rarecellos Posted June 15, 2005 Report Share Posted June 15, 2005 Recently I heard from a Luthier friend there is a new product- laser caliper available. Has anyone seen it? The old $400 thickness measuring machine- caliper, that pen-looking thingy, or whatever you call it, is not really accurate. rarecellos Quote Link to comment Share on other sites More sharing options...
MANFIO Posted June 15, 2005 Report Share Posted June 15, 2005 Why not a normal dial caliper? Strad's calipers were far from being acurate. We don't need all that precision, I think. Quote Link to comment Share on other sites More sharing options...
Jeffrey Holmes Posted June 15, 2005 Report Share Posted June 15, 2005 You mentioned the "pen-looking thingy". Are you referring to a "top on" (measuring through the plates when the instrument is up and running) type caliper (the magnetic type)? I haven't seen the laser style... I'd be interested to know how that works. The magnetic type is accurate enough as long as you calibrate it regularly, but the spring does stretch a bit. Quote Link to comment Share on other sites More sharing options...
GMM22 Posted June 15, 2005 Report Share Posted June 15, 2005 Does the magnetic type require an object to be inserted inside the instrument? Quote Link to comment Share on other sites More sharing options...
nertz Posted June 15, 2005 Report Share Posted June 15, 2005 yes, a small magnet. Quote Link to comment Share on other sites More sharing options...
GMM22 Posted June 15, 2005 Report Share Posted June 15, 2005 If I visualise its use, it appears as somewhat tricky. Is this the case, and is measuring on the far side of the bass bar particularly problematic? Quote Link to comment Share on other sites More sharing options...
fiddlecollector Posted June 15, 2005 Report Share Posted June 15, 2005 Its called an Hacklinger gauge or similar spelling. Quote Link to comment Share on other sites More sharing options...
Andres Sender Posted June 15, 2005 Report Share Posted June 15, 2005 GM people use it regularly to map entire top plates of closed instruments. Quote Link to comment Share on other sites More sharing options...
rarecellos Posted June 15, 2005 Author Report Share Posted June 15, 2005 Yes, I am aware that Stradivari might not have the precision tool we have today. However, there are times that precision is still preferred, at least by me. Even Stradivari had some tools. I hope not everything is done by guesswork. Even the greatest masters have their faults. Do you like Kreisler's playing? I do. But to get certain colors he was known to play out of tune on quite a few occasions. Now, I don't think I would tell my students to copy his intonation- a bit too expressive at times. Let's say I am buying a violin, how do I know if the top has not been graduated too thin?? Well, to find out I would need an accurate caliper. The magnetic caliper being sold is not entirely accurate- you are supposed to hear that popping sound and read the gauges at the same time. The margin of error is too great for me. As far as the laser style, it is just a "Loch Ness" monster, I haver never seen it. So for all I care, it probably doesn't even exist, at least not for violins. rarecellos Quote Link to comment Share on other sites More sharing options...
nertz Posted June 15, 2005 Report Share Posted June 15, 2005 It might be that the Hacklinger gauge is rather tricky to use accurately if you are not practiced with it, but I can’t possibly see how it could not be accurate enough to tell if a new instrument is graduated dangerously thin. Quote Link to comment Share on other sites More sharing options...
MANFIO Posted June 15, 2005 Report Share Posted June 15, 2005 Hi rarecelli! You are right, I thought you were talking about calipers for new making. Quote Link to comment Share on other sites More sharing options...
Andres Sender Posted June 15, 2005 Report Share Posted June 15, 2005 FWIW, I agree entirely with Nertz. There are past threads here which discuss the issue of ‘over thin’ tops. Given that many good classic instruments go down to 2 mm in places, precision in checking for over-thinning is not necessary. The real objective standard is not the measurements (so long as they are within ACTUAL normal ranges, rather than arbitrarily prescribed ones), but how the particular instrument sounds and plays. Quote Link to comment Share on other sites More sharing options...
Oded Kishony Posted June 15, 2005 Report Share Posted June 15, 2005 Do you have a method for adjusting an old Hacklinger guage? Mine is sadly out of shape. I recently purchased a Gaussmeter (measures magnetic fields) but I haven't been able to rig it up as a measuring tool. Oded Quote Link to comment Share on other sites More sharing options...
Jacob Posted June 15, 2005 Report Share Posted June 15, 2005 I also agree. Thickness measurements to the nth degree mean nothing without taking into account the wood quality, the model, and "weight distribution" (another telling phrase from Michael). If this were not so, all those classical Italians wouldn't have amounted to much. I could of course add my own personal experience, but that certainly doesn't amount to anything at all. Quote Link to comment Share on other sites More sharing options...
Andres Sender Posted June 15, 2005 Report Share Posted June 15, 2005 For the price of those Hacklingers they should come with a lifetime supply of replacement springs. Quote Link to comment Share on other sites More sharing options...
rarecellos Posted June 15, 2005 Author Report Share Posted June 15, 2005 For all practical purposes, maybe a Hacklinger (sp?) is enough- but then it is hard to use, and breaks down easily. It would be nice to have something better. Did someone suggest one can find out the thickness of the wood just by playing the violin? I hope not... This dicussion reminds me of the conversation with my auto mechanic... just use a Lincoln penny to see if the tire thread is still good. Actually that's not bad, probably more accurate than a Hacklinger... rarecellos Quote Link to comment Share on other sites More sharing options...
Jeffrey Holmes Posted June 15, 2005 Report Share Posted June 15, 2005 I'm sure something better than the magnetic calipers is down the road. They were certainly an improvement on the old mechanical ones that fit through the ffs... Maybe ultrasound calipers are next? As our industry is rather small, we'll probably need to wait 'till the technology is used to creat a device used in a larger market (maybe tires? ) I'm still curious how a laser might work... Can't get my head around that one (can't see how an optic measurement could be made with the fiddle together). I'm probably just missing part of the method. If you hear more about this from your luthier friend, please let us know, OK? Quote Link to comment Share on other sites More sharing options...
HongDa Posted June 15, 2005 Report Share Posted June 15, 2005 Oded, Here's a copy of a paper that came along with my Hacklnger. [image][/image] Quote Link to comment Share on other sites More sharing options...
rarecellos Posted June 16, 2005 Author Report Share Posted June 16, 2005 Interesting read (it looks like they used an old type writer for that one or is that an Apple II??). The German company that sells Hacklinger should be happy that the Chinese have not made cheaper and better (or worse?) copies. If the spring in that $400 little tool breaks, good luck! Yes, Jeff, as I said the "laser caliper" at this point is just a Loch Ness monster. I will let you know if I get more info from my spies. Maybe we can ask the CIA or the former KGB to make one for us. rarecellos Quote Link to comment Share on other sites More sharing options...
HongDa Posted June 16, 2005 Report Share Posted June 16, 2005 I came across some laser thickness measuring devices on google but they look pretty expensive and for lab use. I'm not sure how this works but it looks interesting: web page Quote Link to comment Share on other sites More sharing options...
Oded Kishony Posted June 16, 2005 Report Share Posted June 16, 2005 HongDa, they are using ultrasonic waves not laser light to measure thicknesses. I can't think of how a laser could be used to measure a violin corpus. Magnets are a good simple method but the Hacklinger version is somewhat limited. An electronic version of a magnetic measurer would be more accurate and versatile. The tool that measures magnetic fields is called a Gaussmeter. Oded Quote Link to comment Share on other sites More sharing options...
violinmark Posted June 16, 2005 Report Share Posted June 16, 2005 Laser Calipers are used extensively in the paper and foil manufacturing industries. It is a contactless means of measuring thickness for material that is travelling about 80mph without disrupting it. (so it doesn't tear) Off the shelf a laser caliper is available that has an accuracy of 0.001 inch and can measure up to 15mm thickness. There is also a laser caliper on the market that is used in the logging industry to quickly add up log thicknesses while they are still on the truck - very coarse. Both are fairly large and expensive for what we would want to use it for. No laser caliper can now measure the plate thickness %100 from the outside, there needs to be something on both sided of the plate. May I suggest that a Hall sensor thickness meter may be a viable and cheeper option than the Hacklinger gauge. It is an electronic version of the hacklinger that works similar to the Hacklinger. Search on A3515 Ratiometric Hall Sensor/ Magnetic Position Detector/ Magnetic Field Strength Meter (or A3422 Magnetic Directional sensor or ATS610 Gear Sensor A3141 Stacking Hall sensor) I think Radio Shack carries them. If somebody wants to give it a shot, I may have a basic circuit schematic to get them started. Example of Hall sensor usage Quote Link to comment Share on other sites More sharing options...
Oded Kishony Posted June 16, 2005 Report Share Posted June 16, 2005 Violinmark, how does it work and how much would it cost? OK Quote Link to comment Share on other sites More sharing options...
violinmark Posted June 17, 2005 Report Share Posted June 17, 2005 Oded, The hall sensor outputs a DC current that relates to the amplitude of the magnetic field it is in. Basic circuit would be a hall sensor ($6), couple bias resistors ($1), a LM741 op-amp ($5), a 9V battery ($5) a small strong magnet ($2), and a lump of IRON (bolt), output to a voltmeter. You would need to calibrate a relationship of wood thickness to output voltage. You might need to experiment to figure out what the right strength magnet is needed to work through a distance of ~1-5mm and not saturate the sensor but still strong enough to stay stuck to the underside of the plate. Attached is a basic ckt. It would need to be modified for sensitivity and you would substitute a voltmeter in place of the LED. Quote Link to comment Share on other sites More sharing options...
Ron1 Posted June 21, 2005 Report Share Posted June 21, 2005 I have an article somewhere, that describes the use of magnetic resonance imaging (MRI) for cross-section images of instrument bodies. An infinite number of cross-sections can be imaged. The article has some pictures of the results, which were pretty cool. The equipment must be a little pricey though.. Quote Link to comment Share on other sites More sharing options...
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