I fit an Aubert bridge blank to my new old fiddle and I was really happy with the look, sound and playability of the fiddle. I was actually quite surprised how well it went since it was my first time fitting a bridge.
Last night I switched from standard to ADAE to cross A and forgot to check if the bridge had tilted. I almost always pull the bridge up to perpendicular when it shifts after tuning changes, but I forgot this time.
After a few minutes of rigorous playing: WHACK!!
Based the pictures below that compare a blank with the broken bridge, would you say I made the bridge overly thin?
I have another fiddle with a bridge that is also this thin (see third picture) and it's survived since at least the 50s (according to the previous owner).
Maybe I'm answering my own question here, but it appears that I did go overboard in terms of thinness.
I found this information from Luthier Michael Darnton of Chicago:
"If the bottom at the feet gets below about 4.2mm, virtually all that happens is that you lose strength--tonal changes stop about there. Below around 1.1-1.2mm at the top, and the thickness of the wood of even the highest quality bridges can't support the strings, and they cut into the top. A less than perfect bridge blank will have that problem when the bridge is thicker at the top. So 4.2mm bottom and 1.2mm top are approaching the boundaries of effective thinness."
Eyeballing with a ruler, my bridge was about 3.5 mm at the feet and probably right about 1.2 mm at the top.
Sigh... at least I know the problem...
Waist was too thin fore & aft. Be sure to double crown, too!
Enjoy. Get that plane razor sharp. I use 25 degree on plane, but have considered going to 30 degree for bridge work. I'd sort of need two planes identical except for that, and I love my old Stanley, so I likely won't do. You may have different results.
Located Chicago if you want hands-on help.
It's quite possible that, in thinning the waist that much, you created a micro-crack that didn't take much to finish. I leave that part a little thicker than the outer parts. I also use artist's graphite to lubricate the grooves and wouldn't expect the bridge to bend while retuning.
I was going to say the same. My bridge very rarely needs to be righted and I retune frequently.
when I do a bridge I put a drop of super glue in the heart and the wings, to help keep them together while carving, I try to do a bunch of bridges ahead of time like that so they have plenty of time to set and dry.
A bridge _blank_, which is what you buy, is too thick, too high, etc. Our school number for thickness at the feet, is 4.3mm. I leave it that thickness up to about the heart (the cut out at top center) at the center.
'Uncle Henry' 1 day