Question from a newbie. (Did a search for this answer but found nothing)
In using tapered pegs for draw boring, does the smaller/tapered end of the peg create a lesser value in terms of engineering (or strength) than a peg that has full contact with both mortise cheeks?



Thank you for the opportunity to ask these questions!

Hi Bob,

I sure others will chime in. I may not be understanding you question fully. Most pegs are only tapered at the tip, and once driven in, they tapered portion is typically outside the joint.

Does this help?

Regards, jay

Hello,

Basically it's two separate principles involved. The one with an insert of tapering long sides, normally called a wedge where there is a single bearing side which gives its own particular advantages like ease of backing it out for dismantling, for example, but also it can be knocked further in to accommodate expansion and shrinking that might be associated with environmental, lets say seasonal changes or wood drying out. The taper of a wedge is ideally associated with a corresponding opening. The other principle is the peg or parallel sided insert, its advantage being consistent cross-sectional strength across the length, taking both instances relative in nature to each other. In that case the pegs, as Jay writes, are mostly only tapered or pointed on an end to ease entry. My own approach, one I take from my furniture background, is to make pegs longer than you might imagine, twice the length of the beam say, give them a pointed end and then bevel one third of the length, this all normally being then removed and the peg trimmed flush.

Greetings,

Don Wagstaff

Hi Bob,

Don made some important distinctions. Are you asking about pegs, (trunnels) or wedges for drawn joinery. Don's description is spot on, and we would have to know which method you are talking about to fully answer any questions.

To add to Don's description, most trunnels are a minimum of ~2/5 longer than the material thickness they are meant to pass through. You will find variances in this, of cores, but that is a mean average as observed in both North American house/barn wrighting and Asian timber wrighting modalities; sometimes that may even be ~1/2. So, for example, if you have a 200 mm (~8") post your trunnel will be 280 mm to 400 mm long. The extra length gets the tapered end outside the joint and also allows you to trim the striking end of the trunnel, should it start to "mushroom," or "split apart," before you have driven it all the way through.

Regards, jay

Most joinery is in compression and hardly needs to be peg. Let's not forget draw bored holes are not all equal, a tapered peg allows for just the right snugness needed to pull the joint together during raising. If you have a 3/4 inch peg hole and a rived octagonal peg the corners will be larger than the 3/4 and will dig into the round bore hole of the mortice, in effect causing it to wedge the tenon and risking blowing out the relish on the back, if driven too hard.

Many old pegs I see are a standard size with little taper and a sharp point hacked on the end. I find this odd in comparison to my preferred longer tapered pegs.

I have no concerns with strength of a tapered peg. On true tension joinery the scale of the joinery is increased, larger hole, longer relish at the ends and perhaps an added wedge. Much different than your typical post, girt or brace joinery. My pegs in this case are still tapered but not as much.

A video showing a tapered peg. It is nice to be able to go through the box of pegs and select just the right peg for the drawn peg hole, they vary in size. Notice the size difference and amount of taper. My daughter just watched this and said " oh, that is a lot of taper" .
https://www.youtube.com/watch?v=-T-txHEaSoQ

Hello TIMBEAL,

Please don't think I'm being too critical, I mean not to be, and I found the video of the young lady making pegs adorable, but I'm afraid that peg would be a reject. Jim's observation was I think, "a wooden carrot."

Being a traditional timber wright, I tend to research exhaustively a vernacular style, then render my components to the same degree and nuance. So, if you don't mind, I have to make some observations about your feed back. Please, feel free to engage me if I seem to be inaccurate on any point; I will try to address each.

Though we can rely on gravity for many types of joints, such is the case with many types of "housed lap joints." Those with tenons, even "thread tenons" and "teasel tenons," are often pegged, (and should be,) for seismic and climate events.

If you are saying "equal," in application, I agree. However, if you are saying there not equal in size, I'm not sure how that can come to pass considering they are drilled. If you are saying they don't line up the same, that is a condition of layout that really should be address. In the countless number of vintage dwelling and barns that I have been part of, I would agree that many present with different degrees of craftsmanship, and yes you can find errors, but as a body of work, they are relatively consistent within a certain style, particularly the bore holes, both in North American and European frames, as well as, the chiseled types of Asia.

If a peg is out of proportion enough to cause relish failure, you have a trunnel that needs to be replaced and/or shaped more accurately.

You should not find this odd at all, this is the way a trunnel is suppose to be made. This is how they are found, in most heritage frames, here, in Europe and Asia. The long taper you are describing is not the way they are suppose to be made. Now if you find them to you liking and they fill the bore hole well on both sides of the joint, then that is to your choice. However, emulating the methodologies of our timber wrights of the past, tends to render a trunnel in a speedy and timely manner, as well as one that is in good proportion. These techniques are many and well tested.

I may be missing some points here. Wedge through tenons, (like you would find on a Swing beam of a Dutch barn and a few of the Bull beam barns,) are wedge then peg at a later time. This nuance is lost to many not knowing that these bore holes are made after wedging and/or not at all. True draw trunnels, whether round or square, rely on the accuracy of both layout, bore mortise execution, and trunnel formation.

Simply put, they should not vary in-size to the degree that one will not replace the other. If they do, they are not shaped sufficiently, and the technique of manufacture must be refined.

Regards, jay

Perhaps, Jay, if you lived in a different time say the future and viewed some of my work you would be making skinny pegs, too.

Spike or screw the half laps, is another choice. Nails were used traditionally. Threaded tenon? have not come across this term.

It is the amount of draw that can make for a tight fit, not the size of the hole. The holes in the tenon and mortice are the same size, just not aligned perfectly in each joint. I am not a CNC machine.


The following quote is a good example of where I can pick out a slim peg and not wreck the relish.
"If a peg is out of proportion enough to cause relish failure, you have a trunnel that needs to be replaced and/or shaped more accurately." ......If your draw is on the tight side and you insert a full sized peg you will bust the relish out.

I have no problem rendering a peg in a speedy and timely manner, as well as one that is in good proportion.

Yes, I have seen wedged half dovetailed tie beams with no pegs, the sad thing is no one came back and pegged it. In one particular case the joint had pulled apart by about 4 inches. It didn't even get iron staples. Don't get to see much dutch barn material in my part of the states.

quote from jay....
"Simply put, they should not vary in-size to the degree that one will not replace the other. If they do, they are not shaped sufficiently, and the technique of manufacture must be refined.

Not sure what you are pointing out, but here is and attempt.
Again, the holes are not varying in size it is the amount of draw that is in question, and hence, by having pegs that are not cookie cut are handy, I don't have to set down on the horse and shave pegs during raising. Although I have been known to do just that, not my preference.

For the OP, I don't see a tapered peg being an issue for the majority of joinery used.

Thank you gentlemen. So nice to be able to ask a newbie-type question and get so many very qualified answers.

Received much info to gestate upon.

I took a TF class a year ago where it seems to me the taper of the pegs was very long, and upon knocking them in, seems they did not contact the far side of the cheek at all, but perhaps I'm incorrect.

Great forum. . .do appreciate your time and expertise.
Bob

Hi Bob,

Can't wait to here what you deliver after your "ideas" gestate for awhile. As you can tell from the posts there are many options and opinions.



Bob, I would guess that you are not incorrect. This seems to be a trend in some areas and I believe a result of break in lineage. There are many nuances to the craft of timber framing and unless you are fortunate enough to have apprenticed with traditional timber wrights and/or done extensive historical work, these subtleties are often lost. Like trunnel techniques. Folks have kind'a developed there own methods.

Once again, good luck and keep us up to speed on your progress,

Regards, jay

Hello TIMBEAL,

I'm glad you responded to my post and I will try and address any points that warrant further discussion and/or validate further certain points.

I do agree that metal spikes of both bronze, copper and later iron, have been around for thousands of years, but only in extremely rare cases did iron spikes ever get used in traditional large joinery applications. Historically, in all global regions that have timber architecture, it is a very rare, to never, occurrence other than in cladding and smaller wood items, such as furniture. There is some application of iron rods, straps and bolts, but even that application is limited in traditional timber framing, usually reserved for public/industrial architecture and/or often added much later to repair a failed joint.

"Teasel" tenons, found here in North America, are a smaller form of the "threaded," tenons you may find in Europe and routinely find in some regions/forms of Asian timber architecture. Often pegged and/or "shim" wedged to resist uplift during wind events.

I was not insinuating that you, or anyone else needed to be a CNC machine, and I apologize if it I sounded that way. I agree with your assessment of trunnels used in draw joints but would point out that the size of the hole relates to the applied trunnel and the strength of the draw and the joint, both of which correlates to the accuracy of the trunnels shape and placement, this is proven historical, and empirically.

I validate this observation, by the tens of thousands of pegs I have either removed, replace or observed in frames throughout North America, and to a limited degree ,the Middle East and Asian. To keep the observation closer to home and this conversation, timbered house and barn frame trunnels are normally hand made, but most are very consistent and uniform in size and shape according to there specific application. The tapper is very seldom left inside the timber but out side, this is the case because the trunnels are most often cut flush and you must observe closely to determine which side they went in from. Pegs with random tappers and/or sticking out is an indication that the frame may well have been relocated and the trunnel a replacement. "Dead Head," trunnels have virtually not tapper in most cases I have observed or researched, often square at the end, such as in a Threshing floor.

I stand by my portion of that quote and put simply it is not the peg that should be adjusted, it is the bore mortise in the tenon, and there is very clear historical precedence for my statement both in observed frames and in my training as a traditional barn wright. You seldom to never see large gouges of any kind in the tools of most modern timber wrights, but often, and commonly, find them in antique stores. The "why," is because this is one of the tools that leads to a technique that was commonly employed but is now lost and seldom implemented. Anyone that has done any extensive restoration or historical research can tell you that offset bore holes are sometimes elongated, this was done with a gouge. So I say again, you do not undersized the peg, you correct the bore mortise, that is the traditional method and the strongest of the two solutions, the trunnel is not suppose to be undersized. Also, note that gouges, both "V" and "out cannel," at one time here in North America, and still in Asian, were very common timber wrighting tools and really should be again.

When the craft of the timber wright began to weaken in the face of the industrial age, and the loss of a vast wealth of knowledge held by the people that went to the different great wars and never came home; many of the finer, but important, nuances of the craft, died with them. I have done everything I can to restore as many of those subtleties I was taught and have learned through research and restoration work back to this craft of timber wrighting. Trunnel methodologies is one that has many refinements that have been overlooked.

I did not mention "dovetailed," joints but I will address your statement. I doubt very much that any one forgot to go back a peg them, seldom were they pegged, some in the mid span of a beam, maybe. They are a gravity joint and shim wedged is the preferred securing method if a "dovetail" joint is employed. The "pull out," failure you observed, (I'm assuming this was a vintage frame,) is a common failing for this joint, and one of it's weaknesses structurally; in frames with the shim wedging you seldom observe this taking place, which speaks to the variances in craftsmanship even in vintage frames.

This again goes back to what I was stating earlier, your trunnels are to be uniform in size, shape and length according to application and if the layout and/or execution of a trunnel mortise is improperly offset, the method to correct this, is to adjust the the trunnel mortise not the placement of an undersized trunnel. Trunnel size may or may not contribute to the overall strength of a frame, there is some very strong academic debates about that still going on. IMO their size are of consideration but in this case, I am strictly addressing the draw trunnel techniques used historically and the methods that have stood the test of time.

Regards, jay