Pinless Bridge Design

[rccosta]

For any of you who have used / actively use a pinless bridge design, what's the best way to secure it to the soundboard?

Is glue alone sufficient?

Do you use 2 small dowel pegs to maintain alignment + help resist shear force?

Other methods?


Thanks!

[Taylor Ham]

The stability of a pinless bridge doesnt depend only on the attachment method and the bridge itself. There must be sufficient bracing, bridge plate, and thickness in the bridge to prevent the joint from peeling off.

Glue should be sufficient if that minimum structure is present to support it. If I'm not mistaken, Lowden uses only glue on their pinless, and so does Greenfield. Asian mfg'er like to put a screw in, but it's not necessary IMO.

That's the way a regular pinned bridge is held on anyway, if the pins were taking any shear load the glue joint already failed.

[JayBee1404]

Originally Posted by Taylor Ham

If I'm not mistaken, Lowden uses only glue on their pinless...

Correct, no dowels, screws, or bolts - just glued. In the early days of Lowden’s pinless bridges I believe there were failures, but the causes were recognised and their methods were adapted. I see no evidence nowadays that Lowden pinless bridges are any more susceptible to failure that other builders’ pin-bridges - no empirical evidence, but that’s my gut-feeling anyway.

[rccosta]

Originally Posted by Taylor Ham

The stability of a pinless bridge doesnt depend only on the attachment method and the bridge itself. There must be sufficient bracing, bridge plate, and thickness in the bridge to prevent the joint from peeling off.

Glue should be sufficient if that minimum structure is present to support it. If I'm not mistaken, Lowden uses only glue on their pinless, and so does Greenfield. Asian mfg'er like to put a screw in, but it's not necessary IMO.

That's the way a regular pinned bridge is held on anyway, if the pins were taking any shear load the glue joint already failed.

I think Greenfield actually uses a pinhole dowel, see this video: https://www.youtube.com/watch?v=sAeXskZHC2o (it should automatically bring you to 39:36 or so - when he discusses the bridge).

Intuitively I would assume the peg would at least help a little bit, but I haven't run any numbers on it. Agreed that bracing and proper soundplate thicknessing is imperative.

[Taylor Ham]

Originally Posted by rccosta

I think Greenfield actually uses a pinhole dowel, see this video: https://www.youtube.com/watch?v=sAeXskZHC2o (it should automatically bring you to 39:36 or so - when he discusses the bridge).



Intuitively I would assume the peg would at least help a little bit, but I haven't run any numbers on it. Agreed that bracing and proper soundplate thicknessing is imperative.

I stand corrected.

Hmm, must have gotten that mixed up with another technique. Some people pre drill the outside pin holes first and use them as registration points for final glue up, but the Greenfield is a pinless bridge. Duh.

[John Arnold]

Dowels may help resist shear force, but bridges generally don't fail that way. They tend to peel up from the back edge, so the glue is failing under tension.
For locating bridges, I use a 1/2" brad in each end of the saddle slot, then pull them out after the glue sets.