Repaired Harbor Freight digital caliper

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.

Reply to
Ron D.
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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

5.4mm thick package alkaline cell. There are slight variations, but the IEC LR1154 equivalents (LR44/LR154, A76, 157/303/357) are all the same size. Where you can have problems is that the SR44/SR1154 silver oxide cells come in the same package. They have about 50% more capacity and a much flatter discharge curve. Some of the cheapo calipers crap out below about 1.4V. The alkaline battery has plenty of capacity left at 1.4V, but the caliper doesn't want to run. If your caliper cames with a silver-oxide cell, it should probably use silver oxide batteries. If it came with alkaline and has a short battery life, it might be worthwhile trying silver-oxide. If you're ambitious, it might be useful to run the caliper off a bench power supply and check how low a voltage will work.
Reply to
Jeff Liebermann

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

Best regards, Spehro Pefhany

Reply to
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.

14.5uA means a year from a silver oxide cell--that's not horrible.

-- Cheers, James Arthur

Reply to
dagmargoodboat

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

Reply to
dagmargoodboat

Why bother including an on off switch?

Cheers

Reply to
Martin Riddle

But -- dial calipers are vulnerable to two problems.

1) Drop or bump them and the pinion will disengage from the rack and shift to give a wrong reading. You can work around that by rotating the dial to re-zero it, but past a certain point, it gets to be awkward to read. 2) Small chips can get engaged in the rack and the zero point will shift every time you pass that point.

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.

Reply to
DoN. Nichols

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.

Reply to
DoN. Nichols

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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

*do* work better.

Enjoy, DoN.

Reply to
DoN. Nichols

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

Reply to
dagmargoodboat

[ ... ]

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.

Reply to
DoN. Nichols

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.

Reply to
DoN. Nichols

Depends on how old the eye is and how good the illumination is.

The old B&S ones, which used glass encoders in the slot where the rack gear would otherwise be were sensitive to coolant in the slot. But the modern units seem to be quite good at not skipping.

I trust them (as much as a caliper *can* be trusted compared to a micrometer) in shop conditions as well.

Agreed -- or to pick up bits of swarf and skip.

I know how to use both -- but then I am (well) over fifty. :-)

But there have been verniers on the thimbles of the better micrometers much more recently than that, so presumably some of the younger crowd know.

Enjoy, DoN.

Reply to
DoN. Nichols

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If I had one of these I'd fit onto the calipers a small solar cell and diode to trickle charge the original battery ie not specifically rechargeable , and replace the lid of its casing with a glass panel and leave on a bright position .

Reply to
N_Cook

Hello, and DeoxIT is the best thing I've ever come across for cleaning and de-oxidizing electrical contacts. It also does wonders with scratchy volume and tone pots and it'll be long while before you have to apply it again. Sincerely,

Reply to
J.B. Wood

Harbor Freight Has the 6" dial Caliper on sale 11/24

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Mikek

Reply to
amdx

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Nice, I like the metal cutting saw they have there just off to the right..

Think I'll do a stop in for that.

Jamie

Reply to
Jamie

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Do note, it is pneumatic. Fine if your setup for it. Mikek

Reply to
amdx

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It is an off switch to turn the *display* (only) back on. They sometimes make it also turn the display back off to make people feel better. :-)

The auto-turn-off time of the display is usually good enough.

Enjoy, DoN.

Reply to
DoN. Nichols

[ ... ]

Actually -- there *are* some "solar powered" ones -- by Mitutoyo IIRC. They would probably be excellent used daily in a well-illuminated shop. In my shop, often dark for days at a time, until a project lures me there, the replaceable batteries are a better choice.

I did recently get an auto-darkening welding hood from Harbor Freight which is solar powered, and based on what I have read about them dying if not used regularly, I've put mine on a folding workstool facing out the window so it sees daylight to maintain the charge. I'll proably eventually have to perform surgery and replace the rechargeable cells in there. There is a temptation to provide a connection for an AC-powered trickle charger so I can store it more conveniently. What would be particularly nice would be an induction coupled charger like those for electric toothbrushes. Just put it on a stand and expect it to be fully charged when I come back.

If the charge is good enough to work on the first strike, it should work fine for the rest of the day, because it will be getting a charge boost from the arc -- close enough to vigorous sunlight. :-)

Enjoy, DoN.

Reply to
DoN. Nichols

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