Official Luthiers Forum!

Here is the latest Luthier Tips du Jour video -The topic is cutting binding and purfling channels by hand.
This video as well as all my other videos are available via my website http://www.obrienguitars.com/videos/, LMI's website or on Youtube.
Enjoy!

Grinding the scraper is such a great idea--but only obvious to me once you pointed it out. I've use my gramil for lots of scoring, but never attempted a fully hand-cut channel. Thanks, Robbie.
Patrick

I'm a little slow on the uptake and could use some help understanding how the "scraper" works on the side channels. What's going on there?

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George :-)

George,

This video explains the process.

What is the advantage of scraping the side as opposed to using the same side of the blade you used for the top cut? Is it primarily because it gives you a wider channel which makes it a little easier to remove the rest with a chisel?

Of course if you glue the linings so that they are proud of the sides (by a set amount) there is no need to cut the binding channel at all. The rebate is formed as a consequence of gluing the linings.
Only took me 30 years to figure that one out!

Michael - You are a far more accurate gluer/clamper than I. :-)

Robbie - Thanks for posting the extended play version. I've been using an LMI gramil for a while now, but somehow missed that video.

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George :-)

I just use a depth gauge, nothing more than a small piece of wood with a step cut out. Just clamp with the spring clamps and check it, adjust as necessary. Doesn't really matter if you are out a touch and of course it does ensure a very square rebate. Failing that clamp the linings a little higher and Plane them down when dry. Both methods are easy.

Sam, in my experience the softwood of the top allows the sharpened part of the blade to make fine lines. However, in the harder rosewood it will "wander" a bit. It can still be done but I prefer the scraping method.
Of course, Michael's method is also pretty slick.

Interesting! Do you use purfling? How do you cut for it? Seems like if you used a bearing, you would need to flatten the sides which would make you binding rabet uneven and need to be routed anyways (although a much easier rout).

Great idea using the opposite end of the blade as a scraper! It's always tough getting a good deep score mark in really hard woods. That should allow shaving a groove gradually, rather than having to stop and chisel away material to allow the blade to go deeper.

I cut my first two by hand and I'm glad I did (but I'm not planning on going back any time soon).

I do have one quick question about the scraper method for the side: Since you're registering off of the top/back do you not end up with a slightly tipped ledge (>90 degrees)?

nice video -thanks for posting! i use a gramil to cut stepped binding channels and i like the feel of it. it's quiet, and pretty quick, and you don't need a chisel or a router to get it done. i would like to point out that there is an issue with the lmii gramil in that the set screw that locks the blade will cut grooves into your top because it's diameter is the same as the width of the flats on the shank of the tool. these grooves will appear when you reach the final depth of your cut when the shank bottoms out on the top. if you leave material for sanding then just sand the grooves out but if you are like me who has the top to finished thickness before binding, you'll be in for a surprise (esp. with cedar). lmii should have made the shank either thicker to use the existing set screw or used a smaller setscrew so the threads aren't exposed. the blade pocket needs to be a bit tighter too because the blades will move around back and forth in the slot no matter how tight you twist the set screw. still not a bad tool, one just needs to be aware of these things though.

I have never noticed any "tip"
Before using the LMI gramil I used a homemade one and I manufactured the compensation for the radius of the top or back into the tool. In other words it wasn't square.

Indeed, not really a problem on normal radii IME. But really tight radius backs, and especially Manzer wedge backs it becomes a problem:

So I made a little block and taped it to the gramil, positioned where the peak rides about 2mm inward from the edge.


It's just coincidence that the angle happens to match the angle of the back there... it really only needs to make contact at the very peak of the block, and since the angle of the back relative to the side changes depending on where you are, you can't match it perfectly all the time. You do have to manually maintain squareness to the side, but it's not hard as long as you can get a good view of it.

Of course, you're still trying to glue an originally straight binding strip into a channel that curves in two directions at once... so it takes some combination of luck, bending skill, and clamping pressure to wrangle it in there

This is a wonderful tip Robbie. I am a hand tool woodworker and am into my first guitar with hand tools. Looking ahead, the binding/purfling channel has always been intimidating to me. But this video really made me feel much better.

In my woodworking I use the scraper technique alot for string inlay and creating small bead or other similar profiles in my work. I am always making a new scratch stock out of old saw blades and have a dedicated scratch stock holder. For some reason I have never translated this method to the binding/purfling channels in a guitar (light bulb moment). In my experience woods that are as dense as rosewood, ebony, coco, etc, do extremely well when scraped. Even when the scraper starts to get dull you can get shavings for ever, especially when compared to woods like cherry, mahogany, walnut, etc.

Again Robbie, great tip. One of my favorites that you've posted. I really appreciate you taking the time to make these videos, they all have been a great help.

Robert, vous êtes grand!
I'm building my first and since i dont have budget for a router, i'm binding with a gramil which i made myself. Some of the tip du jour i found were really helpfull to me.
Merci!

Robbie's tip is great and Dennis's is a great extension.

After going to the effort of building a full Fleischman-Williams style contraption and using it to it's full potential, using a router for binding channels still gives me the willys. I am inspired to go the less power-tool dependent route.

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Jim Kirby
kirby@udel.edu

Thanks everyone. Glad you enjoyed the video.

Robbie, thanks for the reply and all of your videos. They are a big help and inspiration. When cutting the channel on the back, and assuming it's a hard wood like rosewood, would you want to use the scraper side of the blade for both of those cuts (back and side)? Then you would really only be using the 'blade' side that came with the tool for cutting into the top.

Sam,

The scraper techhnique works for the sides. I do not use it on the top or back. I use the regular side of the blade for the top and back.