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Fitting pegs with the aid of an infrared camera


Adrian Lopez
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In Johnson & Courtnall's The Art of Violin Making the authors suggest that in order to test the fit of a new peg one should spin the peg in the peg box and touch the peg against one's lips to make sure both ends of the peg are equally warm where they touch the peg box. I tried this and found it difficult to detect any heat with my body, so I figured I'd use my infrared camera (FLIR ONE Pro) to gauge the temperature. You can see at first glance in the last two pictures that the peg does not have good contact with the left peg box wall, so I will need to shim the peg in the shaper or adjust the blade to better match the reamer's taper. I'm sure most of you have your own approaches to this and they work well for you, but I thought I'd share this just in case anybody finds it useful or interesting.

The scroll and peg box before spinning the peg:

flir_20201125T005953.thumb.jpg.616683276e597ac8a7bc972951b93728.jpg

 

The peg, scroll, and peg box after turning the peg a few times:

flir_20201125T010023.thumb.jpg.cb488aa59e20c9dac773cc2514e2f99c.jpg

 

The peg removed from the peg box, showing only one side getting warmer:

flir_20201125T010037.thumb.jpg.8f7f6e9e423a0544d2dbaa203ab0afd7.jpg

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8 hours ago, Andreas Preuss said:

Looks like overkill to me. 

It I s possible to adjust pegs to hard or too soft and get the infrared camera result right.

For smoothest turning the hole must be smooth (can't be measured with infrared) and I try to get a pinch more pressure on the side of the peg head.

This is only meant to substitute for the specific trick described in Johnson & Courtnall where you touch the peg to your lips. If you don't do that or you don't need anything more precise then of course there would be no point to the IR camera. Luthiers have managed to do without infrared cameras literally for centuries so it's not like this is really necessary, but I find it an interesting visualization and a possible aid. It's not intended to be the sole method by which the fit of the pegs is judged.

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12 hours ago, Adrian Lopez said:

In Johnson & Courtnall's The Art of Violin Making the authors suggest that in order to test the fit of a new peg one should spin the peg in the peg box and touch the peg against one's lips to make sure both ends of the peg are equally warm where they touch the peg box. I tried this and found it difficult to detect any heat with my body, so I figured I'd use my infrared camera (FLIR ONE Pro) to gauge the temperature. You can see at first glance in the last two pictures that the peg does not have good contact with the left peg box wall, so I will need to shim the peg in the shaper or adjust the blade to better match the reamer's taper. I'm sure most of you have your own approaches to this and they work well for you, but I thought I'd share this just in case anybody finds it useful or interesting.

The scroll and peg box before spinning the peg:

flir_20201125T005953.thumb.jpg.616683276e597ac8a7bc972951b93728.jpg

 

The peg, scroll, and peg box after turning the peg a few times:

flir_20201125T010023.thumb.jpg.cb488aa59e20c9dac773cc2514e2f99c.jpg

 

The peg removed from the peg box, showing only one side getting warmer:

flir_20201125T010037.thumb.jpg.8f7f6e9e423a0544d2dbaa203ab0afd7.jpg

Looks great!

If you play the instrument for a while does it show if any areas warm up?

This might be another way of doing modal analysis.

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17 hours ago, Andreas Preuss said:

Looks like overkill to me.

I think the infrared images are kinda cool. Not everyone learns in the same way, or processes information in the same way.

I'm some sort of weird mish-mash between a traditionalist, and a techo-nerd. Think I've benefited from both, slightly more than I've been harmed by either. :D

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10 hours ago, Adrian Lopez said:

This is only meant to substitute for the specific trick described in Johnson & Courtnall where you touch the peg to your lips. If you don't do that or you don't need anything more precise then of course there would be no point to the IR camera. Luthiers have managed to do without infrared cameras literally for centuries so it's not like this is really necessary, but I find it an interesting visualization and a possible aid. It's not intended to be the sole method by which the fit of the pegs is judged.

Agree.

I am just making this point because some violin making novices might get the wrong idea about fitting pegs properly from the beginning.

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