How do I choose new tuners?

   Many of the old mandolins I work on, arrive with broken, mismatched or no tuners at all. So after several years of replacing tuners, and searching for replacements, I now have a small stock of new tuners, used period tuners, and unused period tuners.  With a range available, one is faced with dilemma of..... 'How do you know which one?'  

   It is useful to know a couple of things....... firstly, your mandolin will either need a set to fit a slotted head/side mounted tuners (typical of many German instruments, but also some Italians) with the tuner knobs at the back, or flat head/back mounted tuners, (much more typical of Italian instruments) with the tuner buttons at the side. The latter can be of two kinds, either enclosed or open. The enclosed require a good section of the head to be cut away at the back to fit them, so do weaken the head. 

The crucial measurements are A (the distance between the barrel centres); I (the diameter of the barrels), and B (the depth of the barrels). On back mounted, the string-hole should not be too far above the head, and on side mounted, in the centre of the head-slot. The other measurements are useful, but these are the ones which should tell you if the tuners will fit your tuner-hole set-up or not.

NB. common sizes for A are 23mm, 23.5mm, 24mm, and 25mm so measure accurately. But also beware, the distance between each tuner barrel is not always the same on a given set of tuners.

I am happy to try and fix old damaged tuners, especially for old Italian mandolins, and have done so quite a few times. If they are incapable of repair, then at least I have the original set against which to compare when trying to find a replacement set, as similar in size and style as possible. The most problematic to repair are those where elements are missing, or where the cog is worn.