This contraption?

[baroquecello]

Thank you, gentlemen, for the in depth explanation!

[carl1961]

 

 

 

https://www.thingiverse.com/thing:5561441

[Davide Sora]

53 minutes ago, carl1961 said:

Beware Carl, Davide Sora is a registered trademark (this is true), I hope my lawyer does not see this post, or he will send you an injunction to ask you for the copyright...

[carl1961]

2 hours ago, Davide Sora said:

Beware Carl, Davide Sora is a registered trademark (this is true), I hope my lawyer does not see this post, or he will send you an injunction to ask you for the copyright...

Oh I will remove then, I was really given you credit for the design lol

 

[FiddleDoug]

22 hours ago, Crawforde said:

This is brilliant. Thanks 

how much play is there once it’s squeezed shut to measure/ mark? 

The stop is solid. The only play is a very tiny amount of springy flex in the arms. Considering that it's really used as a "touch" thing for the pencil, it's not significant.

[Davide Sora]

2 hours ago, carl1961 said:

 I was really given you credit for the design lol

 

Thanks, I appreciated it, but I think you can put your name in the place of mine, since the idea is not so original and innovative, and surely you have worked harder than me to do the project for the printer software, than the time it took me to design and build the wooden ones.

Hoping that Don won't make any claims for the idea of the elongated cut...

[CaseyLouque]

@carl1961

What about replacing many tools with one. Since we can 3d print it we have a possibility to improve it? 
I can design an STL when I get off work unless you feel so inclined.

I had an idea for “keys that are stored in the tool that you can change the distance with a quick swap. 
 

could even add spots for neodymium magnets to be inserted  into the part and keys so they “snap in place” 

[Davide Sora]

15 minutes ago, CaseyLouque said:

@carl1961

What about replacing many tools with one. Since we can 3d print it we have a possibility to improve it? 
I can design an STL when I get off work unless you feel so inclined.

I had an idea for “keys that are stored in the tool that you can change the distance with a quick swap. 
 

could even add spots for neodymium magnets to be inserted  into the part and keys so they “snap in place”

It's a good idea, but replacing parts takes time, swapping tools it's faster and less annoying. Not to mention the possibility that the interchangeable parts will not stay firmly in place, or that they will take some slack over time. Perhaps a system with a strong magnet could work, and speed up shim replacements.

But a strong point of my system is the support surface extended to the whole arm, which gives a lot of stability. By reducing this surface with smaller interchangeable parts as in your drawing, the use of the tool becomes more problematic and less efficient.

[CaseyLouque]

I have two other design possibilities but not sure about hinges and the slop they can introduce. 

would address one concern but possibly cause another. 
 

I’ll show anyways. Someone might point out further flaws I didn’t think of.

first would be similar to a compass.

Second would be a ladder type notch on each side.

I may just have to design print and test. 

 

[Don Noon]

I would make a fixed "C" frame with the clamped pencil on one arm, and the other arm I would have a threaded knob like the one below.  I'd use a M14-2 (1 turn = 2 mm), to get a decent range without too many turns, but still accurate enough if you scribe a line on the knob and pay attention.

[Don Noon]

I was starting the min-project of making the marking caliper I described above, looking thru my woodpile for something appropriate.  I'm still too incapacitated to work on violins, but this seemed doable. 

Then I thought I'd look at my Juzek marking caliper.  It was running low on the OEM crayon-type marker, which gave me an excuse to replace it.  I realized I could replace the crayon and holder with a normal artist's pencil if I cut the pencil diameter down a few thousanths of an inch, which I did on the lathe.

Then I thought I'd check the caliper operation on a plate... and realized that I CNC both sides of the plate before scraping, so the marker is useless for them.  It has been over a year since I ran the plates on the CNC, so I kinda forgot.

I still might have use for the marker, as I might hand-carve a few plates in the future, so it wasn't a total waste.

[carl1961]

3 hours to print (While I was sleeping)  picture is first test that proved I needed the throat deeper, changed to 24mm, added 4 sizes

[Nick Allen]

On 10/11/2022 at 5:47 AM, Davide Sora said:

It is very simple, there is a cut in the wood and the screw (with nut) tightens this cut blocking the pencil, there is no contact between the screw and the pencil. The nut is held in place with cyanoacrylate glue to keep it from rotating, the screw is tightened with a screwdriver and the pencil must be moved manually when the screw is released. Traditional yellow pencils should be HB (#2)

I use carriage bolts. They are the round head ones that have the square part under the head that digs into the wood. This locks them in place. Then just put a wing nut on the other side with a washer. No extra tools needed. 

[Davide Sora]

2 hours ago, Nick Allen said:

I use carriage bolts. They are the round head ones that have the square part under the head that digs into the wood. This locks them in place. Then just put a wing nut on the other side with a washer. No extra tools needed. 

I must confess that I have not thought much about what could be better for the locking, I simply used what I had at hand at the moment, which was the screws and nuts that you see in the photos. I didn't even care too much about the aesthetics (just a bit...), for this kind of tools I only pay attention to functionality to save time.

My first prototypes, which I still use, do not even have locking screws, the pencil is held in place just by pressure, adapting its diameter to that of the hole to make it lock but also allow it to slide, even if it takes a bit of strength and it is not at all comfortable to move the pencil, so the screw loking system is recommended.

 

[Davide Sora]

4 hours ago, carl1961 said:

3 hours to print (While I was sleeping)  picture is first test that proved I needed the throat deeper, changed to 24mm, added 4 sizes

Nice!! But the color is terrible

It is advisable to make at least two rather short and not too high ones, to trace the outermost contour lines, and others longer and higher to reach the highest elevations and trace the innermost isolines. To optimize stiffness and also save material. Make sure that the surface that rests on the underside of the plates is flat and smooth, so as not to damage the gluing surface of the plate.

[Evan Smith]

https://www.internationalviolin.com/ProductDetail/t962_marking-caliper-for-vn-va-ce

I have used these, work's ok, but barely,,

It will do a full plate, or one that has been graduated,,,

way too complicated,,,

[Evan Smith]

On 10/11/2022 at 3:47 AM, Davide Sora said:

I

Davide!

What I want to know is,,

why are there glue ghosts on your contraptions?

And is that debris that I see,

[Evan Smith]

Got to get up real early to get ahead of "The Doug"

[carl1961]

1 hour ago, Davide Sora said:

Nice!! But the color is terrible

It is advisable to make at least two rather short and not too high ones, to trace the outermost contour lines, and others longer and higher to reach the highest elevations and trace the innermost isolines. To optimize stiffness and also save material. Make sure that the surface that rests on the underside of the plates is flat and smooth, so as not to damage the gluing surface of the plate.

Agree, Package said wood color , did not do good for the aesthetics .   I had to look that word "aesthetics" up after you said it in the post above. LOL

 

[Marty Kasprzyk]

Is there any experimental  evidence which shows that a nice symmetrical graduation contour pattern helps the sound quality?

[Michael_Molnar]

Instead of a hard graphite scribe, I had one that held a small hobby drill to cut a shape. The drill kept its height, never wore down.

Then I “graduated” to a CNC. Pun. 

 

 

 

 

[carl1961]

3 hours ago, Davide Sora said:

Nice!! But the color is terrible

It is advisable to make at least two rather short and not too high ones, to trace the outermost contour lines, and others longer and higher to reach the highest elevations and trace the innermost isolines. To optimize stiffness and also save material. Make sure that the surface that rests on the underside of the plates is flat and smooth, so as not to damage the gluing surface of the plate.

Thanks Davide for the info. I did not know actual dimensions so I imported your picture I snap shot  from your video into fushion360 and resized until the pencil was 7mm  so I got close, because it was a offset picture it was hard to get length and height (Reverse engineering LOL) I redone to 4 sizes . inside of throat...  Violin-Contour-Compass-124x24mm  Violin-Contour-Compass-109x24mm  Violin-Contour-Compass-124x29mm  Violin-Contour-Compass-160x29mm  

[carl1961]

1 hour ago, Michael_Molnar said:

Instead of a hard graphite scribe, I had one that held a small hobby drill to cut a shape. The drill kept its height, never wore down.

Then I “graduated” to a CNC. Pun. 

 

 

 

 

LOL, CNC nice to get you close , but you still have lost of work by hand. I only been able to cut metal brackets for my 3d printer with my china cnc, I did buy it to rough carve violin plates but never adventured to that level. I am waiting to buy your book showing us how to cnc violins  hint hint.

[Davide Sora]

6 hours ago, carl1961 said:

Thanks Davide for the info. I did not know actual dimensions so I imported your picture I snap shot  from your video into fushion360 and resized until the pencil was 7mm  so I got close, because it was a offset picture it was hard to get length and height (Reverse engineering LOL) I redone to 4 sizes . inside of throat...  Violin-Contour-Compass-124x24mm  Violin-Contour-Compass-109x24mm  Violin-Contour-Compass-124x29mm  Violin-Contour-Compass-160x29mm  

Unfortunately I do not have the exact measurements of those in the photos I posted, because I had made them when I was teaching at school for my class, and they remained at the school (I hope someone still uses them). But the measurements aren't critical, and the pencil is actually 7mm, so you did it right. Regarding the inside length of the longer ones, it must be enough to reach the innermost isoline when the caliper is located on the center line of the plates, therefore at most they must be as long as half the longitudinal length of the violin plate, providing a couple of them longer for violas and cellos. I like to have them as short as possible to keep them as stiff as possible, and more comfortable to handle when tracing. The throat heights you did are fine, mine are about 20/22 mm for the shorter ones and 24/25 mm for the longer ones, with 29 mm you can easily trace on cellos too.

[Davide Sora]

9 hours ago, Evan Smith said:

Davide!

What I want to know is,,

why are there glue ghosts on your contraptions?

And is that debris that I see,

I'm sorry, this time I neglected the finishes a bit, I was saving time, you know, school hours are a little tight (as I said I made these contraptions for my class at school). Glue ghost for the same reason, of the worst kind, cyanoacrylate ghosts, no ghostbusters can get rid of them.