Dial caliper needle shifted

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bouch

bouch

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Hi folks,

I have an old 7" Helios dial caliper. I've had it since I was a teenager, and its still the only caliper I have (never bothered to buy a digital one as this works just fine)

At least until now... The other day I went to measure something, and something just didn't didn't make sense. Upon further investigation, I found that when I zero'ed the caliper, the needle was no longer vertical, it was pointing to about 5 o'clock.

20180130_073935_HDR.jpg

I have no clue how this happened. I didn't drop/bang or otherwise abuse the calipers. When I was opening/closing I didn't feel anything unusual. But clearly the gear for the needle has jumped a tooth or two and now things are messed up.

Now that I've moved the dial, its measuring fine. But its annoying as all hell.

So, How would I go about fixing this? (or should I just bite the bullet a buy a new digital one?)
 
There's two ways to fix dial calipers. One way is the caliper would have come with a bronze shim strip. This would be slid between the rack and the gear to allow them to separate and adjust the position of the needle.
The other way is to take the bezel off. This is done by prying up on the outermost edge of the bezel ring with a small screwdriver. Do a little in one spot then rotate the bezel and pry up about 180 degrees away. The bezel will pop up off of the dial mechanism. Now using a pair of pliers with teeth cut into the jaws firmly grasp the needle (by firmly I mean so that the needle doesn't pop out of the serrations but not tight enough to crush it) then pull straight up. The needle should pop off the stem. Now rotate your dial back to the proper position and close the caliper. Set the needle back on the stem and with a piece of plastic or hardwood gently push the needle down. It doesn't take much. The stem is tapered. Now place the bezel back in place and squeeze it around the edge with pliers until it's back in place.
It sounds like a crude way of doing it but that's how I have fixed my calipers many time.
Usually what happens is you get of chip or piece of grit in the rack gear and when the pinon runs over it it will skip a tooth or two and therefore move from it's proper position.
gbritnell
 
I gave up on a dial caliber with this problem as the rack was damaged and it wasn't reliable. The digital versions are much easier to use and not that expensive.

Attempt a repair but be ready to buy a new one would be my plan together with a few extra batteries. The battery become the new failure point but manageable.
 
Hi folks,

Thanx for the info. I'll check out that video. Right now I have a self-imposed deadline to make a few parts, but once that's done I'll give a fix a try. If the rack is damaged, it becomes a sentimental collectors piece...
 
As long as the reading does not change while you continue to use it that means that it has jumped a tooth. You can either fix that or just use it like it is. No need to replace it or junk it.
 
Cut a strip of aluminum from a soda can (beer can work as well)
Insert the strip to jam between the rack and the pinion gently advance the head until you feel a click. each click is 0.025"

If you get fancy the strip may be cut with a large head and hang up for the next time.
 
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