Mandolin tuning machines
• Gear alignment: There are two basic alignments of mandolin machine stems and posts; worm above the round gear, and worm below the round gear. The early Gibson mandolins featured the worm gear below the round gear as shown in Fig F5 above (our part # 301G or #301N). With the worm gear below the round gear (Fig F5, above), repeated tuning adjustments and constant string tension at the top of the machine's string post tended to twist the post in the peghead so that the round gear was pulled away from the worm gear. This separation caused slack in the gears and possible misalignment of the gear teeth.
Later models, such as the F5, F7, F9, and F12 of the 1930s and 1940s, had the worm gear above the round gear as shown in Fig F5v2 (see peghead photo below) (our part #303G or #303-N).With the round gear below the worm gear (Fig F5v2, above), string tension at the top of the post pulls the round gear into the worm gear, provides continuous positive contact, and inhibits slack during tuning. However, this also calls for the lowering of the string post positions on the peghead as shown in Fig F5v2. String post hole positions must be taken into account when requesting peg hole drilling sesrvices or designing inlays. (The alternate string post positions of Fig F5v2 are indicated in Drawing #18 in The Ultimate Bluegrass Mandolin Construction Manual.)
• Stem length: In addition to the shape of the F5 peghead being slightly different and a bit narrower than the F4 peghead, the alignment of the machines was also different on these two instruments. On the F4, the axis of the tuning pegs was tapered outwards such that the uppermost pegs were further apart than the lower pegs (see Fig F4 above). On the F5, the uppermost pegs were closer together than the lower pegs. This required a different stem length arrangement when the F5 was designed. While some early F4s had machines with longer shafts, most of the F4s had somewhar shorter shaft arrangements than those used on the F5s. Our #302G and #302N machines are designed with shorter shafts specifically to fit the F4 mandolin.
A5 mandolins had stems that were all the same length and our #304G and #304N machines are designed specifically for this model mandolin. Since the stem lengths are the same for all strings, these machines can be used with the gear above the worm gear as shown in Fig A5 above, or inverted so that the gear is below the worm gear. (The position shown in Fig A5 above is what was used on the original Loar-signed A5 mandolin depicted in our ProSeries A5 Drawings and intended for our A5 mandolin kits).
• Post alignment: The outward alignment of string posts on original F4 and A- model mandolins caused each string coming from the post above to be very close or even contact the posts below it making it awkward to change strings on the lower posts. To provide better access to the posts, the axis of the posts was angled inwards (as shown in Fig F5 above) beginning with the Master Model instruments of the mid 1920s which included the F5 mandolin, H5 mandola, and L5 guitar.
• Tuning direction: Because mandolin machine manufacturers used the same gear cutting tools to make the regular and inverted machines (Figs. F5 and F5 v2, above) - and the fact that the later version were the F5 v2 style - the knobs on the original style machines (Fig F5) turned in the opposite direction to tune the strings. As of July 2007, we are pleased to announce that we now offer original style machines (Fig F5) that turn in the correction direction. These are our #301A-G (gold) and #301A-N (nickel) machines.
This 1950s era F7 shows the inverted position of the string posts. Here, the worm gear (attached to the tuning knob) is above the round gear (attached to the string post). Cosmetically, this lowers the position of the posts in the peghead's face. Mechanically, it was intended to provide improve meshing of the gears to reduce wear and diminish slack.
F5 and F4 machine details
This close up of the Handel buttons shows the wonderful workmanship used to inlay the silver wire and shell into the ivory buttons. These buttons were also used on some better model A-style mandolins.
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If you have questions about our machines or other hardware, please email at: siminoff@siminoff.net, or write to us at Siminoff Banjo and Mandolin Parts, PO Box 1388, Arroyo Grande, CA 93421, USA
© Copyright 2007 Roger Siminoff, Arroyo Grande, CA