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Forum topic by pontic posted 05-06-2017 12:00 PM 1068 views 0 times favorited 18 replies Add to Favorites Watch
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pontic

500 posts in 442 days


05-06-2017 12:00 PM

The Journal of Fine Woodworking about 15yrs ago did a test on 90degree joimts and their breaking stregnths. They just did the same test using the new class of PVA glues. They found the same results. They say the eimple 1/2 lap joint with nothing but glue (tite bond III being the strongest) is the strongest. Any screws dowels and such only weaken it. The next it the bridal joint. the stub tenon is the weakest.
What say you.

-- Illigitimii non carburundum sum


18 replies so far

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marc_rosen

126 posts in 3015 days


#1 posted 05-06-2017 01:14 PM

Hey Pontic,
Have you ever done any dentil work?

Although I thought their test was interesting I also felt some of the joints were not tested in their proper application. For example, I would only use mortise and tenon for a chair where you would get the angular pressure exerted as in their test. I would not use a lap or bridal joint here as I don’t think it would hold up to years of use. Other woodworkers may have used bridal joints in these high stress areas with good results, I just don’t think they would pass the test of time like the M&T joint.
I used bridal and lap joints on door frames, picture frames, etc but never where there is any type of flex that would open or close the angle of the two pieces to each other.
. ..Marc

-- Windsurfing, Woodworking, Weaving, and Woodducks. "Most woodworkers are usually boring holes"

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Fred Hargis

4756 posts in 2327 days


#2 posted 05-06-2017 01:18 PM

It’s interesting to follow these discussions. Here’s the thing, it doesn’t seem important to me which is the stronest except in certain cases. For most everything done in the course of casework and such, even the weakest joint like the stub tenon is still plenty strong enough.

-- Our village hasn't lost it's idiot, he was elected to congress.

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pontic

500 posts in 442 days


#3 posted 05-06-2017 03:16 PM

Have’nt done much dentil work have done a lot of Dental work.

I have not quite figured out what they are trying to achieve with these tests myself. Like the both of you say it’s the application and use that determine where one will use a certain joint over another.

-- Illigitimii non carburundum sum

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TravisH

550 posts in 1769 days


#4 posted 05-06-2017 03:40 PM

Not for sure if you can get a group of individuals together in a given hobby and not get individuals that believe their way is the best. These style of articles are just an attempt to bring science/factual basis for discussion. Many are uncomfortable with the material science aspect being brought into woodworking as it seams out of place to many and leaves them with “I believe”, “Just because”, reasons for the way they may or may not do something.

I agree with the above it doesn’t make a difference if no failure occurs with its use. Many guys like to take something that isn’t an issue ever and find a solution for the “problem”.

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marc_rosen

126 posts in 3015 days


#5 posted 05-06-2017 03:46 PM

Hi Pontic,
I’m glad you got my joke and you didn’t need an “I” doctor to help figure it out. (It’s probably one of the most oft used dentist jokes anyway.) Nice work on your projects page, did you make your guitar too? What types of music do you play? (Sorry for turning the thread away from your original intent.) Marc

-- Windsurfing, Woodworking, Weaving, and Woodducks. "Most woodworkers are usually boring holes"

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pontic

500 posts in 442 days


#6 posted 05-06-2017 03:59 PM

Yes Travis JFW’s test articles are there to add the professional standard to their journal. I for one enjoy the material science and engineering aspects of woodworking. That being said I also find the information provided with most glues and other woodworking materials incomplete at best. No MSDS are supplied you gotta ask the store manager and hope he knows what you are talking about. Going back to testing; the direction and rate of application was not varied so this was a very narrow test from a truly material/engineering stand point.
Thanks Mark; no I did not make my Bass Guitar it is a vintage Fender Jazz bass. not a luthier. I play Rock and Blues mostly.

-- Illigitimii non carburundum sum

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Rick_M

10606 posts in 2214 days


#7 posted 05-06-2017 04:27 PM

They do the tests because it sucks in readers, same with all the YouTube videos on the same subject. It’s interesting but joinery is a solved problem, it’s already worked out through centuries of evolution.

-- http://thewoodknack.blogspot.com/

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pontic

500 posts in 442 days


#8 posted 05-06-2017 09:25 PM

So you will like the Purple Kool aid they are serving?

-- Illigitimii non carburundum sum

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MrUnix

5978 posts in 2033 days


#9 posted 05-06-2017 09:33 PM

So you will like the Purple Kool aid they are serving?
- pontic

Ugh… thanks to my college days, I can’t even think about purple (grape) kool-aid without getting a bit nauseous!

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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Rick_M

10606 posts in 2214 days


#10 posted 05-07-2017 12:54 AM


So you will like the Purple Kool aid they are serving?

- pontic

I don’t take your meaning unless they are woodworkers of old and we are drinking together.

-- http://thewoodknack.blogspot.com/

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pontic

500 posts in 442 days


#11 posted 05-07-2017 01:06 AM

Drinking the Purple Kool aid is an American slang term for brainwashing. It had rather ignominious beginnings. It came from the mass suicides of the Jim Jones compound he was a religious leader that had his whole congregation drink poisin mixed in with Purple Koolaid. So when some one says you are serving the purple kool aid means you are being brainwashed.

-- Illigitimii non carburundum sum

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Rick_M

10606 posts in 2214 days


#12 posted 05-07-2017 01:17 AM

I understand the reference to Kool aid, I said I don’t take YOUR meaning. I was under the impression that we were mostly in agreement, that joinery strength tests are pointless. To simplify, I don’t understand who it is you believe is doing the brainwashing or for what result. Nor do i understand the insult since I did not insult you.

-- http://thewoodknack.blogspot.com/

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pontic

500 posts in 442 days


#13 posted 05-07-2017 01:30 AM

Insult? I am not trying to insult you nor any one else. I was referencing it to the Journal. They want you to think they are the big scientific technical gurus for woodworking. That JFWW is a professional journal. It is no more a professional journal than “Dentistry Today”, or the “Lady’s Home journal”
when you said that they do it to suck in the readers; I was agreeing with you. they serve you the purple Koolaid.
So if I insulted you I apologize I did not mean to.

-- Illigitimii non carburundum sum

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MrUnix

5978 posts in 2033 days


#14 posted 05-07-2017 01:34 AM

I’ve heard the ‘drinking the kool-aid’ stuff a lot… but never the ‘purple’ part.
Funny part is that the Jim Jones mass suicide used Flavor-aid, not Kool-aid
(although, it was grape IIRC)

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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Rick_M

10606 posts in 2214 days


#15 posted 05-07-2017 01:44 AM

No problem Pontic, I should have used more words to make myself clear. I wasn’t sure what you meant, that’s why I asked.

-- http://thewoodknack.blogspot.com/

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