Most times you want to sand from the bottom. Take off the strings, tape a piece of sand paper over the area of the bridge and place your bridge and use a bowtie motion or angel-in-the-snow to sand wood from the bottom. Depending how much you need to go you can start with 80 grit then finish with 120-150. Or if it's not a lot, use a higher grit from the start so you don't overshoot too far with a rough grit. Rule of thumb is for each 1mm of lower action, you need to take off 2mm from the bridge. Lots of tips with photos here
I sand mine with a straight motion back and forth in the direction of the neck (not sideways and not twisting). And I don't move very far from the final bridge position since the top shape changes slightly. I just use small movements. I also have a fixture that holds the bridge upright so I don't tilt the bridge back and forth. The idea is you want the bridge feet to match the shape of the top as close as you can get it.
That was my problem @Bones I'd end up rocking the bridge as I was sanding straight back and forth and ended up with slightly convex shape on the bottom. Can you describe the jig you came up with?
Like most of my jigs, it is made out of scrap wood (I used maple but any hardwood will do). The purchased parts are a ball bearing, a pin for an axle for the bearing, 2 screws, washers and wing nuts. There is also a washer on either side of the bearing so that the outer race of the bearing (which is acting like a wheel rolling on the guitar top) doesn't rub on the wooden body of the tool (I hope that makes sense). The bridge just clamps into the tool with the wing nuts. I tape the piece of sandpaper to the guitar top with that blue low tack tape and I also put a piece of tape over the sandpaper where the ball bearing rolls just to not scratch up the bearing too much but that is really not necessary. Also, when you pull the tape I usually use just a little heat from a hair drier (don't over do it) to soften the adhesive and pull the tape perpendicular to the wood grain. Again this is probably not necessary since it is low tack tape but I do it just to be sure especially if it is a new instrument without finish as it is easy to lift out the soft spruce fibers. Let me know if you have any questions.
Archtop guitar makers have a jig that works for their type of bridge -- which is usually flat across the whole base of the bridge (more difficult to fit to the guitar top):
Have you thought about having 3 different bridges with 3 different heights ? Together with a little bit of trussrod adjustment you should always have your perfect setup in whatever climatic environment. Dupont offers different bridges and most of the luthier will make one for you.
But if you are the do it yourself type - just go for it :-)
If you take some time to get familiar with what needs to be done, yes you can do it yourself. Main thing to avoid here is making sure you don't end up rocking the bridge back and forth as you sand. Otherwise it's just sanding some wood basically. But do make sure you understand each step.
Comments
Most times you want to sand from the bottom. Take off the strings, tape a piece of sand paper over the area of the bridge and place your bridge and use a bowtie motion or angel-in-the-snow to sand wood from the bottom. Depending how much you need to go you can start with 80 grit then finish with 120-150. Or if it's not a lot, use a higher grit from the start so you don't overshoot too far with a rough grit. Rule of thumb is for each 1mm of lower action, you need to take off 2mm from the bridge. Lots of tips with photos here
Many thanks
I sand mine with a straight motion back and forth in the direction of the neck (not sideways and not twisting). And I don't move very far from the final bridge position since the top shape changes slightly. I just use small movements. I also have a fixture that holds the bridge upright so I don't tilt the bridge back and forth. The idea is you want the bridge feet to match the shape of the top as close as you can get it.
That was my problem @Bones I'd end up rocking the bridge as I was sanding straight back and forth and ended up with slightly convex shape on the bottom. Can you describe the jig you came up with?
Like most of my jigs, it is made out of scrap wood (I used maple but any hardwood will do). The purchased parts are a ball bearing, a pin for an axle for the bearing, 2 screws, washers and wing nuts. There is also a washer on either side of the bearing so that the outer race of the bearing (which is acting like a wheel rolling on the guitar top) doesn't rub on the wooden body of the tool (I hope that makes sense). The bridge just clamps into the tool with the wing nuts. I tape the piece of sandpaper to the guitar top with that blue low tack tape and I also put a piece of tape over the sandpaper where the ball bearing rolls just to not scratch up the bearing too much but that is really not necessary. Also, when you pull the tape I usually use just a little heat from a hair drier (don't over do it) to soften the adhesive and pull the tape perpendicular to the wood grain. Again this is probably not necessary since it is low tack tape but I do it just to be sure especially if it is a new instrument without finish as it is easy to lift out the soft spruce fibers. Let me know if you have any questions.
@Bones that's fantastic! Thank you.
Archtop guitar makers have a jig that works for their type of bridge -- which is usually flat across the whole base of the bridge (more difficult to fit to the guitar top):
Archtop Bridge Fitting Jig - StewMac:
https://www.stewmac.com/luthier-tools-and-supplies/types-of-tools/jigs-and-fixtures-for-guitar-building-and-repair/archtop-bridge-fitting-jig/?utm_source=google&utm_medium=shopping&utm_campaign=2021-12-gp&gclid=CjwKCAiAn5uOBhADEiwA_pZwcLP4cnU0oJYI9kCqHWgYi1jIMg2C0XppIT0juagaFmW8XzcsDfZLsRoCInQQAvD_BwE
Buco NOVA, DC
Is this something, as a novice, i could try myself?
Have you thought about having 3 different bridges with 3 different heights ? Together with a little bit of trussrod adjustment you should always have your perfect setup in whatever climatic environment. Dupont offers different bridges and most of the luthier will make one for you.
But if you are the do it yourself type - just go for it :-)
If you take some time to get familiar with what needs to be done, yes you can do it yourself. Main thing to avoid here is making sure you don't end up rocking the bridge back and forth as you sand. Otherwise it's just sanding some wood basically. But do make sure you understand each step.