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Calipers!

I recently purchased a digital caliper to make more precise measurements than a basic variety vernier and it works great. I wanted them to measure the width of my table saw for making my sled runners.

After watching a video on making an accurate table saw sled I started to notice more instructional videos using dial calipers.

Of course this could just be a case of frequency illusion but it begs the questions:

  1. If you were given a choice between dial, digital and vernier calipers which one should you pick?
  2. As far as woodworking is concerned what would make one preferential over the other or is this just a matter of personal preference?
  • 1
    What about vernier calipers? I'd argue that they are more attractive than both the digital and dial calipers since they have less moving/digital parts that could go out of calibration. – grfrazee Oct 18 '15 at 19:38
  • @grfrazee I did mention vernier in the question. I just figured that after vernier that someone would want dial or digital. Both of which are arguably i'm sure easier to read. – Matt Oct 18 '15 at 19:41
  • True, you do mention them, but it seems like you write them off as inferior to the dial/digital calipers. My argument is the opposite, though you do have a point about the dial/digital being easier to read. For most woodworking tasks, however, that high of a level of accuracy is unnecessary anyway... – grfrazee Oct 18 '15 at 19:44
  • @grfrazee This is all true...... For the accuracy used in woodworking they are just as comparable. I will include them in my answer and rewrite the question this evening to include them. – Matt Oct 18 '15 at 19:47
  • @grfrazee I tried to add detail to account for verneir – Matt Oct 19 '15 at 1:36
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After doing a fair bit of research the general consensus is use whatever you have available and you feel comfortable with. That being said, there are several points worth making about all three tools and it's important to note the differences.

Dial

  • Works mechanically and usually in 1/1000th of an inch increments.
  • Assuming the rack and pinion are free of debris the accuracy can almost always be trusted.
  • Some would claim getting a reading takes getting used to as you are reading a dial as supposed to just values.
  • Since it is mechanical many trust the readout more in comparison to digital. This could easily be subjective and comes down to the quality of the tool.

Digital

  • Digital readout is instantaneous and requires no affiliation with the tool for a quick readout. Many support switching between metric and imperial.
  • Since it is an electrical component extra care needs to be taken. Moisture and battery life need to be accounted for.
  • At times need to be re-zeroed before use although this is a simple process and a feature if you want to do relative measurements.
  • The value that is presented can sometimes be inaccurate whether it be due to pressure used or the general quality of the tool (read below on how to deal with that).

Vernier

  • Getting values requires a few seconds of thought more than just reading of a display or dial however it is just basic math.
  • Most don't go to the decimal places that dials and digitals are capable of.
  • Make no mistake they can still take simple measurements that are more than satisfactory for woodworkers.
  • Minimal moving parts. Only inaccuracy in results is that of the user making a calculation mistake.

With any tools their precision can be a direct result of the tool's quality. Not to say that cheaper tools cannot do the job just as well as their more expensive siblings but manufacturers tolerance for error should be smaller with the higher end tools.

People will have their own personal preference that might have a certain bias but either caliper can perform the job for wood workers at least*.

Point I am trying to make is that it should not matter which tool you use beyond what you are comfortable with and have available. In either case having a set of gauge blocks on hand will remove any trepidation of the tools potential inaccuracy.

* That is, most woodworkers would not need the same level of accuracy that a machinist might.

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  • Agreed. I have both a low-middle-quality mechanical and similar-quality digital, and have used both for locksmithing (where a few thousandths of an inch can make a serious difference). The accuracy of these two $30 tools seems about comparable. I wouldn't use these two for serious machining, but they're more accurate than almost any woodworking operation will ever need. – keshlam Oct 18 '15 at 6:12
  • @keshlam That's what I was reading. It was machinist that had more serious opinions because their level of accuracy needed to be more so. – Matt Oct 18 '15 at 13:32
  • 2
    One point about electronic: You can pretty much assume the battery will be dead when you need it. – keshlam Apr 20 '16 at 21:42
9

If you were given a choice between dial, digital and vernier calipers which one should you pick?

When I went looking for a caliper I wanted a dial type, based on the following comment in Andy Rae's book Choosing & Using Hand Tools, "A plastic dial caliper is plenty accurate for a woodworker's needs, and costs peanuts compared to more expensive metal versions."

I couldn't find one for sale locally, in plastic or metal, and eventually got a digital model in stainless steel. I did eventually spot a dial caliper but it was more expensive, and it turns out I wouldn't have been as happy with it — Rae is clearly right that they're more than accurate enough for woodworking, however, after using the digital type I wouldn't recommend one on a couple of grounds.

As far as woodworking in concerned what would make one preferential over the other or is this just a matter of personal preference?

Vernier

Potentially slow to read (requires interpretation/calculation by the user, which can introduce error) but in practice for the woodworker this is arguably irrelevant as the accuracy is beyond what's usually achievable in wood.

Can be very expensive, but oddly the plastic versions appear to be the cheapest calipers available (less than the price of a cup of fancy coffee).

Can have both metric and Imperial scales on the one tool.

Very simple mechanically, so little to go wrong.

No batteries required so will work anywhere, any time, without fail.

Dial

Accurate enough for woodworking needs.

Where available, can be cheaper than digital.

Display is often harder to read than on a digital model, but note: the opposite in bright sunlight.

Dial mechanism can be knocked out of alignment or break entirely, rendering the dial readout useless (no user-serviceable parts inside).

Almost all are either Imperial or metric, not both.

No batteries required.

Digital

Normally easier to read. Especially important as your eyesight diminishes getting older! But, possibly important to some users, the typical LCD display is difficult or impossible to read in direct sunlight or bright daylight.

Instant read, so faster to use (particularly when compared to vernier calipers).

More accurate than dial or vernier, sort of. Disregard what you hear to the contrary, they are more accurate in practice than dial calipers; this isn't to do with the build accuracy or better machining of the gearing, it's simply a by-product of the digital display of the measurement (to two or three, sometimes even four decimal places).

Re-zero function at any opening size allows easier comparison measurements (both positive and negative) of e.g. a mortise and its corresponding tenon, two similar drill bits, a jig's pin with the matching router bit.

Can be expensive, but careful shopping will pay dividends here — buy directly from China and you can get what appears to be exactly the same tool as a name-brand version, just without the logo and the resulting mark-up!

Particularly important feature I feel: metric and Imperial on the one tool; and this can be changed on the fly.

Requires batteries for the digital readout. But, they still retain the basic marked scales that a vernier caliper has, and the housing for the digital display is deliberately sized do that you can use its edge to read the measure:
Digital caliper highlight

So for 'rough' measurements they will still give service if the battery has died. I say 'rough' here as of course it's no rougher than the measurements done with a conventional rule, which we rely on as accurate all the time.

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  • Those were about my findings as well. Good find with the book though. I will have to look into that as well. Thanks. – Matt Oct 19 '15 at 16:31
  • @Matt, yes I can highly recommend that book. TBH because of the beautiful colour photos throughout you might initially buy it as tool porn (it's mostly what I got it for originally), but it actually has a great deal of useful info as well. – Graphus Oct 19 '15 at 18:26
  • The simplicity of its construction makes the Vernier caliper a little bit lighter than the other two. I don't think this matters too much for woodworking though. – null Oct 27 '15 at 19:23
1

I have all three of them of good quality each. Each caliper costed me more than 25 EUR. I have to say I did not spent 200 EUR on digital, so maybe they are better?..

So. In my case, dial caliper beats all of them. Second is vernier due its simplicity, as long as you don't need very small measurements. Third place takes digital and it is constantly gets off. You open-close it few times and you always get different numbers. When you open/close it way too much, it gets badly off. Mainly because dial has a rail with "teeth" that makes the guiding wheel impossible to slip, while digital rolls over the plain metal. That would explain the general design flaw.

Another pretty important thing what I really hate digital caliper is this: you basically cannot use the scale on it, because it is just off or just not exactly under the LCD display. Dial caliper, in contrast, has a knife-sharpened edge that stays exactly on the scale. So you look at the dial scale only after you already looked at the main scale.

That said, I suggest either dial or vernier. Ultimately just get both of them. :-)


Edit: in response to comments below, I added the following:

Here. You have it.

Yes, I re-nulled digital. Yes, I opened digital slowly, without jerks. Yes, I tried my best, and digital still sucks. No, digital does not gets fixed, it is just broken from the beginning. No, I do not recommend buying it.

enter image description here enter image description here enter image description here

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  • In the next to last sentence of the second paragraph, you compare dial to dial. I would edit it, but don't know what you are trying to say. Maybe you should make the change. – Ast Pace Jan 4 '17 at 2:05
  • @AstPace sorry didn't get it. In the next to last sentence I say "I suggest either dial or vernier". – isbm Jan 4 '17 at 15:02
  • I spent less than $20 USD on my digital calipers, and they are only off if you move them way too fast. They are super easy to reset if they do, which makes them useful for measuring an offset from a non-zero position. Digital calipers don't use a rolling wheel, they monitor the capacitance against a sort of copper barcode printed behind the scale, counting ticks as they move. And no, vernier calipers are not simple! They take at least a couple seconds to figure out the reading, instead of glancing at the number. – johannes Jan 6 '17 at 15:30
  • Sure, the vernier is not simple. But they are a) reliable and b) does not need batteries. :-) – isbm Jan 9 '17 at 8:43
  • And yes, @johannes you're right about capacitance. I was not really sure how the thing is working, I have to admit it was a stupid assumption, as I found if you move it enough, they got bad. OK, but after looking how it actually working it makes my mind even more firm: they are no good. There are even docs how to fix that thing with a [duct]tape: woodgears.ca/caliper/index.html – isbm Jan 9 '17 at 8:46

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