Drawboring 1 or 2

chest-pegsOn the William & Mary chest in the April 2014 issue of Popular Woodworking Magazine (which mails to subscribers next week), the case sides are frame-and-panel construction (read about how I handle sticking here) with drawbored mortise-and-tenon joints. As my article made its way around the office for editorial review, Megan Fitzpatrick noticed that I used two offset pins in each tenon and asked, “Why, the offset?”

Then it occurred to me you might also wonder, why two pins instead of one?

The short answer to “why two?” is that the rails are a bit wider and two is better than one. The short answer to “why offset” is that I’ve seen too many period pieces with split stiles.

But here’s a more thorough explanation.

Let’s just assume that we all know that drawboring is when we drill a hole through a mortise-and-tenon joint where the hole through the mortise is offset slightly from the hole that is drilled through the tenon and, when a peg is inserted, the peg pulls the joint tighter as it moves through the offset holes…let’s just assume that. So, why would we want, or need, more than one peg through the joint?

Slightly open mortise and tenon joint from chair

Even after re-assembly, a single pinned wide mortise-and-tenon joint has gaps from racking over the centuries.

To me, the answer is twofold. When using pegs (often called pins, which are not to be confused with dovetail pins…) to draw a wide mortise-and-tenon joint closed, having only a single peg means you have a pivot point on which to leverage the joint over time.

I’ve seen it hundreds of times in period pieces that I’ve repaired: If the joint is prone to racking stress (as part of a chair for instance), the end-grain shoulders of the rail begin to crush the long-grain fibers of the stile. This loosens the joint and allows further racking. With two pegs, you lock the joint solidly in place and take away the fulcrum.

Another reason you want to use two pegs on a wide mortise-and-tenon joint is for the same reason you’d want to use two clamps: to equalize the pressure bringing the joint together. If you are making a mortise-and-tenon joint that is 7″ wide, you’d most likely use two clamps to pull it together so the shoulders mate tightly across the entire joint. If you put a single clamp at the top or bottom of the joint, the opposite portion may have gaps. Even if you put a single clamp in the middle of the joint, depending on the type of frame you are making, you may still end up with gaps. Two clamps ensures the shoulders are tight across the entire joint; two pegs does the same thing.

The double pinned mortise and tenon from this early 18th century table is still fairly tight event after about 300 years.

The double pinned mortise-and-tenon from this early 18th-century table is still fairly tight even after about 300 years.

Let’s face it, pegs are the 17th and 18th centuries’ answer to clamps. Much like nails, the idea was to pull a joint together and hold it tight until the glue dries. Again, having repaired hundreds of 17th and 18th century mortise-and-tenon joints (almost all of which were glued) the wider ones with two pegs have generally held up better.

And does a drawbore lock a joint in place forever? Not a chance. I’ve repaired plenty of pieces with drawbored mortise-and-tenon joints that were loose. After a couple of centuries of drying out, being sat on, knocked over, dragged around the home by toddlers, hauled from place to place and generally being used (and abused), you’d be a little loose, too.

So, why bother with drawboring? The answer is simple: It pulls the joint together and cuts down on the need for clamps (or at least, reduces the number you need for a project). For me, it’s also a matter of historical correctness. Most of the mortise-and-tenon joints I’ve seen in period chairs and case pieces are pinned (or pegged if you prefer). With a track record in the hundreds of years, why wouldn’t you take an extra few minutes to drawbore your mortise-and-tenon joints?

Something I’ve also seen with regularity is a double-pinned joint, where the pins are set at the same distance from the shoulders, with a split stile. Occasionally, I’ve come across period pieces that had long or through mortise-and-tenon joints where the pins were offset. On these pieces the stiles tended not to be split between the two pins.

Because the pins are in line with one another, the stiles split over time.

Because the pins are in line with one another, the stiles split over time.

The key is to have long enough tenons so that when you offset the pins, there’s still enough tenon beyond the outer pin to hold. Getting too close to the end of the tenon means little or no holding power for the pin. If your joints are wide enough, and your tenons long enough, offsetting the pins might just save your stiles from splitting too.

— Chuck Bender

p.s. You can see the cover project and the online extras for the April issue at popularwoodworking.com/apr14.

16 thoughts on “Drawboring 1 or 2

  1. cebuchan

    Thanks for this blog and the replies as well. It contains really logical thinking based on experience with older pieces. Very useful to me in thinking about stresses in joints.

  2. Bill Lattanzio

    I love the idea of a furniture repair/restoration blog series. Most of us aren’t going to be building highboys in our spare time, but I would think that a good majority of the readers have some old furniture (myself included) that could use a little repair and refinish work. Now I’m sure there are dozens of books dedicated to this type of work, but I want to hear it from Chuck.

    1. Chuck BenderChuck Bender Post author

      I treat bridle joints just like through mortise and tenons. You can offset any way that makes sense to you. Just keep in mind that the pins can’t be too close to the outside of the joint or you run the risk of splitting both halves. Or you punt and do one pin…

  3. JimWood

    Chuck You mention having experience doing lots of furniture repair in your past experience. I sure wouldn’t mind seeing an article or two on that in the magazine. One area I struggle with if a friend asks me to repair something is how to go about doing the least amount of damage to the piece while getting it apart, when to try to match stain and finish and when to punt by stripping, sanding or some other method and refinish (not my favorite option just because of the increase in workload to strip and refinish). For matching existing finishes hints such as how to and determine what type of clear coat finish (shellac, lacquer, or polyurethane) was used versus straight oil finishes and in the even tit is some sort of film finish over oil or stain how you would proceed getting any repair work to match up.

    1. Chuck BenderChuck Bender Post author

      Jim,

      It’s something I’ve had in mind for the blog since I joined the team here at PopWood. While I can’t make any promises as to when, if there’s enough reader interest, I’ll try to move it closer to the top of my “to do” list.

      Meanwhile, if you have specific questions feel free to shoot me an email with the details. I’ll do my best to answer if I can.

      1. JimWood

        Chuck,
        I was going to shoot you an e-mail, while I realize your e-mail addie maybe somewhere on the website,, it must be buried somewhere because in a casual perusal looking for it I could not find it (and it was very casual I didn’t have time here at work to look to extensively).

        I do have questions. I tell most my neighbors, friends or family I won’t even try to tackle for anything they value (like an antique). I am just do not feel I have the skill for it as all my experience is from scratch construction with new wood. I’ll help them out for basic furniture they just want to be functional again and look at least decent. I’d give you my e-mail here but don’t like spam bots.

        1. Chuck BenderChuck Bender Post author

          Jim,

          You can email me by clicking on my name at the end of any of my blog posts but, for the record, my email is chuck.bender@fwmedia.com (and I love spam…)

          For the most part, my experience restoring furniture has been focused on 17th, 18th and early 19th century pieces (think “Antiques Roadshow” pieces where people nearly pass out when they find out what they’ve got). That doesn’t mean some of the techniques I use won’t translate to post-Industrial Revolution pieces. I just never spent much time repairing later furniture because of the economics involved. If I have five hours invested in fixing a piece that’s worth $75, someone’s losing money. If you don’t plan to make a business out of it, the investment will provide your family and friends with better repairs to pieces that are priceless in sentimental value.

          Feel free to send your questions.

  4. Mitch Wilson

    Chuck, does all of this mean that you recommend drawboring all of your M&T joints for tables and chairs of the type that you have shown here? It makes a lot of sense to me and it certainly is not a whole lot of extra work. Also, if the tenon is long enough, couldn’t you move the pegs farther away from the shoulder? This would add more “meat” to the stile here and possibly eliminate the need for offsetting.

    1. Chuck BenderChuck Bender Post author

      Mitch,

      I try to drawbore as often as I can and placement is always a matter of trade-offs. You can certainly move farther away from the shoulder, if your tenons are long enough, to add more meat to the stile side of the joint but I think of pegs in the same way I think of nails, however. I try not to line up my nails (unless they are attaching mouldings) over short distances because you can easily get a running split between. Offsetting, for both nails and pins, dramatically reduces that possibility. If you object for aesthetic reasons, I actually try offsetting the pins so they are symmetrical from left to right and top to bottom. If the two pins being in plane is more your speed, I have no objection to that either. All are historically valid methods and, in the end, the piece is yours. You should do what looks right to your eye and not do something simply because I said so.

      Chuck Bender

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