Clamping My Bridge

[auscab]

Reading about bridge clamping made me think I would show the way I did my first one.
Its more involved than some of the ways that I have read about , but I thought it gave best pressure through the top to the bridge plate and braces on the inside ,and to the bridge on top.
I glued used Hot Hide Glue and wanted to get it clamped in 15 to 20 seconds, I had a bad experience with my ebony fret board ,I was not fast enough, and with improper clamping with hide glue I ended up with the fret board swelling and lifting along each edge, almost 1mm each side, so this was an attempt to not let this happen with my ebony bridge.

I made up an inner and outer caul by using Plasti bond on a block.
The inside one had notches for the braces, I put the Plasti bond on the block , put it in a bag and pressed it in till it set.This gave a perfect fit across the bridge plate and braces at the same time

I scribed a line around the bridge and took the top back to bare wood

The inner caul was fitted ,double sided tape held it up.

The top caul was trimmed down and cut in three,

I Glued the bridge down with hide glue and three leather pads so I could line it up,
[bridge in the micro wave for 25 seconds]

When I was happy with the position I took of the middle leather pad and put the Middle top timber caul down first, then the left caul ,then the right

It worked well , though next time I do this I will shave back some of the plasti bond from the middle of the top caul so the outer 5mm gets the best pressure,
I would keep the plastic lining on the top caul as well,

I didn't take a picture ,but when the top caul was first made it took two goes to get rid of the air pockets from the first cast, I drilled a fine hole from inside the air pocket to the out side ,filled it with to much plasti bond put the plastic back and then pressed the bridge back down, excess plasti bond leaves through the drill hole to the out side.

Hope this either helps or entertains

cheers

[simso]

Neat idea, Ive actually got one simliar to stewmac where the bridge cawl is adjustable to apply fairly even pressure, but yours would definetly provide better all over pressure

[jeffhigh]

Great Cauls, but I am not keen on the method of clamping, adjusting position, then unclamping and reclamping.
You would be be better off using locator pins and just doing the final clamping
I use drill two 2mm holes throught the bridge slot into the soundboard and install 2mm plastic rods protruding about 3mm.
Apply glue to bridge, push onto pins, clamp, no adjusting position needed

[ozziebluesman]

I reckon spending time sanding the bottom of the bridge so it perfectly matches your top radius is the key to a good bridge glue joint. HHG for me as well just incase it has to come off at some stage.

Cheers

Alan

[auscab]

Great Cauls, but I am not keen on the method of clamping, adjusting position, then unclamping and reclamping.

Yeah clamping and unclamping is not such a good idea with hide glue ,I would agree with that, specially if the timber wants to spring back off .But this was a perfect floss sanded fit. [ if floss sanded is the right term ]

Three go on to get position and glue squeeze out , that's 15 to 20 seconds then one at a time they are replaced, within a minute its over and there is always 2 clamps on

Other ways Ive seen ,the inside caul only covers the bridge plate , and a clamp placed at the end of the bridge is past that ,so it's giving a canter levered pressure ,or over hanging pressure.

Or if it stepped over the brace its not putting pressure on the brace, unless you make it before the top goes down, so thats a curved solid caul with two steps that match brace height that you have to make , a bit more tricky than plasti bond [ PB ] in a bag in which the solid block is a loose fit by 3 to 4 mm all around and the PB molds to the lot.

The way it went together I felt I could apply as much pressure as I wanted because only limiting factor was the crush point of the guitar timbers.

With canter levered pressure ,to much could snap something.

Cheers

[Craig]

Two steel 1/16 " locating pins through the saddle slot which I remove after the glue is dry. This way I can take my time and make sure of bridge placement prior to glue -up. I made this jig for accurate placement of the location pin holes.

NECKBRIDGE JIG 31.jpg (46.25 KiB) Viewed 7241 times

More on how to make (and USE )this jig here" viewtopic.php?f=24&t=2001

As far as the inside caul is concerned , I radius the glue side of the bridge plate/patch and therefore only require a simple flat caul for the inside .

Radius the bottom of the bridge and be fussy about it!! . I have my top caul ( similar to the Stewmac one ) a hair smaller than the bridge footprint so I can easily clean the glue squeeze-out

[auscab]

I like the pin locating idea through the slot, it must be the best way for positioning,specially off that long jig Craig , I'd like to incorporate it with the way I clamped. Scratching my head on that one at the moment.
I did my slot position after the glue down of the bridge with the Stewmac slot cutting jig that holds a Dremel , the only problem I had with this was the Dremel, and it's lack of capability in routing a small slot in ebony. I just bought a CP die grinder that I will give it a go with, just have to fit it to a base first.