What wood for M&T pegs

[dedee]

My project for the coming months is a mini greenhouse like this one.

It will be made from Cedar but has to be in a knock down form as its final resting place (and the glass panels to be used) will be in France with my FIL.

The greenhouse above was made with glued half lap joints with the
side frames bolted to the front and back and shiplap providing more rigidity along the back.

This time I thought I would construct the frames with pegged M&T for two reasons 1) More challenging than a lap joint
2) The pegs should pull the joint together
without the need for clamps (FIL has not one).

Now to the point of this ramble. What wood should I use for
the pegs? Cedar? or woould something harder be better?



Andy

 

[Bean]

dedee
I have made two of these so far but sadly not knockdown ones. Where I have used pegs I have used the same wood or a strong contrasting wood. Having said that I do not think the strength is an issue provided you do not use balsa :wink: The distance the force is acting upon is very small and almost any wood will be able to cope. I would think that resistance to rot will be an important consideration as the end grain of the peg will be exposed.

I hope my ramblings make some form of sense

Bean

 

[ike]

I'd of thought Cedar would be OK as long as its a hardish bit, otherwise I reckon mahogany would work well as it's also 'antiseptic'.

 

[jasonB]

I've used oak pegs for green oak framing, but any durable hardwood should do the job. It is always better to split or cleave the pegs so that the grain runs straight along their length reducing the risk of them snapping.

This deck that I hade about 18 months ago is all held together with oak pegs and could be knocked apart if needed

http://photobucket.com/albums/v156/jaso ... CT0004.jpg

Jason

 

[Chris Knight]

Jason,
That is a super looking deck! It gives the appearance of just resting on the rocks under the uprights. Is that so, or are the rocks on a foundation of their own?

 

[jasonB]

Dug down about 3ft, poured a 6000x600x200 concrete pad then built up 450 square pier from 100mm dense conc blocks laid flat to just below turf level then bedded the rocks onto sand/cenent. Drilled the rocks for a stainles steel dowel with matching holes in the ends of the 8"x8"posts.

Jason

 

[Chris Knight]

Jason,
Thanks. That's not going anywhere soon!

 

[dedee]

Thanks guys.
That deck looks great.
The idea of splitting or cleaving pegs from the cedar makes be me think that square pegs would be easier to make than round ones. Square holes would be a doddle with the mortiser.

Andy

 

[tim]

Andy

A couple of things spring to mind:

1. Where are the pegs going? Pegs tend to work best if they are tapered so some of the peg will probably be proud of the finished surface. If you aren't going to move it again ever then obviously you can trim them flush but if you are going to collapse it again at some point then you need something to get hold of to pull them out - therefore they can't interfere with the glass doors.

2. I think you'll find it easier to keep both pegs and holes round simply because while the holes will be as you say a doddle on the mortiser, you need to make sure that the pegs are perfectly square and the same size as the hole which will be difficult if you are going to taper them (see above). If you keep them round there are several benefits - they seem to be more forgiving when shaping them; the hole has no obvious weak spots (like a corner would be); there would be less chance of a gap so less chance of water getting in.

One final thing is that the pegs should be as dry and as seasoned as they possibly can be so that they don't shrink and become loose over time.

Cheers

Tim

 

[dedee]

Tim, thanks for the comnents. After more thought I agree with about round vs square pegs.
As for their position, I intend to cut them flush, at least on the outside, I could leave them exposed on the inside to aid removal but I reckon the GH will only be moved around the terrase/garden so will not need to be dismantled. Actually the M&Ts will probably be glued, the pegs acting as a pulling together force as FIL does not own any clamps.

Andy