The making of musical instruments such as an ukulele or guitar is a very personal type of effort and amenable to a great deal of individual expression. There is no single way to do something correctly. Jigs and gadgets help the musical instrument builder to do a repetitive operation in an efficient manner. The examples below celebrate the ingenuity of several luthiers as well as some modest attempts on my part to help others ease the path of construction.
- Fox Universal Bender - Charles Fox should be greatly commended for his design of the Universal Side Bender (as described in the Luthier's Mercantile Inc. Catalogue). My suggestion for improvement to the bender is to replace the topmost solid stainless sheet with one which is perforated. The type of perforated stainless sheet available to me appears to have been used for fruit juice straining; the hole sizes are about 1/2 to 1 mm in diameter. By using the perforated sheet, the sides are bone dry and permanently set in about 15-20 minutes since the perforations allow the water to escape throughout the sheet rather than just out the sides. I've been using this idea for more than
six years now on four different size side benders with no problems. Please visit a separate page for additional details for my version of the side bender.
- Vacuum Clamping - in the same Luthier's Mercantile Catalogue is an excellent article by Richard Schneider regarding vacuum clamping of top braces. For those using yellow glue, I
recommend this approach when the materials to be used are relatively thin. Steve Grimes on Maui (shown here with friend Michael) preheats (read: dehumidifies) the top with a hair dryer before gluing the top braces. When the glue is dry, the top rehumidifies and forms a proper top arch (nearly all the time!). I combined the vacuum and hair drier techniques; having glued the
top to the sides first, I then level/bevel the back edges of the sides. I have made a slightly concave, guitar/uke shaped vacuum plate from
Formica surfaced pressboard with two holes - one in the center of the lower bout and one in the center of the soundhole area.
The perimeter of the soundhole and the perimeter of the instrument outline are outlined with closed cell foam tape. The top is now placed on the vacuum plate and vacuum applied; the vacuum holds the top in a convex position during gluing and since the closed cell foam isn't really closed cell, the soundhole hole allows air into the instrument body to prevent it from evacuating and crushing under atmospheric pressure. As seen in the photo, the back and sides are held onto the top with bedspring clamps. No problems with this setup after use with four different sizes and more than
300 instruments being glued.
- Routing Binding Ledges - I use a Ryobi TR-30U "Handy Trimmer" or laminate trimmer (any hardware catalogue) and a 1/4"
left-hand spiral, right hand cutting carbide bit from CMT Tools (800-531-5559). I use the Ryobi bushing edge cutting guide but replaced the bottom plate with a piece of 1/4" polycarbonate which is about 3" wide and 10-12" long extending behind and away from the bit. This long tongue rests on the top of the instrument and makes the tool much more stable in actual usage.
Yellow carpenter's glue is used for wooden bindings; medium viscosity superglue is used to adhere
nitrocellulose binding to the ledge. An alternative binding glue for
nitrocellulose is IPS WELD-ON #1802 solvent cement; WEAR CHEMICAL MASK FOR SAFETY WITH THIS STUFF. It is very important to understand that the nitrocellulose binding absorbs solvent and swells. Therefore one must use the minimal amount of glue possible or wait long enough for the solvent to evaporate out before trimming. For superglue its possible to apply a few inches at a time to the ledge, and then apply accelerator to the binding and press in place for extremely rapid attachment and little or no solvent absorption. Needless to say, there is little room for error in this approach...
I have also used Smith Industries, 20 minute epoxy (which seems to begin
to firm up in about 10 minutes in my shop). The advantage of this
stuff is that the bindings don't seem to absorb any solvent from the
glue; leveling with a scraper or random orbit sander works well for
this glue also.
- Router Cutting of Back Brace Lining Pocket - This is simple to use but tough to describe - anyway here goes. I hope the figure below will help somewhat. A router or laminate trimmer is mounted upside down on a router table or permanent work station. The 1/8" bit extends above the router bottom plate surface by an amount equal to the depth of the lining back brace pocket. A convex shield covers a portion of the top of the bit, with the amount of bit width uncovered being the same as the thickness of the lining itself. A piece of wood placed against the moving bit will be cut to the depth and height but not necessarily the width of the lining pocket. This width must be determined for each brace. The instrument back is placed on the table, braces up and the sides placed on the back as close as possible to the final position. The ends of the braces have been rough trimmed to slightly greater than the pocket height. Where the linings cross the braces, the braces are marked and where the braces cross the linings the linings are marked. Braces are trimmed to a length the width of the lining greater than the mark on the brace, and the ends rounded to match the curvature of the router bit.
The lining pocket is cut with the router to the width of the brace marks on the linings. The height of the brace at the ends is reduced to fit into the pocket. Total time: about 5-10 minutes depending on the number of braces, etc. I've used this for more than 250 instruments, with very few problems.
- Continuity Tester for Installing Pickups I guess it's just bad luck on my part, but I seem to get more than my share of poor soldering jobs in pickups.
So I needed a quick way to test them with my aging Fender amp; but how? This tiny grounded cable comes from the pickup with nothing to latch onto. The figure below shows my solution: a 1/4" end-pin jack with two light-weight alligator clips attached allows gentle attachment to the grounded shielding cable on the outside with one, and the tiny inner lead with the other. Happy me!
If you enjoy the technical side of things, please consider buying my book "Left-brain
Lutherie" . Although no longer sold by StewMac, you can buy from LMII,
MIMF or directly from me.
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