Archive for the ‘joinery’ Category

Tenon Strength

Friday, December 2nd, 2016

In making a tenon there are three variables that the woodworker has at his disposal to modify; they are length, width and thickness. Between tenon width and tenon length I’ve often wondered which of the two variables played a larger role.  It seems logical that increasing either variable will lead to a stronger mortise and tenon joint – this isn’t the interesting part, but rather which one, of the two (length and width), plays a larger role?  Fine Woodworking (#259–Jan/Feb 2017) recently published an article that provides a decent amount of data to answer the question; however, more data points would have been better.  The article is an excellent read and I’d encourage any woodworker to read it.  My biggest problem with the article is that the author made an error in his conclusion regarding the relative role between tenon length and width in how it relates to strength.  The author concluded that the tenon width had the largest effect, but this isn’t accurate when you plot both sets of data and compare the slopes of both lines.  Smaller changes in tenon length, when compared to tenon width, have a larger effect on joint strength.  So, in the end, tenon length rules the day, but tenon width still plays a large role.  I have the plots below in one graph (blue is tenon width, and orange is tenon length), but I blurred out the axis values because it’s not my data to publish – you will have to read the article for all the details.

It’s still a very cool article and goes into other aspects of mortise and tenon strength that are certainly worth reading.



Guided Chisel for Bridle Joints

Wednesday, December 16th, 2015

A block of wood clamped to your stock makes an excellent guide for your chisel as you clean the bottom of the female portion of a bridle joint.  Just make sure that the block of scrap wood that you are using as a guide is square to your stock.

I completed all of the female portions of my bridle joints tonight which will make up the outer frame of my breakfast tray.  Next up are the male sides which I will make similar to a traditional integral tenon.  See how I cut the cheeks.


Joint Strength Again? Ugg.

Wednesday, February 11th, 2015
I seem to be on a roll lately with regard to joint strength.  I hope it passes soon 🙂
I just came across this recently published video by FWW on drawboring. It was recommended to give them a try as drawboring “draws the joint together tightly”.
What’s not mentioned in the video is that pinning a mortise and tenon actually compromises joint strength, as they published previously (FWW #203).  A single pin was reported by FWW (#203) to reduce joint strength by 20%.  The author in the video used 2 pins.  I wonder what effect that would have? Can’t be good.
The only rationale I can think of for doing a drawbore is if you run out of clamps or you like the look of pins.  But if the latter, why not just use faux pins and not compromise the joint strength?

What are your thoughts?