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Demian

What Caliper Do You Use ?

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First of all im a noob, and I need to buy a caliper, so I was looking for brands and if it would be mechanical or digital. Well, I managed to confuse me even more.. :D

I know that calipers can measure up to 0.001" of accuracy or even better so the first question is, is it neccesary for guitar building that the caliper could measure with that accuracy ? beacuse i presume that if it is so, the caliper should be a good one with superb quality.

I know that chinesse calipers are not the best ones but the error margins that they handle can affect us for guitar building ?

Do you know the Asimeto and Insize brands in USA ?

I know that Mitutoyo is a great Brand but here are vey expensive and they are made in Brazil not even in Japan.

And the other question is what do you recomend me a mechanical one or a digital one ?

Can you tell me your experiences ?

Thx

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One that works. No need to spend hundreds unless you have money to burn.

There are some areas where you do need to make sure you buy top shelf and I'm not saying buy the crappest pair you can find, but you don't need to go overboard if you get my drift.

I'm pretty fussy with my tools and I couldnt even tell you what brand mine are, I know they are digital and the batteries keep running flat even though I turn it off. More expensive ones turn themselves off to save batteries.

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I use a cheapy pair of digital calipers. For guitar building you can't go wrong really. I use the internal measuring points for marking out the spacing on nuts before I slot them and the cumulative error is greater from my eye than it is from the calipers.

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+1 for cheap metal digital calipers. I don't like the plastic ones. I also have about 3 pair in the shop because I keep laying them down and losing them.

I also like the set I have that does fractions as it is really handy for translating fractions to thousanths to metric...

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I have a 4" and a 6" pair of the metal digital ones from Harbor Freight and they have worked really well. I also have an inexpensive all-metal set of Vernier calipers that I use for setting to a specific measurement (e.g., 2") and locking them and using that to check as I get the depth or thickness close to the measurement.

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I use the digital lutheirs caliper stew mac sells, I like it because it has a couple extra fetures for fret work, before that I used a digital caliper made by general which was pretty decent. For doing measurments on necks and everything. I use those orange plastic ones with the dial on them made by general because I can modify the clamping parts to be able to get in around strings and stuff.

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When buying tools for fine metrology we need to be really clear about a few things: the differences between accuracy, precision, and the role of tolerances. Once that's clear we can talk about applications.

Loosely speaking...

Accuracy is how close the displayed measurement is to the actual dimensions,

Precision is how repeatable your measurements are, and

Tolerances are how accurate your measurements are guaranteed to be with the out-of-the-box tool.

Consider the analogy of, say, a rifle that's being pointed dead-nuts at a target bulls-eye.

An accurate rifle is one that is consistently close to the center of the target, though the hole pattern may be super scattered around it.

A precise rifle is one that is consistent from shot to shot, even if that tight grouping is waaaay off-center.

The tolerance of the rife is the minimum accuracy and/or precision the maker guarantees it will have out of the box.

Now consider this when you buy cheap-o digital calipers. Your calipers will always always always display a precise looking, +/-0.001 inch measurement on that nice, simple readout. This number has ZILCH to do with your actual dimensions if the caliper is not accurate, precise, properly zeroed, used correctly, or well cared for.

Digital calipers are tools that are only as precise as their manufacture and their operators, but their displays will not imply this. When you read "0.007" on your calipers, when it should say "0.007+/-0.020 manufacturer's tolerance, and BTW you're holding it off angle, pressing too hard, and the tips are bent."

SO, caveat emptor when buying things that seem precise but may not actually be in reality.

Regarding digital vs. dial:

I like digitals for their switching units, zero-setting/relative position measurements, and easy reading... it's what I use at home and at work. However, one thing I do love about dials is being able to see caliper flex. If you press too hard you can watch the needle move, even if the piece is not changing dimensions... something far less obvious on digital calipers. Also, dials are old skool and I love watching that needle spin without a dang battery.

Applications for guitar building.

I've only built a few instruments, but making guitars out of wood is not like making aircraft parts out of inconel. Measuring to +/-0.005 (Mitutoyo tolerances) so you can shape wood is silly, it's an organic and highly heterogeneous material that will swell and contract with humidity changes. Measuring your thickness planing to +/-0.005" is dandy, but it's wankery. I once stopped by my local shop, Gryphon Stringer instruments (jealous, anyone?) to aks Frank Ford of frets.com fame about how closely I needed to cut my fret slots. His response? within a 1/16! I was flabbergasted! All these people pushing micron tolerances on their CNC machines are not accounting for environmental changes, finger pressure, and everything else that changes your guitars are you play them. If the great Frank Ford says you only need to hit +/-0.060, I'm inclined to believe him and still try to do one better... but I'm not sweating that last 0.005" anymore.

SO! In conclusion:

Any cheapo digital calipers you find will probably be just fine for guitar building, but know how your tools actually work and don't rely too much on false accuracy.

Happy building!

:: Dave

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Always good to hear your input on subjects, Dave.

Interesting how Frank put that value out there qualifying it only with reputation. Values like 0.25"/1.5mm** sound like a shorthand answer to achieve productivity rather than anything useful to form a basis for precision (or lack thereof).

Personally, I think that throwing inaccurate values out like that makes for provocative engaging leaders into written articles supporting the statement but doesn't serve much use outside of them....especially when people are often unaware of how and when they accumulate smaller tolerance errors which can easily exceed that tolerance through simple bad practice. I 100% sure that Frank's working methods free him from cumulative error, and if anything this thought process is far more important than a simple exercise in accuracy.

I would hate to think that statement would make somebody somewhere start measuring out a fretboard using a "distance from previous fret" method with a 1/16" tolerance on each measurement. We'd be back in the 50s!

** as you can see, I am happy with that 5% tolerance in Imperial/Metric conversion and 15% tolerance on my conversion tolerance percentages also. :killinme

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I've always used Starret dials (not digital) but I started out working in Aeroplastics where accuracy was vital. I kept most of those tools and now use them when I work on guitars. However, at Martin, we use Mitutoyo digital calipers or snap dials for checking the thickness of tops, backs and sides. As reference, when we sand the wood for out tops to thickness, we must hold +- 3. Our nominal for a top thickness is .130. Anything below .127 is no good. .

On a side note, don't ever think that any pair of dials will hold 0.001 accuracy. They aren't intended for that type of accuracy. If you need that, pick up a good micrometer. Also, to help ensure your tools stay calibrated, pick up a good set of gauge blocks to routinely check your tools.

I've seen nice sets of dials at Harbor Freight. Never bought a pair but they looked like good quality to me.

Edited by zyonsdream

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