New tuners

  I sometimes have a limited supply of replacement period tuners.

There are a few modern tuners that can be used for either configuration, (side or back) but most CAN'T. For back-mounted tuners, the string hole needs to be near the top end of the barrel; for side mounted it needs to be near the middle. 

Slotted (side mounted) head replacement tuners are the most difficult to replace as most modern tuners seem to have string holes at the top of the barrel.

   Furthermore, there was no standardisation in size between tuners, (string post being from 23-25.5mm apart) so the existing tuners, or tuner holes need to be measured very carefully to ensure a correct fit.  If the fit is poor, or you need to widen the holes to fit a set, it is likely that strain will be put on the tuner barrels, which will bind against the cogs and jam, or jump the cog teeth, ruining the cog.

Right, are the kind of measurements you will need to hand when searching for replacements, and are best taken from the old tuners.

Should you need help, drop me a line on the Contacts Page.