I have a Martin D-15 Custom acoustic guitar. It has a new bone saddle,
but the action is too high on the guitar. There is plenty of height on the saddle
for me to shave it down, but I have never done this before, and I'd like to ask
what the proper way to do this is, and, is this a job for a non-luthier like myself?
It sounds like you finally got the guitar you've been dreaming about. Good call as the 15 series is probably Martin's best value. They're very nice instruments. Now, on to the saddle:
The first thing you need to do is to make sure the neck is properly adjusted. If it has too much back-bow, that'll give the impression of "too high action".
Once the neck has been, or has been determined to be, properly adjusted, you need to measure the action at the 12th fret from the top of the fret to the bottom of the string. You'll also need to come up with a measurement for the action you want.
If you can provide those measurements, I should be able to talk you through the rest of the process.
BTW: lowering the action on my D-28 on 1970 was my first DIY tweek. It's a great place to start and I'm sure you can do it.
Best of luck,
Harrison & Paul hit on important points... figure out HOW high the actions is, compared to where you want it to be... then remember that if you want to take the 12th-fret string-height down by, say .020", then you'll have to take off .040" at the saddle to get there. And, yes, take it off the bottom.
Also good to make sure the saddle top is the same radius as the fingerboard, as that sometimes can get lost in the "fussing":) If you elect to make a new saddle, save the old one as a "safety". Should be a fun first job. Nice guitar, BTW.
To piggyback on Mike's radius comment, make sure that the saddle you have actually DOES match the radius of the fretboard - I run into quite a few that are way too flat. This will give some nice buzzing on the middle strings, and high action on the top and bottom strings, resulting in raised blood pressure and frustration.
Check the radius, check that the neck is truly straight, then get to work.
And, to state what to some people is obvious, but other don't know - check the radius from UNDERNEATH the strings, not on top of them.
If it is a drop in saddle (which I think is the case on the 15-series) its easiest to remove material from the bottom of the saddle. A long saddle has to be shaved from the top to avoid misallignment with the bridge in the outer ends of the saddle.
To get an optimal result I think each string need to be lowered individually by shaving the saddle top until You reach the action at 12th fret You aim at. The result will most often be a saddle with a sligthly flatter top radius than the fretboard radius, which is logical given the wider string spacing at the saddle compared to the nut.
Saving the original saddle and working on a duplicate is agood idea. It´s good to have a way back.
Like everyone has said, you take material off the bottom of the saddle - but it is important to keep the bottom of the saddle dead flat so that it keeps good contact with the bottom of the saddle slot. Here is how I do that. Get a slab of glass or a ceramic tile. They provide a nice hard surface that you can assume is dead flat because they don't tend to warp. I use a 12 inch square ceramic tile left over from a bathroom renovation. Place a piece of medium grit sandpaper (e.g. 150) on the tile/glass and rub the bottom of the saddle on it in the direction of the long axis. Be careful to keep it flat and don't roll it off the perpendicular. It is a good idea to use a sharp point pencil to mark a line that you want to sand to. Take it easy and err on the side of taking too little, not too much. You can always take a bit more, but you can't put it back. Well, actually you can recover from sanding too much off by putting a hardwood shim in the slot.
One more trick. When you want to remove the saddle without the hassle of completely removing the strings - put a capo on about half way up the neck and then loosen the strings enough to be able to take the pins out of the bridge and remove the ball ends. The other end can stay in the nut and connected to the tuning posts ready for a quick retightening when you are finished.
I would never take material off the bottom of a saddle. Good saddles are machined to very fine tolerances, and the slot in the bridge also has a carefully machined bottom. The fit of those two surfaces is critical, and it's nearly impossible to take the bottom surface down without compromising it. I see this all the time. You need a vacuum fit to get a good signal. I've seen really supposedly high-end pro shops do that slab of glass thing and never get it right. Often the saddle ends up resting on one edge because of a lack of 90 degrees front-to-back, but more often the bottom surface ends up with a slight arc end to end. Getting all that right by hand is really difficult.
Paul V's advice to make sure the neck relief is adjusted properly before doing anything else is excellent. Tim's advice to get another saddle blank is a good one. I'd only mess with the original if it was all you had, and in that case would take down the top.
I give up, I am taking the guitar to a luthier. I don't trust myself on an expensive Martin,
and I have seen conflicting advice in this forum, so I am confused anyway.
I do appreciate all the comments though. This website has always been helpful to me.