Official Luthiers Forum!

What would be the strongest type of magnets, for example to "clamp" wood while gluing?

We use rare earth magnets approximately 3/4" X 1" and they do if I recall correctly 42 pounds per square inch. Any more and you may have problems getting and keeping them apart.

We've been using rare earth magnets for about 15 years now on all manner of repairs.

Dave has made some unique tools out of them including who we call Big Bertha that is the most powerful one we have. It's actually a bit dangerous and has a jack screw to control the opening and closure of the two teflon embedded faces. So it's non-stick.

I don't think I've used a clamp to close a crack in years because of magnets and all the cool stuff you can do with them.

They can jump so be aware and I would also recommend safety glasses with these, the very high powered ones the faces are metal and routinely chip when smacked together to hard.

Isit adequate to shop for anything labeled "rare earth", or are there significant differences in different types?

I believe N52 neodymium rare earth magnets are the strongest permanent magnet type. Check out K&J Magnetics here. http://www.kjmagnetics.com.

_________________
Jim Watts
http://jameswattsguitars.com

what might be more important is the durability of the magnet...I can say with surety that the ones at Hell Depot are very fragile and even with care start to fall apart after any amount of real use...others that have been supplied to me as part of a project (acquired online) have shown far more resilience...

I have used K & J magnets for years. Never had a quality issue. Care is required. The really big ones can be downright dangerous and will jump a fair distance in an instant.

_________________
“ The meaning of life is to find your gift and the purpose of life is to give it away” Pablo Picasso

I don't remember where we bought ours but I do remember them taking over a year and two orders to receive one order and then two years later we received the original order. We think the package attached itself to the inside of a metal mail box or such hence the delay.

With some creativity they are great and can do many jobs very easily including get into places you can't reach by using a magnet top side to slide the magnet in the box into these areas.

The very thin cutting boards in home stores that are only 1/16" thick make excellent top side cauls and protectors to slide the magnets on.

For cleats they are great and holding the top side magnet where you want the cleat positioned the inside magnet with a small piece of masking tape on it holding the cleat in the correct orientation.

We use them all of the time on cracks too. Once the crack is closed with RH manipulation AND it stays closed at normal RH we use plexiglass, waxed paper and magnets to glue the crack and the plexiglass, waxed paper and magnets keep the crack level as the glue cures.

But again caution Will Robinson they are powerful, can chip and send a metal particle flying and they can damage a guitar if you don't think things out well and use too many too close to each other.

We also made fixtures that are glue resistant and are notched for clamping loose braces and such.

Lee Valley carries rare earth magnets along with various fixtures and holders which will make a nice clamping setup.
https://www.leevalley.com/en-ca/shop/ha ... em=50K0202
or
https://www.leevalley.com/en-ca/shop/ha ... asher-sets
I've noticed that rare earth magnets can be pretty brittle, having something to encase and protect them in is very helpful. The fridge
magnet one gives you a nice handle as well.

A question: Does anyone find a use for mag switches in repair work? They are very handy for jigs and homemade fences for my bandsaw and drill press. Just curious.

I use rare earth magnets for simple things like holding wooden jaws to the metal jaws of a vise. As others have said, they are brittle, and they will jump around, so you have to be careful. But a few rare earth magnets, a Forstner bit and some superglue can yield a dandy little jig or holder in no time.