# Instruments and Equipment > Builders and Repair >  Hacklinger Gauge

## daveb

I am needing one of these to check some graduations on a great sounding mandolin. Anyone using one, and where is the best place to buy one. StewMac is kinda steep.

Thanks,
Dave

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## tope

I think I bought mine at International Violin. Google it and you will find a few suppliers. I have used mine many times and love it and am thankfull I bit the bullet and got it. It ain't cheap but I don't know of another tool that will do the job.

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## sunburst

I've _almost_ ordered one a dozen times, but it just seems too expensive.
I figured out how to make one, or at least something similar, but I can't find a spring with the correct spring rate. Anybody know a good place to look for small springs?

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## Chris Baird

I use one as well. I need one the way I build. They are expensive. There isn't much to it and the actuall materials aren't impressive but it works perfectly.

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## MarkG

I've used one of these for a couple of years, I bought mine from Dick Tools in Germany (honestly, that's what they're called). These currently cost about 285US for the 0 - 8mm version which stewmac sells for 385US. You'd obviously have to pay shipping etc., but that shouldn't be too much as they don't weigh much. They're on the web at www.dick-gmbh.de, they speak english too if you want to call them. They also have some other interesting luthier's tools mostly aimed at the violin builder and repairer.

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## PaulD

It seems like something most folks would use infrequently... maybe something worth doing a "co-op" or shared purchase. If there's a local instrument builder's club, group, or just local luthiers you know it might be worth discussing with them. 

John; Do you ever order from MSC Industrial Supply? They may have an appropriate spring. They also have rare earth magnets that may work well.

Chris; I'm curious why you need one for "the way you build." What do you use it for?

pd

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fscotte

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## sunburst

Paul, I got the magnets from MSC, but I can't find a spring with a light enough spring rate. I've been meaning to try making one from a mandolin string. (I suppose a guitar string would work too, but this _is_ a mandolin site.)

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## thistle3585

John,
 My dad represents a spring company. Drop me a note at andrew@auinc.com. I'll see if I can come up with something for you.

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## PaulD

Maybe tearing into something like an old tape deck (the springs that hold the feed rollers?), VCR, or one of those cheap postal/diet scales. Sounds like an interesting project... those Hacklinger gauges intrigue me.

pd

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## Chris Baird

I build my instruments thick enough that I know if it doesn't sound right that I need to thin it out. I always spend a few days with the instrument strung up in the white; taking wood off from the outside until it sounds how I like it to sound. I need a way to make sure I don't go too thin and that is why I need a hacklinger. Every instrument comes out with different graduations but the tone is consistently how I want it.

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## Dale Ludewig

I recently got a Hacklinger. Yes, they're expensive and evidently the company must hold patent rights on it because the cost is ridiculous. But- it does do what it's supposed to. I've been told (warned)- don't lose the little magnet you put inside the instrument. If you do, it has to go back to Germany, get a new magnet ($.10) and be recalibrated (moving the plastic strip with the markings on the outside of the tube). $50 I was told, perhaps plus shipping. 

However, what the thing does is unique. John, if you find springs of the right tension and consistency, you could stop doing repair and building mandolins and just make Sunburst gauges.

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## Michael Lewis

I looked ar Hacklinger gauges for a couple years before buying one, but it has really been helpful for making maps of the tops and backs of certain old instruments.

By using the Hack on some older archtop guitars (early L5s) discovered some insight to how graduations effect tone and projection. The expected thin area on the recurve, the expected gradual thickening moving away from the edges, and the unexpected thin area around the bridge. These guitars had a tremendous punch but not lots of sustain. For a small guitar they put out a lot of sound, enough to keep up with a big jam.

John, as long as you get a spring in the ball park of the rate you need you just calibrate the thing. Set it on a known thickness and when it clicks you mark that spot, then go to thicker and thicker known items to get your calibration complete. Probably best to use uniform pieces of pre sized wood or cardboard.

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## Jim Rowland

After I retired,I took a job delivering (mainly paint products) for an auto supply store. One item they handled was called a Tinsley gauge,which works on a similar principle to the Hacklinger,except that the magnet is contained in the in the gauge itself and is attracted to the (ferrous)metal body part of a car. The purpose,of course, was to measure the thickness of paint coatings. The price was in the same outrageous range as the Hacklinger gauge. I had the opportunity to question a company rep once about the reason for the price. His answer was that all the money was in the calibration process. I find this hard to believe,but he was not forthcoming with any ancillary information.
I believe that Frank Ford has devised, in his typically ingenious way,a little tool that can measure thickness in some parts of a top through the F hole. Otherwise,we are pretty much stuck with the Hacklinger for accurate measurements throughout the instrument.
Jim

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## PaulD

On a related note... for anyone that's interested: The Fall 2005 American Luthierie journal from the Guild Of American Luthiers has an article about measuring arch-top instruments by Chris Burt. I'm sure much of what he has to say is old hat to most of the builders on this forum, but it was new to me and I thought he had some great pointers. The reason I brought this up is that he uses a Hacklinger Gauge and feels it is well worth the money for what it does. 

Being a consumate do-it-your-selfer and a bit of a tightwad, I'm intrigued with John's efforts to make his own! I'm not at a point that I need something like that and the $300+ price tag could be allocated to other tools that I could put right to use, but I might approach the Utah Instrument Builders Association and see if some of the folks want to split on one.

Paul Doubek

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## Chris Baird

I'm not sure but I'll bet that each spring and magnet is a bit different and that the graduation scale not only needs to be precisely placed but possibly custom made to suit the exact tension of the spring which may vary. 
 But, I'll wager the main reason for the big $ is that the folks making them are actually making a decent living; as in this thing isn't made in china.

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## Dale Ludewig

Chris, I'm sure you're right.

I do have a question that perhaps someone out there can answer, 'cause I sure don't know. Does the spring tension, hence the calibration, change after time, and therefore the accuracy of the gauge? How many times can you pull on a spring, which is what we're doing with the Hacklinger, before the tensile strength (if that's the right term) change?

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## Stephanie Reiser

> #Does the spring tension, hence the calibration, change after time, and therefore the accuracy of the gauge? #How many times can you pull on a spring, which is what we're doing with the Hacklinger, before the tensile strength (if that's the right term) change?


Modern spring steels being what they are, coupled with the mild tension they'd be under in the Hacklinger, I'd bet that you can use it a very long time before any concern. However, you can always check the calibration with a known thickness if in doubt.

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## Steve Davis

As long as the spring doesn't deform it should retain the same properties.

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## tope

My Hacklinger has a decal on it with printed graduations. It looks to me that they have very little time in putting that decal on in the correct location on the tube when they are graduating each individual gage.

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## sunburst

Yeah, it looks like all you have to do is use a known thickness, and get the decal in the right place. I don't know. maybe they have several decals and they have to choose the right one. 

These things are simple technology, made from inexpensive, mass produced parts. I don't understand why the price can't be lower when you consider the price of, say, Grover tuners, or a set of dial calipers. I just spent a lot less to get two bearings replaced in the alternator of my American made car! I'm sure there's more to it than I know, though.

I think I remember trying to get a replacement magnet (to go inside the instrument) so that I could use it to experiment with while I was trying to make a gauge. They wouldn't sell one unless you sent them your gauge for re-calibration, and the price for that was what I considered outrageous. (cha-ching!)

I too have wondered about the spring and whether or not the calibration would stay the same with a lot of use. I also wonder how much difference temperature makes, though I assume any temperature difference would be negligible in the range of human (and mandolin) comfort.

My plan was to make a gauge that could be calibrated by the user in case things change due to use, damage, loss of the magnet, or whatever. Seems like it should take 15 minutes tops. What's so hard about that?

But,...I guess Chris is right. Whoever owns the company that makes those things probably makes a lot more money than I do.

OK, I'll shut up now...

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## PaulD

> Whoever owns the company that makes those things probably makes a lot more money than I do.


I don't know... what do you think the demand is for a Hacklinger thickness gauge? I imagine it's used in industries other than luthiery, but page 1 of a Google search turned up only luthiery applications (not to mention 2 places that sell the Model C 1-8 mm gauge for about $30 less than Stew-Mac). They may have a facility and staff that produces and calibrates a minimal number of these things... the laws of supply and demand would certainly drive the price up in this case. 

I imagine that there are pretty tight tolerances on the springs and magnets, but if there were a difference I could see where moving a calibration sticker might not cut it. The pull exerted by a magnet is an exponential function, and the spring's pull may not be linear either. I wonder how much tolerance deviation it would take to change the scale?

I've got a "DUH" question; how does the thing work?  I see that you stick the magnet in the instrument and pull on the plunger until the internal magnet pulls away from the loose magnet, but I assume the loose magnet doesn't just drop into the instrument to be retrieved like a wayward pick. I can just imagine someone holding a $150k Loar upside down and shaking it to get the magenet out after every measurement!  I've never had my hands on one... it must be more sophisticated than that for the price!

Paul Doubek

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## sunburst

When the magnet pulls away, it goes only a small fraction of an inch, hits a stop, and goes "click". It's still held close enough to the internal magnet that it holds it in place.
Tone bars and such can knock the magnet loose, and I bet there aren't many Loars that haven't had a magnet shaken out of them at least once.

BTW, I don't assume anyone is getting rich from making and selling Hacklingers. That product alone couldn't support much of a business. It just seems to me like anyone who has managed to figure out how to get that much money for something of such simple construction probably has enough business sense to have other ventures working in their favor too.
The demand is so small for the product, that there is not likely to be much competition to drive the price down.

Assuming (a stretch, perhaps) that the magnets and springs are very consistent, figuring out the scale with known thicknesses for the range of the gauge would need to be done only once. Each successive unit would only have to be calibrated to one thickness and the decal applied accordingly.
If there is slight variation in the magnets and/or springs, it would be like setting the intonation on a mandolin at the 12th fret. We then assume everything else is close enough, regardless of string gauge and/or action height.
If the variation is more that a little, you could come up with maybe three different decals and use the one that is closest. 
I don't think it would be practical to produce a new decal for each unit, but, with computers where they are now, that could be done with anyone's desk top computer and a decal printer.

Try as I might, I can't figure out how a Hacklinger needs to cost $300-$400 other than being the only product of it's kind with no competition in the market.

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## PaulD

John, thanks for the clarification. That makes sense... it just doesn't show up in the pictures.

I suspect the lack of competition, patent protections, and import tariffs/duties are the bulk of the high price. MarkG points out at the top of this thread that they are about $100 cheaper in Germany (still a lot of money for a tube, magnets, and a spring). I guess if several of us wanted to order one we should pool and order from Germany and split the shipping. 

I do like the thought of building one from scratch. There's a local electronics surplus (read: Junk) store that I might pop into to see if they have a box of springs. The lightest tension springs I've seen like that are, as I suggested above, in electronic devices such as audio/video tape players. 

pd

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## sunburst

Thanks for that idea, Paul. I think I'll have a chance to do some rummaging in some "junk" this week. 
I had pretty much forgotten about my thickness gauge project after my failure to find a light enough spring, and looking inside old electronic devices hadn't occured to me.

Projects sometimes lie dormant for years before becoming a renewed frustration once again. Looks like this thread has got me thinking about this one again.

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## Chris Baird

I was going to post a link to where I got a c model for $250, but just re-checked, and now 6 months later they are $350! Now that is too much $. Here is the link anyway -- Quinn.

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## mando_pete

I agree that the gauges are overpriced. But consider this...

Each spring will have a different tensile strength and thickness and needs to be calibrated to the individual magnet. The reason being that the thickness and space between coils will actually produce a different magnetic force. 
Each magnet will have to be calibrated to asssert the same magnetic force to each individual sping that is produced. The reason for this is that steel is impure and based on chemical composition asserts a different amount of force to an object.

The forces of attraction and rejection in magnetic objects, to be measured to any degree, are highly dependant on the molecular structure of the objects being measured and the composition of the object being measured.

The calibration from the factory is most likely very labor intensive.

To illustrate this, have you ever bought a cheap compass and wondered why North was off by ten degrees? Because the magnet was a cheapo piece of "fill in the blank".

What sounds unfortunate from this thread is the slap happy application of the label.

I'm not a physicist, I just stayed in a Motel 6 last night.

-- pete

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## PaulD

> ever bought a cheap compass and wondered why North was off by ten degrees


Funny... I thought that was the angle of declination! (12 to 15 degrees around here)  

I guess it would be easy to tell; if several people with these gauges gather in the same place, why don't you stand them all side by side and see if the calibration on the labels is different.

pd

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## Michael Lewis

It's easy enough to tell if the gauge reads correctly by measuring a known thickness.

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## daveb

Well, I guess i'm just gonna bite the bullet and buy one. I found the A model (0-6mm) for $318 at Quinn Violins. In about a week anyone want to rent one ?? LOL !!!

Dave

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## HoGo

John, I made one myself, and besides of being ugly as **** it works. It was pretty simple and I was able to make a modified one that is only 2 1/5" long and doesn't need you to pull a long wire to masure. Maybe I can get this patented.
You can make your own spring... I coiled an 'a' string on a small tube.... You may test several string gauges to find the one that works for you (I believe E or B guitar string will work for standard gauge), but you must have the magnets and the glass tube ready to attach the sting. Have two pieces of wood ready, one of the minimal thickness you are going to measure and the other of maximum. 
You want the magnets to separate almost immediately when the thicker one is measured and have to pull at least 3" until magnets separate for the thinnest piece.
Attach the spring and test what is the range between the two values. If you need stronger spring, consider shortening the spring by one coil and measure again...
After you reach the range length you want, you can take the thick piece of wood and graduate your gauge by measuring the piece and removing some wood, and marking points on the tube at each tenth of a mm...
BTW, I got the magnets from small refrigerator magnets. You can buy them cheaply, but check what kind of magnets was used. The one I have are about 3/8" diameter and 1/16" thick "pills". I used a pair of these on outside for a very strong spring, but you may try different combinations (I'd use one inside the gauge and varying number outside) of different magnets, and maybe you can make two different scales on your gauge, each for different outside magnet....
I hope this will work for you.
Adrian

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## sunburst

Thanks Adrian.
I've thought of making the spring, as you've suggested, and as I mentioned earlier. I just haven't tried it yet.
I've already got tubing, magnets, etc.
The tubing doesn't have to be glass, just non-magnetic, and I don't really care how long the gauge turns out to be. I figure longer pull equals longer scale equals more precision.
Ugly is OK too.

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## amowry

Speaking of ugly, here's the one I've been using for the past few years. They're great for mapping older instruments, but I also use it for recording and monitoring the final thicknesses of my own instruments, because I do a fair amount of thicknessing after everything is assembled.

The spring I used is a stock one from Ace hardware. I think the key is to find one that is as large diameter as possible, because larger coils yield a more sensitive spring for a given gauge of wire. I used the 1/8" rare-earth magnets from Radio Shack. There are two inside the gauge, and I use a stack of two in the instrument. You can dip them in liquid binding to hold them together and give them a protective coating. They're great because they are nice and light, but extremely strong for their size.

The tube I found is about 7" long, but I would have used a longer one if I had one, because as John says longer means better resolution and/or a wider range of possible thicknesses that you can measure. This one goes from 1.6 to about 8.0 mm, with 0.1 mm accuracy up to about 6 mm, and rapidly decreasing accuracy above that.

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## sunburst

I never thought of doubling the magnets.
The spring I've found separates the magnets at zero thickness after only about 3/4" of pull. The magnets will hold on both sides of a piece of wood up to almost an inch thick. Doubling the magnets might get me into a workable range.

I should have started this thread myself. I'm getting a lot of good ideas.

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## ellisppi

They are also used in the composite boat building industry. Why can't you convert magnetic force into an electronic signal and simply have a digital readout. No pulling the *@&%$# spring with your third hand. OK I'll be back in a couple of years with my new patented digital guage. I can make hundreds of dollars off this.

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## oldwave maker

Hacked into some ol' manalin at cmsa, some back grads in blue, top in orange, knock yusefs out, boys-n-girls. Dr. Cohen, Steve Stone and I decided somebody could make good money at loarfest selling genuine virzi bolo ties!

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## sunburst

Yikes! That one got a little thin down toward the tailpiece! No top deformation?

Virzi bolos would probably make more $ than digital Hacks, Tom. Easier to make too.

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## amowry

Thanks Bill-- that's a gem.

Hey Tom-- I struggled with that electronic gauge idea for a while last year. My idea was to use a Hall effect device (which senses the proximity of a magnetic field and outputs a voltage proportional to it) in the base of the gauge, and a microcontroller and lcd to make the conversion to mm and display the thickness. I tinkered too with having a USB interface so you can plug it into your PC and record thicknesses on the fly and import them into a spreadsheet.

The main problem I ran into was that you have still have to have another magnet in the base of the gauge to attract the one inside the instrument, and when you have that magnet close to the hall effect device, it tends to overwhelm the device, making it difficult to sense the magnet insid the instrument. The best results I had were from putting the hall effect device between the two magnets, right at the tip of the gauge, but it still is difficult to get a good reading. I finally decided I was spending too much time on it and abandoned it, but I still think it would be possible (probably easy for someone with a background in this stuff) and I think you could manufacture them very cheaply. I sure would buy one for $50 or so!

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## sunburst

OK, first of all, I don't know what I'm talking about here at all, but, that never stoped me before.

Andrew, if the magnet in the tube causes problems with the hall effect device, why not use just a piece of iron in the tube and a strong magnet inside the mandolin?

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## amowry

I did try that too, but I couldn't get the attraction to be strong enough to support the magnet, even when I used a 1/2" steel rod about 6" long. I was surprised that it didn't work. There must be some solution like that though.

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## Darryl Wolfe

Pic of Loar grads above, Date is actually "January". Thickness at tailpiece, I have 2 other mappings that are 2.6, but not as thin as 2.4

Hack gage, thanks for the great info, I'm making not buying now.

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## PaulD

Andrew; from what little I know about Hall effect sensors, I think sandwiching the sensor between the two magnets is probably the right approach... I suspect you were close. Maybe it's a matter of getting a sensor that is sensitive in the proper range, or amplifying the signal enough to read small changes. I also wonder if you have to have some temperature compensation built in or if the sensor is pretty stable in "normal" temperature ranges. I'm intrigued... by both the concepts of "hacking" a Hacklinger gauge and what it would take to make an electronic version.

pd

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## amowry

Paul-- I think the documentation for the hall-effect devices i got indicated that they are pretty stable within noremal temp. ranges.

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## Spruce

Mr. Bussman's post reminds me of the time a couple summers ago when Bill and I sat around at the Pagosa Folk Festival and Hack'ed every mandolin that came our way...

If you want to really blow your mind in terms of the graduations that various makers use, Hack some Gils, Nuggets, Sullys, Collings, and Old Waves in one sitting, and stare in wonder at the variation in approaches....

Wood does not vary _that_ much....

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## amowry

Yes, I've been surprised both by the range of thicknesses and by how very thick some of the tops and backs are on some very nice-sounding mandos.

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## sunburst

Yeah, that's one of the reasons I haven't bought a Hack. Thicknesses and graduations only tell a small part of the story anyway.

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## Ted Sinoski

Ive used a Hacklinger gage but consider that an electronic sensor solution offers an attractive alternative to a mechanical design like the Hacklinger gage::
- inexpensive
- more accurate
- easily checked and recalibrated
- smaller, can be located at otherwise inaccessible places
- no mechanical parts

The principal of an inside and outside magnet is used but the sensing element is electronic ( magnetoresistor) not mechanical.

A simple sensor can be created from single element magnetoresistor chip (resistance changes with magnetic flux through it) two thin wires and a DVM for measuring resistance. In my incarnatiion, two small .187x.062 disc neodymium-iron-boron magnets glued to one face of the chip and a spherical neodymium-iron-boron magnet .250 in diameter acting as the roving magnet inside the instrument creates a sensor with a usable range of 0-7mm corresponding to a resistance range of about 960-to 1710 ohms. This is nonlinear and you will have to calibrate it for a number of thicknesses. Using it can be tedious (table lookup and interpolation) for a lot of readings but the price is right. The chip, magnets and a positioning wand required about $10 worth of materials  you can build this yourself.

My current version is somewhat fancier and costlier. The sensor is interfaced through some electronics, an A/D converter and a program written in QUICKBASIC on an old DOS computer. However, I can store/check/update a calibration easily and enjoy continuous display of thickness in inches or mm. Accuracy and repeatability are at least .01 mm (.0005) in the lower part of the range and .03 mm (.015) at the upper end of the range. On a violin (original intended use) it is small enough to fit under the fingerboard and tailpiece of a violin and even under the bridge between the feet. It is equally useful on the ribs.

A viable and easier alternative would be to get a digital voltmeter with an RS-232 interface and program to that.

Woody McKenzie, one of your regular members suggested this post.

Ted Sinoski
ted.sinoski@lynchburg.net

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## Darryl Wolfe

Has anyone taken this DIY part of the discussion any further in the past 5 years.  I really hate to shell out that much money

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## j. condino

Darryl:
 Do you have the old bootleg copy of "how to make a hacklinger for $10" article that was all over the web a few years ago and then vanished? If not, we should chat....

j.
www.condino.com

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## sunburst

Imagine a USB electronic "hack" and a free download for your lap top to read the data...
Wish I was a computer wiz, I'd be rich!! rich, I tell ya!!

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## sunburst

Seriously, though, any computer types out there reading this? Is that a possibility?

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## Dale Ludewig

For all we know, there might already be an Ipod/Iphone app for this.  I ponied up and bought one some years ago.  Like some other tools, I can't remember the last time I used it.  But when you do, there's nothing else like it.  So how do the gauges work that measure finish thickness?

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## MikeEdgerton

> Seriously, though, any computer types out there reading this? Is that a possibility?


If the hardware delivers the data in any sort of normal fashion then the software isn't all that tough.

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## Dave Cohen

I just checked in my classical electrodynamics texts (Jackson, Shadowitz).  There is no specific example for the force as a function of the distance between two magnets, but iirc, the force should depend on the inverse 4th power of the distance between the two magnets.  The force to stretch a spring depends linearly on the force constant and the distance the spring is stretched, i.e., Hooke's law.

I may be missing something, but I think that there is really a much more affordable and accessible way to arrive at what this thread seems to be after.  That way would be the deflection testing/compliance mapping developed by David Hurd and independently by Don MacRostie.  All you need are a few dial indicators (really cheap nowadays from places like MSC or Enco) and some scrap pieces of wood.  Given the differences between individual pieces of wood, even in much revered historic instruments, the deflection comes much closer to getting at the behavior of the plate(s) than does the thickness.  Of course, even the deflection doesn't say anything about the internal losses in the wood ("Q").  To fully characterize a plate with the intent of duplicating its' properties, you want both the deflection and some measure of Q.  But even without Q, deflection measurements will get you much more consistency than will thickness measurements.

http://www.Cohenmando.com

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## Tavy

> I may be missing something, but I think that there is really a much more affordable and accessible way to arrive at what this thread seems to be after.  That way would be the deflection testing/compliance mapping developed by David Hurd and independently by Don MacRostie.  All you need are a few dial indicators (really cheap nowadays from places like MSC or Enco) and some scrap pieces of wood.  Given the differences between individual pieces of wood, even in much revered historic instruments, the deflection comes much closer to getting at the behavior of the plate(s) than does the thickness.  Of course, even the deflection doesn't say anything about the internal losses in the wood ("Q").  To fully characterize a plate with the intent of duplicating its' properties, you want both the deflection and some measure of Q.  But even without Q, deflection measurements will get you much more consistency than will thickness measurements.


Which then begs the question... is there a reference data point for how much deflection is about "right" for a given force applied to the top?

Curiously yours, John.

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## David Newton

There was a short "how to" in the GAL magazine either last year or the year before, to build a hacklinger-type gauge. It wasn't a tube, but a arched scale reading.

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## sunburst

> is there a reference data point for how much deflection is about "right" for a given force applied to the top?


There would be an optimal _range_ of deflection for each luthier and the sound he/she is after, but top density and internal damping figure into the equation too, as does the rest of the instrument, so like nearly everything else in lutherie, it's not as simple and deflection alone.

Perhaps measuring deflection would give us more information than a Hacklinger gauge if the goal is to replicate a sound closely, but to simply find out how thick something is, the Hacklinger sure is handy. I was glad to have Gail's "graduation map" for the Mando'-cafe-restoration-challenge mandolin when I was scraping, sanding, and preparing it for finish. I don't think a deflection measurement would have been much help.

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## Darryl Wolfe

Thanks all

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## Dave Cohen

I forgot to mention that the densities of the plate materials also figure significantly in the behavior of plates.  That is another reason why thickness alone can be misleading, and even deflections are not the whole story.

For a restoration project, you might want thicknesses, unless the condition of the instrument is so deteriorated as to need replacement of the plates.  On the other hand, if you are attempting to replicate the sound of a particular instrument in a new instrument, deflection testing/compliance mapping is a more direct route to the goal apparently expressed by the op.  The _American Lutherie_ article on MacRostie's jig can fill that in for you.  You can find the reference and an abstract on the GAL website, http://www.luth.org.  MacRostie has claimed good results by starting with deflection measurements on some valued instruments.

At this moment, I wish I had a nickel for every time someone on this board had posted about how they don't carve each plate identically.  That lends credence and support to the point that thicknesses alone may or may not get you to your desired goal.

http://www.Cohenmando.com

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## mikeyes

Surely there is an electronic device or a sonic device that can do the same thing out there somewhere?

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## HoGo

> Surely there is an electronic device or a sonic device that can do the same thing out there somewhere?


I believe the ultrasonic device is way more expensive than Hacklinger. And probably won't work on wood as nicely as on metals or plastics.



> Seriously, though, any computer types out there reading this? Is that a possibility?


Yes. I'm just half computer-half math type and I have few ideas waiting to get realized. I have to decide which kind of sensor to use and whether to build standalone unit (simple A/D convertor with display) or sensor connected to PC.
But there are so many things to do before I can spend more time on this.

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## Rick Turner

Anyone here have a Lucchi elasticity tester?

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## HoGo

> Anyone here have a Lucchi elasticity tester?


If you want to measure top/back blanks you don't need it. There are simpler ways. And WAAAAAAAAY cheaper :-).

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## buddyellis

I toyed around with this about 5 months ago with a mandolin string-spring, but never got around to finishing the job -- I think a fine piano wire string would work though.  I was wrapping it tight around a small nail, then heating it red-hot, and dunking it in oil to set the spring, and it worked pretty well.

Just realized this was an ancient thread, but like HoGo I've toyed around with some sort of electronic sensor, too, hooked up to a PC via an Arduino or similar interface, but just never have put the time into it.  Maybe one day.  Here's something along the lines of what I was thinking, but magnetic field sensing may be another option.

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## s1m0n

Here's the Hacklinger Patent (.pdf, 309k). More patent info here.

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## HoGo

My previous post was a bit mean so I'll write more now.
The electronic device is no more than one weekend job for your electronic/programming guru friend (if you know someone who fits the description) with the info from Ted Sinoski on page 2. The magnetoresistors are not widely used, so some experimenting will be needed. The advantage of PC connected sensor is ease of (re-)calibration. Standalone unit would have to be calibrated during its making.

Re the question of Rick. All you need is your PC with simple frequency analyser (such as part of Cool edit or Adobe Audition) and mic. Have a look here .

Buddy, are you sure that is Hacklinger patent? That one is quite old. How long a patent is protected? I recall I heard 18 years?

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## s1m0n

> Buddy, are you sure that is Hacklinger patent? That one is quite old. How long a patent is protected? I recall I heard 18 years?


It's the one that Dick Tools, which claims to have exclusive world wide distribution rights, cite on their Hacklinger  product page, so I assume so.




> Hacklinger Thickness Caliper, Version C
> 
> This unique tool allows exact thickness measurements of stringed instruments to be made without disassembly. The small counter-magnet is passed through the instrument’s f-hole and follows the gauge around every edge and curve, allowing the exact thickness to be measured at any place on the body. Accurate to within 0.1 mm, calibrated for making measurements while holding the gauge in a vertical position (horizontal use will result in a measurement error of +3%). Quick and easy to use, with no risk of damaging even the most sensitive varnishes. Ideal for the study of old instruments, locating old crack repairs, making sound adjustments, etc. Also suitable for measuring other, non-ferromagnetic objects (e.g.boat hulls, plastic containers, ceramic vessels, etc.). Comes in a leather sleave with instructions for use.
> 
> Exclusive worldwide distribution by DICK (Patent No. 3611798).
> Measuring range 1 - 8 mm, 1 magnet, wear-resistant plastic tip.

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## buddyellis

> My previous post was a bit mean so I'll write more now.
> The electronic device is no more than one weekend job for your electronic/programming guru friend (if you know someone who fits the description) with the info from Ted Sinoski on page 2.


Yea, I really just need to sit down with the Arduino and do some testing.  Cool thing about that unit is it has the USB interface built into it, so you are pretty well set to start off running with a minimal investment in startup design.  Programming would basically be a quite simple a->d conversion with a bit of simple math to do calibration to a known thickness or three.  The unit can also do output to generic LCD screens, so that is an option, too. My problem is I do this stuff for a living, and really don't have a huge interest in hacking when I get home rofl.  I'd much rather hack on wood.

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## fishtownmike

i would never pay the price these things cost. For a raw build a thickness caliper is all you need. I could see a use for it when needing to check out measurements of and existing instrument. But just because you know the measurements of a great sounding instrument doesn't mean if you build another using these specs it will sound as good. And the stew mac price is actually a lot cheaper then some that i have seen. A few carry this for about $470.00

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## j. condino

> i would never pay the price these things cost. For a raw build a thickness caliper is all you need. I could see a use for it when needing to check out measurements of and existing instrument. But just because you know the measurements of a great sounding instrument doesn't mean if you build another using these specs it will sound as good.


I used to feel the same way and resisted buying one for a couple of decades, and had about a dozen different "Rube Goldberg" type home variations. Since my personal new work has evolved and I'm now also in the psoition where every week I do restoration work on Loars, prewar Martins, D'Acquistos, D'angelicos, and some of the finest new builds in the world, I can honestly say that I would EASILY buy a Hacklinger if I had to pay for its weight in gold if I had to with out hesitation. 

While being able to accurately measure the numbers is just a small part of the total information you need, the ability to accumulate a very precise database over a large number of instruments is still an important tool for me. Since I started using one on every instrument that passes the bench, I've found that, much to the surprise of many customers, I can regularly predict within .5mm what the plate thicknesses are based on the voice of the instrument. 

Also, for doing historic documentation, publishing, and blueprints,  non-invasive, accurate measurements  are not just an option- they are expected, to the point where I've not only had editors check my written measurements- some have double checked my hack'd numbers to make sure we are giving accurate information to the public.

Long before I ever owned one, I used to go to a friend who had one and anytime I wanted to take some measurements, we had a deal where I'd offer up a few rupees or a sixpack anytime I wanted to use his. I always have that offer open to anyone who visits me....

All that aside, I'm usually the first to jump on the bandwagon about what a racket they have going by selling $9 worth of lightweight junk with a $400+ pricetag....

j.
www.condino.com

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## NRMiller1958

Back in 2005 I read the beginnings of this thread and set out to make a gauge for under $5. I ended up spending $2.44, and have been meaning to make a second one, documenting the process, but life took over and and I let it drop.  Seeing this now, I can't stand it any longer...

Buy a set of Radioshack Rare Earth Super Magnets (Model: 64-1895) = $1.99.  Drill a 1/32 hole through one magnet.  Take a 0.016 (A) string ($.45, though you don't need the whole thing) and grip it in your drill chuck along with a 1/8" bit inserting at least 1 in of the string into the chuck.  Run the drill real slow, holding the string tight enough to wind a tightly coiled spring roughly 1/2 in long.  Bend the remaining string 90o so it's parallel to the bit and leave a 5" tail beyond the coils.  Buy a cheap, Bic-type ball point pen whose inner diameter is uniform and just large enough to allow the magnet to slip freely inside (got it free from my church).  Pull out the ball-point part.  Pull out the little plastic plug at the butt end of the pen and cut off the wider end of the plug that keeps it from slipping inside the pen.  

Insert the spring with the long tail sticking out the business end of the pen.  Feed the short tail of the spring through the narrow (hollow) end of the cut plug, then through the magnet with the hole.  Bend it 90o leaving at least 3/4 in of play between the magnet and the plug, clip off the excess and superglue it to the magnet.  Shove the magnet & plug into the pen leaving about a 3/8 in. recess inside.  Now take the wider diameter disc you cut off the plug and tack it lightly with superglue onto the end you just inserted the magnet into.  Take the ballpoint part that you removed and clip off a couple inches of the non-writing end.  Insert it back into the pen, and tape or superglue it to the long tail of the spring (you might have to cut off the end a bit to accommodate both the ballpoint shaft and the tail of the spring).  

Calibrate using known thicknesses (I used a maple wedge).  I marked the shaft of the ballpoint part with a super-fine sharpie since I thought I might have to recalibrate periodically (I haven't).  Mine is marked every 0.002 and it's at least that accurate (same as the name brand).  The inside magnet hangs on even hopping over low tone bars.  My only complaint is the range.  This one measures from 0.100-0.220 pretty well, then it gets sloppy.  Someone smarter than me can probably figure out how to improve this.    

Sorry I didn't document my process more fully.  The hardest part was finding a pen of the right diameter to fit the magnet.  I looked at office stores a while before I lucked out at my church (OK, so the sermon was boring).  You'll have to play with the length of spring, depth of plug, etc. to get the results you need.  But you wouldn't be reading this post if you weren't good at fiddling with stuff.   Once you get it to your liking, pop off the plastic disc and superglue the plug permanently in place.

Oh yes, it also comes with a protective cover (the pen cap) that keeps you from losing the 2nd magnet when you're not using it.  Nothing is wasted...

$400?  I don't think so.

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## Geoff B

man if you had pictures of those steps (or just the one you made) that would be awesome!

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## fscotte

Thread resurrection.

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## Bill Moore

Here's the link I used to build my homemade hacklinger guage. 

Do it yourself hacklinger guage.

I bought an assortment of rare earth magnets from Lee Valley and then found a suitable spring at Home Depot.   I couldn't find a local supplier who carried the specific spring mentioned in the article, but found general specs for that model spring on the manufacturers web site.  I then found something close at HD.   If I can find the part number I'll post it.

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## NRMiller1958

Very nice work...

I tried to post pix of the ballpoint hack described in the above 2009 post, but I'm afraid I couldn't navigate the upload dialogue...I think I like the cigar-tube version better anyhow. 

Mine also has two magnets inside and one outside.  The spring is made from a mandolin string (details above).  Otherwise it works pretty much the same.  I used a fine sharpie to mark my calibrations.  That way if it gets out of whack (which happens if you use it a lot and stretch the spring) it's easy to recalibrate

One problem I have is that the inside magnet is a little tight.  The luthiers' forum cigar tube version looks gives the magnets more working space.  I also like the fact that it's clear & you can see the inner workings.

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## Bill Halsey

I enjoy building stuff from junk when I have the time for it.  Somehow, that's how the Hack gauge struck me.

My wish was to make it one-handed in use, so here's what I came up with a few years ago.  I spent a few bucks on the rare earth mags, but that's about it.  The torsion spring was modified from a discarded vacuum cleaner lid (Miele).  Accuracy is about +/- 0.1mm anywhere on the scale of 2mm to 6mm.



I imagine that a better bearing to support the coil/pivot of the spring might enhance its accuracy.  However, I do my voicing in the white, so exact physical measurements are not an issue for me.  I use this gadget more for doing grad maps of Loars & post-Loar mandos to identify general tonal characteristics as an aid to achieving specific goals in my own work.

There might be promising potential in the use of structural strain gauges (load cells) and magnets, if absolute accuracy were the goal.

Not in my lifetime.

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## HoGo

Once again I'd suggest simple setup a'la ted Sinoski:

http://www.mandolincafe.com/forum/sh...l=1#post209972

Or for those who would prefer something they can buy, read this quite old thread on Maestronet:

http://www.maestronet.com/forum/inde...owtopic=317992

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## lsnyman

I know this is an old thread but wanted to provide a solution.
I have developed this electronic thickness gauge.  Also no fishing for your ball after each measurement.
Contact me ifyou have an interest.
Liam

http://www.youtube.com/watch?v=UNBsi...layer_embedded

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## amowry

Pretty sweet! Nice work. What's the maximum thickness it can measure, and does the accuracy decrease with increased thickness?

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## lsnyman

Thanks.
I have limited it to 7.5mm, which is purely a limitation of the magnet being able to hold the weight. I can increase it if neccessary but you may have told the ball in place. Accuracy does not decrease with distance except for the human factor.
Thanks

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## fscotte

Duuuuuuude.  Please tell me this is real?  That is sweet.  I just may have to get that.

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## j. condino

:Disbelief:  :Disbelief:  :Disbelief: !!!!


j.
www.condino.com

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## Dale Ludewig

I agree with James, I imagine.  Holy Kripes.

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## Chris Oliver

> I know this is an old thread but wanted to provide a solution.
> I have developed this electronic thickness gauge.  Also no fishing for your ball after each measurement.
> Contact me ifyou have an interest.
> Liam
> 
> http://www.youtube.com/watch?v=UNBsi...layer_embedded


Finally... the Hacklinger has been hacked!!!

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## lsnyman

As I have had a lot of interest i am adding more info to the thread.
The device has a resolution of 2 mils or approx 0.05mm. I choose to rate the accuracy at 0.1mm as we are dealing with magnetics and sometimes the measured value may be on the border and toggle between for example 2.25mm and 2.3mm.

<Removed by Moderator, please limit selling to the classifieds. They are free. You can place a link here to a web page, that is acceptable>

Thanks
Liam

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## Chris Oliver

Liam,

Does this have to be recalibrated for other wood species (mostly just differing density)? Spruce vs. cedar vs. redwood vs. maple, etc., etc.?

If so, is this easy to calibrate?

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## fscotte

Can it measure in inches?  I like to see grads as .160" as an example.

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## lsnyman

Hi Chris
No, not at all. The unit will measure the thickness of any non- ferrous material, wood, plastic, aluminum, brass, paper etc.
The calibration is done in the software at manufacture and no calibration after that is needed.

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## lsnyman

Yes, it measures in both mils which is 1000th of an inch and metric mm. The resolution is 2 mil which is approx 0.05mm. Your example of 0.160" would read as 160 mils.

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## fscotte

Nice.  I'd like for someone to get this unit and then give us a review.

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## multidon

Is the ball small enough to fit into the F holes of a mandolin? it looks kind of big in the pictures.

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## lsnyman

The ball is 5/8". I can also make is work with a disc if required.

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## Michael Lewis

Would a smaller ball work?

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## lsnyman

yes, I can make it with a 1/2" ball, just has to be calibrated that way. What size ball will be good for you?

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## lsnyman

UPDATE !!
I have improved the probe to increase the range. It now has an option to read up to 14mm suspended and even to 20mm with the probe below the ball.

Her is a video showing the ball inside a guitar jumping braces. Please excuse the old ugly guitar.

http://www.youtube.com/watch?v=NODOo...ature=youtu.be

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