Nailing M & T joints

[Arthur 51]

I will be glueing and pinning my door frame sections soon and I ordered 3" lost heads from screwfix. Should I have bought ovals (brads) for hammering through the glued M & T joints?

Thanks.

Arthur , UK

[Luigi Zanasi]

Why would you want to nail glued Mortice & Tenon joints????????

Luigi

[Arthur 51]

Why would you want to nail glued Mortice & Tenon joints????????

Luigi

Just taking a belt and braces approach.

It will also help to tighten the tenon into the mortice a little.

Arthur

[Swingman]

Traditional "pinning" of a mortise and tenon joint would indeed "tighten the tenon into the mortise", but it's a bit late to do that in the traditional manner.

You're just adding mechanical fasteners to a joint that, if executed properly, normally does not need mechanical assistance for strength ... but don't let that stop you if you feel it necessary. You do see this quite a bit on outdoor furniture made overseas, but in that case the joints need all the help they can get due to sloppy work and inaccurate factory method engineering.

[Tim W]

I don't understand. Are you nailing into the end grain of the tenon instead of a wedge? You can't be nailing through the mortice and the tenon with a 3" nail, or is that a typo? Anyway if it is indoor work then glueing should be enough. Outdoor work subject to a lot of movement and stresses from the changing seasons might be helped by nails, but that isn't what you asked. Ovals or lost-heads? Either really, drill first if there is a danger of splitting.

Tim w

[Arthur 51]

I will be nailing through the long side of the mortise at about 45 degrees. These are big tenons about 22mm thick by 70mm wide (sapele)

T

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The door frame is an external one and will be exposed to the weather. I am gluing with a PU glue.

Thanks.

Arthur

[Phisherman]

A pin through a M&T joint might weaken it. A well-fitted M&T joint is about as strong as it gets.

[RicodJour]

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I thought you were trolling. I wouldn't use screws at all. I'd use brass or stainless pins set flush with both surfaces. 3/16" or 1/4" pins would work.

R

[whit3rd]

The use of a hammer on an assembled joint is more likely to disturb it than to enhance the fit. There IS a 'nail' approach that is sometimes used, but it's a wooden nail, and is used with bored holes that are slightly misaligned. The wood nail (a tapered non-dowel, with edges that will bite the wood) is driven in, and forcibly pulls the tenon deeper into the mortise. It's a kind of internal clamp.

This nailed mortise is used in heavy timber joinery There, glue is not useful, either because the gaps are too large or because heavy timbers are often assembled green and aren't glue-compatible.

If you have real clamps, and time to let the glue set, and modern glues, the nail is just ... silly.

[Tom Veatch]

Sounds to me like it would be worth considering drawboring and forget the glue.

Tom Veatch Wichita, KS USA

[Father Haskell]

Split the pins from some nice hardwood scrap, much classier than steel nails. Typically, you'd use pins (drawpins) to tighten the M&T, not reinforce it.