Slip-fit Corrects a Slip in Planning

I’ve been working, albeit slowly, on a small desk from the Museum of Early Southern Decorative Arts (MESDA) – I wrote about full-blind dovetails found on the desk in an early post (read it here). The base of the desk holds two drawers set side-by-side. That means there is a drawer runner centered in the base. In this particular desk, the center runner’s tenon extends through the back of the base. I mortised the back for the tenon and planned so the top of the runner would form the tenon to slide through the mortise.

I made the rear tenon ½” longer than necessary to reach the rear face of the back assuming that I could slip the tenon in place, shove it back far enough to allow the front tenon of the runner to slip into its mortise in the front lower rail. The problem came in my belief that I could slip the runner in after the base was assembled. Yep, that didn’t happen.

I could have made it fit, but only if the mortise-and-tenon fit as loose as a football player’s jersey is on a cheerleader. Another option would be to use a narrow tenon and slide the piece in at an angle while keeping the runner level with the bottom edge of the assembled base. Either option meant wedges to hold things tight and that wasn’t going to fly. Also, I wasn’t keen on dismantling the base because that would surely result in something broken and the entire project being chucked into the trash.

After spending a night thinking about how I had screwed up, I came up with a plan to fix my mess. No, I didn’t plan to fill the mortised back then use a bridle joint to hold the runner – that would be great if the back was unscathed. My idea was more ingenious.

I made a runner with a front ½” tenon and cut it to fit between the front and back of the base, then I plowed a groove sized to the exact width and thickness of the back’s mortise into the top face of the runner. The depth meant that I cut away a small amount of the front tenon. Of course, I could add a thin piece there and no one would be the wiser.

Finally, I milled a piece to fit the groove then slid it in from the back of the base. It became apparent that I could trim the front of the filler piece to fill in the thinned front tenon. In the photo, you can see how this all comes together. And with all the flat grain glue surface, there is no way the runner will ever come apart.

If you ever find yourself with an assembled base without the runners installed, give this a try. It worked great for me. As I always say, you learn more from mistakes than you ever do from getting things right.

Don’t forget that you can click on most of the photos to make them larger for a better look!

— Glen D. Huey

If you’re like me and need a refresher course on mortise-and-tenon joinery, check out these DVDs:

“Design Better Mortise & Tenon Joints” by Bob Lang

“Hand-cut Mortise And Tenon” by Rob Cosman

“Mortise & Tenon DVD – Tools and Techniques from a Master Woodworker” by Jim Klingshot

4 thoughts on “Slip-fit Corrects a Slip in Planning

  1. TNWoodwright

    you can also use a loose tenon. Cut the mortise full depth + in the runner. What ever depth you choose in the back.
    The plus in the runner depth is for one or two springs. Makes aq spring loaded loose tenon.
    Push the tenon in and when it hits the mortise on the back it will pop in the hole. Can be down with dowels too

    DAMHIKT :)

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