Cutting down spider bridge inserts?

Cliff Swanson · From: Raleigh, NC

I have a set of pre-slotted, replacement maple inserts that I want to put in a resophonic spider bridge. They are currently about 1/4" too tall, so need trimming. I'm trying to maximize the chance that I'll cut them off square and straight so that the strings will sit parallel, hopefully without having to modify the slots. Any suggestions on the best way to accomplish this? They're not very large pieces of wood of course, and I don't have access to a band saw.

Thanks in advance,

Cat

Chris Walke · From: St Charles, IL

Can't answer your question, but I have a related question:

How do you file out the the slots on the bridge? what kind of file do I get, what size for each string, etc?

I bought a cheap roundneck reso and the 6th string keeps popping out of the notch in the bridge.

Mike D · From: Phx, Az

Cliff, if you have access to a belt/disc sander the disc part works great. If not than a piece of sandpaper on a flat surface, works fine too. Use a block of wood with a 90 degree edge to ride the side of the saddle against, ensuring you'll get it square. The insert should need to be pressed into the spider bridge's slot so it's likely that you may have to do some deepening of the string slots.

Chris, nut seating files are best but for a would string you can slightly deepen the slot with a small file or even an exacto, then use an old string (same dia.) and "file" the slot to a round bottom with it. Don't go too deep.

Cliff Swanson · From: Raleigh, NC

Mike....Thanks. Please check your email as I have a couple of questions before I do this.

Cat

Tim Rowley · From: Pinconning, MI, USA

Cliff and Chris:

I used a common bench grinder to shape the maple saddle inserts, but used the side of the wheel for accuracy sake. On my dobro, I had to take off approximately 3/16" height and just lightly sand the sides of the wood inserts so they would fit into the slot on the spider. Borrow a set of needle files to cut your string slots, and only make them wide enough and deep enough to do the job, no more than that. Work slowly and carefully and, if this dobro is to be played with a bar, keep the strings on a level plane. If it is a round-neck for spanish-style playing, try to approximate the same (very, very slight) radius as at the upper end of the fingerboard.

Have fun!

Tim R.

Tom Olson · From: Spokane, WA

I'm not an expert on setting up reso guitars, but it seems like it would be both easier and more accurate to simply file the string slots deeper, and then trim off the top rather than trying to trim the bottom of the inserts to establish the string height while keeping them square. If you have to file the string slots anyway, why not just establish the string height by filing the string slots deeper? Then you don't have to worry about whether you get the bottoms cut square.

Cliff Swanson · From: Raleigh, NC

I finally got some time to do this project this weekend. I used Mike's belt sander suggestion, and it worked just great. I was really careful just taking a little off at a time down to a line I'd drawn using a T-square. The strings sit fine and are parallel to each other.

Thanks for the ideas.

Cat

Tim Rowley · From: Pinconning, MI, USA

Tom,

If you are able to obtain bridge inserts made of only one type of wood, i.e. solid maple or solid ebony, your idea would probably work. However, the bridge inserts we are getting nowdays from Resophonic Outfitters, Elderly Instruments, and other such suppliers, are constructed of maple on the bottom and ebony on the top. In order to achieve a uniform sound response across all the strings, the idea is to leave as much of the ebony top strip intact as possible. For this reason one has to make the height adjustment by sanding the bottom (maple) portion of the inserts. In the instance where a radius must be formed (round-neck instrument played spanish style) the ebony top strips are sanded "just enough" to produce the proper radius. The string grooves are generally cut after the inserts are installed in the spider. The bottom of the string groove is slanted backwards toward the tailpiece so the strings don't buzz. Cutting string grooves takes only a few careful strokes of the needle file and a once-through "burnishing" with a used string of the proper diameter.

Incidently, some of the cheaper import-type resophonics have been manufactured with "micarta" (fake ivory) inserts and they sound awful, just dry with very little volume. Replacing the inserts with proper wooden ones usually fixes the tone problem and nearly doubles the volume of the instrument.

That's all they are to it, Tom.

Tim R.

Tom Olson · From: Spokane, WA

Tim,

You're absolutely correct. I hadn't even thought about the ebony-tipped inserts. I must have had a brain lapse. In the case of ebony tipped inserts, you would definitely want to sand the bottoms and not change the top too much. Thanks for the explanation, Tim.

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