First mortising jig is a success!


MisterDrow

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I did something similar for my last project.  I had some scrap 3/8 thick lexan from other projects.  That helped visibility a bit.  It worked pretty well but I need knobs instead of wing nuts to keep the fences from slipping.  I'm definitely taking that page from your book.

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Yours is a lot closer to what I envision for mine.

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  • 2 weeks later...
Just a few of suggestions, and you may already be doing this. 

Whenever I'm making router mortises, I make a series of holes at the mortise location by straight plunging the up spiral router bit to the depth desired, with the holes spaced closely together and covering the full length of the desired mortise, I then plunge the router to the full desired depth and move it back and forth to clean out the mortise slot. This seems to require less effort by the router and result in less bit deflection. The resulting mortise will be closer to the router bit diameter when completed. Straight bits tend to clog with chips, resulting in binding, which enlarges the mortise width slightly..

If you are cutting these mortises for use with floating tenons, I found that planning the tenon stock to the thickness of the router bit diameter ahead of time, and then cutting it to size on the table saw after the size you need has been determined, results in very close fitting floating tenons made very easily with very little waste. Also, make the floating tenons about 1/8" shorter than the total depth of the two mortises. A little gap here is Ok, but if you make the floating tenon even slightly longer than the total depth, the joint won't go completely together during glue-up and you will have a disaster.

Floating tenons don't need to be rounded. Make them fit the straight part of the mortise and leave the 1/2 round ends of the mortise empty. The strength of the joint is in the fit of the flat sides of the tenons, the glue used, and the mating flat sides of the mortise. The 1/2 round spaces left will leave a place for any excess glue to go.

When using a router guide fence, always reference the fence to the face side of the board being mortised. If you do this, the face side of the two mortised parts will be perfectly aligned and the joint will be smooth, even if the part thickness is slightly different. It helps to pick a face side of each piece and mark it  before you begin the mortising process so it's easier to keep the pieces oriented correctly during the mortising.

I've been making routed mortise and floating tenon joints for well over 20 years this way and I have never had one fail. I must be doing something right, so I'm passing these tips on.

 

Charley

 

Wow! That is all absolutely fantastic information! Seriously, I'm blown away. Thank you very much for sharing all of that. This is the kind of knowledge that I love here in this forum and I am very thankful to those who offer the information so freely.

For my mortises, I plunged full depth at each end and then took several passes at increasing depths to slog out the middle. The triton router I have has excellent dust collection for vacuums so that helped keep a lot of it clear as I went along but the initial plunges did tend to burn a bit if I went too fast. I chalk that up mostly to using a straight bit rather than a spiral up cut bit. I've got one of those marked for purchase soon, though.

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