# Digital caliper



## will (Aug 28, 2012)

I have been involved with restoring/fixing an old Trek bike and a Schwinn bike. A lot of the measurements for bike stuff is metric. I had been using a fractional dial caliper, then converting the measurement to metric. 

Well - I dropped the caliper and cracked the dial bezel, the caliper also felt a little stiff. I did not trust it any more. This is a caliper I bought from ENCO a number of years back, probably under $20.

Went online and found a Digital Caliper for $12.49. Stainless steel. Great because it can go from fractional to metric with a push of a button. Now, I am not going to be making any parts with a tolerance of .001. I also should point out it is not a Starrett, but for $12.49 and someone who can work with a few thousands tolerance, not a bad deal. I have checked it out against some items that I know the diameter of and it does seem to be accurate. 

Right now, the most important feature for me is the conversion it does..


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## wquiles (Aug 28, 2012)

+1

When I am machining parts, I only trust my vernier, "analog", 50-division Starrett caliper, but for quick checks, specially when going back and forth between inches and metric, I also have a cheap digital caliper 

Of course, another option when needing both inches/metric (at least for OD measurements) is my Starrett inch/metric N.123 E&M

















I know it is a little bit "sacrilegious" but I did cut my larger inch/metric model to a more "handy" size/weight, and this is the one I now use like 90%+ of the time:






Will


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## will (Aug 28, 2012)

Got to love vernier calipers.....

( what do you mean, line up the lines on the two scales, only one actually lines up )


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## Lynx_Arc (Aug 28, 2012)

I have a cheap digital one I got from harbor freight, it is slightly buggy at times it floats off into growing numbers but most of the time it works well and has a mm/inch button to change settings takes a single AG13 battery easy enough to find and does the job quick. I think I paid $10 for it on sale. I would love to have a name brand digital caliper but $100+ not in my budget for the very few times I would use it.


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## moderator007 (Aug 28, 2012)

The cheap calipers work great for me. They are not as nice as my mitutoyo Absolute but are dependable with in .001 or so. One thing that I did notice about the cheaper calipers is that if the caliper seems to loose zero alot then replacing the battery usually solves the problem. They do tend to loose zero sometimes but when the battery is low it seems they will loose zero quite often. I always zero mine before taking a measurement to make sure there set. 

With the mitutoyo's, once you set absolute zero its there I guess to the battery runs dead, don't really know. I have had them about 6 months and have never had to rezero them. I don't mean to sound like the cheaper calipers won't do a good job, they most certainly can within exceptable range. But once you have used a high quality caliper you will not want anything else. So much easier to operate and accurate. I bid and won mine on a ebay auction brand new for $76.00 and $3.15 shipping. It took alot of patience. They are well worth the extra money. I own 5 cheaper calipers and always reach for the mitutoyo.
You can look up ebay item #290764614397 or #300770827055. This guy doesn't respond to emails (buyer beware) but does ship the item quickly and as described new. I have purchased 2 from this seller without problems besides no communication. I think that there not being seen that much because the seller doesn't use the word digital in his item description.


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## precisionworks (Aug 28, 2012)

Some of the less costly digitals work OK & some don't. For $12.49 you can buy another one when the first one goes south. Battery life is often measured in weeks if the battery is left in the caliper (Mitu's run 2-3 years with 8 hours of daily use). Just be sure to remove the battery when you turn out the lights at the end of the day.


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## will (Aug 28, 2012)

precisionworks said:


> Some of the less costly digitals work OK & some don't. For $12.49 you can buy another one when the first one goes south. Battery life is often measured in weeks if the battery is left in the caliper (Mitu's run 2-3 years with 8 hours of daily use). Just be sure to remove the battery when you turn out the lights at the end of the day.



Mine came with an extra LR44 battery, it turns off automatically after a few minutes. Here again, not used for business, just very casual personal use.


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## Lynx_Arc (Aug 28, 2012)

will said:


> Mine came with an extra LR44 battery, it turns off automatically after a few minutes. Here again, not used for business, just very casual personal use.


I recently put another battery in mine after about 5 years, it too turns off after a few minutes not sure how long maybe 5 to 10 or so and I can buy the LR44/AG13 batteries for a dime each in bulk off ebay... 20/$2 if you look long enough.


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## moderator007 (Aug 28, 2012)

According to what I read when I was researching for a good caliper, the caliper is not actual off when the display is not lit. The caliper is still reading position and drawing power the display is just off. The way to test this is turn the caliper off then move it a inch or so, turn it on see if it reads a inch or so. If it does it is still reading position while it is off. According to what I read again, the cheaper calipers used almost twice the resting energy that the mitutoyo used. In (on) operation there was not as big of difference if I remember correctly. The battery you use can also play a big part. The SR44 has a superior discharge curve to the cheaper LR44. I have not tested battery life personal on both just read someone else findings. Like barry said, the best way to save battery life is take it out when not in use.

Found the link: Caliper Battery Life


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## will (Aug 28, 2012)

My display turns on as soon as there is any movement. It seems to me that I have a bunch of LR44 batteries around here. My personal usage just would not justify spending spending lots of money. I do have very good 1 inch and 2 inch Micrometers, which I do use for critical measurements.


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## Lynx_Arc (Aug 28, 2012)

moderator007 said:


> According to what I read when I was researching for a good caliper, the caliper is not actual off when the display is not lit. The caliper is still reading position and drawing power the display is just off. The way to test this is turn the caliper off then move it a inch or so, turn it on see if it reads a inch or so. If it does it is still reading position while it is off. According to what I read again, the cheaper calipers used almost twice the resting energy that the mitutoyo used. In (on) operation there was not as big of difference if I remember correctly. The battery you use can also play a big part. The SR44 has a superior discharge curve to the cheaper LR44. I have not tested battery life personal on both just read someone else findings. Like barry said, the best way to save battery life is take it out when not in use.
> 
> Found the link: Caliper Battery Life



The cheap one I have does go off after awhile you have to hit the ON button to turn it back on it won't come on with movement.


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## moderator007 (Aug 29, 2012)

Lynx_Arc said:


> The cheap one I have does go off after awhile you have to hit the ON button to turn it back on it won't come on with movement.


I do have some that stay off some come on with movement. They are still drawing power. If it stays off with movement, move it a inch or so while off then turn it on. Does it still read about a inch. It was reading the movement if it does. Using power while moving and waiting for movement.

If it comes on with movement then it is idle monitoring for movement but still using power. Same as the ones that stay off but it turns the display on when it senses movement. The ones that stay off are only powering down the display, their still working you just can't see it because the display is off.


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## precisionworks (Aug 29, 2012)

moderator007 said:


> According to what I read when I was researching for a good caliper, the caliper is not actual off when the display is not lit. The caliper is still reading position and drawing power the display is just off.


+1

The spare digital I bought came from MSC & was SPI model 14-792-6. They still carry that one at $50 retail & $25 on sale. I mistakenly thought that the SPI name & the higher price made it better than the $10 models. My bad.

The battery would not last 30 days when left in the caliper. Caliper was stored in the case & kept in a temp controlled office. Long Island Indicator claims average batt life in a Mitu is 1277 days (3.5 years) but let's figure really conservatively and call it 730 days (2.0 years).

The MSC clunker would eat 24 batteries for every one used by the Mitu. Found a nearly new Starrett 102A-6 for $75 and it has never gone through even the first battery. Price is higher, yes, but cost is close to zero. It would sell today for $75 (probably more) so cost for using this caliper for five years is $0.00. It feels just as good as it looks so I picked up the 9" & the 12" models at bargain prices, either on eBay or on one of the forums. 

No tools are higher priced than Mitu & Starrett & nothing else has a lower net cost. I like tools that cost nothing so I keep spending way too much for the ones that cost so little 

http://www.starrett.com/metrology/product-detail?k=120A-6


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## will (Aug 29, 2012)

I have had mine for 2 months now, still the original battery. I'll leave it in and see how long it lasts. If it is a year or so, I won't take it out. 

I suspect there is a wide range of inexpensive digital calipers, some better than others. 

My own feeling on this - If you are in the business of making things using a lathe, milling machines, drill presses etc.. the best is a quality, oil proof digital caliper. 

If you aren't making things. just figuring out what you have for various hobbies, and you are not using it on a daily basis - then an inexpensive digital caliper fits the bill...


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## Lynx_Arc (Aug 29, 2012)

My caliper is a Cen-Tech brand, does yours have an "ON" button?


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## will (Aug 29, 2012)

Mine is a 'no name' brand. inch/mm button on top of display, on/off and zero on bottom of display.


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## Codiak (Aug 29, 2012)

I have the same digital unit for HarborFreight and Menards... both over a year old... both using the original battery... and both under $20


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## KC2IXE (Aug 29, 2012)

I've had a mitutoyo Absolute solar unit for oh, 10-15 years now, works fine. As for not trusting it, when I need more than it will deliver, that's what Mics are for. Can't tell you how many 0-1 Mics I own (Literally, I cant, I've run across too many 'you have to buy the whole toolbox to get X', and then there was the day I came across the garage sale with brand new Miti 0-1 mechanical digital mics - they wanted $5. Bought all 6 sets they had. I have mics up to 6", which is as large as I go - do need some longer units someday


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## precisionworks (Aug 29, 2012)

will said:


> If you are in the business of making things using a lathe, milling machines, drill presses etc.. the best is a quality, oil proof digital caliper.


 Lightweight calipers (dial, digital, vernier) are good enough for wide tolerance work. Each of those types is reliable to + & - 0.001" (0.025mm). For lot of work plus or minus 1 is within the accepted or called out tolerance. When the tolerance is any amount less than that the calipers should stay in the drawer & a more accurate tool is required. 

Heavy frame verniers, micrometers, inside mics, etc. are the tools of choice when critical dimensions have to be hit dead on. Imagine turning down an electric motor shaft for a bearing press fit & using the most expensive digical in the world ... only to discover that you turned the diameter .001" too small & the bearing drops on with a thud. 

That happened at a shop because a newer machinist insisted that his $$$ digital was better than anything else. Motor was 500 hp & weighed about 2000# (roughly 1000 kg). Shaft was typical for that frame, just under 3" (75mm) IIRC. The new guy extracted the rotor without dropping it, got in in the lathe, carefully turned down the shaft for the correct interference fit. A couple of us noticed he seemed to be squeezing the jaws pretty hard & that might be why he went way too far. Shop manager came over with his Starrett mic, took a few measurements & asked the machinist if he had any experience with the flame spray lathe. Nope he said, that's the worst job in the shop (and it was). 

He got really good at flame spray during the next few months :nana: Heard he left & choose another career path.


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## KC2IXE (Aug 29, 2012)

precisionworks said:


> Lightweight calipers (dial, digital, vernier) are good enough for wide tolerance work. Each of those types is reliable to + & - 0.001" (0.025mm). For lot of work plus or minus 1 is within the accepted or called out tolerance. When the tolerance is any amount less than that the calipers should stay in the drawer & a more accurate tool is required.
> 
> ...snip....



I'd bet that 99% of the work out there is +- .001 or more. Heck, I'd bet a lot of work has .005 or more...


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## fyrstormer (Aug 29, 2012)

I have a steel digital caliper I bought for $30 from Garrett Wade. It has a ruler on the side, and the LCD will display decimal inches, fractional inches, and metric units down to 0.01mm. It consistently measures the same thickness for the same sheet of paper, and different thicknesses for different sheets. It's super useful; I'd definitely buy it again.

EDIT: Specifically relating to the original post, I have used the caliper I mentioned in several projects involving my old Pro-Flex bike and my new Christini AWD bike. The caliper came in especially handy when buying an entire new set of (titanium!) bolts for the Pro-Flex.

ANOTHER EDIT: Link for the lazy.  http://www.garrettwade.com/combination-fractional-display-digital-calipers/p/96T01.06/


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## will (Aug 29, 2012)

KC2IXE said:


> I'd bet that 99% of the work out there is +- .001 or more. Heck, I'd bet a lot of work has .005 or more...



From what I remember - A lot of 'square' dimensions were + or - .005. 

diameters would tend be be a closer tolerance - fitted into bearing and the like. Screw holes would tend to be -.000 but plus .005. 

Of course - it would depend on the use of the object being machined.


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## precisionworks (Aug 30, 2012)

KC2IXE said:


> I'd bet that 99% of the work out there is +- .001 or more.


Why are you never close by when I need money? I'll bet a fist full of Franklin's that the number is far less than 99%. How about it 

Things that slide by each other are most often called out in tenths of thousandths - the wrist pin bore in an automotive piston is a good example. The pin does not want to even start in the bore unless it is 90.000° to the bore axis ... although it might start at 89.999° more or less. Bores on the racing engines around here are honed with a $100k Sunnen automatic honing machine & that machine can easily split a tenth of a thousandth into ten more parts. 

Press fits are similar. Small bores (electric motor bearings 500hp & smaller) have the smallest allowable tolerance band you can imagine, often plus & minus three or four tenths. 

Pins can be close call out or very wide call out. I've made dozens of small pins roughly 2"x12" & the call out was +0.000" & -0.062" (plus nothing & minus 1/16"). Probably would have been customer accepted at minus 1/8" & worked just as well. Not my call so we made the part to print. 

It all depends on how good the fit needs to be or how bad the fit can be & still work. Look at some less costly titanium flashlights - external thread is +0.00mm & -0.20mm, internal thread is -0.00mm and + 0.20mm. Best case is that the head screws nicely onto the body, worst case is that the head screws on & doesn't fall off, either one meets the generous QC standards established by the maker. 

If I had to guess the number might be 75% non critical, 15% somewhat critical, 8% pretty darned close & 2% so close that it's scary. All bets are off in third world & developing economies.


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## will (Aug 30, 2012)

The shop I worked at was a small prototype shop. We had one job I will never forget. It was for Brookhaven National Lab. It was for a roller screw, think something like a automotive steering box. The screw part had very large rounded threads and was 10 inches long. We had to cut a diameter on each end that was within .0001 concentric to the bottom of the rounded screw thread. I have no idea how this worked or what it was going to be used for. They supplied the screw. If I remember correctly, we spent the better part of the day setting this up.

We also make component parts for the Grumman Lunar Excursion Module (LEM) These were mostly brackets and for the most part had tolerances of + or - .005, if you will - square tolerances, maybe a couple of screw holes, locations within + or - .005. 

I was in my youth at that time and learned a lot from the shop forman. He still had all his fingers and I thought he was best to learn from...


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## OCD (Aug 31, 2012)

My dad was a machinist for about 18 or 20 years, with about half that working for a shop that was a sub-contractor of (at the time) McDonald Douglas. I never got to see any of his prints or really knew what his typical tolerances were, but I can tell you his tool box has 2 sets of calipers...a set of 0-6" dial Mito's and a set of 0-10" dial Fowlers. He doesn't have any vernier calipers. The rest of his measuring tools consist of all mics....all shape, all sizes, just no digitals.

Most of the parts he made went into F-18's and F-15's. On a tour of McDonald Douglas his shop got to take their family's on in the late 80's, we stopped and he pointed out some parts on a table and said his shop made those. As he leaned closer and looked at the inspection stamp on them, he said "...Actually, I made those". As a kid that was just awesome!

Another similar instance was at an airshow back when you could literally walk up and touch and airplanes, we were looking at the front landing gear of an F-15 and he pointed out a part he routinely made and said there was a good chance he made that particular one. Makes a kid free real proud!

Sorry to get O.T.....I was lucky enough that my dad passed along to me his 0-6" dial Mito's he used at home once he retired as a machinist and brought his tools home along with a nice vintage 0-2" Brown & Sharpe micrometer and a vintage 0-4" Brown & Sharpe depth mic that he never used....and I don't even own a drill press, much less any machining tools....yet!


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## precisionworks (Sep 1, 2012)

Cool story, thanks for sharing 



OCD said:


> ... his tool box has 2 sets of calipers...a set of 0-6" dial Mito's and a set of 0-10" dial Fowlers. He doesn't have any vernier calipers. The rest of his measuring tools consist of all mics....all shape, all sizes, just no digitals.



I worked in one factory where the machine shop foreman hated all things digital. He put up with the two axis DRO on the Bridgeport & the three axis DRO's on the boring mills but that was the extent of his participation in "modern" technology. The first mistake I made there was pulling out a 9" Mitu Absolute for a critical bore job. Just as the jaws were touching the bore he walked over & asked WTF was going on. Tried to explain (in my best rookie voice) but he was hearing none of that. He handed me a well used Brown & Sharpe heavy frame master vernier caliper & a 5X magnifier glass. Last thing he muttered when walking away was "Don't f*** up this bore or you'll be sweeping floors instead of running machines". He certainly had a way with words.

Bought my own heavy frame master vernier, a Starrett 123-12. Added a Mitu copy 18" long. Both were eBay items that sold for not much more than a Happy Meal at McDonalds. Still have both, still use them.

Took the 9" Mitu Absolute home that day & it never went back to that shop :nana:


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## 350xfire (Sep 1, 2012)

lol! I am taking a machine shop class at the local comm college and the instructor is an old tool and die maker. We have 5-14" machines and 5-pretty nice mills. They are all Taiwanese units equipped with DROs. He pretty much told us he didn't trust the DROs and we should use vernier calipers...


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## KC2IXE (Sep 7, 2012)

precisionworks said:


> Why are you never close by when I need money? I'll bet a fist full of Franklin's that the number is far less than 99%. How about it
> 
> ...snip...



Maybe the work you and I do - but remember, I was thinking by the part count. How many millions of PC board standoffs, candlesticks, drawer pulls etc are done for every wrist pin out there? Seriously, there are things you have to laugh at - for instance, I think I saw that 75% of all work is 1/2 diameter or less (which is why the old 3C/3AT etc collet sizes were popular - along with all the screw machines that took some sort of small collets) and something like 95% of all work fits through a 5C collet.

There are a LOT of parts made by the mile, cut off by the yard


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## KC2IXE (Sep 7, 2012)

Will - RE BNL and the LEM - I know/knew people at both places, and I see you are in NY - still on the Island? Love to get together (I'm in Queens)


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## will (Sep 7, 2012)

KC2IXE said:


> Will - RE BNL and the LEM - I know/knew people at both places, and I see you are in NY - still on the Island? Love to get together (I'm in Queens)



I was a mere child at the time, right before I went into the Navy on active duty. I did not know anyone at either BNL or Grumman. The owner of the shop had the contacts with the purchasing departments there. 

I spend my time between NY and Florida, getting ready to head back to Florida soon.


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