Tuesday, May 3, 2016

Project Update: It's Mortise Time

As you may recall, I cut the tenons incorrectly on one of the short stretchers. The good news was I cut it too shallow and needed to go deeper - from 3/4" to 1", This was easily accomplished using Random Roger Green's awesome tenoning jig.

Once I completed the final shortie, it was quick work to cut the tenons into the long stretchers. I don't have a photo of the process because I did them on the Laguna SUV and it's incredibly difficult to take a selfie while cutting a six-foot piece of wood with a 1" band saw blade. I did, though, snap photos of the long ones lined out for the tenon cuts and then all of the completed tenons.

Once these were completed, I could begin the exacting process of redrawing the mortise lines onto the legs. Why do it just once when you can do it four times, right? The thing is, I didn't account for the width of the thin-kerf table saw blade when calculating the dimensions of the short stretchers, so I lost 1/8" from the tenon widths. This I can live with. Though I cut the long ones with the Laguna SUV, I kept the same measurement for the tenons - 1 5/8" - that I used for the shorties. As Random often says, "It will be fine...it's just a bench."

Speaking of Random (Roger Green), he was kind enough to come over Monday evening and help me get things back on track, particularly with the mortising. As you probably know, he dropped off an enormous Powermatic mortising machine for me to use on the legs. The thing is a monster. And I love it. Too bad it must one day takes its leave of Tortuga Early Instruments Worldwide Headquarters.

The first thing Random helped me with was deciding on which chisel to use. Now, these chisels are interesting - they're designed to make square holes. The way this works is a drill bit sits inside of the hollow square chisel and clears most of the material while the razor-sharp chisel clears away the remaining wood. So, yes, it's simply a drill press that makes square holes.

The first step was setup of the mortising tool.

Once Random was satisfied everything was set up properly (drill bit/chisel mounted and depth and width stoppers aligned) and the appropriate chisel was chosen - we ended up using (I believe) a 1/4" chisel - we tested it on a block of scrap wood. Testing is always a good idea, one by which, as you know, I do not always abide.

Then, Random cut me loose on drilling the mortise for one of the short side stretchers and, voila! - it worked!

Everything lined up and looks pretty darned good. The one thing I will do for each of the mortises is draw its complementary tenon directly onto the leg because no two tenons are ever cut perfectly the same. Ever. I used this same idea for the mortises I cut into the bench top, using each tenoned leg to trace the mortise outline and that seems to have worked out okay, as well.

The next steps are to complete all of the mortise cuts this week so we can mount the stretchers, which will involve the use of "draw-boring," something I think you will find quite interesting in a future post.

Until next time...

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