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estebanana -> RE: Best tool for filing saddle? (Jan. 27 2011 1:50:31)
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The best tool for filing a saddle is a file. But first you rip the saddle down to a close height with a saw. A hand saw will work fine. Then you use a metal file with a medium cut. In America and I think in England we call that a Mill Bastard cut file.
Files are made according to how fine or coarse they are. There are smooths, second cut, bastard and rough, for the basics. Then the pattern of the file , Mill is one pattern cabinet is another etc. For fret, nut and saddle work Mill pattern files work great.
For saddles you probably want a Mill Bastard to do the heavy cutting and shaping and then perhaps a 4" Warding pattern bastard or smooth for turning over the top edge. From a bartard cut file you can pretty much move to 220 grit paper for smoothing and then progressively higher until you get to 600. Usually I do file work, 220, 400, 600 and then a quick buffing with white buffing compound.
Ok file work is deceptive, files cut flatter, tighter and straighter than sand paper in almost every case. Sand paper is for putting the finish on the saddle, files are for making it fit tight and clean. If you are going to do your own saddle work here are a few tips and mechanical pointers that will make your work sharper. It sounds like you have tried to fit saddles so I'm not going to go into how you get it to the right height, etc. Just a mini file tutorial:
To get a flat square bottom on a saddle you can use a small block of wood as a guide. Make sure you check the block with a carpenters square to make sure it has at least one square edge. Put that edge down on the file with the file laying on a table in front of you. Put the saddle next to the block an hold snug to the block. Move the saddle length wise along the file putting some pressure down on it. Make two passes at a time checking between each pass for progress. You can check the bottom of the saddle for square with a small carpenters square. I do this by eye without a block and then check it with a square.
For filing, your thumbs and thumb actions are really important. When you are filing you drive the file with one hand and guide it with the other. With your guide hand move your thumb up over the part of the work, saddle, that you want to file. The saddle is underneath the file and your thumb is on top of the file over the saddle or whatever you are filing. Take something for practice like a scrap of wood or bone. Move the file over the scrap and hold your thumb on top of the file and press the file into the work and firmly move it forward in smooth strokes. In filing you will hear when the file engages the material and cuts. Learn to listen to the file to tell how it is cutting.
For making a saddle thin enough to fit into your slot by using a file do the technique I just explained but put the work on top of the file and drive the saddle with your thumb over the flat bed of the file. Trim the saddle to rough height and then thickness it by laying it flat on the file and pushing the saddle under your thumb. If you are close to the correct thickness you can make few a passes over the file and test and file again. Normally when many luthiers do this they also use a calipers at the same time to test different parts of the saddle thickness and keep working to achieve a uniform thickness.
To round over the top of the saddle the small warding file is nice, but if you have one big file you can still do the job. You make a long bevel on both sides of the top of the saddles edge where the string pass over. Here's a basic way you can do it. Take a pass with the file at a constant 45 degree angle over the edge until you take off about a third of the width of the saddle thickness. Do the same on the other side so you have one third flat on top of the saddle and one third beveled on each side. There should be three facets equal in width and smoothness. Then go for the secondary bevel cuts. Take the angle of the file so that you cut the corners off the bevels you have just made. So instead of three facets you have a profile of eight facets more or less. Then lightly pass your file over the corners of those facets ( if you're good enough to have actually accomplished clean facets) and you'll havea rounded over saddle.
You can clean and smooth the bone with little swatches of black wet a dry sand paper again from 220 to 600. The more you use swatches the riper they get and the better they perform at polishing the bone. Half worn out 220 will still shape and cut bone. Worn out 600 will polish. If you don't have a buffer turn the 600 paper over and burnish the bone with the paper on the back on 600 grit swatch.
So there are three file techniques:
Square bottom of saddle with block on file.
Work under file, thumb applies pressure to area you want to remove material from.
Work on top of file driven over file by guide hand thumb.
Then there are other file techniques like draw filing, which comes in hand once in a while in fret work. But that's for another day.
Of course mileage will vary and there are lots of ways of doing set ups with different tools. I find the files to be most efficacious, fool proof, and cleanest.
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