Pinning a M&T joint even when not draw boreing?


Brendon_t

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Hey guys, long time reader but first time poster. I have searched the web but not really found any answers so I figured I would reach out and try to lean on the expertise here.

A while back, my mother asked me to build her a new front door. I had never undertaken a project like that before but agreed loving the chance to learn. The door is made out of 8/4 red oak. The muntins and rails connect to the stiles via through mortises.

Here's the problem.. I decided to do the glue up in two stages since I knew I would be assembling by myself. I left everything in "dry fit" setup and only removed one stile and proceeded to coat the tennons and paint the inside of the mortises with TB3. I can't exactly describe it but I just do not feel like the first side glued up as well as the second side.

Here's the question.. I am terrified that the glue joints on the first side may fail and start coming apart before the door has lived its life. Is there any wisdom in drilling 3/8 in holes and pounding in a slightly over sized peg covered in glue? I know it would make me feel a bunch better about having the joint reinforced but I really don't know if this would actually hold the joint together IF the glue bond was to begin to fail.

Any input is greatly appreciated. Attached pic is of the current state of the project.

And if Marc actually reads these posts.. Love the random shirts in the videos.

post-16319-0-80073700-1413942295_thumb.j

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Nice looking door! I will defer to any more experienced advice that happens along, but I doubt you would gain much by pegging the joints. Without the draw-bored offset, they won't tighten the joint. If the glue fails on the M&T, pegs might keep it from collapsing, but it will still wiggle its way into uselessness.

Since you used through mortices, perhaps you could consider adding wedges to the exposed end of the tenon. May be difficult to execute after glue up, but would at least add tension to the joint in such a way as to make it tighter.

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+1 on wedges. You can either make tapered through mortises/parallel-split tenons or the much easier tapered tenons/parallel mortises. In both you drive the wedges in also coated with glue at assembly time.You can also do fox wedging.

Don't bother with dowelling on a door.

 

Have a look at this article http://www.craftsmanspace.com/knowledge/wedged-tenon-and-mortise-joint.html

 

and here http://www.woodworkersuk.co.uk/blog/tips-and-tricks/woodworking-joints-angle-joints-part-2/

Image C shows a parallel mortise and should show a tapered tenon but the artist didn't quite get the picture right.

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If your worried about your joints because they are more loose fitting than you like then you probably have a valid concern. I can't tell in the pics but it does not look like you used any cope and stick joinery along with your M&T, you also used solid wood. Your lower toe rail is wide so expansion is an issue. Solid wood doors are thing of the past with modern interior heating and cooling. Your wide rails should be provisioned for expansion, preferably towards the center of the door.

What we call a solid door today is a stave core door. Staves are cut, turned on edge and glued back together then covered with thick quarter inch "veneer" although not officially veneer since its so thick. This prevents the stiles and wide rails from over expanding and contracting, breaking the joinery and getting to large in the winter for the frame. I don't know where you live, some place warm and dry you will be fine but here in WA you would have issues.

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PB very good info. Thanks. We live in southern California. 60 degree winters, 90 degree summers. Humidity stays about 25pct year round.

The 9 inch kick panel was cut down to 3 sections then glued back up.

 

It doesn't matter if its three pieces glued together it will still expand and contract across its width.

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The OP asked about pining –v- drawboring. I agree with all the above advice and discussion, but wanted to address the pinning issue in vivo and quite separate from the door application… In other words, does pinning improve joint strength or do you have to drawbore to get any advantage?

 

It’s been quite correctly stated that wedging ads significantly to the strength of a M/T joint and drawboring can maintain joint-integrity in the event of glue-failure… I did want to point-out that adding a pin (non-drawbored) also strengthens the joint, but not to the extent of wedging, et al. It also lacks the glue-failure stability of draw-boring. None the less, pinning has it’s uses… Some years ago, the US Forrest Service’s Forrest Products Lab published a report on the strength of various M/T configurations (there are about twenty recognized configurations of M/T joinery). If memory serves, even minor pinning contributed significantly to M/T joint resistance in several failure modes. Even something as trivial shooting two 21g pins into a standard apron/leg joint (Norm, where are you now?) increased the resistance to racking failure by almost a 1/3rd. Now this is total failure, but we’re more interested in noticeable racking (i.e. minor, but visible, shoulder separation). 21g pins didn’t help much in that regard, but 3/16” pinning nearly doubled the joint’s resistance to noticeable racking in the standard ¾” apron to 1 ¼” leg joinery that we frequently encounter. I believe FWW ran an article some years back showing similar results.

 

On a historical note, many craftsman toenailed joinery in casework – same reason and same result. This is frequently seen in dado-joined shelving. Even a century or two after the glue has failed, shelving can be so thoroughly joined to casework as to make disassembly nearly impossible… It’s quite striking just how strong a couple of well-placed nails really are.  On a side note: while great for the long-term integrity of the piece, pinning/toenailing, etc can make restoration a bitch – case in point, I’m working on an oval entrance table dated to about 1820. The base is carved Mahogany with a rather nice veneered apron. The veneer is starting to separate from the substrate (not uncommon) and would normally be a fairly straight-forward fix, but the original craftsman reinforced the apron/leg joinery by toenailing. This is proving most stubborn – unfortunately, the original craftsman was enamored with nails and rather good at what he did… I’m not sure exactly when/why pinning/nailing/etc became taboo, but it’s quite amazing to x-ray antiques and see just how many fasteners are hidden-away…

 

So anyway, I’m not sure if/how pinning would assist the project at hand, but it certainly does have its place…

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Anyone ever try to overdry, size, and then raise the moisture level of the pin dowel? Can you get a dowel that is a tight enough friction fit that it will not budge even with glue failure?

 

You can wedge a dowel either through or blind. If your doing blind you just have to make sure its right before seating the joint.

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In my work, I've fixed MANY mortise and tenon joints.   I see way more that have failed because of too aggressive drawboring, than ones that are still tight because they were draw-bored. Talking about joints that are a couple of hundred years old.  To me, the benefit of a pegged mortise and tenon joint is that you can get it back apart if it wasn't glued.  As far as longevity of the joint goes, I believe initial fit, and wood selection by grain is most important.

 

When I drawbore window sash, I use the same jig on the drill press table, and a couple of sheets of paper for the offset on the second hole punch.

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Thanks guys. Great info here. I have taken your info into account and wil make a decision here one way or the other.

I guess one last comment can't hurt on my own post so here it goes. . This thing was an absolute blast to build and I learned so much doing it. If I was starting again today, there is a hundred things I would do differently but even if this thing tanks in a few years, it has really pushed me over the mental edge from just putting something together or fixing something to true woodworking.

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