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Will this mortise hold?

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Forum topic by Mcpowell posted 11-05-2017 07:50 PM 658 views 0 times favorited 15 replies Add to Favorites Watch
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Mcpowell

23 posts in 723 days


11-05-2017 07:50 PM

Topic tags/keywords: walnut mortise knot epoxy

I wanted to use this piece of walnut as the knots give this chair leg a lot of character. Unfortunately, after I was a good way into the project, I noticed this knot was going to line up with my mortise. I do have a spare leg I can fall back on, as I made an extra blank, but that will take several hours to complete. After figuring out how this was all going to line up, I decided to push onward, make the mortise and see how solid the area felt. Well, it’s not very solid. I can move the .400” thick area with my fingers. It’s not brittle, but there really isn’t much strength in the area between the mortise and the edge of the chair. I have plenty of epoxy resin. To give you some size reference, the mortise is 2” long and .5” wide.

1) Do you think this will have enough strength to hold if I fill the void/knot with epoxy?

2) If you think the epoxy will hold, should I epoxy first, or glue the joint with titebond and then fill in the knot with epoxy after the glue has set?

Any suggestions?

-- I want to be good


15 replies so far

View jmos's profile

jmos

796 posts in 2203 days


#1 posted 11-05-2017 07:56 PM

Personally, I would not trust it, especially not in a chair. Just think how much lost time if you push on and it fails in use. I’d be safe and make a new leg.

If you do decide to epoxy, I’d think you would be best off using the epoxy to assemble the joint and fill the knot at the same time.

-- John

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Loren

9606 posts in 3481 days


#2 posted 11-05-2017 08:00 PM

Even if the knot doesn’t pop out the distorted
tissue will move strangely and the joint will
probably loosen as a result.

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halfacre

148 posts in 2443 days


#3 posted 11-05-2017 08:28 PM

Is this one of the rockers? If so I would not use it. What happens if you could make the mortise and tenon two or three times deeper which would probably help. And instead of using glue I would use 2 part epoxy and using air pressure after you apply the epoxy let the air pressure force the epoxy as deep as you can get it. I use a rubber tip blo gun for that purpose. Also as the air flows cover the area with a rag or else some will escape and cover the walls.

Halfacre, Jess

-- halfacre, Breckenridge, Tx

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Mcpowell

23 posts in 723 days


#4 posted 11-05-2017 09:05 PM



Personally, I would not trust it, especially not in a chair. Just think how much lost time if you push on and it fails in use. I d be safe and make a new leg.

If you do decide to epoxy, I d think you would be best off using the epoxy to assemble the joint and fill the knot at the same time.

- jmos

John,
This is exactly what my son and I discussed at lunch. Work 3-5 hours and make a new leg, or end up throwing away the whole chair when it breaks in a few years. Ugh…can you hear my whining across the internet?

-- I want to be good

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Mcpowell

23 posts in 723 days


#5 posted 11-05-2017 09:11 PM



Even if the knot doesn t pop out the distorted
tissue will move strangely and the joint will
probably loosen as a result.

- Loren


I know you are right, but I wish your answer was different. ;-)

-- I want to be good

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Mcpowell

23 posts in 723 days


#6 posted 11-05-2017 09:15 PM


Is this one of the rockers? If so I would not use it. What happens if you could make the mortise and tenon two or three times deeper which would probably help. And instead of using glue I would use 2 part epoxy and using air pressure after you apply the epoxy let the air pressure force the epoxy as deep as you can get it. I use a rubber tip blo gun for that purpose. Also as the air flows cover the area with a rag or else some will escape and cover the walls.

Halfacre, Jess

- halfacre

Jess,
It’s not a rocker, it is one of the chair backs. The pictured mortise faces forward. Hopefully the drawing will illustrate.

-- I want to be good

View Aj2's profile

Aj2

1171 posts in 1631 days


#7 posted 11-06-2017 01:27 AM

If you don’t use that piece it would make a good test piece. I would fit a scrap tenon in there epoxy it all together let it cure. Then see how much it takes to break the joint.
I’d be interested to see if it’s strong.
Let the record show I think it will be good if you use epoxy.

-- Aj

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Mcpowell

23 posts in 723 days


#8 posted 11-06-2017 02:16 AM



If you don t use that piece it would make a good test piece. I would fit a scrap tenon in there epoxy it all together let it cure. Then see how much it takes to break the joint.
I d be interested to see if it s strong.
Let the record show I think it will be good if you use epoxy.

- Aj2

AJ,
That is a good idea. I have at least one extra piece of each component. I figured I would screw something up somewhere along the line while trying to build 8 chairs. It might be a month or so before I have a leftover or scrap horizontal pieces, but I’ll definitely test it.

Any suggestions as to how to measure the results? I’m unwilling to waist a good leg, but I guess I could make another mortise from just a block of good wood.

Mark

-- I want to be good

View Gilley23's profile

Gilley23

375 posts in 215 days


#9 posted 11-06-2017 02:56 AM


Any suggestions as to how to measure the results? I m unwilling to waist a good leg, but I guess I could make another mortise from just a block of good wood.

Mark

- Mcpowell

Mark, check this out: https://youtu.be/apsH8eBfjVA

View TheFridge's profile

TheFridge

8287 posts in 1319 days


#10 posted 11-06-2017 03:49 AM

As long as the knot is epoxied in well I don’t see it being that big of a deal.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View Andre's profile

Andre

1488 posts in 1639 days


#11 posted 11-06-2017 06:57 AM

Back side and both ends solid so with a tight fit no problem!

-- Lifting one end of the plank.

View Mcpowell's profile

Mcpowell

23 posts in 723 days


#12 posted 11-07-2017 06:41 PM

So a friend and I were chatting about this and he suggested I build 9 chairs instead of 8. So I think I’m going to give that a try. It just keeps me from having spare parts in the event I really screw something up along the way. So I think I’ll use this leg on my 9th chair.

For this leg with the inconvenient knot….would it be helpful to the strength of the mortise and tenon if I drilled a few holes through the knot, into the tenon, and then screwed them together. This seems like it would provide a bit more horizontal strength to the joint and I could fill the drilled holes with black epoxy (which should match the knot fairly well). I’ll use epoxy as the glue on this one through and through regardless.

-- I want to be good

View pontic's profile

pontic

500 posts in 442 days


#13 posted 11-07-2017 10:02 PM

You could rout or chisel out more of the knot area and about a3/8” above and below it and place it a walnut plate that has smooth strong straight grain. Make the plate about 1/4 ” thick and bed it in there with epoxy. then seat your tenon with epoxy. You know that you have more splits running with the grain to worry about than just that knot.

-- Illigitimii non carburundum sum

View rwe2156's profile

rwe2156

2710 posts in 1314 days


#14 posted 11-08-2017 01:51 PM



would it be helpful to the strength of the mortise and tenon if I drilled a few holes through the knot, into the tenon, and then screwed them together.
- Mcpowell
I think this would weaken it even more and probably cause the knot to fail.

I would route the whole thing out flush to mortise wall and 1” past the ends & glue in a patch.

-- Everything is a prototype thats why its one of a kind!!

View runswithscissors's profile (online now)

runswithscissors

2557 posts in 1858 days


#15 posted 11-11-2017 12:40 AM

Pontic’s suggestion sounds best to me.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

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