Hi Jan. This is a subject that I investigated a few years ago when I was in the process of configuring and ordering my Carter. I noted that Carter uses Sperzel tuners, but not the locking tuners. I spoke with John Fabian at Carter who said that if I really really wanted them (locking tuners), he could put them on but he strongly discouraged me from doing it.
I called and spoke with Mr. Sperzel who was real jazzed about supplying the Steel Guitar trade with locking tuners.
But I spoke more with John F. and concluded that he was right, and that Mr. Sperzel did not understand the issue.
Here's the issue--no matter how well dressed the hole in the tuner post may be, no matter how well beveled & chamfered, the fact remains--if the post has, say, a 1/8" diameter, the string coming out of the locking tuner will be bent around the 1/16" radius of the halfway point of the hole in the post (the whole point of the locking tuner is that there will be less than a full wrap around the post to bring the string up to pitch). Combined with the repeated stress of the changer pulling and releasing, pulling and releasing, let me coin a phrase--
a bent string is a sp.....---well, you get the picture.
Even forgetting the radius issue, a common bit of advice for premature death of a 3rd string is to provide enough winds around the post so that the string departs from the post well clear of the hole and the irregularity the hole creates for a string passing over it.
I put Sperzel locking tuners on a guitar I built and I am a huge fan. They work real well and stringing up the guitar couldn't be easier. I would love this convenience on my PSG but I am 100% convinced that this design would not work.
Hope this made some sense.
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