Dowel Joinery Opinions

[jamie shard]

Great real world testing Jon!

[george wilson]

In the late 50's,when I was young and relatively inexperienced,I glued a classical guitar bridge on one of my guitars with epoxy. Big mistake!! Months later,I was on the phone with the guitar behind me. There was a loud pop,and the classical bridge(about 1 1/8" X 7" ,holding nylon strings,popped off and slapped me in the back! It was a perfectly clean break. I re glued it with epoxy,and months later,same thing happened. I think the epoxy (back then) had continued to get harder and harder until it got too brittle,and lost its mechanical strength. Last time I ever used epoxy on a bridge!!! I hope epoxy has gotten better by now. Even that long ago,I had been building for several years,and I'm sure I had mixed it properly.

[Jon van der Linden]

Where are you seeing 3/16" and 1/4" wide knife hinges? The smallest I can find are 5/16":

https://www.brusso.com/Product/instr..._st_pivots.pdf

I don't believe you could use any knife hinge in 3/8" thick material. By the time you account for the depth of the hinge mortise (1/8"), and screw bite (1/4"), I think the minimum side top/bottom would be about 1/2".

What do you think?

Not trying to belabor the point, I'm actually curious how thin those cabinet components are.

Have you personally seen any Krenov (made by Krenov, not in the style) cabinets with knife hinges where the top/bottom/sides are 3/8?

I seem to remember seeing some units (pictures, not in person) where the top/bottom were thicker than the sides. Perhaps that is how he handled it.

A lot of people make their own hardware, it's pretty easy. You can also buy hardware including 3/16" and 1/4" knife hinges made by graduates of the College of the Redwoods (Sanderson Hardware):

http://www.sandersonhardware.com/blo...product=261164

You're right about the top and bottom often being thicker than the sides. I don't think I've seen a cabinet where the top and bottom were 3/8". But I don't make copies, so measurements in that way aren't something that I'm usually looking at.

[Jon van der Linden]

The range of epoxy resin formulations is pretty big. I know that the kind of stuff I use wasn't available then (water clear, no yellowing, with UV inhibitors, etc.). It would be interesting to know the actual cause of the failure in your guitar, my first suspicion would be that your surfaces were too smooth... epoxy needs some tooth to hold on to, much rougher than normal surface preparation in lutherie.

Most of the epoxy use I see is in cold molded lamination (boats) or sporting goods (tennis rackets, snow boards, etc.). Lots of stress in those applications, and failure is usually from a fairly obvious source like an extreme impact. Asked a friend of my brother in law about how his kitesurf boards held up and he pointed to a scratch on the bottom of his board - apparently it was what happened when he tried to jump the breakwater at Waimea Bay and skipped off the rocks instead. It's amazing how strong it can be, which makes it even more interesting when it fails.

[Gordon Eyre]

A couple of weeks ago my neighbor brought over a silverware drawer from his cabinets and the joint on the back of the drawer had come loose. It was a dowel joint and the glue had failed. I fixed it for him but thought at the time that dowel's are not meant for areas where there is a lot of stress. Personally a dowel joint would be down the list of proper joints IMHO.