Caliper with/without fine adjustment?

[aneevuser]

I want to buy a vernier caliper. Some have a fine adjustment screw, some don't. It's not clear to me whether or not I need a caliper with one.

What exactly are the benefits or disadvantages of the fine adjustment screw? - one potential disadvantage that I see is that it may be easier to overtighten the jaws with a screw control, but I'm not sure if that is indeed the case. I am in fact rather unclear as to the advantages - what can I do more easily - or perhaps only - with fine adjustment?

[thm_w]

Photos of what you are talking about, what precision are you planning to measure to? Normally calipers you don't need anything like that.

Are you sure you aren't looking at a micrometer? In that case you'd get one with a ratchet to prevent overtightening.

[Gyro]

Yes, a fine adjustment screw is useful. It's useful for 'comparator' applications where you want to set the caliper to an accurate position, lock it and then see if something fits between the jaws or not (i.e. has it reached the finished size or is it the required size). It's almost impossible to stop the jaws at an exact figure just sliding it by hand.

In practice, there's no danger of overtightening the jaws, the clamping mechanism will slip first.

Calipers without a fine adjustment screw are fine for just sliding up to an object and taking a measurement, but that's missing out the other useful function of the caliper.


P.S. You should at least get one with a fine movement thumbwheel.

P.P.S. I'm assuming that you do indeed mean a "vernier caliper". Fine adjustment screws are pretty rare on digital ones.

[KL27x]

it may be easier to overtighten the jaws with a screw control, but I'm not sure if that is indeed the case. I am in fact rather unclear as to the advantages - what can I do more easily - or perhaps only - with fine adjustment?

You mean the thumbwheel?
The thumbwheel provides leverage. When measuring stuff down to the thous, any sticking in the slide or any elasticity of the material you're measuring can come into play. The thumbwheel helps to make consistent measurements. It is easier to overtighten the jaws, but it's also easier to let off. You'll have more control over this range of compression. You can take min/max or to just use a consistent pressure for this particular measurement after you calibrate yourself for your own standard.

Most of the digital calipers that go down only to hundredth of an inch don't have a thumbwheel. Not only they have less resolution, but they're also made of plastic and slide better, so the thumbwheel isn't as important.

[Kjelt]

Just get a good digital caliper like Mutitoyo upto 0,01mm and you don't need that wheel.
With a bit of practice you can set it correct to that 0,01mm.
There is a little fastening screw to lock it you set the caliper just a few 0,01mms outside the target, tighten the screw a little bit and now softly tick with your finger so it gets to the exact distance.
Then tighten the screw. Ten minutes practice done.

[aneevuser]

Yes, a fine adjustment screw is useful. It's useful for 'comparator' applications where you want to set the caliper to an accurate position, lock it and then see if something fits between the jaws or not (i.e. has it reached the finished size or is it the required size). It's almost impossible to stop the jaws at an exact figure just sliding it by hand.

Thanks - I hadn't thought of that problem - I guess setting two metal surfaces at sub-mm relative positions will indeed be tricky by hand.

In practice, there's no danger of overtightening the jaws, the clamping mechanism will slip first.

Hmm. What about with softer materials, like plastics?

Calipers without a fine adjustment screw are fine for just sliding up to an object and taking a measurement, but that's missing out the other useful function of the caliper.
P.S. You should at least get one with a fine movement thumbwheel.

You've convinced me.

P.P.S. I'm assuming that you do indeed mean a "vernier caliper". Fine adjustment screws are pretty rare on digital ones.

I do indeed - digital things are full of electronics, which is the work of the Devil and can go wrong, and need batteries.

[aneevuser]

It is easier to overtighten the jaws, but it's also easier to let off. You'll have more control over this range of compression. You can take min/max or to just use a consistent pressure for this particular measurement after you calibrate yourself for your own standard.

By "take min/max", do you mean take measurements with tighter/looser jaws, as controlled by the fine adjustment?

Most of the digital calipers that go down only to hundredth of an inch don't have a thumbwheel. Not only they have less resolution, but they're also made of plastic and slide better, so the thumbwheel isn't as important.

Are there any calipers made of plastic that aren't junk? Surely it deforms too easily under pressure to be reliable?

[aneevuser]

Just get a good digital caliper like Mutitoyo upto 0,01mm and you don't need that wheel.

I'm going to go for good ol' sliding metal-on-metal, with graduations - nothing to go wrong, no batteries to change. And cheaper.

[tautech]

Calipers at least need a thumbwheel and a movement lock.
If needed for Go/NoGo you need the adjustment screw.

Any caliper without a thumbwheel is a right PITA for fine work and for the bulk of uses a thumbwheel and movement lock will serve you fine.

[drussell]

I do indeed - digital things are full of electronics, which is the work of the Devil and can go wrong, and need batteries.

There is, of course, something in between a vernier caliper and a digital...  A dial caliper.

[Gyro]

In practice, there's no danger of overtightening the jaws, the clamping mechanism will slip first.

Hmm. What about with softer materials, like plastics?

In practice, fine adjustment screws have a very light operation, you can easily feel when things are beginning to tighten up. For soft materials you need to use as much of the jaw area as possible to avoid compression. If too soft, then you need to decide what constitutes contact anyway. That's where fine adjustment screw, locking the jaws, and checking for a sliding fit is more useful.

P.P.S. I'm assuming that you do indeed mean a "vernier caliper". Fine adjustment screws are pretty rare on digital ones.

I do indeed - digital things are full of electronics, which is the work of the Devil and can go wrong, and need batteries.

I have one of each - a digital one (with thumbwheel) for when I can't be bothered to think, and a vernier with fine adjustment screw for trickier sliding fit measurements (or when the battery in the digital one has gone flat! ).

A small micrometer is a good idea for highest accuracy - as long as you don't need to go beyond 25mm, and the relatively small contact area (with one surface rotating) isn't too much of an issue. Again, for soft material you need a gentle touch.

[coppercone2]

its useful if you want to measure something then find exactly half of that measurement to mark the half way mark on something when you are doing layout. I have one without a thumbwheel and it is sometimes irritating to get to the thousanth if you are doing a whole bunch of hole marks quickly. I would think its a useful/essential feature if you can afford it. If you want to put holes one inch away from the side in 4 corners, its very useful because you can set it to 1 inch very easily then lock it.

If you are just measuring parts for dimensions without doing marking (i.e. measuring components), it is not useful. So, useful for marking but not measuring. (the beak of a caliper is made of carbide and its meant to scratch little marks in stuff so you know where to put holes).

[Kjelt]

Just get a good digital caliper like Mutitoyo upto 0,01mm and you don't need that wheel.

I'm going to go for good ol' sliding metal-on-metal, with graduations - nothing to go wrong, no batteries to change. And cheaper.

You're choice but even the proffesionals use them these days. It is like saying I want an analog multimeter 
PS battery SR44 costs 3 euro and lasts two to three years.
Oh yeah you als have the absolute setting, you measure for instance one rod of 5mm push zero and when you measure the other rods you can directly see the difference.
But your choice, for the good 'ol mechanical calipers, look at second hand sites, these things are now practically given away.

[Doctorandus_P]

I really dislike calipers with those thumb wheels.
They mess up with the feeling of the force I use to adjust them.
It also makes it harder to open the calipers, as the travel distance is only half of what your thumb does.

The thumb wheel does have the (at least theoretical) advantage of a finer adjustment.
Another disadvantage is that it's only on one side. I've ground the back corner (opposite to the side of the ribbed thumb support) of my Mitutoyo's because I used them in weird angles too many times and the only way to exert a measurement force in those positions was on the back side.

In the end though, it's mostly what your're used to I guess.
Having both variants, and taking turns using them is the most nuisance though, as you have to adjust the measurement force for reliable measurements.

The adjustment with the screw can be useful in some situations, depending on what you use your calipers for. You often see them on height gauges, and I have a 500mm calipers with it, but have not used it much.

Most important though is to avoid the cheap garbage.
I have 3 mitutoyo's and I've had 2 of these for 30+ years and they're still good. Mostly have slight scratches on the backside.

I've bought a bunch of the cheap digital ones, and they all ended up in the garbage. A few years back I bought a digital Mitotoyo CD-15APX and it just keeps on going on its first battery.

I can sorta understand if you don't want to sink EUR100 or more into a set of calipers (even when they last 30 years, that's EUR 3 per year!). But still. Avoid the EUR15 cheapies. There are some decent quality chinese calipers for around EUR 30 to EUR40.

[drussell]

I really dislike calipers with those thumb wheels.
They mess up with the feeling of the force I use to adjust them.
It also makes it harder to open the calipers, as the travel distance is only half of what your thumb does.

On all of the calipers I have that have a thumbwheel, the thumbwheel is disengaged unless you're actually pushing up on it with your thumb.  I've never had those problems you describe.

[thm_w]

Just get a good digital caliper like Mutitoyo upto 0,01mm and you don't need that wheel.

I'm going to go for good ol' sliding metal-on-metal, with graduations - nothing to go wrong, no batteries to change. And cheaper.

You're choice but even the proffesionals use them these days. It is like saying I want an analog multimeter 
PS battery SR44 costs 3 euro and lasts two to three years.
Oh yeah you als have the absolute setting, you measure for instance one rod of 5mm push zero and when you measure the other rods you can directly see the difference.
But your choice, for the good 'ol mechanical calipers, look at second hand sites, these things are now practically given away.

and the whole "nothing to go wrong" thing... some day in the future, OP will do the wrong mental math or look at the wrong graduation, and screw up a simple measurement.

I mean if your budget is less than $40 thats fine: https://www.amazon.com/iGaging-ABSOLUTE-Digital-Electronic-Caliper/dp/B00INL0BTS/ (battery lasts 2 years)

[aneevuser]

and the whole "nothing to go wrong" thing... some day in the future, OP will do the wrong mental math or look at the wrong graduation, and screw up a simple measurement.

That's an utterly feeble argument against a non-digital tool - you may as well say that we should throw away all of our steel rules with imperial and metric calibrations as we may look at the wrong graduation. The calculations required are trivial anyway, and it's entirely clear from the main scale what the approximate measurement is going to be, so it's easy to make a sanity check. And of course, there's that old saying "measure twice, cut once" - if you don't stick to that, you deserve what you get.

Quite apart from that, you've missed the point: you are pointing out a different source of error - an error made by the user - to that which I referred, which was error due to some failure of the device. I think that it's clear that a vernier caliper has fewer failure modes than a digital caliper.

I mean if your budget is less than $40 thats fine: https://www.amazon.com/iGaging-ABSOLUTE-Digital-Electronic-Caliper/dp/B00INL0BTS/ (battery lasts 2 years)

However, you're on stronger ground here, as I came across this yesterday, and yes, this seems to be a serious contender against the Mitutoyos at a more sensible price - maybe I'll go digital after all. Hmm. That bloody analysis paralysis strikes again.

[KL27x]

On the plastic calipers I suspect expansion with temperature is probably a bigger problem then flex of the jaws/slide. You have to be gentle on the pressure when trying to get high accuracy, anyways. Wear on the jaws might also factor in over time.

The plastic ones are lighter and cheaper and less pokey if you want to slide a pair of calipers in your pocket. And $10 is pretty much disposable. That said, I only have one of these plastic wonders, and it's mounted to my drill press for a depth gauge.`

[chris_leyson]

I've used the same 150mm Mitutoyo analog vernier for over 30 years, just as accurate now as it was 30 years ago and I don't need to find batteries for it.

[drussell]

However, you're on stronger ground here, as I came across this yesterday, and yes, this seems to be a serious contender against the Mitutoyos at a more sensible price - maybe I'll go digital after all. Hmm. That bloody analysis paralysis strikes again.

If you've never used a half-decent or better quality digital, you're missing out.  The half-decent ones don't even quickly self-discharge the battery like the el-cheapo ones do if you leave it turned off with the battery in it.

I have various others, but my good digital one is definitely my go-to caliper for sure. 

I have several left around for other specific purposes, too, like a cheap plastic one stays by the CNC engraver to easily measure plate sizes and text sizes and whatnot for making signs, etc.  I don't need to be able to repeatably measure to half a thousandth of an inch for that application, so a cheap one stays right there with the various cutters and other accessories to always be at hand.

You are allowed to own multiple calipers, you know.   

Just don't go crazy and start hoarding test & measurement equipment or you'll end up like those nutters over in the TEA thread. 

[TimFox]

With advancing presbyopia, I had to give up on vernier calipers and restrict myself to dial calipers.  Unfortunately, dial calipers only work for English or metric, not both, but verniers normally work for both.
I bought a good metric dial calipers before traveling to Saudi Arabia for an installation, since the temperature range on most digital equipment is up to 40 C.

[drussell]

With advancing presbyopia, I had to give up on vernier calipers and restrict myself to dial calipers.  Unfortunately, dial calipers only work for English or metric, not both, but verniers normally work for both.

Yeah, switching between metric and imperial and easily converting between the two at the touch of a button is one of the features I love best about the digital ones.

[KL27x]

You are allowed to own multiple calipers, you know.   

Just don't go crazy and start hoarding test & measurement equipment or you'll end up like those nutters over in the TEA thread. 

I keep a set of digital calipers everywhere I know I'll use them. None are sitting in a case. I can buy a new pair of Mitts if and when I need to make a certified measurement, rather than digging through a drawer and hoping I find them.

I keep one at the electronics bench, one at my garage workbench, one set of calipers and one dedicated digital depth gauge at the router table (which is also where I set up my redneck lathe). The cheap calipers work pretty great. I never had the first problem with any of them. They're all trustworthy, up to at least 1.5" or so, to the nearest thou. My oldest one is over 10 years old. It has fallen onto concrete innumerable times, bumped or vibrated off the edge of a bench. The glass cracked and has been replaced with plexiglass. And I had to disassemble it for cleaning, twice, when the buttons stopped responding from the dust creeping inside.

[aneevuser]

Just get a good digital caliper like Mutitoyo upto 0,01mm and you don't need that wheel.

I'm going to go for good ol' sliding metal-on-metal, with graduations - nothing to go wrong, no batteries to change. And cheaper.

You're choice but even the proffesionals use them these days. It is like saying I want an analog multimeter 

I'm a rank amateur though - maybe I should stick with vernier? And as for my analog multimeter - it has 20 thousand ohms for each and every volt, I'll have you know!

But yeah, you may have a point. Maybe I'm weakening - maybe I'll go digital. The ghosts of my youth are returning to torture me - 5 years of slide rules before using a calculator leave a deep impression on a man - the thought of buying a digital caliper feels a bit like cheating.

[aneevuser]

You are allowed to own multiple calipers, you know.   

Yes, but in these post-COVID times, money is scarce, so I'd rather buy a decent tool just the once.

Just don't go crazy and start hoarding test & measurement equipment or you'll end up like those nutters over in the TEA thread. 

No chance - I have the personality to do so, but not the cash.