Official Luthiers Forum!

You can add one more paypal !

Thanks Anthony Rich and Scott. You guys are the best! I think my head is starting to swell

I'm running really low on material to make these, and it will take some time for my partner to get some more material, so any more orders received this week should go out Monday 8/28. Hope that is okay. We didn't expect this many orders! Thanks everyone!
Tracy

_________________
Tracy
http://www.luthiersuppliers.com

Happy for you Tracy!

Better add me to the list as well Tracy. Looks like a really nice jig and I've been meaning to get something like it for a while now. I'll PayPal you through your website.

_________________
Dave Rector
Rector Guitars

Got it Dave! Thanks! And Thanks Serge!
TracyLuthierSupplier38949.5888657407

_________________
Tracy
http://www.luthiersuppliers.com

To all of you that just purchased the Centerline finder, a big thank you! I have sold out of plastic for now, and will have to wait until Friday to have it delivered. We'll make the next round next weekend and it should ship Mon or Tues 8/28 or 8/29.

For those of you who are planning to modify the jig to be able to square your bridge in a specific location, please do not modify this jig just yet. We think we have just come up with a way to add an optional part that will slide along the outside of the jig and allow you to square your bridge in a specific location. It should be available in 2 or 3 weeks if all goes well. It will be very reasonably priced too! Thanks!
Tracy

_________________
Tracy
http://www.luthiersuppliers.com

I'm kind of having a hard time wrapping my brain around the geometry of how this works. I can understand how this would find the centerline of a straight board with parallel sides, but it seems like the tapered sides would cause it to align off center.

_________________
______________________________
Jonathan Kendall, Siloam Springs AR

Jon,
I don't know how it works, but it does! Just kidding. Actually it references off of 4 different points on the neck. When all 4 points are contacted, this forces the centerline over the actual center of the neck. The reason we swivel the arms in 2 different directions is to compensate for a very minute offset if both swivel arms moved in the same direction. So it is as accurate as what you would do by hand, and even more accurate because there is no hand work involved anymore. The jig does all the centering for you. Trust me, it works beautifully!
Tracy

_________________
Tracy
http://www.luthiersuppliers.com

Jon,

The trick is each swivel arm moves in circular way around each screw in which the center line lies through. This allows both adjustability to different neck widths at each position and still keep the line in center.

Do I understand it right, Tracy?

   

[QUOTE=ParamesB] Jon,

The trick is each swivel arm moves in circular way around each screw in which the center line lies through. This allows both adjustability to different neck widths at each position and still keep the line in center.

Do I understand it right, Tracy?

   [/QUOTE]

Yeah, but that only works with parallel sides. With tapered sides, the midpoint of the swivel arm is not over the centerline of the fingerboard. The midpoint of the swivel arm is going to be offset a bit towards the side that's gripping the wider edge of the fretboard.

Not trying to call anyone out here and I'm certainly open to being wrong, I'd just like to understand for sure how it works.

_________________
______________________________
Jonathan Kendall, Siloam Springs AR

Thanks Tracy, Payment is on the way!

_________________
Anderson Guitars
Clearwater,Fl. 33755

Tracy,
Brilliant Idea...looks like you utilized the "dowel hole centering device" principle and incorporated it into the Frank Ford centerline jig. Ingenious! ... Just ordered TWO!

_________________
Dave Bland

remember...

"If it doesn't play in tune...it's just pretty wood"

[QUOTE=letseatpaste]With tapered sides, the midpoint of the swivel arm is not over the centerline of the fingerboard. The midpoint of the swivel arm is going to be offset a bit towards the side that's gripping the wider edge of the fretboard.
[/QUOTE]

John, I don't understand this thinking. Why would the centerline not be over the center line of the board?

[QUOTE=Pwoolson] John, I don't understand this thinking. Why would the centerline not be over the center line of the board?[/QUOTE]

Because each gripping point is a different distance away from the centerline, so the midpoint of the gripper arm won't be centered on a tapered fretboard. I've exagerrated the taper in this illustration, but it's the same principal.


Again, maybe I'm not understanding how it's supposed to align, but it shouldn't be able to work the same way as a dowel centering jig when the sides aren't parallel.

_________________
______________________________
Jonathan Kendall, Siloam Springs AR

Tracy
Jons geometry is correct. What do you think. or is this difference too small.

_________________
Andy Z.
http://www.lazydogguitars.com

Andy,
I'm trying to get in touch with my partner now who is on the road and his phone is off. I'll let you know when I talk to him how he came up with the calculation. Thanks for your patience. We'll get to the bottom of it either way!
Regards,
Tracy

It looks to me (but never was great at geometry) that as long as the two plates swivel off a central axix of the plates the taper would be irrelevent.

The plates should just help secure the ends of the diagonal line accross the fret board as long as the taper is equally angled on both sides it should still find the center, no?

For those of you who have recieved your try this test.

Run your center finder both ways with the high point to the left and the high point to the right as you face the neck with the center at the same fret location.

If both ways hit the center then it works; if both are seperated a little bit then something may be askew.

Scooter B
They swivel off the center but they will hit the edge at different distances
because of the taper.   So inorder for both sides to touch, the center line
will
be off just a bit.   My bet, (I don't have the device yet) is that with the
degree
of taper with a typical fretboard, that the offset will be extremely small

If the swivel pieces were just wider than the fretboard, then the offset
would
be reduced. The greater the difference in the width of the fretboard vs
the
swivel piece, the greater the offset.   (The wider the swivel piece the
further
up and down the fretboard it will hit.....greater difference in width of
fretboard)   Make sense

A way to eliminate this in the design is to have the pieces that touch the
sides come in perpendicular to the center line equadistantly. Then the
taper wouldn't matter.azimmer138950.8236574074

_________________
Andy Z.
http://www.lazydogguitars.com

Ok everyone, I talked to my partner who did the programming and I think we have pieced this together to find out how we made a mistake. Jon is correct, it will not work the way it is currently designed. However, it was worked up in CAD/CAM to take into consideration only a slight taper, and this was the mistake. The more the taper the more it is off. My partner thought a 1/64" off was an acceptable tolerance. But with a normal taper it is more like 1mm off at the bridge. This is not acceptable.

Ok, so now how do we fix it. There are many ways to fix this, but we are just trying to figure out the easiest and most cost effective way to fix it. The problem is that he is out of town this whole week and won't be able to get to the fix until Monday next week. Our fix so far is to add another swivel arm to each hole making it look like an X in 2 locations. This would cause an equadistant contact with the side and eliminate the taper issue. Anyone who wants their money back just let me know. Otherwise, my advise is to sit tight and I will let you know what the fix will be. If it means shipping another updated jig, then that is what it will be. I'm sure I'll make it worth your while to sit tight. By the way, all the orders shipped this morning except for about 5 of them. So most should receive it on Wednesday. Also, we have designed a bridge square additional piece that should slide onto the existing jig allowing you to center and square your bridge all at once. I'll be receiving the prototype Wed, and will let you know if this will work.

If you want to get an idea of how it will work, you could just wrap tape around the dowel on both nut side dowels until the centerline lines up with your marked centerline. Then you can test it correctly. I'll keep you all posted. Thanks for your patience, and from the bottom of my heart, I'm truly sorry about this.
Tracy

_________________
Tracy
http://www.luthiersuppliers.com

Seems like the easiest fix would be to have the "pin" that contacts the neck/fingerboard side adjusted slightly. The fix would be to have the contact that is more towards the headstock side be slightly larger in diameter than the pin that rotates towards the bridge side. Referring back to Jon's CAD drawing, this would shorten the line segment between the midpoint and the upper contact point (as drawn by Jon), bringing the centerline back in line.

(edit: Reading Tracy's post more carefully, this is the same as the tape around the nut side dowel. D'oh, sorry Tracy. Suggested fixes still apply.)

The restrictions here are:

(1) the pivot would have to be set up so that the larger pin was always on the side that rotates towards the head. This is not a problem if the unit is designed to not be dissassembled.

(2) The adjustment in pin diameter would only work exactly for a single taper. This problem could be circumvented by providing a pair of pivot arms for each of several common tapers, but this in turn breaks rule (1) above - there would have to be a foolproof way to make sure that the user was installing the pivot arm with the wider pin on the correct side.

(3) or, have the pin that is to be adjusted consist of a narrow center pin, and then provide a set of sleeves, a pair for each desired taper to slip on the pin for each swivel arm. This fixes rule (1) - the unit would not be dissassembled to change for a different taper. The sleeves could be friction fits over the center pin, or there could be some sort of tapped screw and washer at the end to hold the sleeve on. Or, have the whole pin have a threated insert that screws in and out of the swivel arm.

I'm thinking that there may still be an issue with the adjustment for a given taper not being exactly the same if the fingerboard width changes. I'll work on this more this evening if nobody tackles it today before me.

Jim Kirby

jtkirby38951.3337384259

_________________
Jim Kirby
kirby@udel.edu

I had thought about what you were talking about, Tracy, in adding an extra swivel arm. The problem is that when the X closes and grips the wider side of the taper, it's not going to close all the way down on the narrower side. And if it only grips on the two points, the "swivel X" could rotate slightly and make the jig off center.

I've actually been running around ideas for a jig like this in my head for a while now, but I can never seem to come up with anything that doesn't include a lot of linkages and sliders and such. Seems like there should be an easy way to do this with just a few moving parts.

_________________
______________________________
Jonathan Kendall, Siloam Springs AR

Tracy,

While I am very new here I can tell you are a man if integrity and I am staying on board with the jig and a remedy.

I still don't comprehend the geometry but I trust the census of those that do.

Guess I need to brush up on geometry to prevent costly errors and catch things in advance.

Measure twice cut once is only as good as your tools and using them appropriately.

Jon,
Good information! I'm wondering if it matters that the bottom of the X contacts the side of the neck, but the upper wings of the X will still be parallel to the centerline when it contacts, isn't that right? I'll let my partner figure it out, I don't pretend to be an expert on this, as my partner did the design. I'll keep you posted.
Regards,
Tracy

_________________
Tracy
http://www.luthiersuppliers.com

The X won't automatically stay parallel... When you think about it you could rotate the X at any angle you wanted around the center bolt, so the X isn't confined to being symmetrical with the centerline of the fretboard. (Too many "degrees of freedom" for you engineering types).

Frank Ford shows a pretty nifty centerline finder based on a Charles Fox design. The only downside is that you'd be a bit limited on fretboard width, so you couldn't use the same jig on guitar and mandolin, for instance.

_________________
______________________________
Jonathan Kendall, Siloam Springs AR

Just groove the plexi so that the little arm thingies slide up and down and self-tighten on the neck edges. Don't have them turning like that, and you won't have a problem. I would also use some sort of soft tubing on the posts so as not to mar a finish.
Another consideration would be indexing cams instead of the rotating arm and posts. But that could be costly.
Don Williams38951.4593865741

_________________
"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."