Silucky

MOONLIGHTLUTHIERS BRIDGE SLOTTING JIG

Materials

Router Jigs, Router Joinery Guides, and Routing Accessories. As woodworkers, we appreciate how having the right tool for the job can take your project to the next level. Our selection of woodworking router jigs, guides, and accessories provide professional results. Circle and Corner Cutting.

1. 3/4' X 30' X 20' plywood (cabinet grade, veneer core)
2. 1/4' X 20' X 20' plexi-glass sheet stock (clear)
3. 3/4' plywood scraps for clamps
4. 2 each 1' X 12' stick on felt strips
5. four fender washers with 1/4' holes. These go under the knobs described below.

Tools

1. Dewalt #611 plunge router or similar
2. 4 each 1/4' X 20 jig knobs with large knobs.
3. 1/8' to 1/4' shank adaptor
4. 3/32' down cut router bit
5. 4 each 3/8' or 1/2' hollow rubber bumpers.
6. 12 each 1 1/4' #6 wood screws. Deck screws are best. Wall board screws will break.

Procedures

This only explains how to build an in-situ bridge slotting jig. By adding a backing 3/4' piece of plywood behind the square opening, you can also slot bridges as needed when stuck to the backing sheet. The jig works the same both ways.

This slotting jig is infinitely adjustable to fit any flattop guitar and any slot position or angle. In fact, this jig is so accurate that it can perfectly align a 3/32' router bit with a 1/6' OEM Harmony saddle slot and allow re-cutting the slot only removing the OEM plastic saddle and 1/64' on each side of the original slot. (1/64' + 1/64' + 1/16' equals 3/32' which is the finished thickness of a new bone saddle.)

Verify via very detailed measurements exactly where the saddle slot should be. Many Harmony guitars are not correctly intonated. You may have to rout away the original saddle, glue in some filler wood to match the bridge wood, plane and sand smooth, then re-slot if there is enough wood in the bridge. The foregoing explains a second reason why we almost always replace the OEM bridge with a new rosewood bridge. (The first reason is that Harmony string through bridges are a massive PITA!!)

To align the router bit with the bridge slot location, or to remove an OEM 1/16' Harmony plastic saddle, adjust the router and router bit on top of the jig on top of the guitar body so that the cutting end of the bit is aligned with the slot location.

Images #1 and #2 show the guitar sitting upside down on the jig platform. The platform is a 20 X 30 inch sheet of cabinet grade 3/4' plywood. Very good quality veneer core plywood is used here. In order to cut a flat saddle slot bottom the jig working surface must be flat and stable. Best quality 3/4' birch veneer ply would also work.

Images #3 and #4 show the working side of the platform. The jig with guitar clamped in place so that it cannot move even the slightest little bit is turned over with jig on top. There are two guides bolted to the top with the jig knobs. These plastic sheets are slotted for adjustability. There is also a flat plate with perfectly square sides screwed to the router bottom. I used a cone sander on my table saw to achieve perfect parallel edges on this piece. You can see the guide plate on image 6.

Image #4 shows one of two rubber bumpers positioned to ensure the router can only cut the slot exactly as long required. A tool long slot is a big problem. The guide sheet screwed to the router bottom runs into a bumper on each side.

Image #5 shows the 3/32' down cut router bit installed in a 3/32' to 1/4' brass adaptor and then mounted in the router drive shaft. A down cut bit is important because any other bit will chew up the top of the bridge around the slot as the slot is cut.

Triple check the following before routing a new slot:

Free Router Slot Cutting Jigs

1. Slot location for correct intonation according to scale length
2. Slot depth
3. String width spacing over the saddle as they align with the fret board.
4. Pin spacing according to #3 above and (A) bridge distance from lower bout side of bridge (B) distance from saddle slot. Mid-point of the pins is not necessarily the best location. Pin alignment in a straight line parallel to the saddle slot is best for stability and top strength.
5. Desired action settings Make a wooden straight edge just short enough to fit between the nut and the saddle, less 1/2'. When the action is correctly set at the bridge surface, the end of this straight edge resting on the tops of the frets will hover 1/16' to 3/32' above the sound hole edge of the bridge.
6. Do not attempt to set saddle height until all frets are installed and adjusted. We usually wait until the neck and saddle are on the guitar.
7. Start with the saddle too high and adjust downward. Match the arch of the saddle top to the arch of the fret board. However, the saddle arch is not usually parallel with the arch of the fret board. High pitch strings can be set lower than the lower pitch strings.

There is much more to this procedure than can be explained here. Practice makes perfect. Practice on an old junk guitar.

© David Hanna 2017

(1) Body Upside Down On Jig - Lower Bout 'Clamp'

(2) Body Upside Down On Jig - Two Upper Bout Clamps. Sometimes Four are required. These clamps can be moved to accommodate any sized guitar.

(3) Bridge Peeking Through Plywood Jig With Guitar Underneath

(4) Rubber Bumper Detail (The bumper is just to the left of the black power cord.)

(5) Router Motor With Bit Installed

(6) Router Assembly With Guide Installed. The router is mounted on top of jig with the movable guides ready to force an accurate cut.

(7) Ready To Cut New Saddle Slot. In all cases, the original saddle is routed flush with the top of the bridge before the slot is cut (not shown). A larger straight bit is used for this.

The key component of this jig is the guides. These are 1/4' plexiglass. All edges are made dead straight using a cone sander and the rip fence on a table saw. Can’t do it any other way.

Learn how to make a simple router jig for cutting dado slots. This simple jig makes it easy to cut accurate dadoes with a router. This jig is easy to build and simple to use.

Tool: Triton Plunge Router

Free Router Slot Cutting Jig Tool

Transcript:

Chris Marshall: Hi folks, I’m Chris Marshall, with Woodworker’s Journal Magazine. One of the strongest ways to install shelves in a bookcase — like this one — or a cabinet project, is to fit the shelves into dadoes in the sides. But to do that, the dadoes need to be cut perfectly straight and to exactly the right width for your shelving material. (And when I built this bookcase, I also needed the shelf dadoes to stop right here. Those can be tough to cut accurately with a table saw and dado blade.

CM: So for stopped dadoes like that, I reach for a simple-to-make slotted dadoing jig for my router. Here’s the one I used for the bookcase project. It’s got a platform to support my router base, with a slot down the middle that fits a 1” outside-diameter rub collar mounted in my plunge router. The jig’s base rests against the edge of my bookcase or cabinet side panel, and it squares the long slot across the panel when I clamp it in place. And if you look here, there’s an even deeper slot cut into the base. That’s made by the actual router bit you’ll use with the jig. It will show you the exact position your router will cut the dado slot, so it’s a SUPER handy index to set this jig accurately.

CM: And once the jig is clamped in place, this slot makes sure that my router can’t drift off course when I’m routing my dadoes, because the rub collar can only go in one direction — straight. With this jig, you’ll always rout dadoes with confidence —whether you’re building a bookcase or another shelving project. And in this short video, I’ll show you how to build one of these jigs.

CM: Start by cutting two, 6-in.-wide platform pieces from 1/2”-thick MDF or plywood. I made mine 26” long, which will allow the jig to cut dadoes up to about 18”. But, you can make the platforms however long you need them to be for your projects. (Flipping jig over to show) As you already know, you’re going to need a base piece for the jig. Make it from 3/4” scrap, 3” wide and exactly 13” long. And you’ll also need this 13”-long bridge piece too, to secure the platform pieces at the end of the jig. I made my bridge 2-1/2” wide.

CM: Start assembling the jig by brad-nailing or screwing one of the platform pieces to the base piece, flush with its end. Attach the bridge piece in the same way to the other end of the platform, but this time, to its opposite face. Now we need to fit the jig to our router’s 1” outside diameter rub collar. This will be the dedicated size that you’ll always use with this jig. For the next step, grab a steel rule or a scrap that measures exactly 1” wide. I’m going to set the second platform piece into position here, and then set the rub collar between the platform pieces, over the base. Now, I’m going to slide my steel rule between the platform pieces on the other end, under the bridge. That establishes our 1” slot.

CM: Now clamp the second platform in place carefully, making sure that the slot doesn’t change. Then nail the parts together to secure the second platform. If you’ve built the jig carefully, the rub collar should slide in this slot without extra play. There’s just one last step to do before your slotted dadoing jig is ready for use. Install a bit in your router that you plan to use with this jig. I’ve got a 23/32”-diameter straight bit in mine. It cuts a dado that’s the perfect width for today’s undersized 3/4” plywood.

Router Jigs And Templates

CM: Now install the rub collar and set the router for a 5/8”-deep pass. Rout a slot across the base of the jig on top. Put a piece of scrap wood in front of the base, underneath, to keep the bit from splintering when it exits this cut.

Circle Cutting Jig For Router

Router Slot Cutting Jig

CM: And now you’ve got your indexing slot, so you know exactly how to line this jig up for cutting dadoes. That’s it! Oh, one last thing: it’s not a bad idea to write the bit size, and rub the collar size, right on the jig — so you’ll remember what to use with it, later. These slotted jigs (B-roll) are my FAVORITE way to rout dadoes. Quick, easy and accurate! I hope you like yours just as much as I do. And, if you liked the looks of the bookcase [B-roll] at the beginning of this video, you can find free, downloadable plans plus a video that will show you how to build it, by visiting woodworkersjournal.com. Thanks for watching.