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Question for the chisel specialists..

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Midnight

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I'm fast coming to the point where I need to decide how I'm going to make the wedged tennons for this bed I'm making... I'm at odds between going with either a horrizontal or vertical wedge.. the tennons in question secure the main rails to the head / footboard legs.

little background.
I've extended the tennons beyond the legs absolutely as far as the stock I had would let me, close to 70mm if I remember right.. the tennons are 30mm wide, and 165mm deep...

Up front I'll admit that these were my first EVER M&T joints.. hense prehaps being guilty of making em a bit on the big side.

When I origonally pictured in my mind how they'd look, I "saw" vertical rosewood wedges, long and slim, inda elegent.. C'mon gimme a break. I was on meds at the time...

I'm up against it every which way here... experience wise.... never made a mortice in tennon before, much less one that's deliberately tapered, though I understand full well how it should be done...
Prob for me is laack of proper tooling to make a mortice that deep...

If I have to, I'll bite the bullet and go with horrizontal wedges, although I don't wanna give up on the verticals unless I have to....

I already figure I'm nuts for thinking about this.... but taking that that's a given, what are my options here.??

Forgot to mention that the material is Scots Oak...

Any and all constructive suggestions will be lore than gratefully received.... other than hints to g'wa an boil ma heid... had that done once too often for thinkin about this in the first place...

<edit>
btw if this makes sense.... explain it back to me..... I was up all night last night stressin over this....
got just the one shot to get it right....
 

Chris Knight

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Mike,
I guess you want to do this? http://www.chrisknight.info/gallery/Woodwork/wedged_through_tenon?full=1

The mortice can be made most sensibly by hand on a long piece like your bed frame. You can chop it all out, or more easily get rid of most of the waste with a brace and bit. Attack it from both side and meet in the middle. This way, inevitable (?) inaccuracies won't show. You will need a proper registered mortice chisel for something like this. Depending on what size chisel you get, that defines the thickness of the tenon also. With 30mm to play with, a 10 or 12 mm chisel/tenon should be fine.

Note how the mortice angles back into the bedpost to ensure that everything remains tight.
 

Adam

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I did some wedged tenons recently for a table....

http://www.pbase.com/image/28453912

But I've reread you post and don't think you mean this type of wedged tenon. Have I got the name wrong for the type of joint in my piccy above anyone?

This could be useful anyhow...

http://www.woodworkersjournal.com/artic ... dtenon.cfm

Anyway, what I was going to say was when I made my wedges, I cut some thin veneers, then using the belt sander upsde down, and a sacrificial stick. I used the sander to produce the wedge, rather than carefully paring them with a chisel like I have done in the past. You have to be careful as the wood gets quite hot, and you have to watch your fingers, as it'll eat your finger tips away pretty quickly DAMHIKT. But it's very fast, and effective.


Adam
 

Chris Knight

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Adam,

Your joint is a wedged tenon. The other is a tusk tenon. the wedge in the tusk tenon is comparatively loose actually. Vertical wedges are preferred because as the wood expands and contracts with humidity changes, any looseness is compensated for by the wedge dropping deeper into the mortice - at least that's the theory - I reckon you will need to give it a whack actually!
 

Aragorn

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Hi Mike
I think Chris' suggestion above is how I would do it for such an enormous tenon (you're really worried about this bed falling apart, huh?!) i.e. auger bit.
You mentioned tapered mortices in your post, but these mortices don't have to be tapered - they just have to angled. (The wedge is of course tapered).
Is this going to be a knock down joint or will you glue it all up when finished?
 

Neil

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Hi Chris,

Can I ask which book you scanned the wedged through tenon from? I know I've seen that picture before, but I just can't remember where :oops:

Thanks,

NeilCFD
 

Aragorn

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Looks suspiciously like The Complete Illustrated Guide to Joinery by Gary Rogowski (Taunton)?
Attractive looking joint.
 

Midnight

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Hi guys……..thanks for the replies, AND your patience.. Waterhead.. that’s the pipper I wanna (try) to emulate.. and yes…. This is intended as a knock down joint, the other M&T’s will be glued and probably doweled too… Tusk tennon huh….??? Canna say I’ve heard the name before… but I got the same book…

Re the mortise chisels… I’ve been hunting high and low for a set with decent length blades for this very reason… Any recommendations..??

One last thing.. the bed’s sposed to be a wedding present; what the recipients may lack in skill, apparently they make up for with enthusiasm…. if ya get my drift…. So no… I don’t wanna be hearing that they’re in traction cos the bed joints blew out…
 

Chris Knight

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Axminster do mortise chisels with 140mm long blades which should be long enogh (remember you will be digging the mortice from both sides)

Marples sash mortise chisels are around 165mm (140 mm usable)

If these are too short for your liking, make one from a bit of tool steel, it does not have to be a thing of beauty for essentially one job
 

Aragorn

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So....... not going to be glued eh?!
Is any one else at all concerned about the relatively short length of the through tenon? Given the kind of, er, use it's going to be supporting.
I suppose there'll be about 30-40mm of endgrain timber left after morticing to support the tusk?
Midnight - may be no reason to get worried, but hopefully someone who has used this joint a wee bit can offer some reassurance.
 

Midnight

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Waterhead… thanks bud…. That’s exactly the kinda help I was looking for..

Aragorn…

I’ve had the basic frame assembled a couple of times now, the through tennon joints are tight enough to need waxing before the tennons ease home. Even then it requires suitable persuasion (purely functional, nothing tooooo excessive) Even without the through wedges, the joints are good and tight. That said, I DO appreciate where your concerns are coming from…. That concern was part of the reason I posted in the first place… I’ve never been too proud to admit I need advise.
Couple of thoughts on the issue.. As yet, the construction isn’t committed to the direction of the through wedge; a horizontal wedge may leave more material in the end of the tennon at the cost of being subject to greater sheer loads. The vertical wedge is distributing the same load over a wider area, reducing the pressure on the area. The other thought was…. Leaving the face of the mortise farthest from the leg with a round profile, shaping the wedge to suit. <read the other night that rounded mortises are better able to withstand the kinda forces we’re looking at here… athletics not withstanding.

Bottom line here is I’ve read all I can lay my hands on…. Surfed as many links as I can find, I even have a structural engineer looking at it…. and I’m still not sure…. Talk about nervous……..sheesh
 

Adam

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I'd leave them vertical as you originally intended. If the happy couple do get a bit over zealous and heaven forbid manage to break it, you could always revert to cutting the extended tenon back to the leg, and gluing fixed wedges, or dowel it, or a couple of screws, hidden with appropriate caps.

Adam
 
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