DrKev
Wholenote
It's just a guitar, it's not rocket science.
Posts: 418
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Post by DrKev on Oct 27, 2023 7:43:04 GMT -5
Another woodworking video I thought would interesting here. When and how is wood glue stronger than the wood?
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Post by rdr on Oct 30, 2023 16:50:30 GMT -5
Neat video. Thanks!
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Post by Leftee on Oct 30, 2023 18:52:55 GMT -5
I enjoyed that! Thanks.
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Post by funkykikuchiyo on Oct 31, 2023 10:06:17 GMT -5
His reasoning for breaks happening near the glue line makes a lot of sense, and I hadn't thought of that. We get customers in the shop who break their pegheads repeatedly, and that is what we usually see... doesn't break on the glue line, but incredibly close to it. It makes even more sense there because peghead breaks aren't the same as exerting a large amount of force, but of whiplash when they fall, so flexibility is probably much more of an issue.
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Post by Leftee on Oct 31, 2023 10:49:18 GMT -5
I learned about glued join strength back in HS wood shop. It was neat to see it demonstrated so well in this video.
I’ve found that I’ve migrated to a minimum 12 hour clamp time instead of 24. The only time I really adhere to 24 is if the project wants the additional strength for the work to be done.
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Post by Opie on Nov 1, 2023 6:12:18 GMT -5
I ran my own one man custom shop for 40 years and have used many a gallon of glue. I agree with 99% of what he says. Clamping pressure needs to be adequate, but too much pressure can actually starve a joint. The quality of the joint is very important, sharp knives on a properly set up joiner is essential, a joint with a properly tuned hand plane is the best, but not many people know how to do that properly and consistently. Time in clamps is dependent on the end use. I have built thousands of raised panels for cabinet doors with clamping times in the 30 minute range and can count one one hand any that failed, and those did were because I pushed the blades to far without replacing. Bigger panels or tops of a long length( over 30") stay clamped longer, often 24 hours. They are also made with a spring joint, which has a very minor gap in the middle requiring clamp pressure to draw together. This is done to build in more force at the ends, which if subjected to dry conditions will shrink the wood causing tiny hairline gaps at the ends of the panels. I have also glued up many odd angle pieces where due to design couldn't be easily clamped, and resorted to using high quality masking tape ( the thick stuff that has some stretch to it} to draw pieces together, have seen it years later looking perfect.
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Post by Leftee on Nov 1, 2023 8:20:41 GMT -5
I think I sometimes over-clamp.
Look at me! I’m learning stuff!
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Post by LTB on Nov 1, 2023 14:36:03 GMT -5
Very nice video. Thank you! I have had a tendency to remove clamps at 3-5 hours. I will lean toward 5 hours in the future.
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Post by funkykikuchiyo on Nov 4, 2023 11:44:46 GMT -5
I usually leave stuff overnight, often just for the convenience. Occasionally I wait longer if something is going to get a lot of tension. If there are no forces pulling a joint apart (including the glue itself pushing the joint open), I struggle to see why removing clamps after a minimum amount of time would be harmful. The most basic purpose of a clamp is just holding it still while the glue sets, so if it is not moving, I don't understand why they'd still be necessary... unless half set glue pushes out and widens the glue line slightly....?
Sometimes with something like a crack, peghead glue, regluing a top to the side, there will be some force from the wood wanting to pull the joint apart, and leaving it clamped not only gives the glue time to set, but also pushes the wood into its new position to hopefully want to remain in its new position. Every once in a while, I'll clamp something dry overnight so that when I come to it the next day to glue it, the joint isn't fighting me as much, as the wood has relaxed into its new position. This is rarely helpful or necessary, though.
Gluing bridges with pin holes gives a bit of a window into it, too. When you drill out the pin holes you get a sense of how set the glue in there is. After one day the bridge is on there just fine, but the glue in the holes is still a bit gooey/snotty. It is harder after two days. If I can, I let them sit two days before stringing them up, but I've only had a one-day set time be a problem ever, and it was with a pinless bridge on a cedar top. Cedar is weird like that.
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