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I'm making the joint for the leg shown in the following diagram, using handtools. There are two intersecting through-mortises. A tall one (for the apron running topleft-bottomright in the picture), and a square one (running topright-bottomleft).

double mortise

I have (incorrectly) started my joint with the tall through mortise first. I should have used a sacrificial piece to occupy the first mortise hole while working on the second, but I didn't, and my chisel blow has broken out maybe a 1/4" chunk from the lower inner wall.


leg1 leg2

On the left, the overall view of the leg. On the right, inside view from right side (high-res here).


It didn't break off cleanly, so I removed the chips. On the picture on the right, I've drawn a rough polygonal outline of the breakout.

Can this hole be re-filled with something? Or should I just restart the leg? I considered making an epoxy or glue+dust fill, and re-chiselling around.

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You don't need to repair this.

You're using a tusk tenon, so basically everything is going to be held in place by the wedge. With a different style of M&T joint, secured with glue, one could theorise that the reduced glue surface area might be an issue but it's of no relevance here.

But even if this were a glued joint I still think it's nothing to worry about. If you took apart old furniture made in the heyday of hand-tool workmanship I think you'd be surprised at how often you'd find chipout of exactly this sort this inside intersecting mortises.

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    It also looks like the square tenon is going to pass through a second mortise (sub-mortise? meta-mortise?) in the tall tenon, so this should be nice and secure. The inside, which doesn't show, doesn't matter! – workerjoe Jun 5 '18 at 13:59
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    For the other 3 legs, I've dug the mortises in the reverse order (tall one last), and it eliminated breakout almost completely - even without a sacrificial piece. I haven't disassembled enough old furniture (yet), but that's good to hear. My fear was that the tusk would be pushing against a weakened wall and sink it in. @Joe, correct, I have to punch through another square mortise into the large tenon (forming a wood "donut"), but there will be a gap where the missing chip used to be. – ww_init_js Jun 15 '18 at 7:39
  • Yes not everyone will get the chance to see much old furniture taken apart, a more accessible way to see just how rough hidden surfaces could be in hand-produced stuff is to slide out the beam from vintage marking/cutting gauges and look inside the mortise. The edges of the mortise are basically flawless in most cases (barring damage from use) but inside can look like a beaver chewed it ^_^ – Graphus Jun 15 '18 at 12:22

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