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timber framing peg diameter vs peg hole diameter

Started by metroplexchl, February 06, 2018, 10:21:16 PM

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metroplexchl

So i've timber framed small projects in the past but never using pegs. I've been reading conflicting accounts of the diameter of the peg vs the diameter of the peg hole. If I have a 1" peg hole drilled through the mortise and tenon, wouldn't I use a peg with a 1" diameter?

Some say to use a peg that is 1/8" smaller, some have said 1/8" larger. Logic tells me it should be the same size. I'll be drawboring them of course. I forgot to add that the beams will be 6"x6" already dry white oak beams that I have a multitude of. So no shrinkage.

P.S. this is my first post. A special thanks to the moderators or whomever approved me to join these hallowed halls!

Southside

I can't help you there, but welcome to the Forum.  Perhaps @Jim_Rogers can chime in. 
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Dave Shepard

I rive and drawknife my legs to an octagonal finish. For a 1" peg hole, I would start with a roughly one square blank. The peg will be a touch over one inch across the points, but no more than an inch,  and maybe a little under, across the flats. You would lose your drawbore if you undersized the peg. Welcome to the Forum.
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metroplexchl

I think I'm going to buy some precut red or white oak octagonal pegs. I'm not sure yet. Any thoughts on pre-made vs. handmade?

Dave Shepard

If they are made right, they are fine. If the grain is not straight they can shear in the hole.
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metroplexchl

Just so the most important question doesn't get lost. :-)

If I have a 1" peg hole drilled through the mortise and tenon, wouldn't I just use a peg with a 1" diameter? Not one that is slightly larger or smaller?

BurkettvilleBob

I'm no expert, but that's what I've always done and seen.

Jim_Rogers

1" peg holes take a 1" peg. noting over, nothing under, except maybe tapered tips.

However you said you're doing 6x6's and with a 1 1/2" tenon. Normally the standard is that the peg and peg hole is 1/2 of the tenon thickness. So, you should be using 3/4" pegs and peg holes.

Too large a peg takes more meat out of the tenon and can allow relish blow out.

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metroplexchl

Quote from: Jim_Rogers on February 07, 2018, 01:31:12 PM
1" peg holes take a 1" peg. noting over, nothing under, except maybe tapered tips.

However you said you're doing 6x6's and with a 1 1/2" tenon. Normally the standard is that the peg and peg hole is 1/2 of the tenon thickness. So, you should be using 3/4" pegs and peg holes.

Too large a peg takes more meat out of the tenon and can allow relish blow out.

Jim Rogers

Thank you sir!  I will making 2" tenons. One thing I am curious about is if one has a 4" lap joint, say, would one use two 1" pegs?

Roger Nair

In my practice, I made octagonal long taper pegs (taper about 70% of length) that were flat to flat less than the bore and point to point greater than the bore in an equal measure.  I subscribe to the belief that it is better for drawboring to have the pegs act as springs and that requires flex in the bore.  So when a peg is driven, the joint closes and gets tight, continue to drive you can feel the grip increase and when the vibe and tone says that everything is truly tight, stop driving the peg.  If out of curiosity, the peg is driven out, you should find a little compression set has taken place in the peg.  It is a balancing act.  If drawboring with pegs that match the bore exactly then the potential of damage to the tenon increases, in my view.
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metroplexchl

Thanks for all the advice.

So if I buy or cut octagonal 1" pegs, should they be one inch from the flat part to flat part?

Dave Shepard

You start with a 1" square blank. The points of the octagon will be slightly over 1" but that's not an issue.
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Brian_Weekley

Have you thought about making your own?  They're not hard to do and fun to make.  Once you get going, it doesn't take too long.  This is an excellent video that shows the correct way to rive pegs from a straight-grained log:

https://www.youtube.com/watch?v=RBPw-JuDHQc

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Roger Nair

Good idea Brian.  If you buy pegs, you can always pare them down or adjust the taper as you need  with a block plane, drawknife or spokeshave.  Do a few test joints and target your own peg spec.   Make enough for the raising, be ready to go.
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flyingparks

I bore a 1" hole, and I buy 1" round oak pegs. Never an issue. I've made pegs here and there but on larger projects I like to buy them.

Brad_bb

Draw boring or pegs fit line line (one inch hole and one inch peg) are both acceptable methods. 

I prefer to use hand Riven pegs to start with to be sure I'm getting straight grain.  A lot of timberframe shops are using turned pegs.  A lot of them get them from Northcott Wood Turning (www.pegs.us).  I've never used them.

I buy my peg blanks from Ron Mansour.  He gets very green straight grain, clear butt logs and rives them by hand out of the chunk.  He rives them into Octagons.  Pay Attention to this:  for draw boring, pegs must remain green/wet until you're done working them.  You cannot let a peg dry and then expect to draw knife a taper on them.  You also cannot re-wet pegs.  It just doesn't work.  Water will not penetrate more than 1/16th inch once it has left, especially with oak.  As soon as I receive the peg blanks, I put them in a rubbermaid tote and fill with water.  Wet pegs shave very nicely with the draw knife. Since you are tapering 2/3 to 3/4 of the length of the peg, You can pretty much do the whole peg with your draw knife.  The top of your peg should fit in the hole without play, but not real tight either.  You want the drawbore to become tight, not get stopped by your peg head dia. in the hole.  If that happens, your draw bore doesn't work.  Do some test pieces so you are comfortable with the fit before you do all the pegs.  I like the length of the pegs to be such that you have about equal amount sticking out of both sides of the timber.  I don't trim the peg off flush if it's not necessary.  You do have to if you need a flat face for a wall, or floor or whatever.

For a line to line fit
, I take the same riven blank from Ron, pull it out of the rubbermaid tub of water and draw knife the tip to sharpen it like a pencil so that the tip ends up about 3/8 to 1/2 inch dia.  You get to eyeball it.  Then I leave the peg out to dry.  After a month or two when it's dry, I then have to size the peg for the hole.  Take a 1" drill bit and drill a hole in a piece of steel at least 1/4" or more thick.  You need enough steel to be able to clamp it well or affix is solidly to put up with a lot of vibration.  You need to pound each peg through the die (hole in the steel) and that will shave it to size.  I use a 3 LB sledge.  You will get a workout, so it's best to space it out and do some each day ahead of the job.  I had to do a marathon peg pounding on the last one and had to do 500 pegs in 5 days.  That was rough.  Again you want to do a test before you bore your mortise holes.  Make a peg and bore a hole and check the fit.  It should have some resistance, but not be too hard to pound home.  You get the feel for it doing it.  You don't want it tight enough to shear your tenon.  When draw boring you can feel when it's snug enough and when not to hit it anymore.   When line to line fitting and you think it's too tight, pound it through the die again.  It will shave off a bit more because the first time through, the peg gets compressed some while going through and re-expands as it comes out. So you can re-run it through up to 2 more times to shave a little more off for the fit.
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Heartwood

If we're riving pegs, they would be slightly tapered after shaving and be 1" diameter at the point where the peg would end up at the center of the tenon. Also, the square blank before shaving would be a square about 15/16" on a side, so that after you shave it the ridges on the diagonal diameters are slightly more than 1" and from flat-to-flat slightly less than 1", like Dave and Roger say.  Also, we usually use 1" pegs with 2" thick tenons or very wide or long 1.5" thick tenons. Otherwise most 1.5" thick tenons get 3/4" pegs. Tenon thickness should be 1/4 timber thickness, so if you're using 6x6 timbers your tenons should be no thicker than 1.5". In general, damage from bigger mortises outweighs benefit gained from thicker tenons. You wouldn't go to two pegs in a tenon until you can get the recommended edge distances (1.5 diameters) and spacing (3 diameters), and even then I usually don't add a second peg unless the tenon is over 8" wide or if I need the additional shear resistance. Peg holes also do damage, like mortises, so best to keep them minimal.

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