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Thompson Belly Reducer

4.0
  • 18 Reviews
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Thompson Belly Reducer

Item # 1380
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Thompson Belly Reducer

About This Item

A lifesaving tool set for older acoustic guitars! Helps correct soundboard bulge caused by string tension, without replacing the bridge plate.

Excessive soundboard "bellying," caused by string tension, can make an acoustic guitar difficult to play. It can even damage the top, bridge plate and bridge. Replacing the original bridge plate to correct the problem is a time–consuming job that can unfortunately reduce the value of a vintage instrument.

Respected luthier and restoration expert TJ Thompson developed a simple tool set, the Thompson Belly Reducer, that can fix soundboard bulging without permanent alterations to the top or bridge plate.

The Thompson Belly Reducer is a set of five precision-machined aluminum tools: convex flatteners for vintage–style belly and rectangular bridges, and concave flatteners for the three most common bridge plate shapes.

Aligning the cauls is now easier—magnets are embedded right into the tools. Magnetic cauls stay in place (hands free!) while installing and tightening the clamps.

They're designed for use with the bridge removed from the instrument, and are effective for bridge plates that have been installed with hide glue, aliphatic (yellow) glue, or PVA (white) glue. Simply match the appropriate flatteners to your guitar, heat them to 150 degrees F, dampen the wood on the bridge area and bridge plate, and clamp the flatteners into place for a day or so.

Instructions included.

TJ Thompson recommends using three Ibex bridge clamps.


Video

Trade Secrets!

Trade Secrets!

Fixing a potbelly with the Belly Reducer

Dan Erlewine's got a Martin with a potbelly: string tension has pulled the top into a hump on this 1928 0-18. To make things tougher, the guitar top's encased in a thick layer of epoxy finish! It's an interesting puzzle...

Instructions

Product Instructions

Thompson Belly Reducer Instructions

The Thompson Belly Reducer is a simple tool designed to get rid of the bellying without making permanent alterations to the original guitar top.

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4.0
  • 4.00 average rating from 18 reviews
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3.0

Too soon to tell.

By

Verified Buyer


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.

5.0

less regrets (can I get a time machine?)

By

Verified Buyer


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.

5.0

Fantastic Tool

By


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.

5.0

Extremely effective, this tool kicks belly!

By


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...

5.0

worked perfectly

By

Verified Buyer


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.

3.0

Belly Hard

By

Verified Buyer


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.

4.0

Effective but awkward to use

By

Verified Buyer


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.

1.0

Save Your Money

By

Verified Buyer


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.

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StewMac PDF Catalog, page 30 See Thompson Belly Reducer
on page 30 of our StewMac Digital Catalog