Replies

1. 
   Alan | May 19, 2002 06:21am | #1

   Joe,

   The most usually given formula for determining the size of a mortise is more than 1/3 but less than 1/2 the thickness of the stock.  You are closer to being correct, though.  In practice--especially in 3/4 stock--most people I know just make it 1/3.  That's very convenient on 3/4 stock.

   As for centering the mortise (I assume that's what you want to do:  make both cheeks of equal thickness, i.e., center the mortise) one of the beauties of using a mortising gauge to lay out your mortises and tenons is that there's no need to have it perfectly centered.

   After you have set the gauge to the thickness of your mortising chisel (or whatever implement you use to cut them) all you need to do is to eye ball it as close to centered as you can.  But don't torture yourself unnecessarily trying to get it perfect.  The only thing you have to remember is that when you mark out for the mortise and tenon, gauge them both from the face side.  That way, no matter where the marks actually are, they will be in the same relative position--exactly the same relative position--for both the mortise and tenon.  Then all you have to do is to cut them out on the lines.  Whether they are centered or not the joint will go together perfectly, with the two boards' faces meeting flush.

   Alan

1. 
   JoeCoty | May 19, 2002 08:57pm | #3

   Ok, I follow you, I wasn't using the gauge to mark the tenons. It was easy to center the tenons using a dado blade and creeping up to the width after the mortises were chopped.

   The method you described doesn't depend on centered fittings. In this case I suppose a bandsaw would be easier to cut the tenons to match the marks.

   Altogether this seems less fussy and quicker, thanks.

2. 
   gpwest | May 19, 2002 06:54am | #2

   Joe,

     Instead of being overly concerned with getting the mortise exactly 1/3 the width of the workpiece, I think it's more efficient to mark it as close to 1/3 as practical, but exactly the width of whatever tool you are using to cut the mortise with (mortise chisel, router bit, bench chisel, etc.).  GP.