A website for the serious amateur violin maker, restorer and tinkerer.    A violin front and back (the plates) can be tuned using tap-tones.    Use tap tones to adjust the 2 plates of a violin to get the best sound, the kind of sound you want, or make an instrument that is easy to bow.

This site has something for you if you are either making a violin or you want to improve  a low cost violin or viola.

By tuning the top & back plates you can get a good instrument that responds well to the bow and that can sound like a 1500 instrument.

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 Last updated  15th.   May 2012  (C)   Copyright          platetuning.org

Arching of the front and back, plus f-holes & bassbar

    For arching the plates, the best guidance I’ve found is in Sacconi’s book on Stradivarius’ violins called “The Secrets of Stradivari”, where he gives the ideal ‘contours’ of front and back plates, and tells us just where to put the highest point of the plate.

 You can use the long and cross ‘arching templates’ that so many books get you to cut out and use as guides, but I prefer the method that Juliet Barker teaches at CVM in Cambridge that can be found in her book.   While the inside of each plate is (perfectly) flat use a pencil gauge to create the arching contours of your choice. This ties up well with Sacconi’s ‘contours’ in his book mentioned above.

    I did cut out a cardboard contour guide (like David Langsather’s  and Sacconi’s) for use with the pencil gauge, but in reality? It’s really about a feel and look for arching, especially when you’ve made and handled a lot of violins. The contour guides are guides.

There’s also guidance in any of the various books on violin making in the ‘Really Useful Links’ page, but I discovered that Sergei Murgatov has written a book called “The Art Of The Violin Design” available on the web in English here that includes detailed arching (and sixths gauges) on pages 50 to 61. It includes arching for violas and ‘cellos too. He uses the the ‘Cornu spiral’ or ‘clothoid’ rather than the cycloid as the basis for traditional Stradivarius arching.

    There is an article about using Curtate Cycloids here, and many makers use the cycloid as the basis for arching templates: for instance there is an online calculator here, but this one does not give control of parameter ‘b’ for arching fullness.

  Recently I found that my best sounding violin has much fuller arching Arching based on cycloid - smllthan any ‘normal Strad’ copy, particularly on the back. So I needed to work out theoretical arching templates for this fuller, fatter arching so I can copy it properly.  Using the (curtate) cycloid curves in this spreadsheet I have calculated the arching for various cycloids from ‘flat’ to positively obese.

     Violin back (long) arches most seem to have a parameter ‘b’ of 5.5 (+-1, for a = 10), and I’ve checked that against the Strad. ‘Messiah’, Guarnerius (b = 5.3) and also Harry Wake’s (b = 5.9) and Henry Strobel’s  (b = 5.5) contour guides. The .pdf can be found above left. Note that the arch height is wildly exaggerated in these plots! Some violins have arching so full the cardioid shape cannot plot it at all.

  Don Morris has published some free plans for a “ 1720 Strad” violin. If printed on A4 they need enlarging by 65% to get full scale for a 356 mm body length. You can also buy plans of violins and other instruments off his site. Dimensions are in US inches. A copyViolin back arching 1 - Sergei Mugatov of his plans are here as a .pdf too. Standard measurements for 4/4 and fractional sized violins can be found on Alan Goldblatt’s site.

For belly plate Strad. arching: click on the picture right, and then right click to save it in the new window.  Other belly arching figures are here, and the belly sixths are here.Violin belly arching 1 - Sergei Mugatov

For back plate Strad. arching there’s a picture here, or click on the picture right:

    Other back arching figures are here, and back sixths are here.

 The front and back should really have different arches: the front (the belly) has a ‘flatter top’ to the long arch (and cross arching) than the back: often called a ‘platform’.  An outline and the arching templates for a ‘Strad.’ can be found here as upper part and lower part.

     These can be printed out full size (use the scaling print option for your printer) and then cut and glued together to match ‘X-X’ or the bridge line.

    The scaling is:-   overall length = 356 mm. 

    Max. width of upper bouts at template #1 = 2 x 82 = 164 mm.

    Max. of the bouts at template #5            =  2 x103 = 206 mm. 

      The same arching templates can be used for back and belly without much error for your first violin.

There is a chapter 5 of Roger Hargrave’s book available here on arching  a thicknessing, and a CT scan (!) of violin back and front plates here, which is an extract of a VSA paper by Borman and Stoel.

Bruce Ossman in his book on your first violin (see here) has the same the arching, back and front for simplicity, but there is no need to do so as you can alter it as you make it.

Here’s how Onnes Violins sets the arching on the back of a ’cello he’s making, using various workshop tools, including power tools! The same technique could be applied to a violin or viola but is very risky. He also has an interesting page on thicknessing and tuning the plates of a ‘cello here using a laptop and Apple’s ‘Perfect Pitch’ program.

The Strad Magazine has a scanned copy of Quentin Playfair’s article on cycloids from The Strad, 1999: you can download: Part 1, and Part 2. I met Quentin again when he taught at Cambridge (CVM, UK), and here’s a picture of him (centre) in the workshop. A skilled craftsman who knows a lot, and can tell it with tact. These cycloid shapes are much easier to create (draw) than to describe, especially in maths, as they use parametric equations. But it’s quite easy to create an arching profile using a spreadsheet, and then use the pencil gauge shown on the Tools page and are (much) easier to create than Murgatov’s clothoids!

ThMezzo Violin plate thicknesses - CMH in NYT articleicknesses of the front and back

   The New York Times printed an article in 1994 called “Perfect Violin - Does Artistry Or Physics Hold Secret?” which is available on Peter Zaret’s website here as a .pdf file. He has an interesting modification to the standard bassbar and other good stuff on violins. Anyway, the original article is difficult to read as the text is small, so I have reproduced Carleen M Hutchins’ thickness plans from it (see and click left) for a Mezzo violin (which is an oversize standard violin!), but the thicknesses are all but identical to Sacconi’s plate thicknesses for a normal violin. The text of the article is here.

    Right click it and use “Save target as ...” to save as a .jpg file.

 These plate thicknesses are final thicknesses, so initially your plates should be thicker than these.

  The thickness of front and back plates for great Guarneri ‘del Gesu’ violins can be found here, reprinted from ‘The Strad’ Sept. 2005. Borman Violins also shows some fascinating animations of violin and other plates here.

 There are also plans (A3 size) available for the Ole Bull Violin Project (the Ole Bull Guarnerius of 1744) than can be found on the Christophe Landon’s Violins web site. These include the shape, the arching and the plate thicknesses.

Erik Jansson also gives guidance on thicknesses in his articles “Acoustics for Violin Makers”, Chapter 5, Fig. 5.21, page 24.

Rough thicknessing: back
Fig 2 Back Thicknessing
      I have derived Fig. 2 above to shows where to thin a back plate to reduce either Mode 2, Mode 5 or both frequencies. Again, click on it to see the diagrams in detail. Right click it and use “Save target as ...” to save as a .jpg file.

The thickest point

      There is some agreement between the various reference book and other sources of back thickness data as to where the thickest point on a violin back should be.

Summarising these sources, and ignoring differences in plate shape :-

  • Stradivarius put the thickest point ~ 46% down from the top of the back plate [source: Sacconi and Courtnall and Johnson.],
  • Other sources (e.g. CVM, Juliet Barker and her team] and others) put the thickest point about halfway (50%) of the way down the back, and
  • Guarneri del Gesu usually put it ~ 55% of the way down,

with all distances measured from the bottom of the top block to the top of the bottom block. This ‘thickest point’ then acts as the centre point of the ovals or circles that guide the thicknessing of the central area. It is sometimes slightly offset by ~10 mm. towards the sound post: see the work of ‘Jack’ Fry below.

To get the back to the right kinCIMG4298 icond of thicknesses to start with I use a cardboard ‘pattern’ with cutouts as shown right. It’s a quick and  effective technique I copied off others like David Langsather. So choose your model, make your choice.

There’s an interesting YouTube video here showing how to use a ‘graduation punch’ in thicknessing a plate.

So, if you didn’t over-thin the back, then it is then ready for plate tuning!

Rough thicknessing: belly
Fig 1 Belly Thicknessing
I have derived a Fig. 1 above to show where to thin a front plate (the belly) to reduce either Mode 2, Mode 5 or both frequencies.

    Click on it to see the Figure in more detail.  Right click it and use “Save target as ...” to save as a .jpg file.

  This is a revamp of Erik Jannsson’s work referenced earlier, which itself seems to be based on Carleen Hutchinthinning plates for Modes 2 & 5 - Marty Kasprzyk ’s work of 1982, published in the CAS (VSA) Journal.

  In some forum discussions between Don Noon and Anders Buen on maestronet here one Marty Kasprzyk, a retired product development mechanical engineer, has produced an excellent illustration (click on it, right) of just where to thin a plate to reduce Mode 2 and/or Mode 5.

 As an example using this data, I recently needed to reduce Mode 5 of a viola belly without reducing Mode 2, so I took areas marked the colour orange in Fig. 1 above from 3.0 mm to 2.4 & 2.5 mm. This took Mode 5 from 278 Hz to 263 Hz, but left Mode 2 unchanged at 112.8 Hz.

The f-holes

 The Strad  f-hole shape can be taken for example from Stroebel’s book on violin making, or from an article in  Roger Hargrave’s site library where the article on the Mackenzie Stradivarius violin has dimensioned drawings with f-holes shown. The Strad ran an article on the detailed positioning of f-holes too, which is here. A 1733 Guarnerius is also described and drawn here, with f-holes and plate thicknesses.

The bassbar

The bass bar should be 5.5 mm thick, or 6 mm if the belly has low arching or has wide-grain. Its final cross-section shape will be a ‘parabola’ (inverted U shape): it is better high than wide.

The ends of the bassbar should be 40 mm from the top and bottom edges, but other makers end the bar when it is at the 3/4 way point from bridge line to top and bottom edge.

 The outside of the bassbar must sit 1.0 to 1.5 mm inside the left foot of the bridge, i.e. the bassbar must be under the left foot to take the pressure of the strings and pass the forces and vibrations to the belly. The top end of the bassbar (nearer the top block) needs to be ~2 mm closer to the belly centre-line than at the bridge position, or you can use the ‘sevenths’ method text books describe for more accuracy.   There was an article by Dominic Excell in The Woodworker, Jul ’96 (which alas is long since out of print) available here as a .pdf file. It shows how to cut f-holes and how to position the bassbar using the ‘sevenths’ rule.CIMG4300_1 icon

The picture right (click on it) shows the wood for the bassbar being chalk-fitted onto the belly. I use 2 or more thin blocks temporarily glued on with white glue to hold and guide the bassbar wood during fitting and gluing, and I also use brightly coloured chalk on everything but a Strad.: it’s easier to see than white.


      There are many shapes of bassbar: the fashionable one has a ‘hump’, but some of Stradivari’s originals were just a low flat bar. The Strad magazine has promoted a triangular shape (Jo Curtin, ‘Trade Secrets’, Nov ‘05, available here) with the highest point under the bridge.JL  bassbar smll I have had some success with a ‘flat topped bar’ (left) tapering down from a point 60+ mm. from each, as described by Patrick Kreit, and the shaping is easier. Or some makers keep the bar at full height just for the length of the f-holes. Take your pick.

You must now choose where the highest point of the bassbar is: at the bridge position or closer to the mid point of the bassbar, but best is to put it half way between the middle of the bar and the bridge lineBassbar height icon.

The figure right (click on it) shows the ideal (logarithmic) shape of the top of a ‘humped’ finished bassbar as it slopes from the highest point towards the ends. There are heights from 11 to 15 mm shown, but start shaping at no less than 15 mm.

This graph needs to be scaled of course, as the bridge position (the ff inside nicks) is closer to the bottom edge than the top! A typical finished bassbar is 11 to 12 mm high at its highest point (measured down the the belly on the inside, centre-line side) and is 6.8 mm high halfway (50% of the way) to the end in both directions, and the ‘half height’ point is 56% of the way to the end.

   The bassbar’s height needs to be reduced as you tune the belly plate for Mode 5 to get the Stiffness Factor you want. You will need to keep the bassbar’s top shape correct, so there’s quite a lot of measuring, checking, carving and planing (thumb plane work) to do. Note the bassbar needs to be rounded to a parabolic cross-section but is nearly semicircular at the ends. Reducing the bassbar height has little effect on Mode 2.

Raising Modes 2 & 5 in a thin back.

This thickness data is especially useful if you need to add a maple patch to the middle of the inside of a back that is too thin i.e. has too low a Mode 2 or 5. This is more like ‘doubling’ as it can cover quite and area. I’ve found that a wide patch of say 3 - 4 mm thick (which may be made up of layers of maple veneer) increases mostly Mode 2, and a long (length wise) patch of 3 - 4 mm thick increases mostly Mode 5. You will need to shape and then ‘chalk fit’ the maple patch before gluing or use layers of veneer, but I have sometimes used fluid Araldite (2-part resin glue) to stick a patch on a cheap factory fiddle, as the patch can be fitted less exactly - the resin glue acts as a filler, where animal hide glue does not.

There’s first-hand guidance on thicknessing in Sacconi’s book on Stradivarius called “The Secrets of Stradivari”, and in other books to be found on the ‘Really Useful Links’ page.

‘Fiddlehead’ has been working with the famous Jeff Loen on Strad plate thicknesses, and these can be found here for the Harrison Strad of 1693 for front and back.

Have a look too at David Langsather’s website page for a quick and practical approach. He has the thickest point about 55% of the way down the back.

Osnes Violins in Alaska (!) shows how thickness graduation is done here on a ‘cello, and shows plate tuning, cutting the ff holes, and fitting the bass-bar.  He uses a power router/cutter to remove the excess wood from inside the back of a cello.

Assembling a violin.

  Stewart MacDonald (StewMac) sell various violin items, and that includes a 4/4 violin ‘kit’.  The assembly instructions are rather useful too: they can be found here, and show how to insert purfling, the shape and position of a bassbar and how to attach the neck and fingerboard.


Physicist "Jack" Fry, with the help of violinist Rose Mary Harbison, has been working to rediscover the legendary sound of the Stradivarius violins.  William (“Jack”) Fry has a lot of interesting things to say about the effects of tiny local thickness differences, especially at the end of the fibres that go over the sound-post (over an area shaped like a ‘tongue’ of thicker wood), and an area at the violin’s edge at and above the right-hand f hole. The video of Jack’s lecture (1 1/2 hrs.) can be found at the website above.  His books titled “A Physicist's Quest for the Secrets of Stradivari” (with DVDs) are available here, and an article on him and his quest is here.  Many thanks to Jeff Minniear of Schenectady NY for the links and articles.