SLOTTING AND DRILLING JIG
The LMI Headstock Slotting and Drilling Jig, SPHSSJ, is a well made and cleverly designed fixture that improves the machining of a classical or steel string slot head guitar peghead. This jig consists of the drill jig portion with 3 tuner hole drill guides spaced accurately for fitting 70 mm tuning machines and a face plate router template portion. (See Photo 3). With the headstock secured in the fixture, the tuner holes are accurately drilled using the drill jig portion of the fixture, then the headstock slot is routed out using the router template on the face of the head. (See Photo 16). The fixture is then removed and reattached to the other side of the head for the same drilling and routing process.
The process of accurately drilling the tuner holes and making the slots in a guitar head with hand tools can be tricky, difficult and time consuming at best. With the Headstock Slotting Jig, these drilling and routing operations are made easy, accurate and fast. The entire process, as illustrated here, only takes about 15 to 20 minutes to complete, and the resulting slots and tuner holes are clean and precise. Demonstrated here is a process using a single router. An alternate method using two routers is even easier and faster. This variation will be described at the end of these directions.
To use this fixture you will also need:
- Any 1 1/2+ hp router with router template guides, preferably the Porter-Cable type (See photo 17)
- Long 1/4 " router bit - such as LMI router bit #SPPRC (See Photo 16)
- Electric hand drill
- Small rule for setting router bit depth
- Pencils, rule, etc. for marking tuner hole position on back of headstock to set fixture location
- Bench vice or clamps to firmly hold the neck blank, with attached jig, for the drilling and routing processes
- Eye protection and Ear/noise protection - Use standard router safety procedures.
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Directions for Use
The Headstock Drilling Jig is easy to use following these simple, step-by-step instructions. The accompanying photo series clearly shows each step and set-up in sequence, and in some cases the photos may be more helpful than the text. The directions for using this jig are divided into instructions for Drilling the Tuner Holes and instructions for Routing the Headstock Slots. In all cases, the machining of the headstock must follow the same sequence. The tuning machine roller/shaft holes MUST be drilled before the headstock slot is routed. It is very important that the center hole locking pin be fixed into the center roller hole after it is drilled and the pin must remain in place during all other drilling and routing operations on the headstock (See Photos 3, 11, and 13). This center hole locking pin is absolutely essential to safety, and for tightly securing the neck/headstock into the jig. There are a few important tips mentioned in the text at particular steps in the machining process. Please pay notice to these suggestions -- they will help to insure your success with this jig.
Drilling the Roller Holes
1. Prepare the headstock for machining - The headstock of the guitar neck blank must be profiled (headstock outline) and machined to final thickness. The headstock shown in Photo 1 is profiled and thicknessed - ready for machining. On the back of the headstock, the location of the tuner holes is marked with a pencil line for accurate alignment of the jig. These tuner hole marking lines must be symmetrical side-to-side for accurate alignment of the jig (See Photos 2 and 4).
2. Prepare the Headstock Slotting Jig for use - First, remove the center hole locking pin and the cap screw that secures it in place (See Photo 3). Next, loosen the thumbscrews holding the drill jig block down to the plate. With the two large Allen set screws in the drill jig block adjust the drill jig height above the plate so that the tuner holes will be centered (up and down) in the side of your headstock. With this height set, push the drill jig block firmly against the two stop pins and tighten down the thumbscrews to hold it firmly in place.
3. Secure the headstock in the jig for machining - The headstock must be secured very firmly in the jig at all times. Even a small movement of the headstock in the jig during drilling or routing could be damaging to the headstock and/or tools. First, place the headstock face down in the jig with the headstock placed against the drill jig. Line up the tuner line on the back of the headstock with the tuner hole location mark on the jig, hold the headstock in position. Slide the hold-down plate over to secure the other side of the headstock. Press the bolts of the hold-down plate against the headstock as you tighten the two thumbscrews (See Photo 4).
As you tighten the thumbscrews to maximum pressure the headstock will slightly lift on the drill jig side. Stop tightening the two outside thumbscrews and tighten the center screw against the jig base plate. This should level out the headstock and hold it as secure as possible in the jig (See Photo 5). Even with this tightened hold-down plate the headstock will not feel 100% secure in place in the jig.
When the center hole locking pin is installed in the middle tuner hole later in the process the headstock will be held “rock solid” in the jig. The headstock is ready for drilling.
4. Setting the drill bit depth - The drill jig is designed for either a 13/32" or 6mm drill bit to drill out the tuner roller/shaft holes. The 13/32" hole is just the right size for a good fit for either the 3/8” or 10mm rollers that are standard on classical guitar tuning machines and the 6mm works for most steel string slot head tuners. Before we put the drill bit in our drill we will set the drill depth by marking the bit with tape or a stop collar. The depth of the drill bit will be the width of the drill jig (3/4”) plus the length of the roller. This drill bit depth can be determined exactly by measuring your own tuners accurately and adding 3/4” for the jig, or empirically, by just putting the drill bit next to the actual roller and drill jig (See Photo 6). Either way, the tuner roller/shaft holes should be barely deeper than the rollers or shafts are long, maybe 1/32” deeper, so that the roller/shaft doesn’t touch the end of the hole. Photo 7 shows the LMI 13/32" Twist drill bit, HSSJ1332, set for depth with a masking tape stop collar. Masking tape was wrapped tightly around the bit many times to form semi-soft “stop”. This will work effectively in low production/use situations. Photo 8 shows a stop collar set on the drill bit at the proper depth. 13/32” stop collars are not readily available. This was a 3/8” stop collar that was drilled out to 13/32”. This secure stop collar should be used in higher production. With the depth and stop set, the bit is mounted in the hand drill. A 6mm bit should be used for the steel string version of this jig. The HSSJDB 6mm bit is good for this as it has the extra length required to avoid dinging your jig.
5. Drilling holes in one side of headstock - With the headstock now secure in the jig the neck is clamped in a bench vice or to a workbench for the drilling operation. The middle tuner hole must be drilled first and the headstock must be clamped down tight against the jig with an external clamp during this drilling operation. Hold the drill steady and level and slowly guide the turning drill bit into the middle drill bushing. This is tricky and awkward at first, but with a little practice you can move the bit gently into the bushing and finally deeper into the headstock itself (See Photo 9). The drill bit is deep enough and stopped when the tape “depth stop” just touches the drill bushing (See Photo 10). Slowly back the drill bit out of the hole and clean the wood chips from the hole and jig. Insert the center hole locking pin into the freshly drilled middle tuner hole and secure it in place with the Allen cap screw. Remove the external clamp (See Photo 11). With the center hole locking pin installed the headstock now will not move or shift in the fixture for the subsequent drilling and routing operations. Drill the remaining two holes, drilling in carefully to the tape stop and then slowly backing out again.
6. Drilling holes in the other side of the headstock - Remove the neck with the attached jig from the vice and place it on the workbench. Remove the center hole locking pin and loosen the thumbscrews holding the headstock in place in the jig. Remove the neck and headstock from the slotting jig, turn it around to secure the jig onto the other side of the headstock. Secure the headstock into the slotting jig following the same process as before. Refer back to #3 "Securing the headstock in the jig for machining” and follow the same sequence and procedure to secure the jig to the other side of the headstock. Clamp the neck with the attached jig back into the bench vice, clamp the headstock down tightly to the jig with the external clamp, and drill the middle hole as before. Refer to #5 "Drilling holes in one side of the headstock” above. See Photo 12 for the set-up for drilling the middle hole. After the middle hole has been drilled and the jig is cleaned, insert the center hole locking pin into the middle roller hole and secure it with the Allen cap screw. Remove the external clamp holding the headstock down (See Photo 13). With the locking pin securely in place, carefully drill the remaining holes on this side (See Photo 14).
7. Hole drilling is complete - With the drilling process finished, remove the neck with the jig still attached from the vice, turn the neck/jig over and re-clamp it into the vice with the router template portion facing up, as in Photo 15. The headstock is now ready for routing the slots.
Routing the Headstock Slots
1. Set-up the router to cut slots in headstock - With all of the roller holes drilled and the slotting jig and headstock clamped in the bench vice (See Photo 15), the next step is setting up the router. Use a router that is 1 1/2 hp or larger and has template guides. We recommend using our special, long 1/4” spiral down cut router bit, SPPRC. Mount the bit in the router collet so that it can extend at least 1 5/16” out of the router base (See Photo 16). With this 1/4” router bit use either a 5/16” (outside diameter) or a 3/8” (outside diameter) template guide collar. A 5/16” template guide will yield a 13/16” x 4 5/16” slot in the headstock. The 3/8” template guide will yield a 3/4” x 4 1/4” slot. We used a 5/16” template guide collar (See Photos 16 and 17). We will route out the slot in three passes, each pass with the bit progressively deeper in the headstock. For the first cut set the router/bit to cut about 1/4” down into the headstock - that is a total length of 3/4+” out of the router base. Measure this depth with a small rule or caliper (See Photo 17). The router is ready for the first cut.
2. First router cut - Now the router is set to cut about 1/4” down into the headstock and the headstock and jig are held in the vice ready for routing (See Photo 15). Hold the router firmly and position it so that the tip of the router bit is barely above the headstock surface in the center of the slot in the template. Turn the router motor “on” and slowly drop the spinning router bit into the headstock surface (See Photo 18). Move the router to the left to the edge of the slot and smoothly move the router clockwise around the perimeter of the slot. Move the router to the middle of the slot again and turn “off” the router. Hold the router in place until the router bit finally stops spinning, then remove the router from the jig. If the router is removed from the jig when it is “on”, and spinning, it could damage the jig or headstock (See Photo 19). This is what the result of this first cut should look like.
3. Second router cut - Readjust the depth of the router bit to cut down approximately 1/2” into the headstock. The bit will be set about 1+” out of the router base - 1/2” for the thickness of the jig template and another 1/2+” for the cut. Approach the jig with the router and follow all of the directions in “2.“ above for making the first router cut to complete this second router cut cleanly and safely (See Photo 20). This is what the second cut should look like. The cut is down into the headstock almost through the roller holes.
4. Final router cut - Readjust the depth of the router bit to cut entirely through the headstock. The bit will then be set at about 1 5/16” out of the router base. Follow the same procedures used before and carefully and smoothly make this final router pass clockwise around the perimeter of the slot in the template. The results of this final router pass should look like Photo 21. This slot is now completed.
5. Attach the slotting jig to the other side of the headstock - Remove the slotting jig with the headstock from the vice and place it face down on the workbench. Release the headstock from the jig by removing the center hole locking pin and loosening the thumbscrews holding it down (See Photo 22). Turn the neck and headstock around so that the other side of the headstock is mounted and secured into the slotting jig. Tighten down the thumbscrews on the hold-down plate (Refer to #3 “Securing headstock in the jig for machining”) and insert and secure the center hole locking pin into the middle tuner hole in the side of the headstock (See Photo 23). The headstock and slotting jig are ready for routing the second slot.
6. Routing the second slot in the headstock - Start by securing the neck and attached slotting jig back into the vice for machining, and place the router in position for routing (See Photo 24). Follow the same sequence and directions as for the previous routing. Refer above to #2, "First router cut", #3, "Second router cut", and #4, "Final router cut".
7. Routing the headstock slots is complete - When the final routing is complete remove the headstock from the slotting jig. Photo 25 shows the guitar headstock with the holes drilled and the slots routed. The tuning machines fit perfectly and only minor sanding is required in the slots. Also shown in this photo are all of the tools we used: the Headstock Slotting Jig, SPHSSJ or SPHSSJS complete, with center hole locking pin and cap screw, the router with template guide and 1/4” router bit, SPPRC, and 3/8” hand drill with 13/32" Twist drill bit, HSSJ1332 or our 6mm drill bit, HSSJDB.
Additional Hints and Comments
Not all routers cut with the same ease and power. For our 1 1/2 hp router three (3) passes is about right, each about 1/4” deep into the headstock. If you use a 2 to 3 hp router you may be able to cut the slot cleanly in two (2) passes, each 3/8+” deep. Larger router bits - 3/8” or 1/2” in diameter could also be used with these more powerful routers to rout these slots. Of course, you’ll also need the appropriate template guide collars for these larger bits.
For the purposes of these directions we show the routing process with just one router, but it is faster and easier to use a plunge router that has all three routing depths set. Even more efficient would be to use two (2) routers for this job - one should be a 1 1/2+ hp plunge router set for our required three passes, and a regular 1+ hp fixed depth router. In this scenario, the plunge router is fitted with the larger 3/8” template guide collar. This plunge router is used first, at all three set depths - shallow, deeper, and through the headstock. This is very quick. Then the regular router with the smaller 5/16” template guide collar and the bit extended to cut the whole headstock thickness is used for one clean, smooth pass around the inside of the slot. This pass widens the slot a minute amount to the full 13/16” width and makes an almost finish sanded surface.
The sequence of the machining could also be different than is shown in these directions. We show drilling holes on one side, moving the jig to the other side and drilling the holes, then routing the slot on the side that is already held in the jig, moving the jig back to the first side and routing the second slot. The headstock could be drilled then routed on one side, move the jig to the other side of the headstock and drill and rout that side.