peg size

I am working on Jack Sobon's timber shed. In his book he calls for a 1" peg size. However, in his second book he mentions 13/16" for peg size. I would prefer to use the smaller in a white oak peg. Is there a disadvantage to the smaller peg size for building this shed?

Thanks...Norm Hart

This charming little building has been built hundreds of times, in all sorts of species, with a variety of peg sizes.

I suspect it is forgiving enough to allow the use of 13/16" pegs throughout.

The sizing and location of pegs is a complex and sophisticated engineering exercize that most of us are not qualified to engage in, so we fall back upon traditional patterns.

Get those pegs as far from the end of the tenons, and as far from the edges of the mortised members, as possible.

An impossible balancing act, you say? Made easier by smaller pegs, for sure.

The Guild has been paying for destructive testing of timber joints for years - some results are available on line, and the most recent stuff was published this week in Timber Framing - a benefit of membership.

Norm,

In my experience you are better off relating to peg "hole", rather than peg, diameter. There are a number of reasons for this that are particularly obvious if you are using traditional trunnels.

Pegs (trunnels) are traditionally octagonal (roughly) which means you have to decide whether to measure across the points (looking at the cross section) or the flats. They ar also very often tapered, so you would need to decide where along the length to measure them.

Using a peg that is a little larger than the hole across the points and a little smaller across the flats about halway up the peb is optimum. If the pegs are sawn rather than "riven" (riven is best) then that sizing goes for the entire length beyond the tapered point. This avoids peg "binding" which can easily split a tenon or a mortice cheek. It also allows the peg point to "feed" through the drawbore.

The drawbore is also very important. Drawbore is placing the hole in the tenon a little closer to the shoulder than the hole in the mortice cheek. Depending on how much "relish" (the wood left beyond the peg hole) you have allowed, the draw should be no less than 1/16" and no more than 1/8". Peter McCurdy will also be quick to warn "It's best to avoid having pith in your relish."

Enjoy your timber frame project!

Rudy

At a workshop being taught by Jack Sobon at Hancock Shaker village, he told us the reason he picked the 13/16" size for his peg "holes" was that he got a deal at a hardware store close out sale on a whole big box of 13/16" bits. That was the reason he's using that size.
He had us split our pegs from straight grain red oak stock and then trim them to size on a shaving horse with a draw knife.
His shaving horse had a series of different size holes in the seat, for us to use to 'test' the size of our eight sized tapered pegs.
Good luck, Jim

Jim,

Are you sure Jack had you rive the pegs from "red" oak and not "white" oak? Red oak isn't very good for moisture (rot) resistance as it capilates water through it's open cell structure. White oak is commonly used for trunnels due to its strength and flexibilty, plus its cell structure is full of residual tyloses which stop capilation making it very rot resistant.

In either case it's critical to rive pegs only from the "heartwood" rather than "sapwood". The sapwood is extremely rot prone and much weaker. It can be easily identified in fresh cut oak (best for riving) by its light creamy color. In dryer billets it will often appear dark or mottled due to the beginning of fungal attack. There's usually 1"-2" just beneath the bark.

Once the green pegs are riven, they should be "cross-stacked" or spread out to dry in a shady area. Slow drying is important as is keeping them from growing fungus. A trick the Amish peg makers use is to mist them with kerosene and hang them up to dry cross stacked in wire egg baskets.

If you do decide to rive you own pegs, you are in for a real zen treat. It is good work.

Rudy

Rudy:
No I'm not sure, but you could be right. I have pictures of Jack showing us how to do it, and if someone could explain how to upload them to this board I would gladly forward them for the group.
I was fun to make our own pegs and each student had to make at least ten for the project.
Using a draw knife and a shaving horse is a great way to make pegs.
Also if some needs a set of drawings of how to make a shaving horse I have a set on file that I can email to anyone. Send me an email and I'll forward it to you.
Jim

Thanks for all your input Re: peg size.

I will be riving pegs and will likely use white oak heartwood if I can.

So I understand there is not much harm in using 13/16" or 7/8" hole size as opposed to 1" in the garden shed project?

Thanks again...Norm Hart, Carp Ontario

Rudy & Norm, Jim was right, Jack had us use 8 sided 3/4" red oak pegs. I still have one in the bottom of my tool box, and we did use a 13/16" bit that he bought in a hardware store spcecial! True story, John

Hello all:
Just a note on wooden pegs from Ontario Canada for what it is worth. I have examined many period structures in this area that are still standing after 200 years, in the majority of cases the pins are all manufactured from white oak. Since I had to copy the methods the original timberframe\carpenters used, close examination of the pins revealed their straight grained nature, 8 sided slightly tapered, well pointed, but large and squarish on the end that received the strike of the large mallet driving it home. I have yet to see a mortise and tenant failure due to broken pegs.