Bad calipers? - Page 1
Forum section: electronics / general

author: ArtemKuchin
author_rank: Newbie
timestamp: January 26, 2019, 10:36:29 am
content: I know the topic of calipers came up many time, but i am lost a little.I have bought the calipers from ali express. I tested then OD jaws on calibrated measure blocks. they work fine.But since i did not have any calibrated hole (of known diameter) i just ignored the ID jaws. Afterall they are not usedthat much.Now, i needed to use then i found something strange.First, they are not perfectly aligned. One jaw goes over another jaw.I don't think it is normal. Because, logically, if i open the jaw i will loose the intersection distance.I test the hole and the plug and from the measurements the plug should never go into that hole. But, it fact, it goes inside easily.Also, when measured OD with the very end of the jaw (thin tip) it get a little smaller result that when measured with the thick part of the lower jaw. Maybe 0.02mm difference. Is this normal?Bad calipers?

author: ataradov
author_rank: Super Contributor
timestamp: January 26, 2019, 05:46:34 pm
content: Those are the cheapest of the cheap calipers. They are more or less expected to be this way. Some are better than the others. But they all drain battery like crazy, even when not used.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: January 26, 2019, 05:52:52 pm
content: Quote from: ataradov on January 26, 2019, 05:46:34 pmNot really... my el cheapo pure chinesium inside was 4€ and the button cell is four years old and is still alive n kickin'

author: ataradov
author_rank: Super Contributor
timestamp: January 26, 2019, 05:55:03 pm
content: Quote from: GeorgeOfTheJungle on January 26, 2019, 05:52:52 pmThey may have fixed that part. I've got a couple a long time ago, and they were always drained. I've since switched to iGaging calipers. More expensive, but actually feel nice.

author: eKretz
author_rank: Frequent Contributor
timestamp: January 26, 2019, 05:55:58 pm
content: Yep. Crap tool. Junk it or work around the error. Too funny, wasn't that long ago someone on this site was arguing with me about how cheap Chinese calipers were great quality. You'd never see this happen on a good quality brand.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: January 26, 2019, 06:02:29 pm
content: Oh yesss, I've also got a brokenmitutoyosomewhere, but the chinese one is still working fine. Lemons happen, I guess. And lemons-1too.Edit: not a mitutoyo, it's an onno sokki.

author: blacksheeplogic
author_rank: Frequent Contributor
timestamp: January 26, 2019, 08:28:57 pm
content: Quote from: ataradov on January 26, 2019, 05:46:34 pmMy cheap 'n nasty calipers will go for years on a set of batteries. My expensive precision calipers maybe six months even sitting in a draw.

author: ataradov
author_rank: Super Contributor
timestamp: January 26, 2019, 08:34:11 pm
content: It looks like they have improved quite a bit. From the cheap ones I only have stuff from Harbor Freight (just rebranded Chinese stuff), and they drain the battery.I recently got a couple of those carbon fiber plastic calipers and they seem to be much better with the battery. And I can say, I did not expect them to be this useful, but they totally are. I rarely need precision when just trying to think through stuff, and lightweight plastic calipers work beautifully for that.Decent iGaging caliprs I use on and off for 3 years are still on the original battery.

author: ArtemKuchin
author_rank: Newbie
timestamp: January 26, 2019, 10:06:14 pm
content: Battery is not a problem. Mine work on the same battery 2nd year already.Maybe someone could recommend sub 30$ caliper with 0.01 scale and +-0.02 or +0.03mm accuracy and working both jaws?Or i want the impossible?

author: ataradov
author_rank: Super Contributor
timestamp: January 26, 2019, 10:07:52 pm
content: Quote from: ArtemKuchin on January 26, 2019, 10:06:14 pmiGaging ABSOLUTE ORIGIN 0-6" is $40, and this is probably the lowest price for a decent quality.

author: ArtemKuchin
author_rank: Newbie
timestamp: January 26, 2019, 10:29:01 pm
content: Does it have real working ID jaws?

author: ataradov
author_rank: Super Contributor
timestamp: January 26, 2019, 10:30:02 pm
content: Quote from: ArtemKuchin on January 26, 2019, 10:29:01 pmYes, it is an actual real instrument, not a Chinese toy.

author: KL27x
author_rank: Super Contributor
timestamp: January 26, 2019, 10:45:01 pm
content: QuoteThere's clearly a bur on the tip of your inside/back jaws in that pic. It looks like they were dropped and the tip got dented and bent. This will obviously take up some space and give a low reading by the amount that the tip is bent. Just stone them back into shape? This isn't rocket science. Precision doesn't come only from a machine.Measuring ID of a hole , it is difficult to get the true measurement using calipers, anyway. You have to fuss and take multiple measurements and then take the largest one. There is a micrometer with replaceable jaws for that. You use pins to measure the ID, with the sides of the pins against the insides of the hole. And I think this is probably still challenging. In practice, I find it is often easier to measure the OD of the piece, then measure the thickness of the part from the inside of edge of the hole and the outside. So on a bearing/bushing or a tube, you would be measuring the OD, then subtracting the measured thickness of the material x 2.

author: jpanhalt
author_rank: Super Contributor
timestamp: January 26, 2019, 11:37:39 pm
content: Remember the adage: measure with a micrometer, outline in chalk, and build with an ax.1) Will your +/- 0.4mm Chinese micrometers make a difference in your end result?2) If precision and accuracy are important, why did you buy such cheapo's. Did you expect them to be Mitutoyo's or Starrett's?As for measuring ID's, it all depends on the diameter being measured and the accuracy needed. It doesn't really matter what you use without knowing those facts. Sometimes I just use an old warped yardstick.

author: rf+tech
author_rank: Frequent Contributor
timestamp: January 27, 2019, 05:25:00 am
content: One picture, two problems, both account for the measurement error.The added red line was set quite close to right angle with the beam. LH ID point has clearly impacted a hard surface and bent over to the right, as correctly pointed out by KL27x. Impact appears to have also bent the entire jaw, creating an overlap.RF+ Tech

author: eKretz
author_rank: Frequent Contributor
timestamp: January 27, 2019, 06:14:27 am
content: If that is the case (and not saying it is, those photos are anything but clear) then it's just another indication of poor quality. On a good caliper, should be hardened jaws, and not readily bent.

author: ArtemKuchin
author_rank: Newbie
timestamp: January 27, 2019, 07:40:37 am
content: Quote from: rf+tech on January 27, 2019, 05:25:00 amWOW! Good eyes!I looked at that jaw closely and found the bending place in the base. Yes, it was indeed bended. Where and how is still a question because they were like this since i received them.Overall it is not a bad device for my usage. It is has good return to zero (always returns to zero unless it take them cold and heat up with hand while working), battery lasts already over a year and i tested the OD jaws with gauge blocks and results were good, better than specified +-0.03mm.But again, i see that the main problem is crap metal. Very soft. Easily sanded and damaged. Even the lower OD jaw surface is crappy under 10x lens. Is see dents and deformations.But still it is probably good enough to measure 3d printer filament width and test cubes size while i am considering iGaging ABSOLUTE ORIGIN.

author: ArtemKuchin
author_rank: Newbie
timestamp: January 27, 2019, 08:26:02 pm
content: Here is video with my cheap calipers testhttps://youtu.be/m2vmAs77GMUlook pretty good, if only the ID jaw was not damaged.

author: 6PTsocket
author_rank: Regular Contributor
timestamp: January 28, 2019, 06:40:10 pm
content: The OP brought up an interesting point. I just looked at my old Japanese NSK, which are quite nicely machined, and there seems to be a tiny, tiny overlap in the inside jaws. I assume it so they will open without one jaw getting hung up behind the other. Not sure if this affects accuracy On inside jaws you have to go a little bit before the jaws pass each other enough to use them but I don't see how they compensate for the overlap, or if they even do. It is pretty tiny. Mine drift a bit innitially so it is not absolute zero but the batteries last a very long time. There is no power switch; it just times out. I just changed them and can't even remember when was the last time. Thanks for the info. on absolute zero calipers.Sent from my SM-G900V using Tapatalk

author: ataradov
author_rank: Super Contributor
timestamp: January 28, 2019, 07:15:37 pm
content: Looking at iGaging, I see no overlap. If I put a source of light right behind the jaws, I see a thin sliver of light and moving the head a bit to the right makes that light disappear. Just a few degrees is enough.But looking at the geometry at the top jaws, they are not ground perfectly parallel. They are ground with a slight angle so that if you position the lengthwise split line right along the diameter of the circle, the contact surface of the jaw will be closer to the circumference. I'll try to draw that.Here is my representation of this. The angles are smaller in reality, I've shown them bigger here for clarity.

author: blacksheeplogic
author_rank: Frequent Contributor
timestamp: January 30, 2019, 07:44:37 pm
content: Quote from: ataradov on January 26, 2019, 08:34:11 pmI have some 'plastic' General branded calipers I picked up when in the US from Home Depot.I suspect they are very similar and I can't agree more they just really handy and good enough. Much prefer them in some cases as they don't damage anything.

author: Macbeth
author_rank: Super Contributor
timestamp: January 30, 2019, 08:40:26 pm
content: The plastic ones are handy for quick and dirty measurement, my only complaint is they don't come with a depth rod (pretty understandable really!)

author: ataradov
author_rank: Super Contributor
timestamp: January 30, 2019, 08:47:36 pm
content: These ones do have a depth rod:https://www.ebay.com/itm/150mm-LCD-Digital-Electronic-Carbon-Fiber-Vernier-Caliper-Gauge-Micrometer/153087544602

author: coppercone2
author_rank: Super Contributor
timestamp: February 01, 2019, 01:48:46 pm
content: there is a recent ave review of the igauging. its for woodworkers kinda

author: ataradov
author_rank: Super Contributor
timestamp: February 01, 2019, 04:15:46 pm
content: Quote from: coppercone2 on February 01, 2019, 01:48:46 pmIt is for woodworkers, not "kinda". Here is the product he reviewedhttp://www.igaging.com/page35628.html. It is located in the "Woodworking" section of the site.AvE recently going out of his depth a lot.The real iGaging absolute origin calipers feel and work no different than Mitutoyo.Just for the record, here is the real height gauge by iGaginghttp://www.igaging.com/page59.html

author: eKretz
author_rank: Frequent Contributor
timestamp: February 01, 2019, 06:45:28 pm
content: Quote from: ataradov on January 28, 2019, 07:15:37 pmYeah we're running into the quality issue yet again. If there is overlap, you have a crap product. Here is my Mitutoyo 8" caliper's jaws at the I.D. jaws. The picture straight on shows no gap, but if I rotate the caliper a tiny bit you can see light in the gap. Since the jaws are offset, this is visible due to parallax. Most good calipers I've used have the measuring surface of the I.D. jaws ground with a very small flat. If they come to a full point they will wear out fast if you use them much. I own about 6 pairs of calipers from Starrett, Mitutoyo, Brown and Sharpe etc. and they all have flats on the I.D. jaws with no overlap. These flats on a round inside surface creates a small amount of error when measuring inside diameters, more so in smaller bores. It's almost unnoticeable past a certain size though since the flats are of very small width. This is something that sometimes had to be corrected for in the machine shop - it's called flat-to-round error. We had a table for size correction when measuring a flat surface to an inside diameter with micrometers based on the width of the micrometer anvil and the bore size.

author: ironsniper1
author_rank: Regular Contributor
timestamp: April 26, 2019, 04:31:37 pm
content: Quote from: ataradov on January 30, 2019, 08:47:36 pmi know this thread is a little old but are those calipers any good?

author: ataradov
author_rank: Super Contributor
timestamp: April 26, 2019, 05:55:03 pm
content: Quote from: ironsniper1 on April 26, 2019, 04:31:37 pmDefine "good". They are a bit better than a ruler and provide automatic measurement reading. They are not good enough for typical machining work, of course.But they are perfect for electronics, since you rarely need to measure anything with 0.01 mm resolution.And as far as general operation - they are very good. They don't drain the battery when unused, they automatically wake up on movement, they keep a good 0.