Here is my take on an aid to work with sketchy strength magnets. This is a split off from the Uke crack thread.
They can be positioned as though they are weak magnets then the crushing force applied in a controlled way.
I have incrementally worked my way up to pairs of 3/4"diam. x3/4" tall n48 magnets.
Wood is Hickory ( had it in the pile and it has heroic split resistance).
Nuts and bolt are non magnetic stainless.
White cap is UHMW plastic (packing tape works too)
Steel cups protect magnet corners and knock the mag field down in directions that are not helpful.
Continuing to screw the bolt down forces the magnet out of the steel cup.
You might look at the F-hole clamps here:
Thanks Robbie. It looks like the f-hole clamps are about the only way to go. My reservation is that they are so darn expensive and will get limited usage since they don't seem to be strong enough for anything other than light clamping of top/bottom cracks. I really don't want to go the magnet route because I don't like having them around the house with the kids and stuff. (I don't have a dedicated workshop.) I will probably suck it up and buy them and hope another opportunity to amortize them comes up down the road. It's really the main problem with being a hobbiest at this, the costs really end up adding up and since I might repair 1 or 2 ukuleles a year, it doesn't get spread out enough to make it cost effective.
The middle clamp in the pic is a cheap Jorgensen from the hardware store. Not sure if it would fit your uke but it's relatively inexpensive and has other uses.
The violin F's don't produce much pressure so the fit would have to be very good. and if your never going to work on violins, they don't work for much else.
I have long planned on making some little clamps from white oak but have managed to come up w/ something I already have for each unusual situation.
Hello again David! Thanks very much for helping me to understand the magnets. Also, the pictures gave rise to a possible solution for dealing with flattening the guitarron top before I glue the bridge back on. I feel more at ease with your comment about large quantities of CA glue. I'm going to work up a dry run with my possible solution and if it looks like it might work, I'll post it and see what you think. Again, thank-you for taking your time in helping me thru this.
Hi, David. Do you have other photos of the two outer clamps you're using here? Interested to see the cauls you've made. --Keith
Keith, the clamp in the back is a Stew Mac clamp from the 90's but no longer available as far as I know. The nearest one is available from violin tool suppliers.
I'm not sure what cauls your referring to. For this quick and dirty Uke glue up, I just stuck the F hole clamp into a hole in a wood disk and the caul on top of the bridge is just a scrap of pine I pulled out of the bin.