I have a pair of Digital Calipers that I suspect is out.

3D Printing
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1

I have a pair of Digital Calipers that I suspect is out. I measure M8 Smooth rod and get 8.75mm . I assume the M8 smooth rod is 8.00mm correct ?

They not the very cheap ones and not the most expensive either.

My question, is there a way I can correct the the 8.75mm on the digital Calipers to the correct measurement ? Can I adjust anything on them.

bd7ea4ed6a5ee87ac6c0ce193748dd2e.jpeg

2

make different measures. What about at 20mm? 50mm? 150mm?

Did you had a magnet in range of the caliper?

3

I have the same one, I picked it up a Canadian tire. Always worked well for me. do you have any metal spark plug gappers? They are cheap at the auto stores.

4

Hi @Rene_Jurack I did try different rods & did try different measurements. If it is out, is there a way to alter the Caliper to the correct reading ?

5

I will try the spark plug gappers and see what I get , I should have some, somewhere

6

if it’s not really a “no name” one you can recalibrate them, with plug gappers, by connecting the caliper to a pc, through the serial connector (a sliding lid to the right top corner - per the pic you uploaded) this can be done with an arduino or company provided software. there are youtube tutorials too, so don’t worry.

the main thins is to have absolute certainty about the distances/thickness you’ll measure during calibration.

7

Have you tried to “zero” or recalibrate the calipher?

8

I have a look on Youtube and see how to Re calibrate them

9

Close the calipher complete an then press zero.That is all …

10

Thanks @Erich_HaHaOh , I close the it completely and always press the Zero every time I do measurements. Thanks

11

@Vaughan_Lundin Sorry, maybe you got a monday item …

12

If you want to be sure of the precision of your calipher you can buy a tool like that http://www.twenga.it/spessimetro.html and check the precision. Keep in mind that you can use your calipher for comapring: if you have a tool as a reference you can measure it and hit “zero” all other will be the difference between the “reference” one.

13

I’d rather trust the value from the caliper than the “accurate” dimension of a screw. Go measure your filament diameter if it’s between 1.74 and 1.76 the caliper is most certainly good.

14

I’m betting on the rod being oversized.
Try this: Measure the rod. Lock the caliper with the screw on top. Hold the inner diameter jaws up to an accurate ruler. Does it look like 8mm, or closer to 9mm?

15

When the batteries start running low, cheap calipers start behaving weird.

Change the battery and try again, as simplest solution.

16

well … mine starts “flashing” when low on battery … I don’t know this one.

17

Looks like my Harbor Freight caliper…

18

@Nathan_Walkner Not necessarily. Rather than being fixed error it might be a scale error. eg: 8 reads as 8.5, 4 reads as 4.25, 2 reads as 2.125, etc.

Problem with using plug gaps is that they are so thin the error at that distance could go unnoticed. I personally have a decent set of micrometers (one digital and 1 analogue/mechanical) that I can use as a test if I suspect something is wrong as a test. Mainly the mechanical one is my reference, which I only use as a test and almost never on a project directly.

BTW: Measuring diameter with calipers may seem accurate but you need to be sure you are exactly 90 deg to the length of the rod. You don’t need to be off on angle by much to make a difference.

Also, remember to inspect the measuring edges of your tools. A dent, bend, a piece of tape or a blob of glue can easily throw out a measurement. Same goes for whatever you are measuring (eg: burr on a cut end).

PS: Using filament as a measurement standard = complete folly. Usually that’s one of the things you are trying to confirm the size of, because it can vary so much, even over the length of a spool. Better off measuring filament with a micrometer anyway, as it’s more accurate at smaller distances.

20

Sometimes it’s worth it to get a halfway decent standard to check your tools.
http://www.starrett.com/metrology/metrology-products/precision-measuring-tools/micrometers/Micrometer-Standards#currentPage=1&displayMode=grid&itemsPerPage=24&sortBy=wp/asc
or
http://www.mscdirect.com/product/details/90027095
My work (large aerospace firm) spends a small fortune on standards…make that a large fortune.

21

The only way to truly check the accuracy is with a precision gauge block a dial caliper would be more accurate than digital caliper which really has no adjustments most milling machines maybe 0.01mm accuracy which I doubt medium priced caliper would have. Mitutoyo and Starrett are the way to go!