Official Luthiers Forum!

Inlay or butt between back halves? and why?

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A higher purpose for wood.
Rich Smith
Issaquah, WA

Hi Ricardo;

I do both depending on the type of inlay material.
If it is a thin intricate style that is called for to match the purfling/binding then I will route it in after I join the two back halves. If it is a solid or something I can get in a thickness of .120" plus, I butt join them together. I always use a seam joint strip on the inside in either case, and also use the brown Gorrilla glue to join the back pieces as it is very strong.
If I am routing the back after gluing, I find it is very easy to just clamp a straight edge at the right offset and run my router along it to the correct depth. After I have the inlay in and scraped flat, then I glue the inside seam strip over the joint.
I prefer the butt method using material that is as thick as the backs as it is very quick and easy to complete. A little scraping and you are good to go.

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Nehemiah Covey
www.coveysacoustics.com

Hi Ricardo,

Butt joints for me using LMI Glue and a cross-cut reinforcing strip on the inside. When I trim the back to size I always break the scrap piece to test the glue joint. I have yet to see a failure of the glue.

Mike Franks
www.mjfranksguitar.com

Inlay. I rout a channel .04 - .05 deep. I think wrongly or rightly that having an inlay back strip adds strength by
overlying the butt joint. More surface area equals more strength. Anybody agree?

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Greg
http://garibaldiinstruments.com/

if it's wood/zig-zag/herringbone/ect.. I butt it. If it's abalone I inlay it. But I've been more prone lately to not using one at all.

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John Mayes
http://www.mayesluthier.com

Inlay. Seems like a stronger joint, intuitively, and it's very easy to do. Strikes me as simpler than futzing about with clamping methods to glue two (or more) glue lines at once - I glue backs using a 'tenting' method with masking tape and HHG, which requires little to no complicated clamping.

I'll be doing a herringbone back strip. I am inclined to inlay it based on feedback here. Thanks

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A higher purpose for wood.
Rich Smith
Issaquah, WA

I only inlay - if you glue all of the pieces together, it creates multiple glue joints, which only increases the chance for joint failure. It can be a challenge to keep all of the pieces lined up during the glueing process as well. By inlaying the strip, you strengthen the single joint since you are lapping the glue joint with 1/4" material and glue, plus the reinforcement strip on the inside.

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John Ressler

Have done both, but "when" do it almost always now butt join. I do it before thickness in sander at about .125. Just as easy as join if not easier. I though rarely use a back stripe, as I am not particularly fond of them on a personal basis. Just as strong and never have had a failure.

I have always butted it because it was easier and faster. The center seam reinforcement will be enough for this joint to never come apart. I also like not worrying about if it is seated all the way and if I'm going to sand through while thicknessing, or final sanding. I know of several builders who inlay it, and I've seen 2 occasions where they sanded through because the back angle and sphere of the back caused too much curve. I try to avoid this at all costs. Of course, I'm not expert, just my own experience and what I have noticed.

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Tracy
http://www.luthiersuppliers.com

Yes, "lap" the joint with inlay back strip. That's the word I was searching for.

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Greg
http://garibaldiinstruments.com/

Tracy, I'm not getting the statement about sanding through because of back angle, etc.

Frankly, not sanding through is just as trivially simple as not sanding through the rosette: you surface the back, install the backstrip (inlaid, takes about 5 minutes to set up, test fit and cut the slot, and it goes about 3/4" the depth of the back), then plane/scrape/thickness sand (I tend to do the first two, because it's fun) the backstrip flat, and then, if you didn't thickness first (definintely easy enough to do), thickness the back by sanding the OTHER side. Seating a flat strip perfectly is not something that should be difficult; since it's a little proud, masking tape holds it in place fine, gluing with either titebond, or CA after shellacing the channel.

I've seen quite a few backstrips separate after butt-joining them, most of those are thin pieces of wood held by yellow glue after all. The question is kind of trivial, it's a good idea to flood the back-strip with thin CA in both situations. No need to seal with shellac because of the CA on hard woods IME.

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