Pre-bending purfling edgewise

[dlowry]

Hi,
I put a bwbw purfling strip under my wood bindings, which has to be pre-bent on-edge to fit in the waist to avoid breakage. I haven't found a reliable way of doing this yet, and often end up with a wavy edge on the inside of the bend, as on this guitar - doesn't look good.



They're maple-fibre laminate, similar to these from StewMac, 1.2mm x 2.5mm

http://www.stewmac.com/Materials_and..._Purfling.html

I've tried freehand on a bending iron, but its difficult to avoid twists. Thinning the strips to 2mm beforehand helps, but I still get crimping of the inner edge on the tight waist bend.

Another method was to sandwich the purfling strips between the wood bindings with tape, and do them all together in the Fox bender, but I still had the crimping problem.

Any suggestions?

Thanks,
Drew

[Trevor Gore]

You've tried gluing the purfling to the binding then bending the whole lot together? Works fine for me on Venetian cutaways. (I use LMII white glue for that job, BTW. Other glues will work (e.g. PU) but whatever you use needs to be able to stand the heat bending).

[dlowry]

Originally Posted by Trevor Gore

You've tried gluing the purfling to the binding then bending the whole lot together? Works fine for me on Venetian cutaways. (I use LMII white glue for that job, BTW. Other glues will work (e.g. PU) but whatever you use needs to be able to stand the heat bending).

Hi Trevor. No, I haven't tried gluing them beforehand yet, although I know a lot of builders do it that way. I'll give it a go. Do you trim the purfling to match the binding thickness before bending?

Drew

[Ned Milburn]

Originally Posted by dlowry

Hi Trevor. No, I haven't tried gluing them beforehand yet, although I know a lot of builders do it that way. I'll give it a go. Do you trim the purfling to match the binding thickness before bending?

Drew

Yes, Trevor suggests a good (the best?) way to do it. After gluing the purfling/binding together, then cut & trim to installation size (a bit bigger than final size), bend, install, then scrape to level.

I glue 1 inch pieces (ie: .07mm purfling x 1" x 33" glued to binding at 4.3mm tall x 1" x 33"), then cut to 2.4mm wide after glue dries, finish with a thickness sander to about 2.1 mm, then glue to guitar and scrape to finish (about 1.9-2.0mm thick x 4.8mm tall).

Does this answer your question about matching thickness?? You'd have a hard time gluing individual pieces of binding and purfling together, hence, it is done before final cutting & thickness sanding.

[dlowry]

Does this answer your question about matching thickness?? You'd have a hard time gluing individual pieces of binding and purfling together, hence, it is done before final cutting & thickness sanding.

I don't really have an option, as I generally buy my bindings/purflings ready-made from suppliers. Seems it can be done though - these are from Christophe Grellier's website







He uses an offcut of T&G flooring, but anything with a suitably sized slot would do. Line it with tape and clamp the binding on top of the purfling with string or rubber band.

Drew

[LouieAtienza]

You could get thin stock.the same.thickness as your binding, then use veneer or fiber sheet to build up and then rip on a tabesaw or bandsaw (and clean up on a veneer sizer or belt sander if necessary.) I find this easier than working on the separate purfling , and it saves me some money... though I have had a couple problem pieces that wouldn`t bend right regardless of what I did. I just had to remove and redo it.

[GeoffStGermaine]

I glue my binding and (side) purfling together before bending as I've found this prevents the purfling from becoming wavy.

[arie]

i don't use fiber sandwiched between hardwood (w/b/w)for purfling. the fiber is softer, compresses, and wrinkles. looks fuzzy too. i use all wood and glue up before bending. i make my own from dyed wood purfling and sandwich it together in a delrin fixture for gluing. bend dry.

fwiw, i make small guitars with tight radii and need stuff to stay put and stay crisp. for me, all wood is the way to go.

[WaddyT]

I bend my side purflings in a sandwich with the bindings, and if I get wrinkles at the waist, which is most common, I flatten them with a clothes iron after the fact. Usually works fine.

[dlowry]

Ok, looks like pre-gluing is the way to go. I've already bent bindings and purflings for my current build, but I'm not happy with the purflings, hence this thread. I'll try pre-gluing and bending on a test piece, and if it looks good, I'll redo everything. Always good to learn new tricks The current bindings I can re-use later on a build without purflings.

Thanks for the help.

Drew

[dlowry]

Originally Posted by WaddyT

I bend my side purflings in a sandwich with the bindings, and if I get wrinkles at the waist, which is most common, I flatten them with a clothes iron after the fact. Usually works fine.

I actually did that for the guitar photoed in the original post. The purflings looked fine after ironing, but wrinkled again on glue-up. I still think I'll have a go at pre-glueing just to see how it turns out.

[dlowry]

fwiw, i make small guitars with tight radii and need stuff to stay put and stay crisp. for me, all wood is the way to go.

That's an issue for me also. The guitar model in question has a tight waist and a correspondingly tight radius. I don't get so much of a problem with my bigger models.

[Alan Carruth]

Although I generally glue the purflings to the bindings, sometimes you can't do that. For example, when you're doing 'self binding', cutting the bindings off the sides after they're bent (which looks sweet with curly maple), you need a strip of purfling to go in between. In those cases a slot, not too much wider than the thickness of the purfling, can help. Also, in those cases where it does buckle, sometimes you can correct it, at least to some degree, by putting the bent section down on the flat top of the bending iron, and pressing it down with something flat for a few seconds. I use Titebond 3 these days; it is less prone to coming unglued than most others I've tried, and it acts something like a hot melt glue.

[Tom West]

Originally Posted by Trevor Gore

You've tried gluing the purfling to the binding then bending the whole lot together? Works fine for me on Venetian cutaways. (I use LMII white glue for that job, BTW. Other glues will work (e.g. PU) but whatever you use needs to be able to stand the heat bending).

Concur with Trevor. Tape two purfled bindings together with purfling back to back when bending.
Tom

[Trevor Gore]

Originally Posted by dlowry

Hi Trevor. No, I haven't tried gluing them beforehand yet, although I know a lot of builders do it that way. I'll give it a go. Do you trim the purfling to match the binding thickness before bending?

Because so much of what I do is completely custom, I don't make bulk bindings/purflings. I often trim bindings from the un-bent sides and glue purfling lines on, just using springs clamps (glorified clothes pegs) in a chevron pattern. The purfling is usually wider than the binding, and once glued, I plane them down flush. I prefer to cut the binding rebates deeper than the bindings by a touch and level by bringing the sides to the binding. That way, you can be pretty sure you've removed any excess glue that has a nasty habit of showing up after a few coats of finish (and likely keep your bindings a more even thickness)

Because so much of what I do is cutaways, I bend the binding by hand. I've not had any problems with fibre bindings, but I guess it depends on where you source your stuff. Some multilayer purflings may delaminate, because the glue used to put them together is not heat resistant, but the nice thing about that is that a judiciously applied spring clamp will usually stick it all back together.

All the binding/purfling bends here, including the heel cap, were done as described.