Hi Everyone,

We were having a disscussion over our water cooler at work regarding the mixed opinions and methods of drawboring. ...And I hope I haven't missed a previous disscussion on the topic...

Anyone care to share their techniques?

Anyone have any empirical evidence about the effectiveness of certain methods?

What about the performance of a joint who was draw bored VS a joint who was pulled tight mechanically and then drilled straight through?

Acceptable offsets?

Thanks everyone!

Looking forward to a discussion,

Brock Smith

I think this has been covered somewhere, but I can't find it exactly.

What was the out come at the cooler? Pro or con?

Acceptable offsets depends on the size of the peg and length of the tenon and the amount of common sense. Mostly an eyeballed 1/8". My reasons for drawing the joint is a time factor. It is done when the joint is done, no more tools needed at raising time. you are right there doing the work, the peg hole is the least of the work. It would be risky to bore the holes right on with the joints apart, the risk is miss alignment and forcing the joint apart so that is not a choice. So reason would say draw the joint and have it done. Than there is the shrinkage factor. Basically its just the way I have always done it. Tim

yes to the draw bore
1/8 plus or minus is usual
works better in green wood
it is very risky to draw bore with turned pegs or sawn pegs -- they don't bend like the draw bore peg needs to.

As for empirical evidence -- since there aren't any 500+ year old timber frames with peg holes bored straight through, I guess we'll have to wait to see which is better.

To elaborate on Gabel's point: your client may want a pretty turned peg with only a slight chamfer for their finished look. Such pegs are not very compatible with draw boring. Also with regard to 500+ year old frames: The old timers didn't have access to inexpensive truckers' ratchet straps to pull their frames tight. I like to think they were practical folks who would have used them had they been available. CB.

Hi Gabel,

Not true. It is precisely on 500 year plus frames that one is liable to find non draw bore pegs where centre line mounted tentons for braces on wide posts require the use of parallel pegs. A draw bore will only work effectively when the tenon is offset towards and is fairly close to the reference face such that the peg manages to fill the gap and pull up the joint before it fills the driving peg hole and stops.

Regards

Ken Hume

Ken,

Perhaps my statement was over-reaching, but I am not yet convinced.

Has it has been verified that the peg holes you are referring to are not drawbored? If so, that is very interesting indeed, and raises quite a few thoughts about how they managed to pull the joints up tight enough to drill through them. Spanish windlasses? Drill them in situ after gravity has brought the joints home tight?

I feel compelled to mention that we have quite often and with no ill effects draw-bored centered tenons on posts as wide as 12". In fact, there are about 200 draw-bored pegs which pass through centered tenons on the frame we are assembling now. (These are all 2" tenons centered in 10" posts). I don't know of any reason why it wouldn't work unless your peg was too fat on the driven end to go into the hole deep enough (easily remedied) or your hole isn't deep enough to allow the peg to pass through the tenon enough to draw the joint up fully or your peg was too short.

I have wondered if the tendency to offset tenons/mortices to one side is so that the peg holes won't have to be drilled as deeply in order to drive them to the point that the joint is drawn up fully. I know that I have seen pegholes that were not drilled through in quite a few old frames. Having the tenon shifted over as far as possible keeps the required peg hole depth to a minimum and it keeps the required peg length shorter. Double time saver.



Gabel

Gabel, I have also seen the same thing. The bit wasn't long enough so the builder hacked at the exit side to expose to peg hole, the funny thing is he didn't expose the hole and gave up. In the repair of this tie beam to rafter connection, I finished boring and he was only an inch away. The tie was wider at one end than the other to save on a lot of hewing, they were like this through the whole building, flared ties.

It helps to keep your joinery closer to one side due to the chance that the deeper the peg hole is from the starting face the higher the chance of wandering of the bit and that could lead to a pushed apart or too tight joint. I also drive all pegs from the ref. face. Are you using a guide for the peg holes, or just a square. Tim

Hi Fellas,

Tim, we did not come to a conclusion at the cooler! We do seem to have a full range of opinions, though...

I'm the drawborer in our group, and when I do so, I poke the tenon, dissassemble the joint and re-dill. Gabel, I have been doing so for many frames now with sawn and turned pins with good success. Ken, we also pin center tenons on fairly large members with good success (and I DB them).

Our frames our generally cut from standing dead timber, through pegged, with a drill guide.

And what about offseting your hole by angling the drill with the joint assembled? Do you guys feel this is effective?


Brock

I will at times tilt my brace and bit to further enhance the draw, mostly when I have guessed on the shy side of my 1/8", so I am compensating. I don't prefit and redrill. I use my combo square as a guide to help until I'm into the further side of the mortice than let it go, checking the start and than the realignment in the mortice. I bore them horizontally not from the top as well. My shaved pegs have a fair bit of taper, I peek in the hole at raising and select an appropriate peg. Tim

Hi Guys,


been absent for a some time.
As far a being able to pull frames tight without the handy ratchet ties. The old times did know how to make use off ropes which were available then. Just tie around your framing members and tighten up. Sort of like tie wires for re-bar.
I never tried DB as I found that there is to much friction on large members to pull it tight relying on the peg only. I am always afraid that all I would accomplish is destroying the mortise.
Just my 2 cents.


Enrico

Hi everyone

Good discussion, and I might say one that is important if you are working towards a nice tight framework.

Proceedure for prefitting each bent at UCV and preparing it for the eventual erection day, was to ensure that all the pin holes were predrilled properly, and that meant using the drawbore method. Without this method the joints would be sloppy and allow the frame to eventually develop movement due to wind forces.

We would predrill all the holes through the timbers at the exact location of each mortise, being careful to get them as straight through the timber as possible.

The next step would be to slide the tenon into the mortise until it bottoms out on the sizing lines.

Dropping a hand auger then into the predrilled holes would leave a tell tale marker point on the tenon, we then would slide the tenon out of the mortise, move over the bit approx 3\16" towards the shoulder, and again carefully bore the hole through the tenon.

Too much draw could split the timber so one had to be careful as well.


One point that I would like to focus your attention on is during this fitting and boring process it was very important that the whole framework was as level as possible, so that the timbers as you slid them together for the fitting, would be tight across the whole face of the seating (where they meet), especially on the down side that was not observable from the upper working face



NH

tim,

good point about offsetting the tenon to keep the holes accurate if you are drawboring by the numbers.

we've been scribing mostly for a while so our tenons are pricked when the bent/wall/truss is assembled and then pulled apart and the tenons drilled.

if we're square ruling, if the surface is pretty good, we use either a drill guide or on irregular stuff, we level the stick use a level to guide the bit.

Hi Gabel,

I might just owe you an apology !

I was inside "The Mount" Silchester today in Northern Hampshire. This is a 3 bay cruck house dating from circa 1405 i.e. 600 years plus old and I paid particular attention to the arch braces fitted on the central open hall truss and noted that tapered pegs had been used which of course implies draw boring. Where draw boring is employed then the peg holes are full on the driving side and only partially full on the exit side. That was the case at The Mount. With parallel pegs the holes would be full on both the upper and underside faces. The cruck blades are "see sawn" halved from one tree to make a book matched pair and are only about 7 - 8" thick with wane on the back face so these blades are a bit short of 12" posts that I was previously thinking about.

This finding should not be taken as substantiation of a general rule but I will now fastideously check each centre line mounted arch brace that I encounter and especially those fitted to wide posts and report back on outcomes found.

I can send pictures to anyone who has a particular interest in this kind of feature.

Regards

Ken Hume

Hi Ken,
I would like to see some pictures if its not to much trouble.
karl.hines@glv.com

Thanks.
Karl

Same here Ken, I believe you have my email info. Thanks, Tim

Thanks, Ken. Your web site is an inspiration.

As an way off topic side note, were the bricks in the photos white washed with a lime wash? Tim

Hi Tim,

Limewash has been applied to both the wattle & daub and brick noggin infil on the Queens cruck timber frame shown on our website and we noted that the frame had been painted red at some time in its long history.

Regards

Ken Hume
http://www.kfhume.freeserve.co.uk

hey everyone, as far as the drawboring, I have always prefit, mark the tenon and drawbore, assemble. I have seen the tilt method that derek speaks of but i personally like offsetting and then drilling perpendicular to tenon. If you want to make an accurate mark. Take a peg the same diameter as peg hole find the center of the cylinder on the endgrain then offset a driven nail. Grind the nail head off and make the shank a sharp point. To the point on the circumference where the nail is offset draw a line along the length of the peg. When you put the peg in you can use your line to direct precisely. Tap lightly and you have a good mark. I like watching the 1/16 draw tight.

If you have intersecting timbers that are not perpendicular do you all drawbore towards the nose or square to the shoulder?

In this case, you draw bore in two directions, such as with a brace.....

mo, nice description of the tool to lay out your drawbores..
and I agree with Jim, angled connections are double draws, generally the drawbore follows the grain of the tenon.

Braces are always confusing, the standard draw moves closer to the shoulder, the other direction is away from the butt of the brace. This pushes the brace into the square end of the mortice. See, I really put some mud on that one.

I also draw in two direction, a wedged half dove tail, I want that tenon pushed into the angled seat. If you don't you once again risk the joint being pushed in the wrong direction and fighting the wedge.

I tried draw boring a halved and bridled scarf, I now test fit them and prick, then figure. Dyslexia is no help at all in the matter. Tim

we did a job where a fella that was helping us out was adamantly opposed to drawboring. everyone else drawbored and he did not. when the frame was up you could tell which were draw bored and which were not. it all looked beautiful but there was a marked difference. I say if the relish of the tenon can handle it then by all means do it.

Funny that you ran into a guy resistant to draw boring. A guy I met who just restores old barns said something similar, only he is adamant that draw boring never even existed (at least here in Maine).

He said, quite matter-of-factly, "they put the timbers together, drilled a hole, and stuck a peg in."

There certainly is a marked difference in the finished product. I built a 8 posted shed at out worksite last winter. I randomly DB'd 4 of the posts - I can already tell which was DB'd.

Perhaps Drawboring is related more to the MC of wood? An experience framer might chose to 'straight drill' a tenon on a piece of 100 yr old material?

I'm surprised, Don, by the opinion of the fella you speak of. If it didn't happen on the barns in that area and era, where was is standard practice?

From my experiences working with (primarily) swiss carpenters, DBing is not a practice.

brock

I can't speak to Maine, but every pre-revival frame I have examined where I could see a joint that was taken apart was undoubtably draw-bored.

In England several years ago, I was at a Framing Rendezvous in Oxfordshire, UK and was shown an old timber with a tenon on it by Steve Turner. The evidence for how they marked the draw could be seen as plain as day -- this timber was from the time before drill bits with lead screws, so you couldn't just run the bit down the hole. Instead, when the joint was assembled, they had taken an awl and poked around the peg hole, leaving the outline of the hole marked with little pin pricks on the tenon. Then they had offset the drill bit and drilled the tenon. Steve said they had wondered for years how they marked the draw without an auger bit, until someone had looked closer and seen the tiny crescent shaped pricked outline on a tenon.

I wonder how much we all miss when we look at a frame or a timber or a joint?

I can't speak from having taken apart anything, but in reading about traditional TF, references to Draw Boring appear everywhere. (I think I've even heard of it in furniture making).

Anytime I'm studying a topic, if I encounter repeated references (by multiple authors) to something, I feel pretty certian it occured.

The guy I talked to who flat-out denied draw boring ever happened is a bit of an oddity. He has restored many many frames and has a good reputation, so I'm inclined to believe much of what he says, but when he said (with distain) that draw boring didn't happen, I just about laughed...and my opinion of him went down a few "pegs."

I think he has his theory because he hates the concept of anything "over-engineered."

But many texts about old barns here in New England refer to the practice of Draw Boring.

I just kept quiet...

If that ain't the truth!

Neat about the crecent-shaped outlines. Very neat...

I think draw boring is one of those things that's immensely practical and so effective that it had to have happened. And it's closely related to wedged through tenons...tightening a shoulder up...at least those we can see. (I have certianly seen these used in furniture)

Ken Hume:

What about over there, was draw boring standard practice in your opinion, or is it an American innovation?

I forgot to mention that the timber we were looking at came out of a barn and was said to be from the 17th century.

On my last raising the crane operator had mistakenly put his hands on the wrong levers and lifted the truss we had just set and pegged. He lifted the truss, top plates and post 4". All this was hanging on two pegs, one on each side of the english tying joint truss. 3/4" pegs, 4" tenons, when I knocked out the stressed peg to view the damage I noticed the peg had the tenon shape impressed into it and it was cracked. Any draw bored peg will have a similar impression, hopefully with out the crack. I believe one more way to tell if a joint was draw bored is to look for the tenon impression. Tim

I can attest to draw boring being a common, perhaps standard practice in historic frames in Maine. Quite often you can see the layout marks for the hole on the tenon scratched onto the tenon just like all of the other layout marks were scratched onto the timbers with an awl. I believe that if the holes were misaligned too much they would reduce the size of the pin to avoid straining the tenon relish or pin too much (doesnt that give an engineer the willies!). Some pins come out of old frames cracked but it is hard to tell if the strain was from building movement or just too much strain in the draw bore.

Jim

Hi Don & Jim,

I am sorry about the delay in replying to the draw bore question. This topic has probably been done to death elsewhere on this forum but yes indeed draw boring is well proven to be a very early practice that predates the founding of the American Colonies at least by 2 or 3 centuries and probably much more.

The important thing to recognise from and engineering standpoint is that drawbores are employed in conjunction with tapered pegs (or is that pins) and so when a peg is being driven it pulls the joint together up the inclined slope of the peg. Driving home the peg is thus somewhat of a "musical" or resistance based process. Knowing when to stop driving is therefore very much an experience based affair in order to prevent tenon relish pop.

Old draw bore pegs that are removed exhibit parallel deformation over the span of the tenon though whether this happens straight away or over prolongued periods of time is difficult to say.

One other understated factor that comes into play is mortice "slop". Most american timber framers employ engineers squares to ensure perfectly parallel and straight sided mortices but examination of old frames reveals that mortices tend to be more bellmouthed starting at say 1.25" opening up to 2" at the bottom with all the load being taken on the tenon shoulders and peg. This means that the tapered peg is actually unsupported over a short length either side of the tenon and thus is able to deform elastically rather than fail in shear. I have a wonderful photos of this practice taken in Laurie Smith's cruck framed house in Wales (Gwernfyda - dd 1552) where a tie beam was partially sawn through to create less of a step over and into an inserted upper chamber. See Fig 24 in TF 70 [Dec 2003].

I shall risk being a little controversial here in stating that I think that the current "tight" fitting parallel mortice side practice is probably techically misguided and certainly less forgiving.

Regards

Ken Hume

Ken, are you saying we can be a little more slack in the fitting of our joinery? The bell shape at the bottom of the mortice is difficult to avoid with hand tools. When working, say hewn timber you don't have a easy reference to gauge the walls of the mortice, it can be a guess at times. It is sure easy to create the bell effect rather then the opposite result let alone a perfect fit. Which goes along with a perfect pre drilled peg hole, it won't happen. Did the old timers build the bell shaped mortice on purpose? I believe they did, but it wasn't for the benefit of the peg. That is a bonus.

My example was with a small oak peg. A recent small frame I helped move had soft wood pegs, tamarack. It wasn't stressed, it sat on a slab, it had draw bored pegs and they were deformed, just sightly, enough to tell. It was 8 years old. The old frames with stress placed on joints could confuse the subject. Tim

Ken,

This happens fairly quickly as we have removed pegs from a frame we built only a few months earlier and the pegs had the parallel deformation, or as Tim mentioned the tenon impression, just like pegs I have seen that are 150+ yrs old. It was interesting to dissassemble some of our work.

Hi Gabel,

Thank you. It is indeed fortuitous that we have been able to benefit from your relatively short time based and hence verifyable evidence, sadly however we cannot make the same comparative observations (i.e. before and after) on joint that is now several hundred years old.

Hi Tim,

It is the mortice face and tenon shoulder that does the work in a mortice and tenon joint and thus the face to face mating should be well aligned even if a hewn surface is the start point. Mating faces should be regularised (flatened) to provide reliable reference points that can then be transferred by scribing to create the mating tenon shoulder face cut lines.

As per the reply given above to Gabel is no longer possible to say with any certainty whether old time practices were technically driven or arose simply from working experience or even expedient shortcuts but since M&T face / shoulders are not necessarily at right angles when compared with the line of the joint then any slop provided in the joint will allow the tenon to slide in and will even accomodate a slightly "offline" tenon without the mortice sides interfering with the fit of the tenon in the joint.

I did not previously mention about the effects of drying of green timber i.e. on shrinkage & deformation of the joint but very tight and parallel mortice / tenon joints made in green timber must tend to promote cracking as the timber dries since there is no "forgiveness" in the joint and thus I think that slop is and was probably a necessary technical ingredient in making a M&T in green timber.

Your thoughts and observation are very welcome since what is in the process of being outlined here in this topic might be considered to be quite revolutionary (and maybe even a relief) to some when they compare what is being discussed herein with the standard "workshop" type approach that is generally taught to beginners and is also seen to be reflected in various "how to" timber frame books.

No offence intended to anyone.

Regards

Ken Hume

Thanks for the input, Ken. After yours and others comments I think we can agree that draw boring is/was historically widespread...an old technology ("old tech").

As to your comments about tapered pegs... To my mind, the fact we see tapered pegs reinforces the theory of draw boring even further. Fact is, as we know, because holes are offset in draw boring, you need a tapered peg to align/fit through everything... Seems this is why we see tapered pegs. Otherwise a chamfered peg would have been adequate to get it in the hole.

I know some assert that tapering is just a result of drawknifing them on a shaving horse, but there are also rived and turned pegs out there... It would be interesting to see if joints pegged with these were drawbored. I would guess not, given you need the taper for draw boring, etc.

Most all pegs I've seen here in old barns are tapered... ~ 90%

As to your sloppy mortise assertion, it sounds like a good practice to allow for stress/movement, esp. wracking. Old buildings weren't on frost walls. And like you say, a tight shoulder is really where the strength of the joint is. Slop can be done w/out infringing on that critical factor.

Putting "slop" in a mortise is probably counter-intuitive, as well as more difficult to accomplish w/ today's power equipment, however.

"Mating faces should be regularised (flatened)...

sounds like the begining of square rule, doesn't it?

I sure hope no one thinks my joinery is sloppy or crude by my comments. Although I do push it right up to the line at times, all in the name of efficiency. Which brings me back to why I draw bore, efficiency. Square rule is efficient, too.

This discussion reminded me of the French Snap. It is a fairly crude but efficient method in shaping a tenon and would leave the shoulder tight and the bulk of the tenon possible shy of the mark.

Ken, the article on daisy wheels was great. It kept my kids and I busy for a number of winter evenings playing with the compass. I just read about the "illegal" windows. Did you do work on the frame in Fig. 24? The tie has a patch. Tim

What's the magic number? 3/16ths?
Having just done a large frame with Mark, and no draw boring (or little) I can see the benifit. But dread the sound of "POP"

Hi Tim,

I did not work on the frame in Fig 24 - if I did that would make me about 480 years old ! I have however slept in the bed shown in Fig 24. The more observant of you will note that the leg of the bed appears to be propped up on books and that is because a large hump in the floor has developed due to subsidence in the front wall.

Don,

I agree your comments about modern day power equipment not providing adequate "slop" clearance in the mortice and thus I rather suspect that frames made thus will be much more subject to the development of large shrinkage cracks.

Regards

Ken Hume

Maybe there's another word for "slop" we can use... that way it won't sound like "sloppy," which as Tim pointed out, can lend a negative meaning.

What about

"tolerance"

or

"allowance"

Anyway, I was giving this some thought... seems like we're talking about two different animals, even two different time periods here.

What Ken seems to be asserting is that it made sense (long ago) to cut mortises with some "allowance" factored in because of the conditions, principaly no modern foundation, and green timber.

Settling of both wood and building were certianly going to happen.

So I'm wondering, and the question might now be, if we need to make mortises in frames today with "allowances" given we don't have those concerns in new construction: modern foundations and kiln-dried stock reduce movement issues considerably.

(I assume stock is often KD these days)

thoughts??