My first drawing in my previous post was based on Mr. Brungraber's
table on page 75 of the red book. That joint is drawn to the min. specs based on a peg dia. of 1.0"...provided I understand the table correctly.
Don,
To me, the link you last posted for peg spacing, paints a totally different picture then the sketch in the red book.
One thing I noticed is there was no specs for a 1.0" peg. What's with all these oddball sizes of pegs. How many peg dies does a man gotta make?

It doesn't make sense to invent a new joint for every situation you might come across. These tables and and formulas would have us doing just that if we didn't have common sense.

Since Engineers like doing math so much, would it be possible for someone to fill in the blanks for a table of our design (the common timber joiner).
Perhaps we should start a new thread where we could exchange ideas about what we would like to see in a design hand book that would benefit us because we would actually be able understand and use it.

What would really be neat is if a lot more members participated in these forums and were not afraid to speak their minds...respectfully.

Thane

if you define every new situation as 'every situation with different loads, differing tension conditions, differing species, differing piece sizes' - then yes, you may need to design a joint for each different scenario.

for most joinery, rules of thumb work just fine - that is most joinery that is not in tension, not holding down an open structure, not containing the spread of the roof, etc. etc. etc.


don's original post specified that you use the metal 'peg' table as a guide.

figure out your loading per joint
figure out what minimum size bolt will do the job in the species you are using.
use the bolt diameter you just calculated to fill in the 4d, 3d, etc. numbers.
replace the bolt with a peg of appropriate specie and diameter to do the job, at the dimensions you just calculated using the bolt diameter.


don - is that correct? or what you intended to convey?



then make sure that your tenon is properly sized to take the loading - so relish, thickness, etc.

double check against the material left over in the connecting member... just to be sure you don't snap a post or a beam.


you could develop a spreadsheet with a bunch of common values and pull downs for piece sizes / peg #s / etc. to work through 'common' situations.

and as to odd sizes - if you calc out that a .625" diameter oak peg will work, you could use 3/4" or 1". likewise if you calc 3/4" to work you can use 1", if that is all your peg jig will make.

Yes Mike, that is my understanding of Dr Schmidt's method. I also agree that for most situations this is getting into the realm of navel contemplation. Just another tool for the toolbox. The oddball sizes come from my metric conversion. I was mostly looking at the trends to see if they agreed between practitioners.

Reading Jonathan Shanks papers, in green oak he was down to 1.5D mortise edge spacing using 3/4" pegs and said all failures were in the pegs not the members. I can see more peg failure in smaller sizes. This method of conversion from steel specs to wood is probably not so easily linear, simply for now a closing approximation on the way to reflecting reality. His graphs were interesting, wood pegs failed nice and slow. Even after failing the broken pegs had to be drug through the mortise and withstood a pretty healthy load.

Good stuff from Ben Brungraber's article; Keep the peg low in the tenon so that when the tenon shrinks it won't be hanging on the peg. Don't spread pegs more than 5" apart to avoid splitting wood as it shrinks. His article predates the others by about a decade so I think there is also some evolution of thought. He was presenting at the conference where Jim and I heard Dick Schmidt present his method as was Buddy Showalter from the NDS. Buddy did acknowledge that more research was needed in this area. I've emailed back and forth with him not too long ago and they, like so many of us in construction, have been through cutbacks and tough times that I'm sure will delay projects.

I digest slowly, lots to think about, as with anything the more you look the more there is to see.

I like the thread idea Thane.

On wedged half dove tailed through tenons I have draw bored in two direction, sucking the joint to the shoulder and down to the dovetail. I think this assist with the drying issue and helps with keeping the weight off the peg after it is dried. Have I been seeing this correctly?

The 5" peg spacing makes sense to me. If 5" is the max distance apart what is the limit in how close they could be? I see the size of the tenon having much to do with this. You only have so much space on an 8" wide tenon.

I read of late here on this topic in a link where "they" don't want pegs larger than 1-1/4", there was not an explanation but unless it was a very large tenon it would be removing a lot of wood and the relish would be the weak link, I believe there is a happy medium.

I have used half a 2" peg, that is split down the length, on an extended through tenon acting as a wedge under the tie on a king post. Still trying to figure out if it was a peg, pin, or a wedge? For that matter are all peg/pins wedges if they are draw bored?

Tim

Also, in the talk DonP is mentioning the speaker told how he figured edge distances in the post with a housing. And I believe he didn't count the housing depth as a reduction in the post width. And in other words he figured the distance from the edge of the post as if it didn't have a housing at all. This added to the available distances for figuring out the placement.

I too remember hearing about not placing pegs too high in a wide tenon, and that they should be favored towards the lower side of the tenon.

So, in Thane's drawings, posted above, I'd delete the top peg and use two pegs offset in the post so that they aren't both in the same grain line.

As I remember one general rule of thumb for peg placement with 3/4" pegs through 1 1/2" tie beam tenons were 1 1/2" off the tenon's shoulder, with a 1/2" housing would make it 2" off the edge of the post. Two inches up from the bearing edge of the tenon to the first peg hole. And the second peg was up 2" from that and another 1 1/2" away from the shoulder, making it 3" from the edge of the timber.

Thanks for clarifying Don.
All that said I and most everyone I've worked with only do peg calcs when we are uncomfortable where the loads are heading, or if it is clearly a tension situation we haven't seen before. (And when I say 'I' I mean that I'll drop pegs in with best guesstimates based on overall loading and if required let a pro check my assumptions... but I don't go through some voodoo chart juggling spreadsheet crunching math gymnastics to get there...)



In my formative years in a TF shop learning to cut and layout entirely by hand everything was done with a framing square. No magical calculations on 90% of the joinery, and specific truss or tie joinery would have a detail on the drawing. Everything else was left for use in the shop to figure...


It definetely helps to keep pegs low on a tall beam, as the assumption is that beams will shrink down as gravity tends to settle everything. So Tim, pulling down and in is an OK thing to do. Same holds for brace and rafter connections - pulling into the corner of the joint makes good sense to me. This assumes you are drilling perfectly straight and true holes through 8-10-12 inches of material - so its all sort of relative.

Tim - I think philosophical ramblings aside - that a peg is a peg and a wedge is a wedge. Wedge being wedge shaped - tapered, with the possibility of further adjustment. I doubt that after a joint is seated further beating on a peg will pull it tighter - but a wedge certainly allows this if things loosen up, assuming you are not fighting the pegs if it is a combo...

(and yes, I guess you could cut a peg in half along a taper and make a wedge peg...)

Thanks guys.
I think that I took this peg placement issue way too seriously.

Speaking of pegs and wedges. My pegs are tapered slowly to about
half the length. Using an appropriate sized mallet, the peg is tapped in until the mallet bounces. At that point the joint is tight and the ends are cut off. I suppose one could leave the frame stand for a month and then re-tap the pegs again before cutting off.
Thane

I wonder if there is a chart which says how far the mallet, dropped form a specific distance, will bounce back, species specific too? Or you could tap it in till it feels good.(smily face) I don't think re tapping them is necessary. I do go around and check them once the frame is up and standing in its proper place. A wedge on top of a WHDT is a different matter.

So, is it a weg or a pedge?

Really I am not bashing engineers, I very much appreciate what they do. Now I have to go figure the coefficient of static friction on a block, on a plane at a certain angle, all unknown till I mock it up with different surfaces and test it all with some sin and cosin stuff. I am even learning what all the buttons on a calculator do, like the EE button.

Tim

That sounds like vector mechanics to me. It brings back memories from physics class many years ago. I'm sure you should be able to find a table for friction coef. on line somewhere.
You have fun with that.

Thane

Hmm. If frames drifted as easily as threads we'd have to have engineers sign off on every post.

Tim - I think you are describing a wedgie (or maybe a pedgie?).