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wedged through m & tenon joints

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paulc

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I am currently making my first workbench from Chris Simpsons design in 'The essential guide to woodwork' . Though it is stated here that sofwood will suffice for the underframe , I have experienced some cracking in the leg bottoms(red deal) when making the crossrail mortices. I have tried to salvage the legs by using wood glue on the cracks , but have yet to dry assemble the frame. My questions are - the proposed wedged m & tenon joints place the wedges within the tenon and I think that the tenon may split , would it be better to put the wedges between the tenon and mortise wall -top and bottom - rather than within the tenon ? some of the cracks so far happened when I tried to hammer in a tight tenon . How loose/tight should such joints be ? Any info would be great , Cheers .
 

Alf

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Paul,

Joints should be a push fit ideally. Okay, so maybe quite a hefty push, perhaps even with the odd tap from the persuader, but you shouldn't need to whale away to get them together. As for the wedges, you need to provide some clearance for them within the mortise, otherwise you will split something. Essentially you just need to slope the end sides of the mortise a tad to give the wedged tenon somewhere to expand into, a dovetailed mortise in effect. If you're still concerned, you could consider a pinned M&T instead perhaps? Dunno if that helps; joints aren't my strongest suite. :roll:

Cheers, Alf
 

Aragorn

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At the end of your sawcut for the wedge, (i.e. around 2/3rds of the length of the tenon) drill a hole thru the tenon (about 3-4mm). This acts as a relief point for the stress and helps stop the wood splitting.
Wedging top and bottom is also very effective and is used a lot in today's joinery trade.
Or just glue it all together with polyurethane glue and you won't have to worry about the joinery at all!
 
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