Caliper repair question

[ZINOM]

Hello all,

I have a 6" Phase II dial caliper that has a bit of schmutz in the small brass gear that follows the rack (at least that's what it seems to be).

My question is: should I go ahead and try to dismantle it to the point where I could clear the chip or speck of grit?.....I had a problem in the past with it getting stuck when I extended it to the 5" point, and the local Machine tool supply guy said not to dis-assemble it 'cause it would be a can of worms.....that problem sorted itself out in the end.

I have removed the long rack cover part, but am not sure if there's anything to beware of in going ahead any further.

Any advice would really help!

John

[vmil3]

Spray the rack liberaly with WD40, now move the short arm with the gear back and forth over the rack. Inspect rack to see if the obstruction is now in the rack, clean with WD40 and a tooth brush. this has worked in the past for my calipers.

[Allan Dimmock]

Some good info here http://longislandindicator.com/calipers.html

They suggest that you don't take them apart. There is some gotcha with the preload on the internal gearing, if i remember correctly

[Flying-Phantom]

A watch (clock) repair shop can often repair dial calipers.

[Bill Pace]

I had one of the el-cheapo $15 dials that went on the fritz, was real 'sticky', so figuring I didnt have much to lose and it wasnt working anyway, I went into it. Actually wasnt much to it --obviously small and futzy--, the trick was to re-align the needle back in the 12 oclock vicinity. Didnt really find an "aha!, theres the problem" , seemed to just be an accumulation of dust?, crud?, anyhow, a cleaning with some low air pressure and WD --and realigning the needle--and it worked again.

[Herm Williams]

While WD40 works to clean/flush out the rack I have found that electrical contact cleaner works better for me.The left over from the wd40 acts like a magnet for dust and swarf eventually the small teeth get packed up again.
my two cents worth
re

[Randy]

I've disassembled (and successfully reassembled) Mitutoyo and B&S calipers, and while the tiny gears and torsion springs are fiddley, it ain't rocket science, or even watchmaking. The hardest part may be just figuring out how to remove the crystal! If you have good eyes (or magnification), steady nimble fingers, a few jeweler's screwdrivers, tweezers and a paperclip or two you have a fair chance of success. Of course, it takes some smarts to figure out how the anti-shock and anti-backlash mechanisms work, but you're hanging out on this forum, so you can't be too dumb.

But short of full disassembly, I think flushing with contact cleaner, as Herm mentioned, is a good first step. If that doen't help, then removing the crystal, needle, dial face and the cell that hold the dial may expose the mechanism enough to clean without further dismantling the gears and springs.

BTW the only special tool I've used is a watch hand puller. Without that you'll have to come up with some clever way to pull the needle off without marring the dial face or risk bending the spindle. Have fun and let us know if you're successful.