Official Luthiers Forum!

There's a good thread regarding an imperfect plate joint match up -- but did you know that there many wood workers and luthiers too (David Russel Young, Overholster in their books) who actually swear by the "spring joint" edge gluing method ---- what do you think?
https://www.finewoodworking.com/item/26 ... d/page/all

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Ken Cierp

http://www.kennethmichaelguitars.com/

Overholtzer built 1 or 2 guitars ,and back in the mid 80/s Young went to work at hans weisshaar to be a bowmaker .when I spoke to him in hollywood ca . 1990 he was a full time bowmaker. So what does that mean . Well as a former cabinetmaker a gap of abt .005 in the middle is ok using a lot of clamps on 3/4in stock .I/ve joined about 300 backs and tops(guitars ukes violins cellos) . I prefer no gap , zilch, nada.To me it is the most reliable way to join. I have about 10 different planes set up for different species of wood and set at different angles to accommodate the density of the species that I am cutting. One would test some sample joints using both methods and see which you find most favourable . My test is to throw the joined parts on the floor to see if they come apart. Cheers

I'm with Ernie. A sprung joint may be great for laying up table tops, but I want that joint perfect. These days I'm just sticking paper to the jointer bed and having done with it. My planes are either not sharp enough or not set up right, with a dash of doing it wrong, and I don't have time to futz with it. Not very luthierlike, but I've gotten over it...

Yeah the nerve of those two luthiers writing and selling all those books and training so many at a time when little information was available in print. But I digress.

So if a person does not have or want 10 planes, is a spring joint an option? Google spring joint plenty of people think its the way to go, articles in Fine Wood Working, Tommy Mac loves hand tools planes in particular - he's a proponent of spring joints.

Seems the same dynamics apply whether it's a guitar plate or a table top.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Hey, spring em if you like, man. I'm sticking with a clean joint.

I had thought that from the thread title that you had sampled a current harvest. Gotta get my brain out of the seventies.
But seriously, why would you want to introduce tension into your panel. Its not really that hard with a tuned up jointer to achieve a perfect edge that requires minimal clamping pressure.
While The author of this article claims a high success rate, to me it goes against the basics of good work practices. I am sure That over the past thirty years I have glued up hundreds ,possibly thousands of panels and this is not something I would consider.
I am not sure how well this would work on a 1/8 thick top or back, condsidering the increased clamping pressure required.
My dimes worth.

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My memory is so good, sometimes I remember things that never happened.

Speaking from a cabinetry point of view, spring joints work just fine, and aren't a product of poor joinery (well, some are) when all aspects of the mated surfaces are well formed. I'll use a spring joint on a two board glue up, but there is too much distortion with multiple board glue ups.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

I also like a nice tight joint but a spring joint must be fine or it wouldn't have as many proponents as it's had over the years. It's not a new thing.

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Jim Watts
http://jameswattsguitars.com

Ken: As I think you know, I started out using David R. Youngs book and was a proponent of the spring joint. Since then have used both a spring and straight joints. Think there are spring joints and then there are SPRUNG joints. With sharp clean edges and a spring joint of a couple of thou. when you put the joint up to the light it looks like you can drive a truck through this tight gap. At the same time this small gap is easily closed during the glue up. Using either joint, as long as they are done correctly, after the smoke clears I have not seen much difference in integrity. A spring joint is the joining of two concave edges. Where some folks have gotten into trouble is trying to join two convex edges, not being able to produce either of the desired edges. This resulting mostly from poor tools and the lack of help or a mentor. Spring or straight work for me.
Tom

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

Surprising nobody's mentioned what happens when you introduce water (glue) to the edges of the boards before (or during) the jointing process.
It is an essential part of it after all.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Wow, completely misread this one. Count me in as no spring on top and back joints.

Great thread title and makes me think of Budujolais nouveau....

I am always much more comfortable having a gapless joint before gluing.

By the way I used to be a candling sort checking my joints for gaps in a window in daylight or against a high intensity light bulb (pre-Al Gore fat-arse CFLs) but my friend Link Van Cleave who is a master woodworker taught me to simply inspect the joint very closely with my own eyes and I could see the gap, if any. When I started doing this sure as shootin Link was right.

I've never had a glue joint in plates come apart and hope to remain this way.

Just to reiterate one doesn/t need 10 planes to make a good joint spring or straight.I/ve seen J/ bogdanovich do it with a LN block plane . To do 20in plates . I would use at minimum a 12in plane .A cheap stanley jack plane can be bought for anywhere between 10 - $30. I use a shooting board. Must stress that plane has to be fiddled with and set up very sharp in order to get a smooth cut. There are chinese sellers on e- bay selling Bosi (indonesia red sandalwood) jack planes from 30-40$ an these just needing sharpening of the HSS blade .They are an excellent alternative to the stanley as they need little maintenance and can be easily set up for shooting an edge. quickly. Usually I aim for about a .002 cut to get a perfect match on the plates edges.Lay down both plates on your shooting board at the same time. Good Luck.

I remember that from back in the day in Young's book. I've used that method on several guitars and in fact if I shoot a board today and there is a tiny spring in it then I'll leave it at that. I've never had a top fail. I have had a back fail but that was an entirely different problem. I like to try and see no light but if see a tiny well shaped spring joint I'll leave it at that. I have the tenancy to shoot just the opposite curve, as I'm sure most of us do, so then I'll focus on getting the middle and sometimes that makes a perfect spring joint. And I'm talking the very finest sliver of light that comes through. It's important to note though that if you use a spring joint then you need to clamp tight and not just give it a hide glue rub or just use masking tape. That's the whole point of the joint.

A concave joint to the tune of a few thou is ok with me. I prefer a perfect match but don't always get it.

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Steve Smith
"Music is what feelings sound like"

There's a couple of very interesting extensive threads currently running for hand plane learners and lover's.

As for spring/sprung joints -- one theory is that the plate halves or table top boards release moisture out the end grain thus the plates or boards shrink across the width at the ends more readily and quicker than at the center. Kind of makes sense?

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Ken Cierp

http://www.kennethmichaelguitars.com/

Ken: The only thing is that the ends on a top are covered by binding, where as the sound hole has exposed end grain. For me the spring joint with minimal gap just assures me that there will be no gaps in my glue line.
Tom

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

I'm with meddlingfool on this one. I use my jointer, and look for no light passing. Just put new blades in the jointer; works a lot better than my plane.

Another theory is that the tiny gap is helpful in preventing a glue starved joint caused by clamping too tight -- maybe?

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Ken Cierp

http://www.kennethmichaelguitars.com/

Better concave than convex for sure.

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wah
Wah-wah-wah-wah
Wah

Never intentionally made one but have heard about them.

Some serious old school jointers have the ability built in.

http://www.northfieldwoodworking.com/Te ... hments.pdf

Kevin Looker

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I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

I kind of started this thread because I had read that Martin indeed had their plate edge jointing process set up as described in the illustration that Kevin posted above. The comments were pretty compelling since a very well respected luthier (you all know) was allegedly the source of the insight.

Anyway, I contacted one of the Martin factory engineers seems not so, his first response was like huh? (really had my answer) so I sent him the link from my OP:

Hi Mark,
I have not bothered you in a long time -- hope all is going well.

I read somewhere that Martin uses a spring joint on the top and back plates, each half concave a few .000 Is that true? And if so what is the reasoning?
Thank you in advance,
Ken

Hi Ken,
Not to my knowledge. We run our top and back panels through a joint edger as a set to get them as straight as possible before gluing them together.
Thanks,
Mark

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Ken Cierp

http://www.kennethmichaelguitars.com/

no Martin doesn't use a spring joint they are true and flat when glued.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

A sprung joint makes sense on thick, long stock jointed by hand and clamped with lower pressure wooden or wedged clamps that will not get the pressure at the glue line much above single digits. The moisture from a long, wide glue joint leaves the work differentially, with the ends and surface shrinking a little faster in width than the center. With modern, inexpensive 800-1000 pound clamping force panel clamps and good power jointers, the reasons for a sprung joint go away. Also don't see a 3/16" thick by 20" long joint seeing much in the way of differential drying.

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For the times they are a changin'

- Bob Dylan

I make mine perfect before gluing but I did overhear someone whom I consider incredibly knowledgeable about wood and wood movement speak to this- basically he said that if you get the edge perfect on a square plate once you cut the body profile on the outer edge the mating edge will no longer be perfect- I never tried it but haven't forgotten it either.

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Burton
http://www.legeytinstruments.com
Brookline, MA.