Dial caliper question

[sumquak]

when closed the needle should point straight up at that zero. if it doesn't it probably has skipped a tooth on the rack. you can fix this by opening them and sticking a paper clip into the gear and try to get it too skip back. i've had .100/rev calipers jump in .025 increments or 1/4 of a turn on the dial and this has worked every time. you might also have heavy wear in that area only and might constantly skip. like Charlie says it's a basic rack and pinion.

 

[rlockwood]

in order to calibrate measuring equipment, you need to start with a known object of higher tolerance than the equipment you're attempting to certify. A coin is not a certified measuring device. Check it against something of known size. Thats not a cheap set of calipers, and theres really no way for them to get screwed up..

 

[M1tch]

try drill bits as a tester rather than a coin which might have some wear on it. just measure on the shank of the drill.

 

[klabeaume]

Why not use a feeler gauge? Should get it close enough for a dial caliper.

 

[losikid]

Does it repeat zero?

Close it, set zero, slowly open it all the way, close it completely (slowly), check if its on zero. Do this afew times.

Best thing to reference that's easily accessible is a drill bit. As long as its newish, and not an cheapy, they should have a pretty good tolerance. If the shank doesn't measure out right, also check the tip of the flutes

 

[BigSki]

A dial caliper is a VERY basic rack/pinion system. It either works or doesn't.

true to a point. I have a set that started to behave the way that the OP is describing, I opened up the whole mechanism and discovered some x-fine grit (most likely from a cut off wheel) had got worked into the 'centering' mechanism. There are 2 small clock springs inside of the gear train for centering the needle to zero, the grit that got into my calipers over worked these springs causing one of them to become so weak it effected the accuracy of the 'zero' setting.

My opinion to the OP- your calipers are compromised to the point that they can not be relied upon to give you an accurate reading, toss them into the scrap bin and start over with a new caliper, or if you buy another used one, take a test piece of material with you ( one that you know the dimension of) and measure it multiple times to be sure that you get the same reading before you purchase them. "thumbsup"

 

[Charlie-III]

true to a point. I have a set that started to behave the way that the OP is describing, I opened up the whole mechanism and discovered some x-fine grit (most likely from a cut off wheel) had got worked into the 'centering' mechanism. There are 2 small clock springs inside of the gear train for centering the needle to zero, the grit that got into my calipers over worked these springs causing one of them to become so weak it effected the accuracy of the 'zero' setting.

Springs?? I almost want to open my dial calipers to see if I have springs. I believe it's just a rack & pinion, thus no springs.

I do know that some digital calipers get wonky when they get wet, the water messes with the measuring head and reading the magnetic strip in the "handle".

 

[Cave Dave]

Most likely a chip has been run thru the rack and pinion and they are are junk. Personally I hate the .200 dial anyways. You should pick up a set of digital calipers from harbor freight.They are cheap and very hard to ruin like dial calipers are.
One thing to remember is calipers are more of a comparison measuring tool than an accurate tool like a micrometer.I check zero and than measure a 1 inch gauge block almost every time I pick up any of my calipers.
Anyways,pick up a set of digitals you will be much happier with them.

 

[rlockwood]

Springs?? I almost want to open my dial calipers to see if I have springs. I believe it's just a rack & pinion, thus no springs.

I do know that some digital calipers get wonky when they get wet, the water messes with the measuring head and reading the magnetic strip in the "handle".

some have springs as an anti-backlash device..

 

[Armistice]

I second Harbor Fright calipers. I've had them for years (05- 06ish), but only since I've started doing stuff to my crawler have they gotten a real workout. Only thing so far is the glass plate over the readout has fallen out, but doesn't affect measuring

And out of OCD habit, I open> close> zero my calipers way too many times than I should before I even measure something, haha :mrgreen:

 

[C*H*U*D]

...I threw it in the tool box... Like maybe throwing it in the toolbox jossled the needle around....

If this is how the previous owner treated them, I think your problem is fairly obvious. If they are still good, and you continue to treat them this way, you might as well go back to a ruler.

 

[rlockwood]

Why not use a feeler gauge? Should get it close enough for a dial caliper.

all the feeler gauges ive ever seen fall under about 0.050", which doesnt do much for testing the linear accuracy of a caliper. A 1-2-3 block, better yet a 2-4-6 block are far more ideal-- but im assuming he doesn't have either of those kicking around. With non-smooth slide movement, there is clearly something wrong with the set. I'd disassemble them and see if a tooth is missing, or if its just gummed up.

And stop throwing them in toolboxes.

 

[BigSki]

Springs?? I almost want to open my dial calipers to see if I have springs. I believe it's just a rack & pinion, thus no springs.

I do know that some digital calipers get wonky when they get wet, the water messes with the measuring head and reading the magnetic strip in the "handle".

Yup, 2 little 'clock' springs. I figured that the calipers were already hosed up, so I couldn't possibly make them any worse so I opened them up. The hardest part was removing the pointer without bending it.