Mortise and tenon newbie needs some guidance - Woodworking Talk - Woodworkers Forum
 
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post #1 of 7 Old 06-17-2012, 11:11 AM Thread Starter
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Mortise and tenon newbie needs some guidance

Hi, first time posting and looking for a bit of advice on making mortise and tenons. Making a bench using 2.5" square legs, and 2x4s for the apron. I've already cut 1/2" wide mortises 1" deep. Length of the long apron will be 44" including the tenons. Will 1" tenons be enough, or should I make them 1.25 and miter the tenons? I was planning on not using a stretcher if that makes a difference.

Thanks in advance!
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post #2 of 7 Old 06-17-2012, 12:27 PM
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What are the dimensions of the bench?

How much load will this have?

I think the legs will need some lateral (side to side) support lower down, which is what a stretcher would offer.

Without any lower lateral support between the legs I do not expect a deeper mortise would help. I would be concerned about someone accidently bumping into the side and then the joint failing even with deeper mortise.
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post #3 of 7 Old 06-17-2012, 01:26 PM Thread Starter
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I was going to make the bench 48x14 and use it for seating. Bad idea with no stretcher?
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post #4 of 7 Old 06-17-2012, 02:11 PM
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benches and tables

You need to understand some of the physics involved in the structure. Think cardboard box open on both ends, so you can see through like a tunnel. Kinda collapsable, huh? Close one end...still not very good. Close the other end ... much better.
Simply put, rectangles collapse, unless reinforced with either panels, stretchers or triangular braces in the corners. The mortise and tenon acts like a small brace and the wider the apron the greater the strength.
Adding an additional stretcher at the bottom creates an additional brace, however it's still a rectangle from the side so it's not a very rigid structure, but it's way better than none at all.

Triangles will not collapse unless the joint fails. A rectangle with a diagonal brace will not collapse unless the diagonal comes off or the joint fails. Farmers and harvest tables and benches often have a center stretcher or rail which then connects to the legs by means of a cross brace.

Benches and tables are subject to horizontal side forces when bumped into or moved/dragged with loads on them, so the bracing is necessary to prevent racking and joint failure.

Here's some examples of tables.
Some have no stretchers, just aprons, others have stretchers: http://images.search.yahoo.com/searc...=harvest+table

Here's some simple benches:
http://images.search.yahoo.com/searc...x=wrt&y=Search

I think this one is particularly beautiful and has some hefty mortise and tenons! http://images.search.yahoo.com/image...mb=AyhczztaeH5

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 06-17-2012 at 02:17 PM.
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post #5 of 7 Old 06-17-2012, 02:29 PM
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How tall are the legs on this bench? How many people will sit on the bench at one time? Will it be used for long term sitting or just short term like changing shoes? Will children be putting loads on the bench.

If the environment for the bench is rather benign and the legs are relatively short you may get by without stretchers. Increasing the tenon length by 1/2" would be significant.

George
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post #6 of 7 Old 06-17-2012, 03:09 PM Thread Starter
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Legs are 17.25" tall. Planning to use it as a dining bench, so one maybe two people at a time. I think everyone has convinced me it's probably best to use stretchers.
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post #7 of 7 Old 07-01-2012, 02:29 PM
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I completed a kitchen table bench two months ago with identical top and leg dimensions. I used 1 1/4" tenons on the aprons and also added wooden corner brackets with hanger bolts. Finished bench is quite sturdy.
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