| Fitting standard Classical Tuners with Bearing Bushes |  |
Fitting standard Classical Tuners |
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Fitting Instructions
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classical Guitar
Steel String Guitar
Lacote Guitars
- Fitting - original 19th century Lacôte method
- Fitting - New method
- Standard 35mm x 117mm
- Standard 40mm x 127mm
(Old style)
| Fitting standard Steel String Slotted Head Tuners | Download as PDF |
| Fitting standard Steel String Solid Head Tuners | Download as PDF |
Fitting - original 19th century Lacôte method
For this method of fitting, all slotting etc. is done working from the bottom face of the headstock. The machine head plates fit straight up to the bottom face of the headstock side walls, with the gearboxes entering the slots, and the ends of the string rollers also fitting into slots in the centre web of the headstock.
The tuning machine plate is secured with four woodscrews and the ends of the string rollers are retained by a keep-plate usually made from the same wood as the headstock and also secured with four woodscrews.
The gearboxes are 14.0mm deep, 7.0mm thick and 21.0mm long, so with this method of assembly, the slots in the headstock side-walls to house the gearboxes should be 15.0mm deep, 8.0mm wide and (if using an 8mm dia. cutter) 29.0mm long. On old instruments the centre distance of the string rollers is usually about 41mm (i.e. 82mm centres over three rollers) so if the slots are 29mm long, there remains 12mm of wood between the ends of the slots, which is ample for a woodscrew.
If closer roller spacing is required, the length of the slots can be reduced to about 26mm by using a 5mm dia. cutter, or to 22mm long with a little chisel work to give square corners to the slots.By one means or another, the roller centres can be reduced from 41mm to about 32mm with 10mm of wood still remaining for the woodscrew.
If headstock side-walls are 15.0mm wide, an 8.0mm wide slot will leave 3.5mm of wood on each side, which should be ample for strength. At 15.0mm, the side-walls are wide when compared with say 7.0mm for fitting a conventional machine head, but this can be compensated for by having a much slimmer centre web, which only needs to be wide enough to support the ends of a pair of string rollers, say about 12mm for plain-ended rollers, or 13mm for rollers fitted with end bearing bushes. This enables the overall width of the headstock to be no more than one fitted with conventional machines; also the fact that the string clearance slots are less widely spaced apart reduces the change of angle of the strings as they pass across the nut, which may contribute to a smoother tuning action.
Fitting - Using the New Lacôte method
Where the 'old 19thC method' had slots in the central web, the new method allows for holes in the central web and tuners slide in at an angle. Best illustrated by looking at photo 2 on the Lacote Page. This design also allows for an unbroken bottom face and sides.
Please refer to the above drawings to follow these instructions.
- Mark out on the top face of the headstock blank, the centre line positions of the string rollers, the string clearance slots and the shaded area (to be machined out to take the insert block).
- Machine out shaded area to leave a floor 1.5mm thick.
- Make a close fitting insert block from same material as the headstock blank and fit to completely fill recess.
- Draw string roller centre lines on face of insert, remove insert, mark positions of string rollers on side face of insert with hole centres 6.0mm up from bottom face. Drill 10mm dia. holes through insert for string rollers. The ends of the holes in the insert block must be covered with a strip of thin adhesive tape to prevent ingress of glue. First remove just sufficient material from the sides of the insert block so that it will still enter its recess in the headstock blank with the adhesive tape fitted. Securely glue the insert block into the headstock blank.
- On the bottom face of the headstock blank, mark out the positions for:-
string roller centres,
string clearance slots,
slots for tuning machine gearboxes,
slots across inner side walls for string roller clearance.
It is suggested that the slots across the inner side walls for the string roller clearance should be machined first, to avoid having to machine cross-grained across a thin wall. The slots for the tuning machine gear boxes should be 15mm deep. If the headstock blank is 15mm thick, the slots should be machined right through. These slots will be sealed, and also the insert block will be covered when the veneer is added to the top face.
It is important that the 7.5mm dimension from the bottom face of the headstock to the centres of the 10mm dia. holes in the centre web is accurate, because this is the dimension on the tuning machines from the mounting face of the plate to the string roller centre.
When using single gear units, the minimum centre distance between string rollers is 37.0mm, and the length of the slots in the headstock to house the gearboxes should be no more than 23mm in order to leave the maximum amount of wood for the woodscrews.
For tuning machines with two or more mechanisms per plate, a convenient centre distance between string rollers is 36mm as this allows the slots to be 26mm long, machined with a 5mm dia. cutter and gives 10mm between slots for a woodscrew. The minimum centre distance can be as close as 32mm if the slots are made 22mm long with square corners.
String rollers fitted with self-aligning bearings:-
These units ensure that the string rollers will always turn smoothly and silently, the bearings cannot be seen when fitted and there is no wear on the headstock holes. Plain ended string rollers can be used with the original Lacôte design of headstock with the keep plate, but in operation a self-aligning bearing is still preferable.
A feature of these units is illustrated on Fig3 and shows that the string rollers do not need to be square to their locating holes in the centre web of the headstock. Thus the insert block in the centre web can always have straight holes drilled through, even though the string rollers may be at varying angles due to the headstock tapering in width, or having curved edges and string clearance slots.
Finally, if the tuning machine plates are to be inlaid flush with the bottom surface of the headstock, the minimum thickness of the headstock blank (not including the top veneer) should be increased from 15 to 17mm. If the plates are inlaid by the full plate thickness, i.e. 2.0mm, then the 1.5mm dimension of floor thickness below the insert block (see section C-C of Fig2) can be increased to 2.5mm and the dimension on the insert block from the centre of the 10mm dia. holes to the bottom surface of the block from 6.0mm to 7.0mm.
As standard, the tuning machine plates are 13.5mm wide, 2.0mm thick and extend 13mm beyond the gearboxes at each end, thus a plate with three gear mechanisms spaced at 36mm centres would have an overall length of 119mm, though plates of any width or length can be supplied.
For plates which are to be inlaid, the design can be modified so that when fitted, the inner edge of the plate is flush with the edge of the string clearance slot and the outer edge of the plate just covers the slots for the tuning machine gearboxes. This arrangement gives the maximum width (and strength) of wood between the inlaid plate edge and the outer edge of the headstock.
None of the machining operations for fitting Lacôte-principle tuners are difficult. Monsieur Lacôte used his method 170 years ago (without any power tools), and the system I've described for modern guitars boils down to making one insert block and six little slots. How I've managed to use so many words to say so little, I shall never know! If you have any queries, I shall always be pleased to hear from you. "