We've come to realise that figuring out a right-sided machine head (otherwise known as a Tuner) from a left can be rather tricky. It's a question customers often need help answering - we've created this blog post in an attempt to simplify the conundrum.
Refer to the images below for further clarification but generally: For a guitar that has all of the machine heads inline, left machine heads fit right-handed guitars and right machine heads fit left-handed guitars.
If the head-stock of the guitar has 3 on each side of the headstock (in the case of a 6 string guitar), then the guitar would use 3 of each type of machine head (3x left and 3x right). If the guitar is held vertically in front of you with the front side of the guitar facing you, the machine heads on the right would be right-sided machine heads and the ones on the left would be the left-handed machine heads.
How to Physically Tell Which Are Which?
If looking at a machine head with the shaft facing away from you, the handle will be slightly to one side of the shaft. If the handle is to the right of the shaft, then it is a right-handed machine head. If the handle is to the left of the shaft, then it is a left-handed machine head.
If you have the wrong machine head it's not the end of the world. You might need to drill a new hole for the screw to fit on the opposite side as the previous machine head but it is better to use them for the side they are designed to fit. There is a hole in the shaft of the machine head where the strings feed through and they are designed to pull the gear in a certain direction. Using the wrong machine head will pull the gear in the opposite direction and thus might need replacing sooner rather than later.