interference fit / walnut / mortise and tenon corners

[andrew whicker]

Hi all,

I'm making a coffee table with lots of mortise and tenon corners. I tested out the joints with poplar first. Found the right shims, jig location, etc. However, when I made a few pieces out of the walnut, I created some cracking in two female pieces.

The 1/2 dado blade I'm using makes about a 0.520" wide cut. Should I make the female around .510" (.010" interference)? Should I shoot for line to line (.520" female and .520" male)? I'll try some stuff when I get home tonight, but might as well as while I'm still at work..

PS: This probably sounds more accurate than it really is, but I'm using dial indicators to find my distance from the blade to the tenon jig. I'm also planing down two pieces of wood to set the tenon spacing. One spacer for the female, one spacer for one of the male cuts. The other male cut is made with the tenon placed against the tenon jig. Anyway, I can get pretty accurate with the tenon jig to blade spacing, but the wooden spacers / shims is sort of dumb luck.



cheers and thanks!

JIG:
0409172112.jpg

CONCEPT:
IMG-20170411-WA0003.jpeg

POPLAR RESULT:
IMG_20170412_120322_775.jpg

[Denis Kenzior]

If you're gluing these, then the tenon should be .004 undersized. E.g. .004" smaller than the mortise. Glue will swell the joint and produce a tight fit.

[andrew whicker]

You da man, thanks