Official Luthiers Forum!

Salti

I've looked at those SM clamps and wondered if they are powerful enough - the tightening knob is designed for finger-tight only otherwise there would be a screw slot at the top of the outside knob. Does this amount of pressure work with a glue like Titebond??

You could use all-thread for the bolts and double glued nuts on the tightening ends with a nut and a wingnut outside on the top and 2 nuts outside on the interior side as well as using the furniture bolts on the inside of the 2 screws. You could even add their leveling screw along one leg with the same all-thread and put a spot of leather on the contact side of the furniture bolt. If the bent area of the body were dipped in the liquid rubber handle coating, it would not damage the soundhole edge.

If you made your own you could save a bundle over what these cost - $100+ or so for 4.

I like it

Ed

Another thought might be to use 1/2 inch steel tubing (3/8th i.d.) with 3/8 cross dowels (barrel bolts) soldered into the ends, all thread bent into an "L" for turn screws with T-nuts soldered on the ends and then dipped in plastic.

https://www.homedepot.com/p/Everbilt-1- ... /204225751

https://www.woodpeck.com/jig-and-fixtur ... dowel.html

https://www.amazon.com/Stainless-Round- ... B00IAVJ8YU

You're right that the knobs on those aren't very big but I can get them tight enough. One could always drill a hole thru the knob and install a cross rod or glue a bigger wooden knob over the top.

Great idea for clamps Salty. The screws on the SM clamps are a little small, but I manage to get squeeze out, so they work. Great idea to glue on larger caps!

Good idea for a solution Tai, and congratulations on the new website!

Pat

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Pat

By the way for those who are going to bend a rod or bar, get something thick, and heat the bar up with (preferably) oxy-anything torch (acetylene, gas, doesn't matter, it just needs to get hot) and bend it hot. Anything thin enough to where you can bend it cold won't be stiff enough to hold clamping pressure without deforming, and anything strong enough to be stiff won't bend well without heat (like it will probably crack or break if you try to forcibly bend it cold). I just chose welding just because it results in a stronger clamp.

I only recommended oxy-anything torch because conventional propane torch will likely not get the steel hot enough to bend... especially if it's a big piece. Maybe with a larger torch tip that spreads out the heat and puts out more btu will do the trick. But don't buy those BernzOmatic oxygen cylinders. They are very expensive for what they are... basically low pressure oxygen that gives you maybe 3 minutes of oxygen. Get a cylinder from a welding supply shop.

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Cheap, cheap, cheap! https://www.aliexpress.com/item/4000112 ... b201603_55

Cheap cheap cheaper

https://www.harborfreight.com/hand-tools/clamps-vises/c-clamps/5-inch-deep-throat-u-clamp-45916.html

Ed

I've used these SM clamps on a number of both new and repair bridges, they are plenty tight enough for either HHG or Titebond.

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Steve Smith
"Music is what feelings sound like"

That is a slick little piece there sir. Nice work.

While I lean towards wanting to spend more of my time making guitars rather than jigs and tools, the maker community I belong to locally would be all about making these clamps. It’s part of their ethos. Someone in a local group recently asked about making something that was readily available for $24 because they didn’t want to pay that much. I thought, “this is insane,” but another local maker took it up as a personal challenge. If I had to deal with overseas shipping on a consistent basis, I might be inclined to be less highbrow.


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The last few years I have tried to keep my hobby on a "break even" basis (I still haven't quite managed to do it). Past excesses have left me well stocked with materials and basic tooling, but occasionally I'll see a specialized tool offered by a vendor that would be nice to have. As a limited production item the price tends to be much higher than that of a similar mass produced item. If I can make that tool for a much lower price (valuing my time as $ 0.00) then I will often attempt it. Sometimes I succeed and sometimes I fail. Often I am inspired by what others have done.
Our tools are something we keep with us, so doing things to make them our own can be as rewarding as the things we make with them.

Here is a small improvement:



Used acme screws instead of normal screws. Allows larger clamping pressure and no worries about stripped screws...

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

If you are open to suggestions, I really like having the leveling bolt on the upper leg of my StewMac soundhole clamps. It makes gluing bridges a lot easier to set up. Also, that jagged edge on the lower leg of your clamp (where the step is) gives me the heebie-jeebies. I would grind off all of the rough corners, everywhere.

Who needs a clamp?

Well, the problem I see with that setup is, how would you ensure that the bottom is supported?

I use a caul directly under the bridge to be clamped because the clamping pressure will cave the soundboard otherwise, causing a bad joint. Unless you supported the area under the bridge with either sticks or something. But I rather not do that because it just creates more complications and ways things can go wrong.

As for bridge moving while gluing, I always use a pair of plastic bridge pins as locator. If that isn't possible (classical guitars) then some other means will be used to pin the bridge in place.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Tai

The Acme thread is courser so does not allow greater clamping pressure given the same force in tightening. The Acme threads are more quickly adjustable than conventional bolt threads and the pressure developed by the Acme's is fine for wood work. Of course if you put a wrench on your screw, you can make enough pressure to do anything you want.

Instead of the third screw for leveling, I have used wooden wedges that work just fine. Tape them to the top with blue tape.

Ws

Acme thread is more durable and won't strip like conventional threads.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

If you work in an industrial setting you will never see coarse thread (acme) used in situations where high torque is required. Coarse thread is weaker than fine thread. Why? Because with coarse thread you sacrifice the size of the shank for the pitch of the threads. The shank is where the strength of a bolt resides, and when you take away metal from there you weaken it.

Every good vise I have seen all use acme threads, milling machine lead screws, lathe feed screws are all acme thread. Those are extremely high torque applications. Fine, conventional thread can strip when you torque them too much.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

In structural engineering school I learned that the strength of the bolt is directly related to the threads. They have a lot less area to shear than the stem of the bolt. Acme threads are not prone to stripping out because the bearing surfaces are perpendicular to the axis of force.

Looks like the making of a good clamp, are you going to fancy it up?
maybe some French curves might be suitable.
I'll be interested to see what sort of a garter or captured end that you use for the clamp.
Got a bunch of cheapie f clamps, lighter thread than what your using, and some need a new foot already, as do old ones.
Im sure many would be interested in what you design.

Tomas

Tom

McMaster Carr used to have a cheap replacement foot for those that have fallen off - a little springy washer thing that popped onto the ball at the end of the screw kept it in place. All I could find they have now is a more expensive, fancier one, but here it is, right side of the page:

https://www.mcmaster.com/c-clamps

Ed

Thanks Ruby50
I would never have thought that some of these wee trinkets ever would be sold separately.
I believe.those are for the type with a ball or pad already.

The clamps I have are bare thread at the end, the Achilles heel of the cheapest f-clamps you can buy.
Thought about welding feet onto them, and might just about have of them enough now, to have at it.
Those feet would make things easy, as I imagine that a greater surface area of a non swiveling clamp head might make things
difficult during the rush of gluing.

Tomas