The other day Gene Howe asked about my process for obtaining the correct angle for stave cuts.  He probably envisioned reams of scribbled figures and diagrams, coffee-stained napkins with intense isometric sketches, and the like.  No, I used a free Stave Calculator posted by a guy who makes and sells his own drums.  A modern day Galileo. https://uniontownlabs.org/tools/stave/

 

Our exchange reminded me of an equally useful calculator link I was gifted by a luthier in Tatamagouche, the village in Nova Scotia.  An online Taper and Angle Calculation application hosted by Magafor (I think they make and sell specialty boring bits).  http://www.magafor.com/841/uk.htm

 

At some point a gent asked me to procure a 'good' violin for his daughter.  Jeff, of Little Deer Isle, Maine let a late 1800s copy of a famous 1813 violin go.  He warned me that the pegs were of the old 1:20 taper.  While I could shave new pegs, a reaming tool to 'touch up' the old pegbox would be costly, hard to procure, and perpetuate the problem:  When a new peg is needed, will an inattentive technician jam in the peg of a different taper?

 

After careful consideration, I modified the centenarian pegbox doing the unthinkable.  Removing wood.  Some haughty luthiers scoff, but is their scorn manufactured?  A sixth-generation European-taught technician was straightforward:  Yes, it is fine, to a certain point.  Based on rarity, age, value.

 

Break time!  I'll pick this story up in a bit.  How I used the angle calculator to turn this pile into a fiddle. 

 

 

 

 

 

 

 

 

 

Looks like my grandfathers of violin.

 

I found some neat formulae here-

 

https://www.blocklayer.com/

39 minutes ago, lew said:

I found some neat formulae here-

 

Thanks!  I'll use this on my first effort!  https://www.blocklayer.com/woodjoints/dovetaileng.aspx

 

When I put in steps 20+ years ago I did it the old fashioned way, drawing out rise/run ... times have changed!  Your link has several formulas which would work for staves. 

 

I used the angle calculator to determine exact angle of a 14" run (the length of a violin's strings) to rise 29.5mm (bridge height).  When that failed, what I had to do to reduce my rise by 10mm ... A collection of successes which led to a super fiddle crafted a few decades after the French Revolution being returned to playability.

 

(Failures x 20) + (Finally getting it right x 1) = Success

 

Along a related line, here is a calculator to determine compound miter for staves, tapered side totes, etc.   If you don't have MS Excel, you can download, then import into Google "Sheets" that is a free clone.  Hidden inside is some trig, but you can just keep your eyes closed and enter the values. https://cdn.popularwoodworking.com/wp-content/uploads/calc.xls

20 minutes ago, kmealy said:

Hidden inside is some trig, but you can just keep your eyes closed

How did you know? I've (actually) piped boilers in steel and copper with no tape measure. 

I think I had some trig for breakfast when I was in the hospital?

I tried to teach myself trig in an Home Study Engineering Course back in the '80s. 

 

That was the end of the course

On 3/5/2022 at 8:34 AM, Dovetail said:

 I'll pick this story up in a bit

As promised, I've posted the entire image series with recollections in Free For All (hobby luthiery) under the title:

 

Restoring an old fiddle

Don't even get me started talking about trigonometry.

I always go off on a tangent.

 

One technique I learned many years ago for setting an angle.  To verify, I made a 37 sided segmented section.  (an odd number so you can't just do two haves and plane out the middle). 

• Compute the angle that you need to cut. 
• Take the tangent function of that angle. 
• On a piece of scrap something measure over 1000 mm (slightly longer than a yard) and up the tangent of the angle. (tangent is side opposite over side adjacent of a right triangle) in mm. Scrap picture frame mat works well for this because it's 40"
• Draw a line between 0 and the tangent value point.
• Carefully cut along that line a few inches (or cm).
• Cut of the piece and use that to set your saw bevel or miter angle.

Must've been what the surgeon used to figure out where to stab me in the back? I suspect trig wasn't his strong suit in college.

43 minutes ago, Grandpadave52 said:

Must've been what the surgeon used to figure out where to stab me in the back? I suspect trig wasn't his strong suit in college.

That would be a sight to see"a trig suite"