StewMac Crack Repair Tools Video

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Dan Erlewine demonstrates how the StewMac Crack Repair Tools work in this informative video.

Video Transcription

[on screen text reads: Stewart-MacDonald - Stewmac Crack Repair Tools]

Dan Erlewine:  These crack tools are for acoustic guitar repair, the level cracks that are out of flush in the top of a guitar or the side. And it can pull a crunch out of the lower waist where you could never reach. And you do that by putting a wooden clean on the inside of the crack with glue to support it and pulling it into place with the crack clamp from the outside.

The crack clamp

The Crack Clamp is simply a winch. It's a block of polyurethane, which means you can clean glue off it easy, mount it with the guitar tuner and it acts as a winch, pulling a string up through the crack, bringing a cleat into place. The cleats you make are lightweight and you make them out of the kind of wood that you're working on. There's rosewood and maple and a spruce one.

The cleat cutter tool

There're 5/8" in diameter, and plenty strong enough for a good glue job, but not so much as to add weight to the top and hurt the sound. And you make them with this Cleat Cutter Tool that we designed. It makes a 5/8" diameter plug with a 16th of an inch hole in the center.

What I have here is a piece of 3/16th acrylic for a little extra flattening effect. Got a hole drilled for my music wire. Actually I have two different cracks going here. There's one here and one there. It's not one long crack. I don't always use a secondary call like that. Sometimes they'll go right on the crack with the tool itself.

The pin vice and air gun

Another part of the tool set is this little Pin Vice. It holds a short piece of the music wire so you can come down on a crack, poke it through the crack to get you started. Then it's easy to run the wire through it when you do the job. There's a lot of cracks and fissured cracks where there's fractures of wood that it's hard to work glue into you can do that with the Airgun. It's got a suction tip and you can blow glue in at about 10 PSI.

My advice is if you're using tight bond or whatever glues you're using water it down a bit on the first application so the water helps draw other glue after it. That's a tip I learned at the Martin repair shop. So this is a tool that can clamp together parts that you can't always reach. I could reach that. I probably couldn't reach that with the sound hole clamp, and you can't use a Sound Hole Clamp on a guitar side. Imagine this. You've got a split all the way down the side, and it happens. With the curve call and you can heat acrylic with a hot heat gun, you can have an exterior call that fits perfectly and run a whole line of clamps all the way down the side and pull that side together.

And the last reminder is when you put a cleat on a crack, put the grain on an angle across the length of the crack, about a 45 degree angle. And when you're done, from the outside all you have is a repaired crack with a tiny little hole that you punch through with your pin vice. Easy to fill and hide.



Dan Erlewine

Guitar Repairman and Builder

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