Thompson Belly Reducer

Ordered this product to repair a severely warped and bellied vintage Gibson J-35. It didn't work very well. Perhaps the guitar is too far gone. Maybe it works fine on normal bellied problems. I'll see soon, I hope. The directions (to me) are very basic, and do not give enough information. Good directions (to me) consists of possible problems and possible cures. I've not given up on it yet however.

The TBR really got me "over the hump" on a couple of Martin 0-17's I made improvements to. Wear thin gloves, do a dry run, follow instructions, and prop the clamps as Dan suggested in a recent "Trade Secrets" article. That article really shows the proper use as well as tangible results. You'll notice the improvement too. I envision other uses for the TBR as well. Thanks, TJ!!

As the pricing of vintage instruments increases, the more we as craftspeople touch an instrument the more our work can negatively affect the value. Buyers are becoming increasing aware of bridge plates and often devalue a instrument based on its replacement. A bridge plate removal also offers many opportunities for unwanted outcomes even for advanced repairers. I've been using the Thompson designed Belly Reducer for about a year and can report back that it has spared many instruments from the slice of my plate pulling tools.

A couple tips that may already have been brought up in the instructions or previous reviews. Perform a cold dry run first to be sure you have the necessary clamps and general feel of how you will set the cauls in place. It's a lot like working with Hide Glue, time is critical. I marked my cauls with a sharpie to denote treble side and also up and down positions to save a few seconds after they came out of the hot pot. This tool is most functional on bridge plates that closely match the footprint of the cauls so don't expect miracles with an oversized plate. Now if TJ could design a time machine so I can back and heat straighten all those old bridge plates I yanked.

I have using the Thompson Belly Reducer on numerous guitars for the past year. Results have been excellent on hide glued instruments. The precision machining of the pieces matches the Martin vintage stuff really well. Good results with PVA glued plates and helpful with various other applications too.

Seriously, I have used this tool on two vintage guitars which would barely have been salvageable without it. Excellent results, and the repair increased the value of the guitars, which wouldn't have happened if I removed the bridge plates. If you carefully follow the directions it's as easy to use as hot hide glue. Very glad I have this tool! Now if only stewmac would sell one that would flatten mine...

I have used the Thompson Belly Reducer on several vintage Martins with excellent results on all of them. In each case I followed the instructions as written and left the piece clamped for one week. The tool left each top very flat. I had little trouble with placement or with the plates cooling too fast during placement. I used leather gloves to keep from burning my hands and had no problems.

I like this tool's concept, but the application is an issue as can be read in other reviews here. I'm hoping StewMac will develop a process to apply the inside plate.

I've been using the belly reducers with great success for about a year. They are well made, and straightforward to work with. They are intended to work best on guitars asembled with hide-glue, but testing on PVA glued guitars has shown good results.
Some dexterity is required while working with hot cauls inside of guitars, but they're easy to get used to.
I've also found the convex (outer) cauls excellent tools to un-cup bridges that have cupped from age or heat. Just heat up both the caul and bridge and then clamp together with just enough force. Don't overtighten though as you run the risk of cracking the bridge.
I plan on ordering a third set for our busy shop here at Folkway Music.

Apart from the construction of acoustic steel guitars I now and again get the opportunity to repair vintage ones. Most require neck reset and bridge problems resolved. I've used the TBR on a 1931 Gibson LO and various Martins including circa 1890 2 1/2- 18, 0-28 and a 1926 0-18.

The difficulty I found is getting the inner plate in position while hot and keeping it there until the top plate is firmly clamped. Thin gloves help, the use of thick gloves is just prohibitive. Where bellying is behind bridge area on straight bridges, usual, the use of the belly bridge clamp has proved effective. Inner clamps would benefit from either a removal handle or built in positioning clamp.

Tried it three times with no noticeable difference. By the time you get it installed it has lost all heat content. The guitar I used it on is not severely bellied. If you closely inspect the bellying on a guitar you will see that it is primarily behind the bridge, not under the bridge.