Modern precision, vintage style. For slotted steel-string guitars.Our precision plate-style 16:1 machines feature the same gears and patented threaded worm bushings found on all Waverly guitar machines, for maximum tuning efficiency. 1/4"-diameter brass string shafts with 35mm / 1-3/8" spacing are mounted on cast polished bronze baseplates. These artistically engraved plates age to a handsome patina. Slotted, round-head mounting screws included.Direct replacement designNo additional mounting holes to drill when replacing similar vintage machines on older Martin, National, and Dobro guitars. More efficient operation and better feelPatented worm tension bearings eliminate the "play" inherent in other designs.More efficient operation for more precise tuning16:1 gear ratio. Patented worm tension bushing eliminates looseness.Long life with less wearStainless steel worm gears have twin bushings. String post gears are machined from bronze alloy; more durable than brass.Authentic knobs and string shaftsGenuine mother-of-pearl gives the translucent Black Pearl knobs a luster that stands out from plastic imitations. Brass string shafts are 1/4"-diameter with 35mm / 1-3/8" spacing.Installation TipsMounting screws: Pilot holes required. Installing delicate screws into hard wood requires great care and accuracy. Use a 5/64" drill bit for the pilot hole before installing these screws. Lubricate the screw threads with cutting lubricant (also wax or a bar of soap) to reduce friction and help them thread properly.