Thread: mortise and tenon joints

i use the rule of tenon thickness should be 1/3 the thickness of tenon stock. so for 35mm boards i'll use a 12mm thick tenon. I dont use tenons thicker that 12mm so if the need arises, i would use 2 tenons on really thick tenon stock. the depth of mortice ill make at least 4 times tenon thickness, preferably 5 times. there is little benefit to going deeper than 5 times, if you need extra strength, wedged through tenons would be the go. the width of the tenon i dont use any set rule, but for a 90x35 board, i would just use a 65-70mm wide tenon.

as far a home jig for mortising. there are many plans on the interwebs, here is a pic of mine. its a very common design and works really well. you would need to run the mortises, then move the fence...or add a packer piece for the second run.

Originally Posted by Lappa

I'm building an outdoor table from Australian and overseas hardwoods. The legs are 100 X 100mm and the apron rails 90 X 35mm.

I have two questions;

1) What width and length should the mortise slots be and how deep should the tenon go into the legs?

The mortise and tenon primer seems to indicate that each shoulder (cheek) should be 1/2 the tenon thickness. This would give me a tenon 19mm thick with each shoulder (cheek) 8mm wide.

However, other articles I read and jigs I see, seem to indicate a mortise slot of 12.7mm (1/2") maximum.

2) If I go to a tenon of 19mm. The max. size spiral upcut bit is 12.7mm. I cannot buy templates for my Triton router at the moment and there is no indication of when they may be available in Australia. Does anyone have a home jig design that would allow me to use a 12.7mm bit to accurately mortise the 19mm slots?

Thanks

As mentioned in a previous reply, using double 1/2" mortice & tenons should work OK for you, and they're easy enough to make. The Wood Whisperer web site recently published a video demonstrating one way of easily producing double tenons on a table saw, and double mortices using a simple shop-made router jig.

Have a look at this video: http://www.thewoodwhisperer.com/vide...osts&apt=video

Regards,

Roy

Slightly off topic.

When I started my apprenticeship (1966) in the joinery workshop I had 3 jobs being paint/priming, fitting flywire to timber screens and cutting tennons by hand to which I did 1000's of em which gave me the tomtits but without realising at the time it was teaching me to saw/cut timber by hand true and square.

Here's some light reading about the design, strength, failure modes and proportions of draw bored mortice and tenon joints (albeit in timber framing)

joint_report.pdf

DESIGN CONSIDERATIONS
FOR MORTISE AND TENON CONNECTIONS
Richard J. Schmidt
Christopher E. Daniels

A Report on Research Sponsored by the
Timber Frame Business Council
Hanover, NH

Department of Civil and
Architectural Engineering
University of Wyoming

Regards,
John

Thanks to all those that replied. New router and bits - ready to start tomorrow