Official Luthiers Forum!

I hear both ways. Raidus for a better fit and just glue it flat..
A repair guy in St Louis said he has reglued a lot of bridges in his 25 years of repairs and he sands them flat
and clamps them up and has never had one pop off again.

So is there a right way or a wrong way??

Gary

I vote radius.
I made a radius sanding block.
I got lucky and noticed my latest eir bridge blank has a slight bow to it,
which is...... 25'!
Lucky!
I guess I'll have to radius the bottom of the saddle .

I'm pretty sure there is no "right" and "wrong". Radius makes the most sense to me, but it does bring up a related question that I was pondering just minutes ago... how do you clamp it? Make a clamping caul that matches the radius, clamp with a flat caul and a lot of pressure, hide glue rub joint, rub joint plus clamps with light pressure and no caul, or something else?

It depends on your top radius. For 40' and over I do not think there is any need to shape the bottom of the bridge, so gluing flat is the best option. There is virtually no gap, and with string tension the top will go back to a nice, gentle curve. For a tighter radius it is better to shape the bottom, although I've successfully glued flat bottom bridges on a 25' radius.
I've been using a 5' cylindrical top for some time, I really have to match that curve on the bottom of the bridge.
You want your bottom caul to match the bottom of your bridge, and you don't want excessive clamp pressure to completely crush your top's fibres (and finish), or even worse, crack the bridge.
The only time I used finger pressure with HHG to glue a bridge was on a uke.

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

For the little time it takes I always radius, I made a sanding board to match the 28' top radius. I have had one bridge start to lift but it was my own fault, I had trouble with my clamping cawl and the hide glue was I think starting to gel when I got it clamped. My brain said I should start over on it but I didn't and paid later with extras work.

Fred

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Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

I've glued lots of flat bridges on radiused tops without failure. That was before I knew that radiusing the bottom of the bridge to match the top is a really good idea.

It depends on whether you are repairing or building, for starters.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Ya, know - some of us repair guys try to do it just like the builder did (only after the guitar has broken, or been damaged). We're not stupid, ya know. We have the same skills builders have, plus a few more. Ever had to reglue a peghead after some yahoo used hot glue on it? Try cleaning that up.
Builders use new stuff and have straight edges - repair guys deal with splinters and various stupidities inflicted by owners.

Don't assume your mad skills are higher on the totem pole than repairmen, Tony.
Some of us are hot stuff.

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"Act your age, not your shoe size" - Prince

I always match the radius of the top, building or repairing.

Chuck

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Gary: If one has gone through the trouble to very carefully radius one's top why would one glue on a flat bridge...??? As to the caul I make one that has the proper dome to fit on the inside during gluing. I glue top first and before gluing the back make and fit the caul. Once you are going to glue the bridge it's easy to tape the caul in place through the sound hole. Some folks may not even use a caul.
Tom

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A person who has never made a mistake has never made anything!!!

'Tis true - there are some repair guys who just shouldn't spend time at the bench.
I've had to do plenty of rework in the past.

However - I still stand by my statements above.

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"Act your age, not your shoe size" - Prince

My bad, Todd. You were just acting like Tony.

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"Act your age, not your shoe size" - Prince

Howard...
For me it is building..

I have just heard of both ways and it seems that general feelings is to raidus it.
I never thought of raidusing the caul...

Are you that are raidusing the bridges also raidusing the bridge plates or do those conform to the top when clamping??

Gary

Bridge plate conforms to the top in the radius dish in the gobar deck.

Ok sounds good to me.. I use a 25' top so raidus it is.

Thanks for the good info..
Gary

It could be the number of repairman with a full set of building skills and vice-versa is staying the same, but simply being dwarfed by the vast quantities of hobbyist builders and barely trained "guitar techs" (such as are popping up in GC's across the country all of a sudden) that have no building skills and hardly any repair skills.
We live in the information age, where if you have an internet connection, you're a luthier or a guitar tech, seemingly overnight!
I mean no disrespect to anyone on this forum, most of the gentleman that frequent this forum are very genuine about their respective skills.

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Old growth, shmold growth!

That may be. It does seem like there are more "wanna-be's" in the mix since the internet allowed anyone to post videos and tutorials without benefit of review by experienced peers. As I remember when ASIA was formed, that was one of our stated goals - to provide a method of certification for apprentices and journeymen in the field of luthiery.

When I closed my shop in 1990, and let my membership in ASIA lapse, I must admit I willingly remained separate from the scene, and only in the last year have I dipped my toe back into the community of luthiers.

I'm sure I've missed a lot in that time - whether for good, or for bad. Thankfully, I still have all my tools and enough clients and family to keep me busy when I wish to be.

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"Act your age, not your shoe size" - Prince

My thoughts are why bother pretending to make a radiused top if you are going to glue a flat bridge on top? Like Todd stated, the bridge will be the strongest brace on the guitar so if you had a nice radiused top before glueing a flat bridge, the crown of that radiused top is now likely flattened by the bridge. In other words, I don't see how the bridge would be forced to take the radiused shape of the top......instead the top will take the shape of the bottom of the bridge. So again, why bother radiusing if you are going to flatten the radius out?

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Formerly known as Adaboy.......

Just a Tony who is arrogant..... sure you wouldn't like him.

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"Act your age, not your shoe size" - Prince

However counter-intuitive, this is simply incorrect. Two obvious truisms come to mind: first when you use a shallow radius (over 40') your top is almost flat and a flat bottom bridge can be pressed into place with finger pressure with no gaps. Second the radius will change slightly depending on RH, the mood of the top/brace system and so on, so the chances of it being exactly 40' (or 60' or whatever your dish is) are about null.
Lastly, gluing a flat bottomed bridge can alleviate some of the excessive bellying that can happen with shallow radiused tops. As the glue shrinks, and later with string tension the bridge (and the top with it in that area) will naturally lift into a more domed shape. This is a known technique and I know quite a few successful builders doing this. I've never seen a curved bottom Martin bridge (although I do not know what they're doing now).

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

I guess I am in the minority here because I never radius the bottom of my bridges and I have yet to ever have one come flying off, no bridge/top distortions and or cracks or anything. Having said that, I had a classical guitar in for a repair that had a pronounced radius a few weeks back. It took me 5 minutes with a scraper to fit it perfectly. So it has nothing to do with wood working skill or time or anything like that, when I fit a bridge to one of my tops there is no noticeable gap present, so whats to radius?

I've removed PLENTY of old MArtin and Gibson bridges that have had the bottoms curved. However, I believe that the bottoms of the bridges curved AFTER being glued, as the top distorted over time, wood being the elastic material that it is.
It seems to me that the bridge will only conform just so much before popping off.

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Old growth, shmold growth!

It's not about that, Todd. WE don't get to choose where our instruments are taken by the owners. Yes, we can wish our client wouldn't go to so-and-so's shop, but it's their choice.

Years ago Roger Sadowsky wrote an editorial about the same thing, and said about his clients "They are gonna go to the other shops. Count on it! Get used to it!".

Sure, there are guys in town I'd rather not see my work visit - but WE don't get to choose. That's all I'm saying. (hijack over)

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"Act your age, not your shoe size" - Prince

I'm a know-almost nothing hobbyist, but I try to shape all parts of my guitars (and related gluing cauls) to match one another. Not because I think I fully understand the physics of how a guitar works, but because minimizing the amount of stress one introduces during construction seems like a generally good idea to me.

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George :-)

Then there is the philosophy of building under tension, of which using using a radius dish (or form) is part of. No plate conforms naturally to a given radius, or curve, and one has to force it with respectively shaped braces.

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/