Don’t try this at home! Experiment with several cheap guitars until you get this procedure working just right. The intersection of time and temperature is everything. (Too much heat over too much time will ruin the top.)
To paraphrase Dirty Harry: You got to know your limitations, not to mention the limitations of what the finishes and materials can handle.
First, use a router to mill down the existing bridge to approximately 1/16 to 3/32 inch thick. This lets you apply heat evenly all over and all at one time. Please see the page titled "The Router Platform" to perform this operation.
We don't attempt to modify the original Harmony string-through bridge. That is just not worth the effort. Anyway, our shop made pin bridges are top quality quarter sawn Brazilian rosewood (dalbergia nigra).
Next, make a heat reflector out of acid free picture backing media 1/8 inch thick. Cut an opening to exactly fit the shape of the existing bridge. The silver stuff is heavy duty metal duct tape. Not classic duct tape but Nashua metal tape: the thick stuff, not the thin version.
You do have a 1/2 inch thick aluminum block cut to the same shape as the exiting bridge, correct? Good, proceed.
Cut a hole the same shape as the existing bridge in a 3/8 or 1/2 inch thick plumber’s heat pad.
Since a heat pad of the same outline as an H1260 bridge is not available, use an old clothes iron to heat the thicknessed bridge pad. Set the iron to medium heat.
Please note this critical detail: During this procedure, I have a little HVAC thermometer stuck in the side of the aluminum block. This is not shown here.
The aluminum block should not exceed 180 degrees for more than one minute. Higher temperatures are not needed. The old white PVA glues release at 160 degrees. Hide glue generally takes 180 degrees. Most Sovereign bridges are attached with PVA glue.
Once the desired temperature is reached, stop heating and see if the bridge remnant will release.
For bridge removal, we highly recommend the Bridge Spatula sold by Stewmac.com. This is item number 4466. You can also use this to serve apple turnovers.
Note the red arrows below. These show the best spatula removal direction for most bridges. If you notice the spatula working into the top, stop immediately and change direction.
Caution: Most irons can easily reach over 200 degrees very quickly. Since the OEM bridge was milled down to 1/16 or 3/32 inch thick, it won’t take much heat to remove that sliver of bridge and it will not take more than a few seconds of too much heat to ruin the top.
We use an iron as a heat source only on the H1260 string through bridges. We use silicon heat pads on rectangular bridges. Other bridge shapes require other custom made aluminum heat blocks.