, if it’s just as fast or slower to align your table saw blade with a lesser degree of accuracy (by using a square against the blade) then you’d be sacrificing accuracy for no logical reason.

I think you’ll find that pushing a dial indicator jig against your blade (after it’s calibrated – which is a quick process), is just as fast as pushing a square against your blade.  The difference is that the dial indicator jig will offer you greater accuracy.