Is there a rule-of-thumb for the location and/or size of a peg relative to the shoulder of a mortise-and-tenon joint? With the cross-grain situation, it seems like there is a conflict between pegging too far from the shoulder, creating problems with either splitting the tenon or loosening the joint from expansion or contraction of the mortised member, or pegging too close, and taking the risk of splitting out the mortise.
As an aside, should a wedged mortise-and-tenon be expected to never loosen if done correctly? I’ve yet to see a wedged mallet or axe with a wood handle that didn’t loosen up eventually. Granted that a mallet and axe get pretty severe treatment, though.
I guess what got me curious is seeing cut-away examples of pegged joints that failed. Lots of places talk about sizing the mortise and tenon, but I haven’t seen any discussion of pegs.
Froed
Replies
Froed,
I don't have a ton of experience, but I have done 7 Stickley style chairs and 14 Windsor stools in the past 2 years. The primary thing I keep in mind with pegging M&T joints is ALWAYS orient the peg grain perpendicular to the grain of the piece. This way the expansion of the peg is less likely to split the piece along the grain. As for the distance from the edge of the piece, it depends on the length of the tenon and the diameter of the peg. On a 1 inch tenon and a 1/4 peg, I use 5/8ths. Chairs get heavy use and no problems after 2 years.
Dr. Bill
Dr. Bill, thanks for the tip. When you say orient the peg grain perpendicular to the grain of the piece, do you mean have the growth rings perpendicular to the long axis of the tenoned piece? That seems to make the most sense to me, to minimize peg expansion along the grain of the tenon. I'm not doing chairs yet, but I am in the process of making a workbench, so it'll definitely see more stress than, say, a hall table. Then again, with my kids, maybe not, ha ha...
Thanks again,
Froed
I don't recall reading anything on where to place the pegs or how many for that matter. I usually put them between the shoulder and the 1/3 to 1/2 way point to the end of the tenon. If I use two across a wide tenon I'll put them at the quarter points. I've never given a thought to the grain direction of the pegs or dowels since they're just a snug fit in the hole and not driven like a wedge.
John O'Connell - JKO Handcrafted Woodworking
Life is tough. It's tougher if you're stupid - John Wayne
Thanks John, I appreciate the input. I guess I've seen something written about a lot of different aspects of woodworking, but hadn't seen anything on pegs, so I was curious. I'm in the middle of a bench base, and it seems like a couple drawbored pegs would stay tight longer than wedges, though I don't really have much experience to base that on. The tenons are about 2-1/2" long, and if I put the pegs about 3/4 - 1" from the shoulder, I thought that would be reasonable for expansion and contraction of the foot. Sound reasonable?
Thanks again,
Froed
Yes, sounds about right.John O'Connell - JKO Handcrafted Woodworking
Life is tough. It's tougher if you're stupid - John Wayne
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