Official Luthiers Forum!

I just cut the binding channels on my second guitar. What I've noticed on both guitars is that in the transition area between the waist and the lower bout the channel isn't cut quite deep enough and the binding stands a little proud of the top back. The channel depth is perfect at the waist and around the widest portion of the lower bout.

It seems this must be caused by the body depth changing quickly in this area due to the radius and body taper coupled with a base that is wider than the diameter of the bit. Does this seem to be the cause for this? Any approaches to eliminate or minimize this issue?

How do you handle the proud binding? Do you scrape the binding down level with the body (after glued in place) leaving the binding narrower in this region? Do you scrape/file the channel till the binding fits properly then glue in place? Maybe you have another approach?

Thanks!

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Formerly known as Adaboy.......

I always install my bind a little proud and scrape down.

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Jim Watts
http://jameswattsguitars.com

the sides of the binding should be so you sand the side to meet the binding and keep the top just so you can sand the binding and purfling to the top and back ( or scrape ).

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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

I'm thinking there may be some confusion about your issue being the binding ending up in sone areas too proud of the back/top, or too proud of the sides. I suspect the former, but I'm not sure. In any event, uniformity of the cut height or depth depends on how you are registering your router on the guitar surfaces. Easy to see how channel height can be affected by your router base registering on the back radius in this area, but the problem should not be evident around the top which has very little done. Uniformity in the other axis requires "flat" sides and holding the router exactly parallel to the sides at all times.

the key is the donut or a bushing that will locate with as few contact points as possible. You may need to do an adjustment cut in the upper area on the back if your are using a location device that is using a large area of contact.

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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

The radius and shape of the back or top have an influence on this as well. It seems the tighter the back or top radius the more pronounced the effect can be. It's about the geometry between the object and the tool. You can't reasonably index at the exact cut line. I check mine carefully and fine tune with a sharp chisel.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

Actually if you can control parallel and the location points you can cut these very accurately . You want to locate with as small a contact area as possible with the cutter held in parallel to the sides. Units that are hand held or have other variability factors make repeatability difficult.
If your back is very hard arched or a carved top like a Les Paul you may need to to step cuts and then work the channel. The more complicated the binding perfling scheme the more accurate your process needs to be.

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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

I'm still struggling with the problem of the binding ending up being proud of the sides at the waist and could use help on resolving it. I understand this isn't the fault of the jig, but the person who adjusts and sets up the jig. I first had this problem with a simple jig I made myself, so I bought a Fleischman-type jig from John Hall. Very nice jig, but I had the same problem.

I'm using a 25' top radius and a 15' back radius. I have left the sides a little thick so I can scrape them down to meet the binding, but I would still like to have depth of cut as uniform as possible.

Can anyone suggest the steps I should go through to optimally adjust my jig? (Binding jig adjustment for dummies?) If I seem a bit slow on the uptake, because I haven't inferred the specific actions needed from the principles that have been stated above, that impression is accurate. I brings some strengths to lutherie, such as a good ear for tone, but sadly, my aptitude for understanding and fine-tuning machinery is only so-so.

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Tim Allen
"Never hurry, never rest."

Thanks, Todd. I will check for that next time. I plan to use fish glue to give myself plenty of time.

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Tim Allen
"Never hurry, never rest."

Hard to beat roping when trying to get bindings tight.

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

Thanks for the tips. You were correct that the binding is a proud of the back but not so much the top. I'm using a 25' radius on the back. I'm fairly certain what causes this is the width of the "doughnut" riding on the back being wider than the bit.

I haven't yet glued the binding in place so I'll try scraping/sanding/filing/chiseling the channel lower in this area.

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Formerly known as Adaboy.......

Tom, what kind of rope is that you are using?.......and where did you get it?

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Formerly known as Adaboy.......

Darryl: I have used a couple of different types. But what I look for is something with a bit of stretch or give to it. This lets one make every wrap with tension on the binding. I think the cord shown in the picture may be nylon carpenters cord that they use for chalk marking. Available at most large hardware stores.
Todd's elastic bands look like a good way also. By the way that is the process (elastic bands) that I use to glue backs and tops. Certainly gives lots of pressure.
Tom

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

if you are using wood binding think about using a clamp I use a small bar clamp at the waist. This is the one area of concern for lifting. If you are using a bearing cutter the depth of cut shouldn't be the problem. Using a clamp you can get the pressure to hold the binding in position.

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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

Not sure I'm understanding all the answers here, but I had a similar problem on an hourglass dulcimer once. The channel was just not cut deep enough at the waist. I even removed the binding, made a new binding, cut the channels over again slightly deeper this time, and same thing. When you look closely at that instrument, you can tell the binding is not as wide at the waist as the rest of the way around. And, Dulcimers are basically flat compared to a guitar.

I was using the StewMac routing jig (hand held) with my Dremmel. I never did figure out what caused it, but whatever it was, after the second try I learned it was repeatable.

My solution (at least on that instrument) was to use a thicker binding so the thinner section was less obvious.

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Phil

http://www.oleninstruments.com

"Those who tilt at windmills are only considered insane by those who can't see the dragon."