SETTING THE BRIDGE ON A NEW ACOUSTIC

SETTING THE BRIDGE ON A NEW ACOUSTIC

Brian Howard

www.howardguitars.com

  Here I will show how I remove the finish underneath and set a bridge on a new acoustic build. This whole process is very quick and efficient, about 30 minutes start to finish. I have already set and glued the neck. The finish under the fret board extension was removed in the same manner I will describe here.

  I begin by taping off a large area of the lower bout with blue tape. I am very careful to apply the strips of tape as tight together as possible without overlapping. It is very important to have as flat of a surface on top of the tape as possible with no gaps between the pieces to hold dust and debris to get  good results. If the bottom of your bridge does not mate nicely on the top without gaps or rocking now is the time to adjust that by placing a piece of sandpaper (I use 180) over the tape and flossing until a good fit is achieved. This example was fit prior to finishing so that step is not shown.

  Then using a fine tip sharpie I layout my centerline. This would be the centerline of the strings and not necessarily the exact centerline of the body. Be careful! The spruce under the tape is very soft and you do not want to etch your centerlines etc. into it under the tape! Using a small piece of tape on the edge of the bridge I mark its center as well. To position the bridge for scale I use my compensated scale measurements and measuring along the E-string lines position the bridge by measuring to the front edge of the slot. I am using an 18” rule so I do a bit of math and measure from the 12^th fret. You can see my measurements for the two E-strings on the post it I have right on the top.

  Once I am happy with my placement, I carefully trace around the edge of my bridge with the sharpie. Since I set my bridge based on a pre-routed saddle slot, I now check to see how square my bridge is to the centerline. It is not perfect but I would rather live with my bridge out of square a bit more than 1/64” and have the best possible intonation.

  I can then cut out a section of tape at the bridge location. I use my exacto knife and very lightly and carefully cut the tape. You only want to cut the tape, if you cut the wood fibers at the edge of the bridge footprint your bridge will most likely pop off in the not too distant future. I am cutting inside the line I traced by about 1/32”.

  To remove the finish I am using my Dremel tool with The Stew Mac adjustable base and a 1/8” end mill bit. The small flag of tape you see on the bit acts as a fan and blows the dust and chips out of the work. I start off with the depth of my bit just touching the surface of the finish through the window in my masking. I am running the bit rather slow, around 5,000 RPM. I then dial the adjustment down as I move the tool in a small circle somewhere away from the edges of my footprint. The tool will now start to cut into the finish. Watch carefully as you lower the bit and as soon as you see the finish come up and leave bare wood stop and lock the adjustment. I now cut the whole way around the edge of footprint with a double pass and then rout out the center portion.

  This seems a lot more intimidating and dangerous than it actually is. In fact I caused more touch ups trying to scrape the finish out of this area than I have using this method.

  If you did this correctly you should now see some areas that re still coated by a thin wash of finish/sealer. I scrape these back to bare wood with a utility knife blade. It is essential to have bare wood here for the glue to bond to but also not create a recess deeper than the actual finish itself. This is also a good opportunity to measure your actual finish film thickness after buffing etc.

  I can now remove all my tape and proceed with actually setting the bridge. I reposition the bridge on the top in the same way as I did earlier and secure it in position with a single clamp. I then drill my pin holes for the two E-strings. I will uses these to make sure the bridge goes down on the exact position I want.

  I file a small chamfer all the way around the bottom of the bridge. Tis will allow my bridge to seat down against the wood of the top tightly as my finish is just under .005” on this example.

Here is pic of some of my bridge clamping gear. This always stays together as a tool set. I Make cauls and accessories to my basic shop made clamp fixture as needed and add them to the kit.

  And here is the bridge glued and clamped in place.  In 24 hrs I can string it up.

Thanks for following along.