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The tuner is an essential part of the instrument, and relatively high precision, in order that it works well under some tension, so it is not always possible to repair damage to them, but some basic repair work can be undertaken successfully. Very little equipment is needed, but an understanding of how they work and are put together is essential, so if you haven't already..... before starting, go and have a look at the tuner anatomy page!! If you need help, drop me a line on the Contacts Page.
Anatomy	Enclosed	Cleaning	Buttons	Jammed	Types
Typical damage

Here a mandolin arrived with mismatched tuners, probably because one side was ruined. Finding a matching pair is often very difficult.		This is the result of rust. The tuners were completely seized, and could only be removed by disassembling. Though this is only possible where the cogs are secured by a screw!!		Perhaps, most common.... here the buttons have broken and been lost.

Here a cog is missing, easy to fix in this set as they have screw-held cogs, if one is able to find a replacement piece of the correct size and teeth configuration.		In this aluminium set, the lug that hold the tuner spindles/worm gears have given way. There is no saving this one.. :(		In this old set, the tubular brass barrel, made by being folded over at the outer end, has split open under turning pressure. These it IS possible to repair.

Repair of Tuners
Outer Barrel Repair It is possible to make a new outer tuner barrel, if you can find brass tubing of the correct diameter. The tubing I use has an outer diameter of ?mm and an inner of ?mm.		Once cut to the correct length, place over the inner tuner barrel in order to locate the correct height for the retaining pin hole. Then drill the string hole. It will be necessary to secure in a vice to do this.
Missing retaining pin Occasionally I find a loose tuner barrel caused by a missing retaining pin. The easiest way to replace this is with a simple piece of nail. The nails I use must have some lead in them as they bend, and cut relatively easily.		More importantly, once the new pin is cut and fitted, a little longer than the diameter of the barrel, it can be hammered to spread the ends. It is this which actually holds the pin in place and the two barrels together.
Detached worm gear Often, under string pressure, especially if something is out of alignment, the housing/lug that hold the worm gear are forced out of the tuner plate. It is possible to refit these sometimes, if there is not too much damage.		First make sure the plate is flat. Then file back the 2 lugs at the base of each housing. Squeezing with a pliers helps as you do not want to reduce the volume in the lug more than necessary. When it can be forced back into the holes, expand the lugs with a hammer to fill the holes, in a similar way as with the barrel retaining pin.
Missing Cog Sometimes you will find tuners with a missing cog. This is perhaps the most difficult repair.	Any replacement will need to be of the same kind, with the same number of teeth, or it will not mesh with the worm gear.
Missing worm gear Sometimes the worm/spindle and tuner button assembly will rip out and be missing.	Again, to repair this, you will need to find an exact match to mesh with the cog.	NB. if it is possible to find this, and make the repair, it will often not hold up well under tension. Getting the lugs seated securely is very difficult.
Jumping Cog Sometimes you will find that the thread of the cog or worm or both are worn, and the tuner 'jumps' under string pressure		It is sometimes possible to remove the string barrel and cog as above, and clean up the threads, but it doesn't always work.	NOTE: I have found that tuners which jump in one direction, sometimes will work in the other.... a last resort, but better than being unable to tune it.