Official Luthiers Forum! :: View topic - Routing bridge footprint

I have always pinned my bridges with two 1.4mm brads into 1/16” drill holes at each end of the saddle slot. I see no downside whatsoever and many upsides as once you have located the bridge you never have to worry about it moving during locating or glue up.

I put low tack masking tape under the pinned bridge then score around the bridge with a #11 blade just through the tape and touching the finish.

I score a second line about 1/32” inside the first after the bridge is removed and rout to that line with a 1/8” down cut bit in a Dremel mounted in the StewMac base.

As a cautious soul I usually don’t go full thickness, but almost, and finish off with small sanding blocks and scraping. Getting sharp corners on the wings is important.

Knowing you are down to wood and not leaving a thin layer of sealer seems almost a tactile as well as a visual thing. Early on I got fooled a couple of times.

I would say I commonly spend a good hour at least on prepping the bridge footprint.

I have found that the finish is not always the same thickness over the whole footprint. Seem to commonly be slightly thicker at the wings.

I then rout an appropriate edge recess in the bridge.

This is just one way that has worked for me. I would also love to hear how others rout their finish.

Author:	bcombs510 [ Mon May 18, 2020 8:19 pm ]
Post subject:	Routing bridge footprint
Hello, A few questions from different aspects of clearing the bridge footprint with a router. What I’ve done on previous instruments is cut an outline of the bridge into tape 1/32 or so smaller and then finish right over top of the tape. I’ve used this method with Endurovar, French polish, Wipe on poly, UV cured and it worked fine and about the same in all cases. Fast forward to today and I have two ukes that are ready for finish removal for the bridge footprint. Neither of these had tape or frisket put down first, they are going to be my first foray into clearing with a router. What I had intended was to force myself to clear finish all the way to the edge of the footprint so I could learn to do it. They are ukes for friends and free so if it’s not perfect it isn’t the end of the world. I’m starting to chicken out tough. I think starting with a uke might have been a mistake because how am I going to pin the bridge securely while I score around it? Anyway - here are some questions. - Anyone have hints on how I might pin the uke bridge to score around it? I’m trying not to drill holes in the saddle slot but if that’s the way, it’s the way. This is the way. - Anyone have recommendations on the router to use? If going the full footprint should I invest in something like a foredom hand piece? Or will a Dremel and the SM base I have already suffice? The finish is UV poly so tough as nails, if that affects the feedback. Brad Sent from my iPhone using Tapatalk Pro

Author:	Bill Higgs [ Mon May 18, 2020 10:09 pm ]
Post subject:	Re: Routing bridge footprint
I don't think you'll need to pin the bridge. Just lay down some tape under the bridge and trace the bridge onto the tape. Then cut maybe 1/16" or less inside the outline and cut along the line, pulling the center section (the part under the bridge) off of the top. Now just simple use the routing instrument of your choice(Dremel, Foredom, something small with easier control). The other nice thing to do is to create a little recessed shelf all the way around the perimeter of the underside of the bridge equal to the depth of the finish and width of 1/16". I think John Hall may have something on this.

Author:	Terence Kennedy [ Mon May 18, 2020 11:08 pm ]
Post subject:	Re: Routing bridge footprint
I have always pinned my bridges with two 1.4mm brads into 1/16” drill holes at each end of the saddle slot. I see no downside whatsoever and many upsides as once you have located the bridge you never have to worry about it moving during locating or glue up. I put low tack masking tape under the pinned bridge then score around the bridge with a #11 blade just through the tape and touching the finish. I score a second line about 1/32” inside the first after the bridge is removed and rout to that line with a 1/8” down cut bit in a Dremel mounted in the StewMac base. As a cautious soul I usually don’t go full thickness, but almost, and finish off with small sanding blocks and scraping. Getting sharp corners on the wings is important. Knowing you are down to wood and not leaving a thin layer of sealer seems almost a tactile as well as a visual thing. Early on I got fooled a couple of times. I would say I commonly spend a good hour at least on prepping the bridge footprint. I have found that the finish is not always the same thickness over the whole footprint. Seem to commonly be slightly thicker at the wings. I then rout an appropriate edge recess in the bridge. This is just one way that has worked for me. I would also love to hear how others rout their finish.

Author:	DennisK [ Mon May 18, 2020 11:27 pm ]
Post subject:	Re: Routing bridge footprint
I have done this using dremel and SM base, and it works fine. You're barely grazing the surface so tool deflection is a non-issue. I just hold the bridge down with finger pressure while I score around it, although it is pretty dicey on a slick finished surface where you can slide sideways if you don't push straight down. To protect the finish, I tape a piece of paper to the guitar with a hole cut in the middle exposing the bridge area. I usually need to fiddle the router depth as I go, to cut through just the finish and not create a pocket in the wood. With the SM base, you can turn the tool itself, using the threads in the tool/base to make fine depth adjustments without having to mess with the thumb screws. Scrape with a razor blade to remove any roughness left by the router. Don't forget you can always practice on scrap.

Author:	Greg Maxwell [ Tue May 19, 2020 7:16 am ]
Post subject:	Re: Routing bridge footprint
All the above. I use a Foredom. Tiny adjustments are needed as you work. You can use double stick tape to temporarily locate the bridge without pins.

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Author:	Clay S. [ Tue May 19, 2020 7:37 am ]
Post subject:	Re: Routing bridge footprint
Brad wrote: "The finish is UV poly so tough as nails, if that affects the feedback." Ukuleles are generally low tension instruments. Some people just butt glue the necks on with wood glue. With a polyester finish you could probably just super glue the bridge on top of the finish in the finest Pac Rim tradition.

Author:	SteveSmith [ Tue May 19, 2020 10:49 am ]
Post subject:	Re: Routing bridge footprint
Terence Kennedy wrote: I have always pinned my bridges with two 1.4mm brads into 1/16” drill holes at each end of the saddle slot. I see no downside whatsoever and many upsides as once you have located the bridge you never have to worry about it moving during locating or glue up. I put low tack masking tape under the pinned bridge then score around the bridge with a #11 blade just through the tape and touching the finish. I score a second line about 1/32” inside the first after the bridge is removed and rout to that line with a 1/8” down cut bit in a Dremel mounted in the StewMac base. As a cautious soul I usually don’t go full thickness, but almost, and finish off with small sanding blocks and scraping. Getting sharp corners on the wings is important. Knowing you are down to wood and not leaving a thin layer of sealer seems almost a tactile as well as a visual thing. Early on I got fooled a couple of times. I would say I commonly spend a good hour at least on prepping the bridge footprint. I have found that the finish is not always the same thickness over the whole footprint. Seem to commonly be slightly thicker at the wings. I then rout an appropriate edge recess in the bridge. This is just one way that has worked for me. I would also love to hear how others rout their finish. Good advice, pretty much what I do too. I am a believer in pinning the bridge; I lay down masking tape, spend quite a bit of time locating the bridge exactly where I want it, clamp it in place and then drill for pins. 3/16" pins for a pinned bridge, 1/16" pins in the saddle slot for pinless. The pins I use are stainless steel dowel pins from McMaster Carr.

Author:	bcombs510 [ Tue May 19, 2020 10:52 am ]
Post subject:	Re: Routing bridge footprint
Thanks, all. Most of the comments have been about going a bit shy of the actual footprint. Does anyone go the whole way? Does the process described change?

Author:	Terence Kennedy [ Tue May 19, 2020 1:59 pm ]
Post subject:	Re: Routing bridge footprint
bcombs510 wrote: Thanks, all. Most of the comments have been about going a bit shy of the actual footprint. Does anyone go the whole way? Does the process described change? If you want to go all the way I would score the finish well at the actual outline taking care not to hit the wood, and rout to about 1/32" of that line and finish with chisels and scraping. I have found that these little micro chisels Stew Mac sells to be helpful for freeing up the thin edge of finish that remains. https://www.stewmac.com/luthier-tools-a ... -of-4.html

Author:	Ed Haney [ Tue May 19, 2020 2:15 pm ]
Post subject:	Re: Routing bridge footprint
Obviously you have located the bridge on the uke top. Pins are not necessary but I still like to use them. 1. Use painters tape on the outside of at least one edge of the bridge to mark the location. This is easy to do if there is at least one straight edge on the bridge. If not it is still possible to mark the location with tape. Tape is not needed on all sides, but just enough so it is clear exactly where to lay the bridge. 2. On a separate surface (a self healing mat is much preferred but glass can work too) lay down 2 strips of 2" painters tape (NOT the stretchy kind!) with at least a half inch or more overlap. This tape should be at least 3/4" or more bigger than the bridge on all sides of the bridge. 3. Put the bridge in the center of the tape and hold it down firmly with your fingers and cut through the tape with a brand new razor blade around the edges of the bridge. 4. Carefully pull up the tape in ONE PIECE around the outside of the bridge. (The inside piece that was under the bridge remains on the mat and is not used.) Now place this piece on the uke (or guitar) top so that the bridge shaped hole in the tape is exactly located where the bridge will go. Obviously you can tell where this is by covering up the previous tape used to mark the location. 5. Test the accuracy of the tape's shape by placing the bridge on the top inside the hole in the tape. It should fit perfectly if you were careful. 6. Now put the bridge aside and you have only the top's finished surface showing under where the bridge will be. The tape is protecting the finish around the bridge from the routing operating and its providing the guide for routing. You can rout up to the tape's edge or just inside the tape's outline as you prefer. Score the finish at your desired location before routing. One good thing is that the tape outline is very easy to see compared to the scored line. 7. Use your preferred routing method as many discussed herein. 8. You can glue the bridge in place and then remove the tape outlining the bridge.

Author:	Ruby50 [ Tue May 19, 2020 5:58 pm ]
Post subject:	Re: Routing bridge footprint
A trick my daughter learned from the late Paul Hostetter is to use a mezzotint rocker to score the finish. A tool used to score a copper plate for printing. It looks like a toothed plane blade and breaks the finish in many places so that cracks don't travel and everything is controllable. She likes the 1/2" width Ed

Author:	Barry Daniels [ Tue May 19, 2020 6:33 pm ]
Post subject:	Re: Routing bridge footprint
That's interesting, Ed. How do you use the tool. Do you drag it laterally, or just crunch down vertically?

Author:	bcombs510 [ Tue May 19, 2020 8:10 pm ]
Post subject:	Re: Routing bridge footprint
Thanks for all the replies. As usual some mix of the advice here will get me there. I did some testing tonight. I have a test panel with a thin layer of UV finish from where I worked in test panels at Brian Howard’s shop a bit over a year ago. The bridge is still flat on the bottom so it gave me a perfect setup to have a few goes. Here is what I’m using. I have the SM base and a dedicated 4000 model Dremel, the foot pedal, and the cute little air pump (which seems to do little). I used a down cut 3/32 bit from drill bit city. I first tried Ed’s approach and that is what I’ll use if I decide to route the footprint short and put a rabbet on the bridge. Having the blue tape as a guide made it super simple to see what was going on and where I was. This is likely the method I’ll use, especially for the first one. I also tested scoring around the perimeter after double stick tape the bridge down (thanks Greg ). If I decide to go all the way to the full footprint I’ll use the scoring method. What I noticed was that as I got close to the line the finish would sort of snap off right at the scored line with left a nice clean edge. I don’t know if that happens for all finishes but the UV finish behaved this way. Either way it turned out pretty good but I will likely leave it short, for now. Brad Sent from my iPhone using Tapatalk Pro

Author:	DennisK [ Tue May 19, 2020 8:33 pm ]
Post subject:	Re: Routing bridge footprint
Take a strip of masking tape about 2" x 1/4" and wrap around the router bit so it sticks out to the side about 3/4", and then give it a twist. Instant propeller to blow away chips without having to mess around with the air pump

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