Replacing the Soundboard on a 1977 Martin D-35, PT. 2
1. Using a custom sanding block to remove old glue and level any raised wood fibers. 2. Referencing the original and replacement top bracing with a thickness caliper. 3. The gently curved blade on this guitar-brace chisel makes it easier to trim and shape the new braces to match the originals. 4. My custom workstation made from a shaped piece of Formica countertop attached to a ShopStand and Guitar Repair Vise from Stew-Mac.
In my previous column, I described how a 1977 D-35 arrived at our shop with a big hole in its Sitka spruce soundboard. After concluding that the damage was so severe that the top could not be restored without compromising the guitar’s sound—not to mention its looks—I began the process of outfitting this fine instrument with a replacement soundboard I’d purchased from Martin more than 10 years ago.
After removing the ebony bridge and mahogany neck, and then separating the original soundboard from the body, I was ready to clean and remove any old glue or raised wood fibers from the kerfing, neck block, and tail block.
I made a leveling sanding block from materials I had laying around the shop. For the platform, I used a long rectangular piece of Corian. First I leveled the 1/2" plank using my thickness sander and then I attached a soft rubber handle. To the bottom of this 26" long custom sanding block, I attached a length of 220-grit Stikit Gold self-adhesive abrasive paper (item #5768 at stewmac.com). This is the perfect grit and material for the job.
To stabilize the body on my workbench, I used a plywood cradle (#5657) and body support blocks (#5656), both of which are replacement parts for StewMac’s TrueChannel routing jig. I’ve discovered that many jigs and tools can be used in other ways than originally intended. I’m sure many of you have come across this and perhaps you’ve adapted tools this way too. Using a gentle back and forth motion, I used the sanding block to square the top surface of the kerfing.
I’m really excited about my new workstation. It consists of a Formica countertop shaped like a dreadnought top that’s attached to the ShopStand and Guitar Repair Vise (#5391). This is just the cat’s meow for freeing up needed work space at my bench. The best part of this workstation is how much easier it makes gluing, clamping, and carving braces.
For starters, the height of the ShopStand is adjustable and that really takes the stress off my back. Also, if you’re looking for a good source of Formica, check out your local businesses that install countertops. The sink cutouts are usually taking up space and collecting dust and the staff is usually more then happy to move them out. The sink cutouts are perfect for band sawing out the work platform, as well as many other uses in my shop.
With a thickness caliper (#5193), I measured the original top braces and then used a guitar-brace chisel (#1629) to trim the braces on Martin’s replacement top to closely match the originals. This chisel has a specially curved blade that makes it easier to carve the smooth curves needed for scalloped braces and tone bars with feathered ends.
Diamond fret levelers (#5259) work well for keeping my chisels sharp in the shop. I do like to finalize the cutting edge with an 8000-grit Japanese water stone, which is available online from both Woodcraft Supply and Luthiers Mercantile International.
Here’s a tip: When working with extremely sharp tools, I often wear a safety glove made of Kevlar, Spectra, and stainless steel to protect my hand and fingers. I know a few too many people who have slipped with a chisel for the first time, causing severe tendon damage followed by surgery. Safety, safety, safety!
With a very busy schedule, it’s hard to make the time to keep chisels sharp. But remember that a dull chisel needs an increase of pushing pressure and that can invite accidents. A well-sharpened edge allows the tool to do the work—a better situation for you.
I hope this column has provided you some enjoyment and invaluable insight into the beginning stages of retopping this 1977 Martin D-35. Looking forward to next month!
John Brown is the inventor of the Fretted/Less bass. He owns and operates Brown’s Guitar Factory, a guitar manufacturing, repair, and restoration facility staffed by a team of talented luthiers. His guitar-tool and accessory designs are used by builders all over the world. Visit brownsguitarfactory.com or email John at firstname.lastname@example.org.