Repaired Harbor Freight digital caliper

I never have been able to get much visible effect of so called corrosion removers. Oleic acid probably being best, but supposedly the cramolin chemist also had input on making deoxit. On a short term test I can visibly wipe off oxide with an alcohol swipe, being just as effective. Most of the removing is mechanical in nature, and any liquid helps.

Greg

I have a cheap Caliper too and it recently went flakey.

I did my standard trick: Remove battery. Short battery contacts: Insert new battery. Worked.

Mine uses an LR44 and you HAVE TO use an LR44, not a substitute battery that you can get a Radio Shack. Mechanically they are not the same.

I tried a paste of cream of tartar from the spice rack in the kitchen on the battery terminals on a long forgotten remote control that had spewed its battery guts to make a nasty, green mess of the copper-nickel strips. Worked amazingly well, better than anything else I've tried for that particular problem. YMMV, of course.

The oleic acid is only about 5% of the contact cleaner. Over a period of time, it will help remove any oxide deposits. However, at such a low concentration, it should not be expected to dissolve a substantial oxide accumulation. Basically, any detergent will do as well if you can live with the residue.

More on Cramolin:

Cleaning brass clocks. Note the section on oleic acid.

The oleic acid therefore has two functions: to remove the oxide layer from the metals and to act as a soap to remove the dirt and oils. The cleaning solution has about 90% ammonia solution with about 5% oleic acid and 5% acetone added, thereby leaving plenty of excess ammonia molecules to keep the solution alkaline. The acetone is to accelerate evaporation. Oleic acid also has the advantage of being common, cheap, and non-toxic. It's a by product of corn and veggie oil production.

Scroll down to "Cease and Desist" contact cleaner. Much the same as my home made formula except I won't use acetone because it eats plastic. Ordinary isopropyl alcohol is safer.

Homebrew cleaners and protectors:

The comments on the effects of silicones plus salt in WD40 are interesting.

My cheap electronic caliper goes nuts when I transmit on UHF anywhere near it. However, it doesn't require the battery removal ordeal to recover. I just reset to zero and continue.

I beg to differ. The general package name is LR44 in an 11.6mm dia x

Be sure to check how high a voltage too, and report back. ;-)

Best regards, Spehro Pefhany

I just measured a Harbor Freight (Chinese) 8-incher.

Drain: 13.5uA (off), 14.5uA (on) Battery low threshold (blinking display): 1.37V Lowest operating voltage: 1.01V

So, it's clearly made for silver-oxide cells. The battery low threshold is set appropriately for a silver oxide cell (e.g. SR-44).

It's a lousy threshold for using alkalines--they're barely broken in at that voltage.

-- Cheers, James Arthur

You can get the silver oxide cells occasionally from Big Lots, a card of 5 goes for something like $2.50. Other than that, drugstores have 'em for something like $3-5, per cell (!).

And yes, they're mechanically the same.

-- Cheers, James Arthur

Why bother including an on off switch?

Cheers

But -- dial calipers are vulnerable to two problems.

Vernier calipers don't have these problems, but are more difficult to read with aging eyes and poor light.

Yes -- there are ways to fix both, but a lot more fiddly than fixing an exhausted battery on the digital calipers.

And the digital calipers have two other advantages over dial and Vernier calipers:

a) Switch between metric and inch modes at the push of a button, even converting readings already locked in. (Actually, some Vernier calipers have both scales, so this does not apply.)

b) Ability to reset the zero where-ever you want, so you can set it to zero on a target dimension, and then read how much you need to machine off in a lathe to see how many passes before you are close enough to do serious measurements. You can even keep a calculator handy to divide by two depending on whether your cross-feed dial reads in diameter or radius.

c) (O.K. Three for some people. :-) -- the ability to transfer the measurement to a computer (without typing errors) for statistics or other similar processing.

I have three 6" (150 mm) digital calipers, and a 12" (300 mm) digital caliper. (Not counting two old B&S 6" ones which require mercury cells for power, which are made of unobtanium.)

I also have a two dial calipers -- a 6" Phase-II, and a 150 mm Starrett.

And two Vernier calipers -- a 6"/150mm and a 24" (I forget whether that one has metric units as well.)

However -- the ones which I reach for most of the time are the digital ones -- because of the memory feature and the ability to switch measurement systems to match what I am working on and with.

One 6" digital stays near the main lathe (12x24" Clausing) and one near the little CNC lathe in the opposite corner of the shop. The cheapest digital ($18.00 at a hamfest) lives up here by the computer for when I want to measure something quickly.

I keep a spare cell (or set as appropriate) in the case of each digital, so I am not out of operation for very long if the cells in the caliper go bad.

The dial or the Vernier get used when I expect to be away from batteries for a while -- or in case the production of batteries ceases thanks to some apocalypse. :-) (Or the 24" one for when I need to measure beyond the range of the 12" digital.)

Enjoy, DoN.

Most of the newer ones dont really switch off -- just the display is blanked to save power, so the reading is preserved. (But, the battery life is not as good. On the Starrett ones which I have, the battery holder slides in and out, and by sliding it less than 1/16" you can disconnect the battery (thus extending the life) at the cost of having to re-zero when you power them back on. I normally do exactly this.

The Mitutoyo is not as convenient to disconnect the batteries, so I live with it -- but it also has an extra feature. Aside from remembering when turned off -- it can remember two zeros -- the absolute zero, and the incremental zero (say you zero it to tell how much left to remove in the lathe), and by pushing a button, you go back to the absolute zero without having to clean the jaws and check.

Enjoy, DoN.

How fast it dies is in part a function of the quality of the batteries used. There are two series, "44" and "357" which are interchangeable (and both magnum handgun calipers, FWIW) which can be either Alkaline cells, or Silver Oxide cells. The Silver Oxide (usually a "SR" prefix to the number) gives *much* better life -- at a significantly higher cost. However, those more expensive ones are the ones which I tend to use. The same in the digital micrometers, which read down to 0.00005" or 0.001 mm.

They are nice to have -- and typically the more expensive ones

Enjoy, DoN.

Or different quality of battery as I just posted above. :-)

Enjoy, DoN.

It's really not worth it for 1uA.

If I designed these, I'd shoot for 2uA active draw, like the Mitutoyos, and set the battery low threshold at 1.1V (for alkalines). The battery consumption is the biggest fault with these. Apart from that, they're impressive.

I sometimes think about wiring up a "AAA" or solar cell and just forgetting it, but for $0.50 a year it's not worth the trouble.

-- Cheers, James Arthur

Cream of tartar is potassium bitartrate. Mix the powder with some white vinegar or any weak acid and you get a paste that can be used as a cleaner:

For cleaning up the green slime left after a battery exceeds its warranty, I use ammonia cleaner. I also like the foam it produces. Copper (cupric) oxide is soluble in ammonium hydroxide, but not in water.

A micrometer should never be stored closed. (Thermal changes in dimensions can stress the components and reduce accuracy. Vernier calipers should not have a problem as long as you don't *lock* them closed -- either with the slide or the fine adjust slide.

Most modern digital calipers only shut off the display, and keep the counters and sensors powered up, so they can know where they are when the display is switched back on -- and some will even switch the display back on when it senses motion above some minimum value.

Enjoy, DoN.

Yes, some old navy guy contacted me and I stuck it in there. Have not updated anything for a while.

Greg szekeres

But he said "Vernier calipers" which have no such mechanism. Though people tend to lock the slides, so thermal stress distortion could be a problem with them stored closed and locked.

Assuming non stainless steel jaws. (I've never seen calipers with carbide faced jaws, unlike good micrometers.)

There is your problem -- cheap cells. Don't use the LR44 (those are alkaline batteries), use the SR44 and SR357 (Silver Oxide cells, with much longer life). Then things will probably last at least six months in storage. The SR44 and SR357 are pretty much interchangeable. I don't even know why there are the two series -- though you will often find them with both designators marked on the same cell or packaging. :-)

While I tend to use the digital calipers by preference. Half as many calipers needed to cover the metric and inch measurements.

Enjoy, DoN.

I bought some oleic acid from bill. I tried diluting it with isopropyl alcohol, seems to mix well.

My old cans of spray of Contaclean got all sticky and the metal was looking bad where it contacted the fluid build up. I think it also gummed up pots. Contaclean is Cramolins replacement for cramolin. I'm not trying to order it anymore because it costs watt too much to ship into the states. Interesting though, my old vial of cramolin never gummed up on the injector tube. The can of Contaclean clearly states to remove before operating, with a cleaner. Gummy!! I can't remember if I dried pure oleic acid to test for gumminess. Probably does. Deoxit does not gum. Never tried to dry up pure red caig in the vial injector. Deoxit is only 5% concentration in the spray.

Greg