Dado work in place of a lot of morties? - Woodworking Talk - Woodworkers Forum
 
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post #1 of 15 Old 05-04-2015, 04:24 AM Thread Starter
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Dado work in place of a lot of morties?

I do a lot of attaching legs to apron boards.

In my time, I started with morties and tenons, to give that smooth transition and strength of course.

As of late I been replacing the morties with a much easier dado joint.

It's easier and imo stronger because the full board is carrying the load oppose to a thinned down tenon from same board.

Table legs and bed post specifically when a lot of weight is carried across the longest lateral apron.

Suppose I wanna sip on my coffee and chit chat the two.
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post #2 of 15 Old 05-04-2015, 07:52 AM
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Are you meaning a stopped dado? Do you have a pic?
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post #3 of 15 Old 05-04-2015, 09:04 AM
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pretty sure a "stopped dado"

http://www.woodworkingtalk.com/f5/ta...bracing-20431/

Lola Ranch, AKA Bret made some cool leg braces using stopped dados in the thread above. They would be a whole lot easiier and much faster than mortices..... and as I argue in the discussion probably just as strong. The major difference is the small area of material on the leg above the tenon is missing in this method. I would chisel the bottom of the stopped dado square to compensate for any tendency toward racking.


more discussion here:
http://www.woodworkingtalk.com/f2/wo...joinery-26027/

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)

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post #4 of 15 Old 05-04-2015, 10:43 AM
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Quote:
Originally Posted by micheal1 View Post
As of late I been replacing the morties with a much easier dado joint.

It's easier and imo stronger because the full board is carrying the load oppose to a thinned down tenon from same board.

Table legs and bed post specifically when a lot of weight is carried across the longest lateral apron.
I would caution you do rethink this.

First of all, you'll never have a load problem as long as the tenon is at least 1/2-2/3 the width of the apron and if you pin the tenon, you have an extremely strong joint.

Second, one of the main functions of a m/t joint is to provide stability by preventing racking. This is achieved with the tenon plus the shoulders. I would think this would be especially important in a table or bed.

third, how deep are you making the dados? If you make them deep enough to really work, then you're removing alot of material from the legs and weakening them.
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post #5 of 15 Old 05-04-2015, 11:10 AM
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maybe so....

Quote:
Originally Posted by micheal1 View Post
It's easier and imo stronger because the full board is carrying the load oppose to a thinned down tenon from same board.

Table legs and bed post specifically when a lot of weight is carried across the longest lateral apron.
Quote:
Originally Posted by DrRobert View Post

First of all, you'll never have a load problem as long as the tenon is at least 1/2-2/3 the width of the apron and if you pin the tenon, you have an extremely strong joint.

I don't think he wants to have a tenon...

Second, one of the main functions of a m/t joint is to provide stability by preventing racking. This is achieved with the tenon plus the shoulders. I would think this would be especially important in a table or bed.

The "shoulders" of the board would be the ends of the board IF they were seated in the dado and held there by a brace.

third, how deep are you making the dados? If you make them deep enough to really work, then you're removing alot of material from the legs and weakening them.

If they are made deep enough to really work, then it's not a good joint using your logic....
If there is only a dado and no shoulders on the tenon, then I would agree, not as strong. However there are ways around that issue.

This brace doesn't exactly apply since there are shoulders on the tenon, but the idea would also work if there weren't any:



A sliding dovetail would also work IF the idea is to eliminiate making mortises:

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; 05-04-2015 at 11:17 AM.
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post #6 of 15 Old 05-04-2015, 12:14 PM Thread Starter
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Well I feel kind of dumb. I have only been doing wood working on my own for about six years. That's still entry level imo....what is wood racking?

I'm sure I dealt with it but never knew the correct term to identify it.

I imagne it's when the joint rocks back and forth? Close?

Okay... I recently built a table and the legs were roughly 3x3". I did a full daddo the depth and height to match the 1x3 apron into the leg. No stop, it ends flush with the outside of the leg. That 1x3 has a full shelf/lip to now rest on attached to the leg.

The apron is glued and tacked in place with a few brads. Granted I had to putty a few pencil lead sized holes but it worked great and is strong.
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post #7 of 15 Old 05-04-2015, 12:26 PM
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This might not be a great answer but I have used dowels (with a dowel jig) to attach aprons to legs with great success. It is faste than M&T (which I do also)
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post #8 of 15 Old 05-04-2015, 01:02 PM
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imagine a cardboard box ....

Quote:
Originally Posted by micheal1 View Post
Well I feel kind of dumb. I have only been doing wood working on my own for about six years. That's still entry level imo....what is wood racking?

I'm sure I dealt with it but never knew the correct term to identify it.

I imagne it's when the joint rocks back and forth? Close?

Okay... I recently built a table and the legs were roughly 3x3". I did a full daddo the depth and height to match the 1x3 apron into the leg. No stop, it ends flush with the outside of the leg. That 1x3 has a full shelf/lip to now rest on attached to the leg.

The apron is glued and tacked in place with a few brads. Granted I had to putty a few pencil lead sized holes but it worked great and is strong.
Take an empty cardboard box and fold the bottom and top inside. It won't even stand on it's own. Now fold the bottom in. It is more stable. Next fold the top in and it's much stronger against lateral forces. Next put a diagonal brace across the opposing corners..WOAH much stronger. Diagonal bracing whether small corner blocks or full length will always make for a stronger joint.

A joint should be mechanically strong first, and rely on the glue bond second. The shoulders on the tenons resist "racking" and don't allow the tenon to shift .... until the glue bond breaks. A pinned or wedged tenon won't allow this and could be assembled "dry" with no glue if desired.

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)
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post #9 of 15 Old 05-05-2015, 06:08 AM
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Michael,

If I understand you correctly what you are doing is basically a lap joint, not a dado.
A dado is by def a crossgrain groove, such as one would make for a shelf or divider.

If you were making a true dado it would look like the pic with the sliding DT except it would be square. The problem with a lap joint centers around crossgrain gluing, which can result in the apron splitting if there is any wood movement (of course, with a 3" apron this is unlikely, but with a wider apron it is a real possiblity).

In furniture making, the basic idea is the joint itself is the structural part of the furniture, not a way to join two boards. We avoid the use of fasteners such as screws and nails and we don't fill holes.

There is a reason the M/T joint has been around for like 4000 years, and if you will give it a try, you will find it to be extremely strong and stable. If pinned or drawbored the M/T is just about the strongest joint on the planet.

If you don't want to go that route, then I would suggest dowelling as the next best alternative. One of the very first projects I ever made was a coffee table it was all dowelled together and 28 years later still rock solid. I remember when my boys were little them jumping up and down on it.
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post #10 of 15 Old 05-05-2015, 06:15 AM
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Woodnthings,

Maybe he doesn't want M/T's but I'm trying to convince him to go back.

The pic with the brace and the dados is not going to be as strong as a M/T so I disagree with you there. The shallow dado for the ends of the brace is not going to be a very strong joint, IMO. You would be better off with a shallow sliding DT.

The sliding DT is, of course, extremely strong and stable, but much more difficult to make than the M/T, so if you're looking to save time thats not a choice. But it is an excellent choice for a table, especially one that may be subject to some abuse such as frequently being moved, etc.
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post #11 of 15 Old 05-05-2015, 08:30 AM
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he doesn't want M&T

You can "try to convince "him if you wish, but I am providing him with other solutions. We all know a M&T joint is strong and time tested, but until you have some evidence to prove which design or method is not as strong, then your opinion is all we can go on....just like mine or anyone else here. Further, strength is relative, so he may not need the "strongest" just the most expedient and still structurally sound.

The sliding dovetail can also be made using a router table exclusively, no hand tools, so it can be done very quickly.
https://www.youtube.com/watch?v=q3oS1CYW6Go

The brace I posted serves 2 functions. Obviously it's a brace. Second, it draws the apron into the dado under pressure and maintains that pressure, unlike a mortise which is just held by the glue, unless it's pinned.

The braces look fairly complicated an initial glance , but actually can be made several ways with a single bevel setting on either a table saw or RAS. Here's a build thread I started:
http://www.woodworkingtalk.com/f2/le...allenge-33352/

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)
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post #12 of 15 Old 05-05-2015, 05:30 PM Thread Starter
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Went to my local shop and played with the festool mortieser. Awesome tool, wow.

Price is steep but worth every penny.
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post #13 of 15 Old 05-05-2015, 05:33 PM Thread Starter
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Domino xl
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post #14 of 15 Old 05-11-2015, 12:28 AM Thread Starter
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So I saw this video on a thread a few post up:

http://www.finewoodworking.com/how-t...ngth-test.aspx

half lap is the strongest in this test. Same joint I was talking about only using the wrong terminology to describe it.

Pretty cool video and really shows the true physics at play when load is applied to a joint. To me, pin holes always presented themselves has cracking points.

On F-16s, any from of cracking, 9/10 times is around a rivet or fastener hole, that logic just transferred over for me into wood.

Last edited by micheal1; 05-11-2015 at 12:38 AM.
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post #15 of 15 Old 05-23-2015, 02:51 AM
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More joint testing: http://woodgears.ca/joint_strength/

Eric
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