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davewyo

TWW Outdoor Sitting Bench

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I generally round the tenons with a chisel and rasp, especially when there are so many to do. To me it seems slightly quicker and requires less physical effort.

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I'l drink to "less physical effort"....now where did I put my straw?

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I am looking forward to watching this Dave.  I was going to ask the same thing about the tenon.  I do the same as you, although I will square the mortises on occasion just to keep the skill  set in shape. 

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With those mortise and matching tenons I'd just chop the " round section" off entirely isn't adding anything for strength and either square or rounding is a PITA for that many tenons.I blame the domino for making me realize the tenon doesn't need to perfectly fit the hole. Once it's glued the shoulder covers it up and no one will know.

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9 minutes ago, Chestnut said:

With those mortise and matching tenons I'd just chop the " round section" off entirely isn't adding anything for strength and either square or rounding is a PITA for that many tenons.I blame the domino for making me realize the tenon doesn't need to perfectly fit the hole. Once it's glued the shoulder covers it up and no one will know.

It's funny you should mention it. I was thinking precisely the same thing.

I'm going out to the shop this afternoon and my goal is to complete the dry assembly of all those M&Ts. If rounding is going too slow I'm going with your option.

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7 minutes ago, Chestnut said:

With those mortise and matching tenons I'd just chop the " round section" off entirely isn't adding anything for strength and either square or rounding is a PITA for that many tenons.I blame the domino for making me realize the tenon doesn't need to perfectly fit the hole. Once it's glued the shoulder covers it up and no one will know.

I am not going to say that you shouldn't do this, I am just not sure I would agree with this.  You have to keep in mind that mortise and tenon is a cross grain joint and over time a cross grain joint can fail due to wood movement.  This is why some people draw bore  M&T's as added insurance against glue failure.  If you get glue failure, a loose fitting mortise and tenon will just fall apart.  I guess it all depends of how long you want something to last. 

 

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1 minute ago, Chet said:

I am not going to say that you shouldn't do this, I am just not sure I would agree with this.  You have to keep in mind that mortise and tenon is a cross grain joint and over time a cross grain joint can fail due to wood movement.  This is why some people draw bore  M&T's as added insurance against glue failure.  If you get glue failure, a loose fitting mortise and tenon will just fall apart.  I guess it all depends of how long you want something to last. 

 

Maybe if the tenon is 8" wide and 1/2" thick but in something that is less than 2 inches the surrounding material is going to constrain the small movement of a 1/4 inch thick tenon. If this wasn't the case plywood would self destruct in time. Who knows it might..... but i doubt it.

Also if the wood movement was an issue in this sense all of my furniture would have fallen apart already. I see 10% to 65% RH swings yearly and that's enough to cause problems in 4 years. So far all of my stuff is as sturdy as the day i built it. This may have been more of an issue in the distant past when all of this "conventional wisdom" was created when glues were not what they are today.

Last point there still has to be some room for the rounded ends (like 1/256") and it's enough that the joint will separate causing a gap at the shoulder especially considering the tenon will more likely fail on the shrinking side of things making the mortise loose. This is still joint failure even though the piece didn't fall apart and rounding or squaring isn't going to prevent this. If you don't believe me cut a mortise fit that perfectly put it together with out glue and then put force on the joint like a lever would. I'd bet that's goign to come apart.

 

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Okay, lets just say I am not a fan of taking short cuts in my woodworking I do this hobby for the joy of it and to challenge myself to do things to the best of  my ability, this is just a personal opinion.  To me what you are suggesting is a short cut or lazy approach.  If you build a piece of furniture and put it in place and never touch it again then you are fine.  But if it gets moved, used, or weighed during the course of its use, which are all things that will give some racking and movement,  then I think it is best to use the best technique you can to make it last.  If you don't need or want it to last, then fine take the shortcut.  Case in point, this type of bench built with tenons as you suggest, any sitting and moving on it is going to have an increased chance of failure.  

  

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What you call short cuts i call being efficient. For example the truss bridge was a "short cut" to make the stone arch bridge cheaper and easier to build. Engineering is basically taking a design and removing all the unnecessary bits to minimize production and material costs. All of my furniture is designed and built to outlast me and who ever gets it after me but my resources are not infinite.

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Let it be a lesson to beginners where the strength comes from in a M&T joint. It comes from the glue on the cheeks meeting the side of the mortise. The edge of the tenon and the ends of the mortise are an end grain connection and offer no additional joint strength. If you want to use them for alignment purposes that is something entirely different. Center lines and a mallet do the same thing faster and easier.

If we were really worried about strength in a joint we'd all be doing bridle joints or half laps..... M&T isn't even the strongest option in our joint arsenal. The M&T is a short cut  if you want to really boil it down.

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i don't totally disagree with Nut but would like to add that the shape of a tenon isn't all about strength of joint, it's also about alignment.  A properly fit tenon makes the adjoining piece stay put laterally as well as add strength to the joint.  Wasting away the sides, if done properly, will still only allow a certain fit.  But take away too much and you're going to create a slip fit with a little bit of movement.  

If I have a lot of mortises to cut I generally use a hollow chisel mortiser making the shape of the tenon a moot point.  I'd argue that would be the way to go in a production environment and not altering the shape of the tenon.

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My view. The alignment to the face is the most important. The alignment to the left and right is pencil marks. And the mortice is wider than the tenon. Once in the clamps with very slight pressure, a little bit of tapping to get the pieces on the marks. Then tighten the screws. Creating a shoulder on 4 sides of the tenon.Small amounts of wood removed left and right will not compromise any meaningful strength. Any slight variations of the spacings is not important as the eye has no clue. Here, what matters is all on the same plane and tight joints.

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1 hour ago, davewyo said:

maybe two beers.

Good timing mechanism.   Thats some nice clean grain too.

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7 hours ago, Chet said:

   Thats some nice clean grain too.

Yeah, I've been trying to get straight-ish grain for the top. The legs won't be straight grain, and I need to decide if I want to cut into a new board to make the aprons the same.

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I really like that you took the time to make good fits in the joints!  Was it absolutely necessary?  Probably not but, it was still a good lesson that taking the time to do it right pays off if for nothing more than piece of mind.  

Great looking bench Dave!  Your attention to detail especially with grain is always spot on!

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On 3/6/2019 at 7:03 PM, davewyo said:

There are 32 M&Ts in the top alone! 

This is the type of task where you just need to get in a mode with some nice music in the back ground and chip away at it.  You end up being done before you know it.  If your like me, the last few probably took about half the time as the first few.

Seat section looks like it came out real nice.

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That bench looks outstanding. Great job on the M&T’s. This is a great project to build. What type of finish are you thinking?

I’ve built about 10 of these so far. People seem to love them around their fire pits. Made all mine out of Mahogany scraps from work (ya I know, very lucky) and made some Sipo dominos also from scrap from work. Just used Cabot’s deck stain as the finish since they would be outdoors anyway. They’ve held up very well so far after about 3 years. 

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