Dial gauge troubles

[Roger HartParticipant @rogerhart88496]

I have an old J E Baty (marked HI-TECH) gauge marked .0001″.  It was very sticky and after a good clean it sort of works OK but.

The return to zero is a bit unreliable,  seems to be affected by how far or fast it returns when it will shift the return reading by about 5/10ths thou.

I have some experience with small mechanisms and made sure all wheel teeth were clean and the dial needle is firmly ‘on’.

There is some sort of friction/safety clutch on the measuring rod to gear train 1st wheel which looks to be the only source of variability.

Any ideas?

 

[roy entwistleParticipant @royentwistle24699]

have you lubricated it? if so what with?

[Roger HartParticipant @rogerhart88496]

Yes,  with watch oil

[bernard towersParticipant @bernardtowers37738]

I have rebuilt a couple of dial gauges an found they work better with no lube IMHO

[roy entwistleParticipant @royentwistle24699]

wipe the oil off the pivots and plunger with a tissue and try again

[SillyOldDufferModerator @sillyoldduffer]

Though it might only need a clean and a tiny drop of light oil, an old DTI could also be worn, or more likely, the innards are bent due to being bumped or dropped.   A powerful loupe might see the damage, better a microscope.  Small flaws matter to delicate instruments working in the tenths region.

Maybe bad maintenance in the past.  Clocks are famously damaged by over oiling.   The oil attracts dust and becomes abrasive, and then gums up.   The mechanism literally grinds to a halt, and then the bearings have to be replaced.  The old ones have enough slop to upset the gears.

How elaborate was the clean?  Clocks and watches are stripped down completely and the parts put through an elaborate sequence of agitated chemical cleaners, and inspected for damage, especially the pivots, before reassembly.  Iffy parts are replaced.   I think a tenths DTI would need a similar deep clean.

Dave

 

 

 

[Roger HartParticipant @rogerhart88496]

Thanks all.  I stripped the mechanism and cleaned again.  Also removed plunger rod (which seemed OK) and found some sticky goo on it (laziness!).  Cleaned rod and rack and replaced.  No oil this time.  Seems much better,  a 1/10ths DTI does seem a bit more fussy – but worth persevering.

Will return to testing after the hols – family stuff calls.  Merry Christmas all.

 

[Nigel Graham 2Participant @nigelgraham2]

Thankyou for this thread – I have a DTI with reluctant return action so will take that advice, too!

[Clive FosterParticipant @clivefoster55965]

Nigel

Rule one with fixing DTI is clean, clean, clean, clean again and polish the plunger rod.

Clive

[roy entwistleParticipant @royentwistle24699]

I was once told by an old watchmaker  If you think about oiling it, that’s enough

[Grindstone CowboyParticipant @grindstonecowboy]

I find that the very slightly oily film left behind if you clean the parts with lighter fluid is more than enough lubrication.

Rob

[peak4Participant @peak4]

I’ve fettled a couple where I couldn’t work out why they were stiff initially.
It turned out that the rack and pinion were slightly too well engaged for want of a better way of putting it.
The rack, in my terminology, being the teeth cut into the plunger shaft.
The depth of engagement should be adjustable, but the means isn’t always obvious.
On one clock, it needed the crystal, hands, and clock face removing; this exposed some screws to allow the body to rotate in the case and set the clearance.

Bill

[Mick B1Participant @mickb1]

When I worked for Baty’s nearly 40 years ago I had a little Emco Unimat 3 and was looking for a general purpose dial gauge. The Chief Inspector prepared a 0.0005″ D4 gauge for me with a 0.300″ range of travel that gave a lot of versatility. I still use it for most purposes.

He advised me not to oil it.

The only time I’ve noticed inconsistent return to full extension, it was due to fluff collecting under the flat head of the stop screw at the top end of the rack spindle. After very simple cleaning it was returning within a tenth or so every time. Normally for checking concentricity or parallelism I advance the gauge so as to extend the return spring to about half total travel – that generally cuts out dependence on any mechanical limit in the gauge.

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