Ken Bennett

I've done hundreds of inlay jobs in the last ten years for guitar companies, banjo companies, hobbyists building kits, and on my own guitars. Nobody has ever sent me a non-radiused board. It's either a radiused, slotted board. Or it's a whole neck with board radiused and slotted. Or a whole guitar. Sometimes already fretted.

Routing is not a problem on the radius. And having the cavity follow the radius is sometimes an advantage. For times when I need the bottom of the cavity to be absolutely flat I use a fixture that holds the board with flat rails along the edges and an extra wide router base that won't slip of the rail on one side.

I make different style bottoms out of plexiglass for the Stew-Mac Dremel router base. My standard base is smaller than the one that comes standard on it.

Hey there everyone,

I'm new to this forum and building guitars in general. I know the anatomy of guitars and know how to wire/solder so that is not a problem. However, I could use some advice from more knowledgable folks about shortcuts I could take to make it easier on me with the structural part. I'm not sure how hard it is to build a semi-hollow body versus a solid or straight hollow but I love the sound and I'm willing to dedicate my time to it.

Basically what I am hoping for is:

1) A supply checklist (what items I will need such as a router, sander, drill - things of that sort... even small stuff)

2) Places to buy expensive supplies cheaper (such as wood and maybe the router)

3) Schematics, dimensions of other hollow or semi-hollow body guitars.

4) Advice, frustrations, lectures, shortcuts.

Please help me out with some pointers, I know it is going to take hours and hours of forum scouring regardless if I have shortcuts or not. Any help is appreciated.

-Dan

I have everything except a design. I'm just building my first 2 archtops. Just got an order for one more, but they want a thinner semi-hollow.

The only tool I had to buy was a convex-sole plane to carve with. Got the Lie-Nielson for $95.

You can save money on wood by buying lumber instead of blanks cut to size for specific parts. You'll probably be using maple which can be bought from the same hardwood suppliers that cabinet and furniture makers use. You don't have to use Master Grade wood. A well made design will sound great and look very good even if it's made of plain wood.

Advice? Frustrations? Here's a lecture: There are no shortcuts. Take your time. When you make a mistake, decide quickly whether you have to scrap that part and start all over or live with the mistake and forge ahead. Don't expect perfection. But don't hesitate to do something over if you know you can do better.

Good luck. If I find a design I'll let you know.

How does your experiment measuring the increase in pitch of bent strings help you figure out an ideal intonation scheme?

theodoopoulos,

Your formula is theoretically fine. I'm curious about it's application. Are you using the formula to determine the neck angle of an existing guitar? Or are you using it to calculate the desired neck angle of a new guitar design?

Sincerely,

Ken

Man, That is an awesome piece of wood!

Welcome... Looking forward to seeing more of your work.

Binding

Patch with similar wood, then solid color body or sunburst

Hi Chris,

Sounds like you have cut into an ebony board that has been dyed. Some builders do that for a consistent color. You can leave it natural. Lemon oil will darken it a little, and fine sandpaper will burnish it smooth and shiny. Or dye it to restore the black finish. Stew-Mac has the stuff. I've never used it, but they say it works.

http://www.stewmac.com/shop/Finishing_supp...oard_Stain.html

1.5 twelfths

Tough crowd isn't it Wes...

Here you go:

http://www.alliedlutherie.com/truss_rods.htm

Those from Allied are the thinnest. I like them because they are exactly 1/4" wide, so it's easy to find the right router bit.

I'm confused. Why would your neck tenon be any different from a standard mandolin?

I'm assuming that you mean 10-string instead of 5-string. 5-course would be the correct term. A normal mandolin has 8 strings arranged in 4 courses, 2 strings per course.

So your 10-string just has a slightly wider neck than an 8-string. Why not simply make the tenon proportionally wider?

Warrior guitars are an example of what you are trying to do. The neck heel is not much thicker than a typical bolt-on. The length of the heel inside the body is very short.

In recent years they have extended the heel up into the neck pickup area. The neck is glued in, then the pickup cavity is re-routed. It ends up looking like a regular neck heel with a foot about 1/4" thick that extends up under the pickup. The pickup then has enough clearance, and the neck joint has more glue surface. The body is pre-shaped. The neck heel is blended into it after the glue dries.

With oil finish you're going for a natural look. Filling the grain wouldn't be necessary in my opinion.

Here's one of my guitars with oil finish and no grain filler.

Very flat indeed, Wes.

I did some drawing, and measuring, and calculating. This is pretty interesting.

It turns out that my guess about the 10" radius nut going to a 20" radius bridge was close enough. The fretboard would go from 10" to about 17.5" (16" would probably be just fine). And this would be conical. The rate of change in the radius is linear. Checking at 5 equally spaced points along the scale, the radius changes by the same amount from point to point. See column A below.

In the case of a 12" radius at the nut going to a flat bridge such as the banjo I'm about to inlay, I estimate that the radius does not change by the same amount from point to point. The change is less near the nut and gets greater and greater as you move toward the bridge. See column B:

-----------------A-----------------B

nut................10"..................12"

5th fret..........12.5"...............18"

12th fret........15"..................32"

24th fret........17.5"...............72"

saddle...........20...................infinite(flat)

When the banjo neck arrives it will be interesting to see if the Nechville is radiused anywhere near like the numbers I came up with in column B.

Consider a neck with the frets removed (to be refretted later). Dot inlays.

And using the Stewmac fret radius sanding blocks, is it better to....

Using an existing 16" radius fretboard, sand it rounder to a 12" radius (w the 12" block)

-- or --

Using an existing 12" radius fretboard, sand it flatter to a 16" radius (w the 16" block)

???

(please don't ask why )

I deduce that this is totally hypothetical. Let's break it down. We can ignore the Stew-Mac brand name on the blocks; let's say we have generic radius sanding blocks. We can also ignore the dot inlays; they are easy to sand and can be replaced cheaply and easily if necessary; they have no bearing on my decision.

If the fretboard had binding, then I would rather flatten a 12 to a 16; that way if the slots became too shallow, then it would be easier to deepen the middle of the slots than the ends; we could use a short blade that fits in between the bindings. But we don't know that it has binding.

If there were a lot of chips from removing the frets, I'd rather fill those than sand them off. And what if the surface needed leveling? In both of those cases I would want to keep the same radius, but that's not a choice.

If the hypothetical player preferred one radius over the other, then I would change it to his preference; that means that either answer could be correct.

In either case we would have to reshape the nut, so that does not inform the decision.

Will the luthier see any difference in the two choices. Considering the information given, as an engineer or artist he would do it either way. As a manager he would advise against it unless he could charge extra.

What the hell is a linear radius at the nut? What the hell is a "linear radius?". Infinite?

Linear bridge..not linear radius...Linear....in a line...no radius.....flat.....

Calm down boo....

Means a radius at the nut,flattening out to no radius at the bridge.

Even after reading the wikipedia article, I couldn't imagine this ever happening in real life, a radiused nut and a flat bridge. But I understand it in theory, and I see how it is a type of compound radius that is not conical.

Then I got a call from Nechville Banjos. They are sending me a neck to do a fretboard inlay, and wanted to remind me to be careful not to change the compound radius when I level the inlays. Radiused fretboards on banjos is a new thing. Nechville may be the first. I have talked with them about it before. They said that their radius is not exactly like a normal compound radius. I wonder if that means that they are leaving the bridge flat?

Also, some classical guitar makers use radiused fretboards now. Do they have flat bridges too?

These banjos and classical guitars may be two examples of the non-linear compound fretboard radius as described in wiki piece.

I'll measure the Nechville. It should be easy to figure whether it is a cone section or not. And I can find out whether they are using a flat bridge.

Gah, I spent an entire hour trawling through links and some of my books trying to find reference to this and drew blanks. Curses. I think that (surprisingly) the Wikipedia article was closest when referring to "example 4" which looks like the profile of a board having had a transition to a larger radius dialled in higher up. Your outer strings thing bothered me when I first thought about it too, but my biggest thought was to the "non-linear" change in action.

Conical for president.

Well, we agree on the main point: the bridge must be altered if the fretboard is altered.

It may not be absolutely necessary, but a compound radius feels pretty good. It's definitely an improvement over a 7.5" constant radius.

I have tried different things and settled on a 12" radius for all my guitars and basses.

That may change if I build a bass with 6 or more strings or if a customer wants a tighter radius at the nut.

Both methods have their uses though. Compound is very simple to create.

Right. The compound radius is simple to create. There seems to be some confusion about it though. For example, you said:

... a tight even action won't be given by a truly compound radius as the central strings will suddenly have a higher action where the upper radius kicks in.

That doesn't seem right. If the FB is a true compound radius (conical), and what you describe happens (middle strings have higher action at the upper end of the FB), then the radius of the bridge saddles is wrong. That's the topic that got me into the thread: the question about coordinating the FB radius with the bridge radius. When that's done correctly, the action will be consistent.

Take a Les Paul, for example, which has a 12" radius at the nut, the whole fretboard, and at the bridge. Then if you change the FB radius from a straight 12" cylinder to a cone--by flattening the board at the higher frets--, then yes, the action will be higher for the center strings in the upper register. You have to finish the job by also changing the radius at the bridge flattening it even more than you did the FB.

So if a fretboard has a compound radius of 10" at the nut to 17.5" at the 24th fret, and the bridge has a radius of 20", then the action will be totally consistent across the board.

If I'm thinking correctly, then a cone can be reduced to a right-angled triangle with the perpendicular distance from the adjacent to the hypotenuse being the radius at any given point. So yeah - scale length is indeed irrelevant as the radius of any given point can be calculated from the gradient, which in turn is calculated from the radius of two specific points. In the case of a fingerboard, the nut radius and that at the bridge (usually).

I think that is right anyway. Bleh.

Untitled_Project: Yep, a tight even action won't be given by a truly compound radius as the central strings will suddenly have a higher action where the upper radius kicks in. It's feasible to run say, something like 10" from frets 1-7, 12" 8-12, 16" 13+ so the transitions aren't too crazy. It'll be more of a perceived change between radii unlike a conical profile though.

If you used GregP's method (making the compound radius with a flat bar), then there won't be any transitions. The radius changes continuously as it does with a true cone.

There are white pigment stains. But pigment stays close to the surface, so any sanding would remove it. Must be bleach.

After 3 years of being gone and forgotten.......

IT'S ALIIIIIIVVVEEEE!

Got a quick question about bridges and compund/conical fretboards. My nut will be a 10" radius and the bridge is at a 20" radius. The neck will be 24 frets at 25.5 inches scale length.

What will the fretboard have to be radiused at? (10"-0 fret to ? at 24th fret)

Off the top of my head...

The scale length is irrelevant because the ratio of the length from the nut to the 24th fret to the overall scale length is the same for any scale length.

It seems that the radius at the 12th fret would be the mean (average) of the two radii at the ends: (10 + 20) / 2 = 15

Furthermore, the radius at the 24th fret would be the average of the radius at the 12th fret and the radius at the bridge: (15 + 20) / 2 = 17.5

This may be wrong as I am notoriously bad at doing arithmetic in my head. Also this does not take into account the fact that the string spread is greater at the bridge than it is at the nut. That may or may not matter. My guess is that it does matter, at least a little, but maybe not enough to worry about.

I'm guessing 17.5" radius at the 24th fret.

The black and white theme really looks nice.

I'm curious how you developed the arching. Is it freehand or based on patterns?

Looking good so far.

This is one case where there is actually a fairly scientific way to determine the right thickness before bracing. It is a technique called "quenching the fundamental" that uses tap tuning.

Start with the top fairly thick. Tap and you will hear a clear note of definite pitch, a fundamental with not a lot of harmonics.

Gradually thin the top. Check the tap tone as you go. It will get lower and lower.

Suddenly the clear single note will become a combination of notes that sort of sounds like a low pitched gong. Stop thinning at this point.

I like this technique because it is easy to describe and easy to do. You will arrive a good thickness without even knowing what the number is!

(Then you have to do the bracing. I don't really have a clear-cut system for that. It does seem that tall thin braces work better than low fat ones.)

Hey, I have a right-handed guitar playing son named Gabe. What you could do is reshape that truss rod cover into an oval. Then you could inlay it anywhere, or make the guy a key chain or something.

OK, I've done thousands of guitar inlays. Here's what I would do.

We glue inlays in with water thin super glue. First insert the inlay into the cavity. Then run glue sparingly around the edge of the piece. We use those pipettes from Stew-Mac. Most of the glue will seep into the gap between the wood and the shell. So you don't necessarily have to remove the inlay.

After the glue dries thoroughly, scraped off the excess with a razor blade. You may want to clean the whole fretboard and buff it or at least oil it with lemon or orange oil. Otherwise the inlay that you just repaired and the wood around it may look different than the rest of the board.

If the inlay is not exactly flush, trim it down with a file AFTER the glue sets completely (I wait overnight if the glue had to fill a large gap), then scrape and polish.