The leveling beams are to be used with strings off and are part of a fret leveling method that does not need string tension to provide excellent results.
People's methods evolve and change over time. Can't speak for Murray but he is making these beam and selling them and clearly they are to be used without strings on.
The following replies in this thread got me remembering that Jeff Suits once said he was thinking about offering lapped U-channel for sale. He hasn't posted here for awhile, but he used to live just a few miles from me. Does anyone know of his whereabouts now?
Oh, ok, Hesh, that makes sense. Would you use a straightedge to check it to find individual high or low frets or just go right to a sanding beam and hit all of them? Thanks.
Michael proper fret dressing is an art and takes time to learn and understand. We teach a method using leveling beams and our class takes an entire day with folks compelling a fret job on one of their instruments. These are mostly builders so far in our classes.
Long story short every fret is marked with bluing (magic marker) just like a machinist does and then with a leveling beam the frets are kissed to see from the ink where we hit, where we don't. Truss rod is adjusted for optimal material removal (where it needs to be removed and leaving other area alone if possible). Fall-away is induced after the 12th, relief is added or removed from each respective side of the neck as required for the specific neck with hand pressure while using the beam.
Ink is reapplied, results are "read" more work is done if necessary. It's an entire process, pretty detailed and provides excellent results. After one of our fret dresses we can usually get action of 2/64th" high e at the 12th and 3/64th" for the low e. Not recommending this action but two of our pro clients, one who used to play with Joe Pass and on his D'Aquistos (2 of them) (originals not post Fender) he likes action this low and can play it too.
What's important and why the fret rocker is not intended to be anything beyond a quick and dirty check for a proud fret is to always address the entire fret plane as a whole just as the strings see it. Methods that only check three frets at a time are only seeing the relationship of those three frets and any inaccuracies are greatly multiplied as you move up or down the neck.
With a precision lapped leveling beam checked on a calibrated surface plate with accuracy of .001" or better the fret rocker doesn't cut it.
Thanks for the detailed explanation, Hesh. Greatly appreciated.
This is taking a while. Not enough hours in the day. I finally got the fret ends beveled and then the sharp edges knocked off with a fret file. My DIY, over-engineered bevel too was made from a Stew-Mac 12" radius block. I angled each side longitudinally the same angle as the neck and vertically, 20 degrees. I went with 20 degrees for the bevel so that I could space the strings out just a little more, as I've always thought they were a little cramped on this guitar.
That does look pretty slick and clean. Nice job! And those frets are REALLY BIG.
Michael really nice work there - you should be very proud of your excellent efforts!
Speaking of big Jescar frets…here's a couple recent fret jobs…
EVO 58118 on a Gibson Firebird V and a Carvin DC-400