drawbored mortise and tenon

The other day I was working at some parts for some joined stools; and was able to get a few photos of some of the drawboring process. I still haven’t assembled this particular stool, but cut most of the joinery. The stool is for a demonstration I am doing down at Colonial Williamsburg on Feb 2; so it’s one of those Julia Child scenes; where I make most of the parts up here, then chop two mortise-and-tenon joints down there & presto! joined stool.

The essentials of drawboring a mortise and tenon are simple. The holes for the pegs which secure the joint are intentionally offset in such a way that a tapered peg, when driven through the holes, will pull the tenoned rail up tight against the mortised member. No glue, no clamps. Simplicity itself. 

 

test fitting tenon
test fitting tenon

 

Here I am testing the thickness of the tenon in its mortise. I pare the tenon with a wide framing chisel; then I will saw & split off the upper 3/8″ of the tenon.

 

marking holes on the tenon
marking holes on the tenon

 

Once I’m satisfied with the fit, I insert the tenon and mark with an awl the location of the mortise’s holes on the face of the ten0n.

piercer bit for boring tenon
piercer bit for boring tenon

 

Here is a detail of the piercer style bit used to bore these holes. This bit is about 1/4″ to 5/16″. I eyeball the amount to offset the holes, towards the shoulder of the tenon – “about the thickness of a Shilling” says Joseph Moxon.  This view shows a drawbored joint, unpegged, so we can sight through the offset holes. This much offset is perhaps a tad overdone, but it will work.

drawboring joint, unpegged
drawboring joint, unpegged

 

I make the pegs from split, straight-grained oak. I shave them with a chisel to a tapered octagon. I eyeball the size. Here is a cross-section of the peg’s path through the intentionally mis-aligned holes.  This view is of a sample joint I made about 15 years ago. It has many of the hallmarks of seventeenth-century New England joinery: an undercut front shoulder, a tenon that is shorter than the mortise is deep, and in this case, no rear shoulder to speak of at all. This joint is only fastened with 1 peg, plus this 2nd one that is cut through. It has been handled by thousands and thousands of people over 15 years, and is as tight a joint as one would ever need.

 

cross-section of drawbored mortise and tenon
cross-section of drawbored mortise and tenon

9 thoughts on “drawbored mortise and tenon

  1. Follansbee: I was busy straightening you out regarding the a pair of compasses. I look up and here you go on and on about drawboring! It is past my bed time. I quit. I hope you will someday soon replace the shot of the drawbored joint you made over 15 years ago. It is a funky treasure. Hey, I know it works all too well. It is a mystery, but let’s not frighten folks away with our crudities! You do better in your sleep! All the other shots are fantastic. Good work. Good evening.
    Alexander

  2. Hi Peter

    First, I want to mention that I have been reading your blog lately and really enjoy it.

    When doing a drawbore joint with two pegs, (in case of leg to apron joint) do you think that it is necessary to offset the mortise holes to prevent possible split in the leg

    In a case where the face of the leg where the mortise holes are to be done, you can see the annual ring running down the leg(rift or quarter sawn).
    I would think that one would look at the actual grain in the leg and try to put the holes so they are not over the same “annual ring”.

    The grain on a leg does not always run straight down, so one would need to check it to figure how the holes should be offset if need be.

    Have you seen some old furniture suffering from split mortise caused by drawboring?

    thanks

    Martin

  3. @ David Chapman Perhaps I used “federation” incorrectly. But what I meant was: Some states have a very strong central government and week subdivisions (states, provinces, prefectures…). Federalism is the system which emphasizes that states (individual Buddhist sects, by this analogy) should have most the power to experiment and be what they want to be while the central government only has central functions like defense and legal systems — or at least that was the way federalists intended it.So my point, is that we should not shoot for a homogenous whole but allow variety between states and encourage it so we get more spiritual laboratories.Sorry if I keep mixing the analogies.See wiki articles of federalism and federation — am I mistaken?Anyway, a separate post on each:(1) Preserving Variety(2) Caution Flags(3) Variety of Ethicswould probably be clearer.I just happen to agree with you so it is easy for me to sort these out. If any of your partial discussions had pricked one of my sensitive buttons, I may not have heard as clearly.

  4. Good post. I learn something new and challenging on sites I stumbleupon on a daily basis. It’s always interesting to read through content from other writers and practice a little something from other websites.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s