failed Dial Caliper

Hi all,

A while back (longer than a warrantee period!) I bought an 6"/150mm Imperial/Metric Dial Caliper from one of the 'usual suspects'. It didn't cost a fortune and initially, it worked perfectly.

Over time I put it to one side for no real reason, except that I found myself using either my similarly sized vernier caliper or digital caliper more.

Anyway, I picked it up to use the other day and to my disappointment, I found that it no linger worked!!

It now fails to show any reading below about an inch or above 4 inches and reads sporadically between those extremes.

As far as I can see, the pinion gear, that drives the dial, is completely disengaged from the rack at the closed/open extremes of movement and is only marginally engaged between.

I have little hope of fixing it (seems a same to throw it away, though!) - the caliper dial mechanism is glued to the body & the rack is glued (and screwed) down too.

I just wondered if anyone had come across something similar before?

It seems odd that it once worked...but now, after few months of sitting in a draw it doesn't

cheers

If the supplier was ‘suspect’ then the life expectancy of a tool may be less than most would hope for? Care to name the suspect? If it is bang good, I, for one would not be unduly surprised.

When I was a miller/turner back in the mid 70s, loads of workmates bought the then-new dial calipers and many suffered issues similar to what you describe - even when the caliper was from a 'reputable' maker. For that reason I've never had one, and lived on verniers, mics, and more lately digitals instead.

However, I have to admit that, since those old days, I haven't heard similar current stories about dial calipers. So I don't know whether makers are reaching down for the old standards again(!), or whether dial calipers are endemically prone to such faults and their use has receded in the interim?

No No! I didn't mean a 'suspect' retailer...I meant that the retailer was one of the usual 'names' in online ME tools & supplies.

I really suspect that I've simply been victim of a 1-off, rather than a wider quality issue...so I'd rather not name names, in case the wrong impression is given. Also I've long lost the receipt, so I can't prove who this caliper came from.

Everything I've bought from this retailer before & since has been of excellent quality.

P.

Thanks...very interesting...

P.

Corrosion is the only thing I can think of that would cause the difference between when you last used it and next time you picked it up. Either teeth have corroded away/stripped or the shafts/bearings they turn on have failed.

To that I would add the possibility of workshops being hostile to delicate tools. Temperatures swing between hot and cold, they may be damp, and they are always dirty - fumes, oil, swarf, and grinding dust. In them tools get dropped, vibrated, and bumped. And of course the biggest hazard to any tool - lending it to trustworthy friends who promise to look after it!

Besides, calipers were invented by Satan. Vernier's are hard to read, dial mechanisms break, batteries go flat and you lie to your wife and starving children about how much that Mitutoyo cost...

Dave

The pinion is usually spring-loaded for mechanical safety

Therefore, if the rack gets dirt or swarf embedded ... the pinion will skip merrily over it.

Cleanliness is next to sanity

MichaelG.

I think Micheal has the answer.

Sticky mechanism on the spring loaded pinion preventing it from swinging back into proper engagement with the rack. As its dead probably nothing to looks from giving it a blast up the innards with a miracle aerosol hoping to free things off. Not WD40 tho'. Needs to be the type that doesn't leave a sticky deposit behind. Just a trace of long lasting, instrument quality oil.

Had similar issues due to build up of stuff in the rack bought to a head by a large lump. After extracting the lump I carefully cleaned the rack a couple of times. After the initial clean of the rack it was clear there was a lot of stuff caught up in the pinion which worked out onto the cleaned rack and subsequently needed removing. In retrospect the action of the caliper had got very bad over time. Should have investigated sooner.

Always annoyed me that you cannot find verniers having the easy to read double length scale and proper knife-edge internal jaws.

Clive.

Not at all.. there is no corrosion at... were it not for that fact that it is not working, one might think it brand new!

Indeed looking at the pinion gear (with suitable magnification) I can see that it is simply not engaging with the rack.

P.

Hmm.. interesting...peering at the mechanism, the pinion gear seems to be slightly above the rack (when the jaws are (or close to) 'closed' ). so it may be stick 'up'. Is this what you meant by 'string-loaded'?

I wonder if a squirt of air from my compressor might persuade it back in to proper engagement..I shall try?

P.

Harsh words from Dave,but,so true,so true !!

Neither a borrower nor a lender be--------Else you end up with nothing.

.

You are the first to mention 'string-loaded' Paul

... I wrote 'spring loaded'

MichaelG.

.

P.S. ... careful dismantling, inspection, cleaning, and re-assembly is usually a better idea than 'a squirt of air'

hehe.. it may be that the problem here is that spring is in-fact made of string.,...!!

P.

My two (8" and 200 mm) Mitutoyo dial calipers have a little tool made from bent flat wire in the box to lift the pinion away from the rack if major resetting is needed.

Clearly the makers were aware of possible pinion skipping rack teeth issues. Having a tool in the box suggests that its something you should expect to have to deal with at least once in the useful life of the caliper.

Clive.

Wonder if these links are of any use ? one is resetting a dial calliper dial to zero the other is a discussion on this forum from which the first link may've come !

John

**LINK**


**LINK**

Found another one as well   https://www.youtube.com/watch?v=UrvB_eF6CLU a bit noisy and not the best video but there is some info there

Edited By JohnF on 23/01/2019 17:38:34

Why not open it up and see if you can repair it. If you fail you have lost nothing but a little time. +1 on the pinion disengaging.

I have been using cheap Chinese digitals on routine work. My expensive Mitutoyo digital is saved for critical work.

ah.. it appears my reply from yesterday didn't stick.. so..

Thanks for the You Tube links!

Unfortunately, opening it up isn't an option. The dial/bearing assembly is bonded to the caliper body, so disassembly would result in a 0% chance of re-assembly.

Peering at what I can see of the mechanism, the dial's drive pinion seems well supported & fully extended...ie, its not 'stuck' away from the rack.

I think the problem is that the way the caliper has been assembled, the rack simply does not engage (more than a though or so...some times...) with the pinion. The rack is both screwed & glued down. were it just screwed, I'd attempt to shim it a few thou...but as it stands I would guess that any attempt to un-glue it would result in a very bent rack.

I have a feeling that this is a hopeless quest...but I'll hold onto it, in case I get a burst of inspiration at some point in the future!!

Thanks all for your input!

P.

Edited By AJW on 25/01/2019 11:15:28

Opening it up is always an option! It's putting it back together that might not be. My mum has never forgiven me for 'fixing' her clock...

Seriously though, if it's unusable, why not try tearing it apart? We're all agog to know what's wrong with it!

Last time I used my ancient Japanese analogue multimeter the needle kept sticking. As its at least 30 years old I assumed the movement had failed. Stripping it down revealed a tiny spider living in the hairspring. A quick eviction and the meter's as good as new. Possibly your caliper has swarf in the mechanism? I milled some steel recently and the swarf came off highly magnetised, an effect I'd not noticed before. A fragment of that would be a pig to get out of a delicate mechanism like a caliper.

Dave