Caliper vs. Micrometer For Auto Work?

[BikeRider]

I've been doing a fair amount of auto repair and maintenance work and I'm thinking of getting a relatively inexpensive set of digital calipers but first want to get a sense of why I need them and what I might do with them that I can't do, or do as easily and accurately, with my micrometer set.

Note that I'm not asking for recommendations as to which set of calipers to get, but rather what they're generally used for in auto work, that other measuring tools like micrometers or dial indicators either can't be used for, or aren't as good at as decent calipers are.

I already have one such application but which by itself doesn't really justify buying calipers. I was going to replace the bracket bushings for rear sway bar on an old Camry, and found out that this particular model and year Camry came with two types of sway bars, one 15-16mm in diameter and the other 17mm. So I had to first measure it to see which one it was.

I tried to do this with my 1" Harbor Freight analog micrometer, with the car on the ground, but it was hard to get the "pins" to seat and lock on the widest part of the sway bar. Calipers would have made quick work of that, I'm sure. But, such a one-off job doesn't really justify a new tool. Which is why I'm trying to find out what else calipers are best used for on cars, if not essential for some tasks.

I'm about to take apart the manual trans on a different car, a 1G DSM AWD, to fix some issues, so perhaps it would be of use there, compared to the micrometers, dial indicator and steel ruler I already have. I'm also going to need to measure the step for its stepped flywheel, before and after it's machined and to see if it even makes sense to machine it or just get a new one.

Once that's done, I have to replace the timing and balance belts, idlers, tensioners, etc., on this car. And I might also have to replace the piston rings on yet another car, a Kia Rio. Would calipers be useful and perhaps essential for any of these jobs, and perhaps other common can tasks?

Additionally, I'm trying to decide whether I need certain caliper features, like "absolute origin", a USB or Bluetooth PC connection, or fractions. I'm not even sure what "absolute origin" is useful for or when you'd need auto-entry via USB or BT, and all of the cars I'm working on are Metric, now SAE.

Btw, the two calipers I'm most strongly considering are both by iGaging, one without and one with "absolute origin". It's about a $10 difference, so I'm leaning towards the latter, only it doesn't display fractions, but I'm not sure how often I'd need that. I can't justify spending a lot more for calipers at this point, for high-end ones like Mitutoyo, Starret or Fowler.

 

[Buckgnarly]

I have and use the **** out of this one.
https://www.amazon.com/dp/B001AQEZ2W/?tag=atomicindus08-20

I use calipers WAY more than micrometers, and at that price it's totally worth it. I do like to toggle from metric, to decimal, to fractions...I am not a machinist and do not have decimal to fractions memorized!
Digital is just easier than dial also in my opinion.

I did regear 2 axles last Summer. and double checked the Igaging caliper to a Starrett micrometer and my Blue Point digital caliper, and it was pretty much spot on.

 

[BikeRider]

I have and use the **** out of this one.
https://www.amazon.com/dp/B001AQEZ2W/?tag=atomicindus08-20

I use calipers WAY more than micrometers, and at that price it's totally worth it. I do like to toggle from metric, to decimal, to fractions...I am not a machinist and do not have decimal to fractions memorized!
Digital is just easier than dial also in my opinion.

I did regear 2 axles last Summer. and double checked the Igaging caliper to a Starrett micrometer and my Blue Point digital caliper, and it was pretty much spot on.

Yeah that's one of the two that I'm most seriously considering. iGaging appears to be the most highly-regarded lower-end brand and these calipers the most well-regarded of their more basic ones, the other being the one with "absolute origin".

But, what do you use them for, specifically, instead of micrometers, and does one need "absolute origin" or PC auto entry for home auto work?

 

[cvairwerks]

Calipers tend to work better for rectangular measurements, such as lengths, where mikes work better on cylindrical measurements. For most things automotive, calipers are easier to use, and a 6" caliper is a heck of a lot cheaper than a 6" mike....
Absolute origin has to do with the tool knowing where it is when it's powered back on....doesn't take but a couple of seconds to close a caliper and hit the zero button. Unless you are doing recordkeeping or SPC work, there really isn't any need for BT or USB out.... just more stuff to fail.

 

[Buckgnarly]

Yeah that's one of the two that I'm most seriously considering. iGaging appears to be the most highly-regarded lower-end brand and these calipers the most well-regarded of their more basic ones, the other being the one with "absolute origin".

But, what do you use them for, specifically, instead of micrometers, and does one need "absolute origin" or PC auto entry for home auto work?

For the gearing mainly shim thickness, but everyday use includes bolt length and sizes, hole sizes, bearing sizes, shaft sizes, thickness.... basically anything that is less than 6"
I like the cheap ones because I don's have to handle them as carefully....not that I do, but they have held up well so far.

 

[stuart]

100% agree with cvairwerks

 

[anndel]

I have both calipers and micrometers and find myself reaching for the calipers 90%+ of the time.

 

[Packard V8]

Calipers are best for when quick and close are good enough. Digital calipers can toggle between inch and mm; a huge advantage.

Micrometers are for when it's critical to know the dimension of a machined surface within tenths.

jack vines

 

[d.mcfarland]

I got rid of all my micrometers once I got a digital caliper.

 

[bwringer]

The cheap digital calipers are the bee's knees for 99% of what you need to do on vehicles. Modern car and motorcycle stuff is pretty much all metric (with a few exceptions), so being able to measure directly in MM with no squinting at verniers or conversion math is pure luxury. Much faster and easier, with far fewer opportunities to screw up.

The cheapies tend to eat a battery every few months, but at ten bucks apiece you don't have to fret too much about getting them dirty or damaging them. And every set I've used has proven very accurate.

The cost difference between a cheapie and a name brand is stupid-crazy. Yeah, they're worth it if you need certification or something and you never ever drop anything... but 10-20X the cost does not translate to more usability.


Use a micrometer only when you actually need that level of precision.

And again, the price gap between cheapie and name brand is many, many times greater than the performance gap.

I have an inexpensive digital micrometer from Horror Fright that I use for measuring motorcycle valve shims. It's proven to be dead nuts accurate and reads directly in MM. Again, the cheapies run down their batteries more often, but for 1/10 or less than the price of a Mitutoyo, I'm happy to remove the battery between uses or buy a few extra button batteries.

For those of us grubbing around in engines or monkeying with filthy suspension bits, there's a compelling argument that the expensive name brands are less functional. There's a lot of utility in cheap enough to just jam in where you need to measure without worry and plenty good enough accuracy.

 

[anavrinIV]

Unless you're rebuilding an engine, calipers. Even cheap ones will get you within a couple thousandths reliably which should be all you need for the things you're talking about. If you needed to know bearing journal diameter for clearance or size an OHC lifter that might be a different story but calipers are far more useful in most other aspects. Plus you can measure hole interior dimensions with a set of calipers, you would need a set of internal mics (and external mics to measure them) to do that and it would be much more cumbersome and a whole lot more expensive.

 

[BikeRider]

Thanks all for the useful advice. I'll probably get one of the iGaging ones. Not that much more expensive than the cheap ones and they have some nice features that seem worth the modest extra cost. There are basically three models I'm now trying to choose between.

One is $30 and has fractional readout but no absolute origin. One is $42 and has absolute origin but no fractional. And one is $50 and has both fractional and absolute origin plus a depth gauge attachment. I'm now leaning towards the latter one because it basically has everything.

But I'm still kind of confused. How is absolute origin different from and better than just setting it to zero? Is it basically a matter of not having to zero it out every time you turn it on? And on the units without absolute origin, if you need to set zero to a position other than with the jaws fully closed, do you have to do it each time you turn the thing on, which I can see as being annoying and prone to inaccuracies? I.e. do units with absolute origin not only remember the zero point every time you turn them on, but even if the zero point is other than with the jaws closed?

 

[cvairwerks]

Absolute origin is really only necessary of you are working where you need to make repeated measurements and don't want to take the time to check the zero every time you power the caliper up, or you are doing comparison work where you need to know the deviation from a set dimension. In that case, you would set your control dimension as the absolute zero point and any measurements you made would show the deviation from that point....sort of a digital go-no gauge.

 

[jayemm]

You are getting a lot of good advice from these guys (gals too if any). I spent a number of years in a manufacturing quality control job and used digital calipers a lot everyday. We used Mitutoyo absolute calipers exclusively and they are worth the money for intensive use and the battery life was awesome.
Having said that, they were used probably 20 times more than micrometers for more uses than you can think of. Want to convert mm to inch, just open to mm length and push button to convert to inch. Measure hole depth ,step height, distance between holes and the list goes on. Want to make a radius gage out of cardboard, just use the points of the ID jaws as a compass (not recommended for hard materials)
This is not a purchase to be timid about spending a few bucks. The Igaging brand seem to be pretty popular as a quality set that is reasonably priced. You don't need Mitutoyo quality or price. You might consider the Aventor brand sold by Shars Tools. They also have an ebay store with better prices. Cheaper calipers seem to eat the button cells as they draw current even when switched off so you might consider calipers that take a larger coin cell such as CR2025 or similar

 

[APEowner]

I use calipers for just about everything outside of the engine. It's all the accuracy that's required, quicker to use and less of an expense if I drop them.

 

[SeisMec]

The cheapies tend to eat a battery every few months.
...
I have an inexpensive digital micrometer from Horror Fright

Did you mean digital caliper? If so, FWIW my battery has lasted over a year since I removed a layer of foam from the plastic case it came in. I think the foam was triggering one or more buttons.

 

[RedneckWelder]

I have a cheap Fowler dial caliper it works well and has held up for several years. Mainly use it for hydraulic fitting sizing.

We use micrometers mainly for the oddball stuff like shim pack measurements when doing powertrain work.

 

[RedneckWelder]

I have a cheap Fowler dial caliper it works well and has held up for several years. Mainly use it for hydraulic fitting sizing. The cheap digitals while they work well, tend to eat batteries and the expensive ones are too nice for what I do.

We use micrometers mainly for the oddball stuff like shim pack measurements when doing powertrain work.

 

[Citation]

Thanks all for the useful advice. I'll probably get one of the iGaging ones. Not that much more expensive than the cheap ones and they have some nice features that seem worth the modest extra cost. There are basically three models I'm now trying to choose between.

One is $30 and has fractional readout but no absolute origin. One is $42 and has absolute origin but no fractional. And one is $50 and has both fractional and absolute origin plus a depth gauge attachment. I'm now leaning towards the latter one because it basically has everything.

But I'm still kind of confused. How is absolute origin different from and better than just setting it to zero? Is it basically a matter of not having to zero it out every time you turn it on? And on the units without absolute origin, if you need to set zero to a position other than with the jaws fully closed, do you have to do it each time you turn the thing on, which I can see as being annoying and prone to inaccuracies? I.e. do units with absolute origin not only remember the zero point every time you turn them on, but even if the zero point is other than with the jaws closed?

Most calipers work by counting how far you went from a known zero. So long as the caliper keeps a good count you know where you are.

Absolute calipers don't need to count, instead they know based on a more precise mechanism.

Think of it this way, if you have a tape measure without numbers. You can still tell something is 106" long but you have to count from zero. With numbers you can look at any part of the tape and know how far you are from zero.

Most of the time the difference doesn't matter. If you move the caliper too fast the system can lose count. Since the calipers work on capacitance, some oils/metal particles etc might get on the slide and also cause the caliper to lose count. Battery life is another area of concern. Some calipers simply lose zero when they power off. Others keep track of count even when off. That means they are using almost as much power when on vs off. This is why some cheap calipers have poor battery life (that and they often use **** batteries). With ABS designs the caliper doesn't loose zero even when powered down (or during battery changes). The poor battery life of many generic calipers is one of the worst things about them. However, with more calipers using 2032 lithium cells vs 1.5V LR/SR44 cells this isn't as big an issue.

I personally really like the iGaging stuff. The non-ABS models with fractions are actually really nice. The only issue I have with fractions is I wish I could limit it to 64ths, vs 128ths. I'm not sure the ABS ones are worth the extra $10. At work we have both.

 

[BikeRider]

Sounds like absolute origin isn't vital for my needs, more of a nice to have feature. But since it's not much more than the version without it, I might as well splurge and get this feature. You can not use a feature you have but don't need but you can't use a feature you don't have but need. Of course scope creep now coming into play as for just another $8 I get fractional output AND a depth attachment. But now I'm spending $20 more than the basic $30 version. Decisions...

 

[BikeRider]

Most calipers work by counting how far you went from a known zero. So long as the caliper keeps a good count you know where you are.

Absolute calipers don't need to count, instead they know based on a more precise mechanism.

Think of it this way, if you have a tape measure without numbers. You can still tell something is 106" long but you have to count from zero. With numbers you can look at any part of the tape and know how far you are from zero.

Most of the time the difference doesn't matter. If you move the caliper too fast the system can lose count. Since the calipers work on capacitance, some oils/metal particles etc might get on the slide and also cause the caliper to lose count. Battery life is another area of concern. Some calipers simply lose zero when they power off. Others keep track of count even when off. That means they are using almost as much power when on vs off. This is why some cheap calipers have poor battery life (that and they often use **** batteries). With ABS designs the caliper doesn't loose zero even when powered down (or during battery changes). The poor battery life of many generic calipers is one of the worst things about them. However, with more calipers using 2032 lithium cells vs 1.5V LR/SR44 cells this isn't as big an issue.

I personally really like the iGaging stuff. The non-ABS models with fractions are actually really nice. The only issue I have with fractions is I wish I could limit it to 64ths, vs 128ths. I'm not sure the ABS ones are worth the extra $10. At work we have both.

Ah, I see, it's not just a difference in features, but in underlying methods of measuring. If I'm understanding your correctly, there's a different kind of encoder being used in units with and without absolute origin, the latter more accurate or at least reliable. Might as well get it if so.

 

[Citation]

Ah, I see, it's not just a difference in features, but in underlying methods of measuring. If I'm understanding your correctly, there's a different kind of encoder being used in units with and without absolute origin, the latter more accurate or at least reliable. Might as well get it if so.

Yes, I'm not sure how the absolute models operate but they are different. Mitutoyo's patents likely expired recently hence others are copying the design. Absolute calipers are not more accurate, just different. If the calipers aren't junk either is just as accurate under normal conditions. If you don't mind spending the extra money there is no down side (well the cheap ones have the largest display).

 

[ericm]

Micrometers are more accurate than calipers. But caliper level accuracy is all you need for a lot of things and they're more versatile. I use calipers way more often than micrometers now though when I was building two stroke engines I used the micrometers and bore gauges fairly often. Measuring devices are like screwdrivers or wrenches in that you end up with a bunch of different kinds.

 

[BikeRider]

Thankfully I already have a decent set of micrometers in the 1, 2 & 3" range. Yeah, they're Harbor Freight, but they seem pretty decent and got good reviews and are probable more than good enough for my needs for when calipers aren't the right tool.

But as I've found out the hard way, there are times when a micrometer is either hard to use, hard to read, or just plain overkill for the task, and calipers would probably work just as well if not better. But I'm glad I bought them, they weren't too expensive (I got them last year before they ended the 20% off coupon thing), and I've used them several times already where they came in handy.

I like having the right tools for the task even if it's a rarely done task. The one time you need to do it can make the difference between doing it right or at all and not doing it and holding everything up. Like say snap or lock ring pliers, or an axle nut socket. So I'll get a set of calipers, almost certainly one of the iGaging ones, the only question still being which one.

 

[BikeRider]

Yes, I'm not sure how the absolute models operate but they are different. Mitutoyo's patents likely expired recently hence others are copying the design. Absolute calipers are not more accurate, just different. If the calipers aren't junk either is just as accurate under normal conditions. If you don't mind spending the extra money there is no down side (well the cheap ones have the largest display).

One of the YouTube reviews I just saw suggested that absolute origin calipers were actually more accurate, if not in an absolute sense then at least in actual use, as the zero point was always zero, while calipers without this feature had the wrong zero point under certain conditions.

So the AO ones must have some more accurate way of determining sensor location relative to the moving part. I'll have to research this further to find out for sure. No real need to do that, I'm just nerdy that way with an engineering background.


...Ok, that didn't take long, literally a minute. Turns out that, as I suspected, absolute origin calipers (or really any measuring instrument that have this feature) use encoded position markers that tell the device where it is in an absolute sense, so no matter how many times you move things or how fast and in which direction, it knows where it is.

Whereas calipers (and other measuring devices) that don't have this feature rely on an accurate counting of non-encoded markers to know where it is relative to zero. I.e. they literally count the number of markers passed beyond the zero point as you slide the device. So if you move things too fast or too often, it can skip or doubly count markers and lose position.

It's basically the difference between using a ruler that has a fixed 0" and 12" marker and every marker in-between to measure a fixed distance, and using a measuring wheel. If you use the ruler properly there's no chance of error, while if the latter skips or slides or jams or hits a tiny pebble, it's not going to get a proper reading.

Obviously with digital calipers the markings are electronic ones, or ones that an accurate electronic sensor can detect, but with an absolute origin one it doesn't have to count as it can literally tell which marking it's nearest, so no room for error, whereas with a caliper that uses the counting method there's always the chance of skipping or double-counting markers.

I assume that the absolute positioning method requires a better calibrated series of markers and more sophisticated sensor, thus the higher expense. I'm also assuming that I understand this correctly, as I literally just started looking into the topic of calipers yesterday. But, again, engineering background with some electronics both digital and analog, so I can get up to speed fairly quickly.

 

[Citation]

One of the YouTube reviews I just saw suggested that absolute origin calipers were actually more accurate, if not in an absolute sense then at least in actual use, as the zero point was always zero, while calipers without this feature had the wrong zero point under certain conditions.

So the AO ones must have some more accurate way of determining sensor location relative to the moving part. I'll have to research this further to find out for sure. No real need to do that, I'm just nerdy that way with an engineering background.

It's likely due to the count skipping I mentioned. If you move the head fast or if you get something like coolant/dirt etc on the slide it can cause a missed count. Since most of my caliper use is clean and dry I don't have that issue.

 

[BikeRider]

It's likely due to the count skipping I mentioned. If you move the head fast or if you get something like coolant/dirt etc on the slide it can cause a missed count. Since most of my caliper use is clean and dry I don't have that issue.

As I describe right above, if I'm understanding this correctly, I think that absolute origin calipers use a different, literally absolute, counting system, that avoids this issue. To use another example, it's like knowing that you've driven 10 miles by counting mile markers along the way, compared to by looking at the mile post that literally says X miles and subtracting from it the mile value at the post that you started from. You can't go wrong with the latter method but you can go wrong with the former.

 

[dscheidt]

Another really huge advantage of absolute calipers is that they should have vastly improved battery life, because the encoder is easier to drive. Mitutoyo claims something like five times life compared to their regular encoders. That's worth a few bucks to me, because it means they're more likely to work when I go to use them.

 

[Citation]

As I describe right above, if I'm understanding this correctly, I think that absolute origin calipers use a different, literally absolute, counting system, that avoids this issue. To use another example, it's like knowing that you've driven 10 miles by counting mile markers along the way, compared to by looking at the mile post that literally says X miles and subtracting from it the mile value at the post that you started from. You can't go wrong with the latter method but you can go wrong with the former.

That is correct.

 

[Ralf11]

or ... Learn to read a vernier on your caliper

 

[mikegt4]

A bit off of the "which is best" topic, I have found that a cheap plastic caliper is a great addition to my junkyard tool bag. Often part differentiation is determined by slight differences in dimensions. A perfect example is sway bar size in the OP.

https://www.harborfreight.com/6-in-utility-caliper-63664.html

 

[BikeRider]

A bit off of the "which is best" topic, I have found that a cheap plastic caliper is a great addition to my junkyard tool bag. Often part differentiation is determined by slight differences in dimensions. A perfect example is sway bar size in the OP.

https://www.harborfreight.com/6-in-utility-caliper-63664.html

Good point and I'll definitely pick up one of those for those rough measurements. And I'm guessing that for my current needs it'll suffice. But I'll still get one of the "real" ones, just haven't decided which one. The one I like is $50 which is a bit more than I hoped/expected to pay.

 

[SeisMec]

a cheap plastic caliper is a great addition to my junkyard tool bag.[/url]

I got a couple of those when they were a freebie.
But, IMO plastic is too fragile for a rough and ready tool bag.
You can get the same thing in steel for about $10 in many auto parts stores.

The same $10 will also get you HF 6 piece "just checking what ballpark I'm in" set.

The metal calipers also have a thumb screw to lock the jaws.

 

[DeeKay]

Personally I like a good old Dial or vernier caliper, no batteries to die when I need the thing and pretty much impossible to kill. If I need metric just divide by 25.4

 

[Ign]

Personally I like a good old Dial or vernier caliper, no batteries to die when I need the thing and pretty much impossible to kill. If I need metric just divide by 25.4

Dial completely impractical in anything less than a very clean machine shop and preferably actual clean room.

One tiny bit of sand, dirt or just machining chips in that rack and they're screwed. Sure, we've all limped them along with an annoying rough spot or "skip", but it's less than ideal and completely unnecessary in this age.

Vernier....yeah no thanks. My eyes just started to go downhill and the old joke used to be machinists always go blind from squinting to line up tiny lines....on mics, on vernier calipers, on lathe cross-slides and on and on

That said, the absolute mechanical simplicity and durability of vernier can't be denied!!

 

[DeeKay]

Dial completely impractical in anything less than a very clean machine shop and preferably actual clean room.

One tiny bit of sand, dirt or just machining chips in that rack and they're screwed. Sure, we've all limped them along with an annoying rough spot or "skip", but it's less than ideal and completely unnecessary in this age.

Vernier....yeah no thanks. My eyes just started to go downhill and the old joke used to be machinists always go blind from squinting to line up tiny lines....on mics, on vernier calipers, on lathe cross-slides and on and on

That said, the absolute mechanical simplicity and durability of vernier can't be denied!!

I've had the same dial in my service truck for a long time, never been a problem for me, I just keep my tools clean. Maybe I've just been lucky haha, To each their own I guess

 

[Bacon!]

Another really huge advantage of absolute calipers is that they should have vastly improved battery life, because the encoder is easier to drive. Mitutoyo claims something like five times life compared to their regular encoders. That's worth a few bucks to me, because it means they're more likely to work when I go to use them.

Are you certain about this? I vaguely recall that I've seen the opposite stated, that the absolute feature causes a huge drop in battery life because it has to power the memory for the tracking even when the screen is turned off (never really turns off except for screen). I'm wondering if Mitutoyo is managing to find a way to extend life but it is still far worse than with a caliper that turns completely off.

The greatest advantage I've seen in battery life is get something that uses a CR2032 instead of LR44 cells.

 

[Whitworth]

I've got several different digital calipers. Mitu are best with battery life. Regardless Absolute or not. But different brands use different batteries so that may be the important factor.

I-gaging products, have a couple of those, they are OK as a value purchase, but don't hold a candle to others.

Fowler is a good mid-range value, but Mitutoyo is the best.

 

[Citation]

Are you certain about this? I vaguely recall that I've seen the opposite stated, that the absolute feature causes a huge drop in battery life because it has to power the memory for the tracking even when the screen is turned off (never really turns off except for screen). I'm wondering if Mitutoyo is managing to find a way to extend life but it is still far worse than with a caliper that turns completely off.

The greatest advantage I've seen in battery life is get something that uses a CR2032 instead of LR44 cells.

I think this is more about who does the circuit design but a traditional caliper that keeps tracking movement when "off" will have the highest power draw.

With an absolute type caliper the zero position can be written to non-volitile memory which takes no power. I know the Mitutoyo's take some amount of power when off but it is very little. If you take the battery out and leave it out the zero position will reset. However, if you just take the battery out long enough to change it zero will be retained. So how ever it works it seems to take very little power but not zero.

Turning the whole thing off is a good way to save power. TESA does that with their Shopcal models. They basically force you to re-zero every time you turn it on. I would much rather that vs a dead battery if I haven't used the calipers in 2 months.

Battery type also makes a difference. Mitutoyo calipers come with silver oxide batteries that have more capacity than alkaline cells (LR vs SR44 - about the same mAh but voltage stays a bit higher so low voltage trip takes longer). If you use an LR44 in a Mitutoyo you will find the battery life isn't nearly as good as you recall. As you said, the CR2032 batteries have a lot more capacity (about 3x more thanks to the higher voltage).

My personal experience is this: I had a set of generic Chinese calipers (better built than the current HF stuff). They worked nicely but the battery was dead in just a few months if I didn't take the battery out. In my old lab we had several sets of the $30 iGaging calipers. We got perhaps 2 years out of the batteries. We kept a few spares around. My Mitutoyos get a few years out of a battery. I think my TESA calipers are at least 5 years on the battery but they aren't used often. So long as I get 1-2 years on a battery I'm OK since I keep a lot of various coin cells around.