This shows steps to plug and drill a new tuner post hole.
This was an all original one owner never repaired Harmony H1270. We noticed the tuners were extremely hard to turn. The tuner plate was sitting about 1/32 inch away from the side of the gear head wood. No doubt that is why this guitar had very little play wear. It was very difficult to tune. Bad news for a 12 string. Those are tough to tune even when the tuners are easy to turn.
The post holes were badly miss-aligned on both sides. Did Harmony not use jigs to drill these holes?
Find the miss-aligned holes by removing all of the posts from the strip except for two that fit correctly. Add another post. If that one fits, add another until each incorrectly drilled post hole is located.
First plug the original hole with matching Honduras mahogany dowel rod.
Remove the offending tuner post from the tuner strip. (Leave the other posts in place if they fit without binding.) Then put the tuner strip back into the gear head. So, the tuner strip now serves as a template.
Find a drill bit size to exactly match the hole in the tuner plate. The bit is inverted here to show fitment. The gear plate is correctly aligned because the remaining posts fit correctly. This procedure aligns a starter hole in the correct location. By "starter hole" I mean a 1/8 inch deep hole drilled with this smaller bit.
Starter hole drilled. Remove the tuner strip. Whoa, look how far off the original hole was. No wonder the tuners were so tight.
Though not shown here, we used the smaller drill bit shown above to align the 1/4 bit guide in this old Stanley dowel guide. View down the guide bearing to verify alignment. As it happens, all of the parts on this Stanley jig are glued together. We use this guide for one purpose and one purpose only: to re-drill Harmony H1270 tuner post holes. This is to say this jig now has only one purpose in life which is drilling tuner post holes. This tool is invaluable for re-drilling holes accurately (positioned and with accurate 90 degree angle) in tuner holes on slotted gear heads. It is the only jig I know of that is adjustable front to back and, of course, right to left. Here the new 1/4 inch tuner post hole drilling is underway. The bit is a brad point bit. Those drill the most accurate holes.