Japanese Tool Box #2: Finishing Cutting Mortises

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Blog entry by ruddhess posted 04-08-2015 05:15 AM 1541 reads 0 times favorited 2 comments Add to Favorites Watch
« Part 1: Cutting Sides & Square Tenons Part 2 of Japanese Tool Box series Part 3: Dry Fit & Glue-Up (Sides Only) »

At this point I am cutting the mortises from both sides with hammer & chisel – not using the 3/4” forstner bit. This is the first one.

Two done, six to go.


One thing I discovered during this experiment: the mortises on the first board that I cut using the 3/4” forstner bit were a tighter fit for some reason. The second board mortises were all done with hammer & chisel and came out a bit oversized as shown in the pictures. I was able to keep from making the last four mortises (13/14/15/16) as big as the previous four (9/10/11/12) using only hammer and chisel. So it’s a learning curve getting it just right. I guess some folks make their mortises first and then cut the tenons. Not sure that would have enabled me to make tighter joints or not. I’ll have to experiment some more.

-- Rodney, Arkansas

2 comments so far

View djwong's profile


176 posts in 3824 days

#1 posted 04-08-2015 08:01 AM

A few things really help me when cutting mortises by hand…

Be sure to knife in your lines for the front and back of the mortise. As you are cutting the mortise, stay at least 1/8” (1/16” when you have more control later) away from your knife lines. Cut half way from one side of the board, flip it over and cut from the other side. The final cuts to your knife lines should be very thin cuts so that the chisel does not push past the knife lines. I like to use a guide block for these paring cuts. If practical, I will clamp a board lining up with the knife line on all the mortises. That way the baseline will be the same on all the mortises. I will sometimes use a machinist 1-2-3 block as the paring guide for the chisel. Place a chisel in the knife line and align the block to the chisel, and clamp. A neat trick I picked up from Chris Hall’s “thecarpentryway” blog, was to use a little camellia oil on the endgrain to prevent breakouts when paring. It softens the fibres so they are easier to pare. One caveat is that you have to wait several days for the oil to evaporate before applying glue.

Practice makes perfect, and it looks like you are off to a great start.

-- David W. Cupertino, CA

View ruddhess's profile


117 posts in 1814 days

#2 posted 04-10-2015 03:13 AM

Awesome tips! Thanks David! I will refer back to this before I cut mortises on my next project! I actually like working with the chisel and hammer. I need to take some time and make a traditional wooden mallet though. :-)

-- Rodney, Arkansas

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