There are two types of Tune-O-Matic (TOM) bridge. The original style, called an ABR style, is normally set with the screws facing forwards, towards the neck and looks like this:
Some types have a bent wire spring holding the screws down, as the saddles sit in an open slot and the saddle_adjustment screw can fall out when string changing. Most kit TOM bridges are based on this style bridge.
After Gibson moved from Kalamazoo to Nashville, they used a modified TOM bridge, now commonly referred to as the Nashville TOM bridge:
The body of the bridge is deeper, and the intonation adjustment screws sit lower and are held in place at both ends where they pass through the body so the saddles can't fall out. The bridge is also wider, and there is a wider amount of intonation adjustment available on the saddles compared to the ABR.
On the ABR bridge, the top of the intonation screws sit at the same height as the top of the bridge. If the screw face backwards, then the stop tailpiece has to be set quite high to stop the string hitting the screw as it passed backwards and down (and you don't want that to happen). Also, the proximity of the screw to the string makes it quite difficult to get a screwdriver in cleanly. So the ABR bridge is normally fitted with the adjustment screws facing the pickups so that the stop-tail can be set lower without the strings catching the back of the bridge, and to allow better screwdriver access to the adjustment screws.
On the Nashville bridge, the screws are set a lot lower in relation to the top of the bridge and have smaller, more compact heads. The lower placement of the smaller screws means that they are now more difficult to access if the screws face the pickups (as the bridge pickup gets in the way more) and that if the screws face backwards, they are well out of the way of the downward sloping strings, so Nashville bridges are normally fitted with the screws facing backwards.
On the ABR, they are normally supplied with the three treble side saddles fitted with the flat face forwards and the three bass side saddles fitted with the sloping sides forwards. This is simply because the treble string intonation will normally require the treble string saddles to be set nearer the neck than the bass side saddles, even with the angled bridge installation. On the Nashville, they normally have the saddles all facing the same way, presumably because of the greater intonation adjustment distance available.
If you rotate an ABR TOM so the adjustment screws face the other way, then the saddles still end up facing the same way. This is not the case with most Nashvilles as supplied.
For an ABR, if you need more forward intonation adjustment on a bass side saddle, then you can reverse the saddle orientation so that the flat side now points forwards towards the neck. Likewise, if a treble side saddle needs more rearward movement, then you can reverse the saddle orientation so that the flat side now points forwards towards the neck.
On a Nashville, then they normally come set up for rearward facing screws and the flat sides of the saddles facing the neck, so it's only if you need more rearward adjustment that you'd need to reverse a saddle.
It's easier to change the saddle orientation on an ABR bridge than a Nashville one. On an ABR, you only need to remove the retaining spring (if fitted) and the saddle +screw can be lifted out of the slot, the saddle unscrewed, reversed and replaced. On the Nashville bridge, the screw is held in place by a small circlip. This need to be removed before the screw can be unscrewed fully from the saddle and the saddle lifted out of the slot. Reverse the saddle, screw in the screw, then replace the circlip.
You can happily fit ether bridge either way round, but doing so will mean you need to re-intonate the guitar,. because the saddle positions are now wrong for each string. Just remember that the strings shouldn't be touching the back of the saddle (or the intonation adjustment screws) so if necessary raise the stop tailpiece until you can slip a piece of paper between the string and the back of the saddle. Or you can do it Joe Bonemassa style, fit the strings backwards through the stop tail piece and run the strings over the top of the tailpiece instead, giving you 5mm or so more height, which allows you to screw the stop tailpiece down more, ideally so it's screwed hard against the body for maximum solidity.
Last edited by Simon Barden; 26-03-2018 at 05:21 PM.
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