Wedged M&T joint

[9fingers]

I'm about to make my first wedged M&T joints

The tenon is 18 x 70 and the mortice is a fairly good fit. It is not a high stress joint and the wedges are goint to be fitted more for appearance than extreme strength.
My question is about the slots for the wedges. Are these normally cut witht he same taper as the wedges, at a slightly more acute angle than the wedges to allow for a close fit when wedged or simple in a parallel kerf cut.

Some references I have found on line suggest a hole to be drilled at the end of the cut to stop splits but nowhere have I found detail of the cuts themselves.

Help please!

Bob

 

[AndyT]

The slots are straight saw cuts, but you need to pare the edges of the mortice at an angle. The idea is that the tenon spreads to a dovetail shape so it can't pull out of the matching mortice.

So, on your dimensions you could make your wedges (say) 3mm wide, tapering to 1mm. Mark 3mm back from the edges of the square-cut mortice, and pare at a slight angle. (Use a wedge as a guide to the angle; it does not need to be much.)
Leave about 5mm of the mortice not tapered, so as to keep your reference points right to make it all square. Saw the slots to stop 5mm from the root of the tenon.

In softwood there's no need to drill holes to stop splitting; in hardwood there could be if your wood is a bit brittle.

 

[joiner_sim]

Andy said it all pretty much perfectly! I would normally do the saw cut straight at a very slight angle if anything!

 

[9fingers]

Thanks Andy & Simon.

Simon, when you say cut at an angle, do you mean the cut is a wedge shape or the kerf cut is made at an angle to edge of the tenon?

Cheers

Bob

 

[joiner_sim]

the kerf cut is at angle.

 

[9fingers]

Thanks Simon

 

[joiner_sim]

Only slightly though, not much at all. The mortice should have wedge room chopped in.

 

[dexter]

Also if you're cutting haunches in the tenons then use the waste section as the material for the wedges as it will be the exact thickness required, and cut the wedges from the tenon before you Finnish the haunch, it will save a lot of fiddling about.

Dex

 

[Steve Maskery]

And if your mortices are close to the ends of stiles, keep a good bit of extra length on the stiles until the glue has dried properly. If you cut your stiles to length before assembly, you run the risk of popping out the short grain between the tenon and the end of the stile.
S

 

[dannykaye]

if your wedge is 3mm you need to pare back 1.5 mm on each side of the mortice not 3mm

 

[AndyT]

if your wedge is 3mm you need to pare back 1.5 mm on each side of the mortice not 3mm

Not if you are putting two wedges in each tenon, and as these are 70mm wide, that's what I would do.

 

[Mr T]

Hi Bob

The important thing with decorative wedged mortice and tenons is to get the wedges to appear the same thickness, this depends on making the wedges uniform and driving them in to the same depth. I try to cut the wedges on a wide piece then cut a number from that piece and ensure that I drive them into the same depth, using a piece of packing as a stop.

Decorative wedged mortice and tenons in a piece say "look at us, what a good maker"! if they are not uniform the skills of the maker are exposed.

Chris

 

[9fingers]

I glued up a couple of joints today and the results were OK for first attempt but I will need to do more practice joints before I try making 'feature' wedged tenon joints.
These two will be underneath the piece and not likely to see the light of day too often which is probably a good thing!

Thanks for all the tips and info.

Bob

 

[grahamar]

Hi,

Don't know if this link helps at all- it's got quite good pictures of at least one way to do it.

http://americanwoodworker.com/blogs/techniques/archive/2009/09/08/wedged-mortise-amp-tenon.aspx

Although theres probably better/safer ways to cut the wedges than shown.

Graham