HF's Digital Calipers

[lynnl]

I was at HF earlier today, perusing their digital calipers. I'm mainly a dial guy myself, but the metric capability would be handy on those rare (for me) occasions.

I took one out of the box for a test drive, "...hmmm, feels like it has sand in it." Put that one back and tried another, "...holy smokes, this one has gravel in it."

Is that as good as it gets for those things? (These were labeled "Pittsburg." Seems like I've seen other names on them at times.)

The only digital I've used is a Starrett I bought at an auction. It's silky smooth, but the batteries last no time, and the functioning (i.e. metric vs imperial) I could never quite figure out.

[dp]

The biggest problem I've had with them is battery life. You have to remove the battery if you don't use it often because they suck the life out of those little cells in a matter of days. I've tossed them all away.

[mars-red]

I've got one of the cheap-o import ones that Enco sells (i think they're $22 right now), and I like it well enough. Not as smooth as a nice one, but not gritty. Battery life has been ok too. They seem to last me 6 months or so, with very occasional use. I don't think it matters how often you use them, really, they seem to use as much battery when they're off.

[CCWKen]

The two I got from HF years ago are Cen-Tech brand (item# 47257). I have one here at my desk for measuring what-knots I bring in and one in the shop and they are both smooth as silk. I still find myself using the dial calipers in the shop more often though because of the battery. I leave the battery out until I get ready to use them.

[EVguru]

Battery life;

SR44 not LR44

[Gravy]

I have several that I bought when they were on sale for pocket change. The Cen-Tech branded ones are OK for the price - smooth & repeatable, even if battery life is marginal. The Pittsburgh labeled one is an utterly worthless POS. Feels gritty, resets to zero at random while moving the jaws, switches between inch and metric when it feels like it. They are clearly very different products from different manufacturers.

[lynnl]

Well, sounds like a good purchase to NOT make. Life is already rich enough in faulty items, without adding another.

[J. Randall]

Battery life;

SR44 not LR44

+1, they last a couple of yrs. in my digital import, instead of a couple of months. I bought my digital at the local farm store, seems like it came from Spain. I have been really happy with it.
James

[KJ1I]

Here's another I guess I don't understand. I have a Mitutoyo digital I keep in my main tool box in the basement. I got tired of going up and down the stairs to get it then return it. With the Harbor Freights on sale for under $10, I figured "What the heck?" I now have three in various places around the house. One is over 2 years old, still on the original battery, and when occasionally checked against the Mit is always within .001. I'll admit, the "action" is not as smooth as the Mit, but none of them are "as rough as gravel". Maybe I've just been incredibly lucky, or maybe my expectation of a $10 tool is slightly lower than that of a $100 tool.

[PStechPaul]

You might want to check the other thread on calipers: http://bbs.homeshopmachinist.net/thr...recomendations. This was about the problems I had with my HF calipers and how I fixed them a couple years ago but now they went bad again and are now just a precision monkey wrench with a ruler.

More technical details about their operation and battery life are in a usenet thread I started when I first repaired mine:
http://www.diybanter.com/electronics...l-caliper.html

There seems to have been a change of manufacturers when they switched from the Cen-Tech brand (which I have) to Pittsburgh, and the overall quality and feel was worse. This is noted in some of the customer reviews on the HF website. There also may have been a change in the auto power-off feature, but this is not really that useful since it just turns off the display. I measured the current with display on as 14.5 uA and 13.5 uA off, but the SR44 cells are rated at 17.5 mAh which should give about 14,000 hours or 1.5 years. However, the low battery threshold was found to be 1.37V and minimum operating is 1.01V. The silver oxide cells have a flatter discharge curve so they stay above 1.37 volts longer than the LR44 alkaline. But the SR44 are about $0.75 each (or more), while the LR44 can be found for about $0.15 each.

The electronics may be sensitive to moisture and I have a damp environment which is sometimes condensing, and that may quickly deplete the battery and degrade the connections as I think happened with mine. I am planning to get another digital HF with fractional as well as decimal and metric, for $20, and also a dial type for about the same.

I also have a cheap plastic digital caliper that only reads to 0.01" or 0.1 mm, and seems accurate enough, but it goes crazy near a CFL or circline fluorescent lamp. And I also have a plastic dial type with the same resolution, and it seems smooth and accurate. Plastic tools are useful when working with magnets, batteries, or live circuits.

[Mike Nash]

I was at HF earlier today, perusing their digital calipers...

I took one out of the box for a test drive, "...hmmm, feels like it has sand in it." Put that one back and tried another, "...holy smokes, this one has gravel in it."

Wow, that was exactly how I felt about the two I tried in Birmingham a week ago although I tried the gravel one first I really, really liked the size of the display's digits and the fraction capability, but I just couldn't like them that much.

I would really like to have a digital caliper that shows all three at once (inches, mm, fractional inches) without having to hit the button. That would be massively handy to me so many times.

[Mike Burch]

I've had a $25 anonymous (i.e., almost certainly Chinese) steel 150mm/6" digital caliper for years. It's perfectly smooth. Identical instruments are sold in NZ under various names.
I think I once changed the battery.
Whenever I've checked it, which isn't often, it has always been within a thou of my micrometers.

The batteries that do go flat in a couple of weeks are those in the DROs on my Sieg C3 lathe, which is why I never use the things, and indeed wish I had not asked for them to be factory-fitted in place of the usual dials. They are bulky(preventing my turning the compound far enough for one-face thread-cutting), they add to the backlash, and putting the batteries in requires a microscopic screwdriver in the delicate fingers of an under-nourished six-year-old.

[David Powell]

Just to meet a challenge made in Jest---

Some years ago one of my friends, a very capable machinist and mechanic, built , completed and ran a 3 1/2" gauge locomotive ( The Raritan design). Just to meet a challenge made in jest over a beer ( or maybe a tea we like both) the ONLY measuring tools he used were a measuring tape, and a digital caliper( But I do not remember what breed, knowing him probably good quality secondhand ) As part of the same challenge he did the milling on a small round column mill, holding all the work in a 6" vice which he left on for the whole job. The engine goes a whole lot better than many others. Again , to me it proves that is is not the tools that really make the job good or not, but the man using them appropriately knowing their limitations and being prepared to work round them. Regards David Powell.

[cwolfs69]

i have a 6" and a 4" that i thinnnk i got from amazon very cheap, $10-15 each . use them in my pen work about 100 times each day. never put back in box. around glue, solvents, casting resin and machine chips and they are working fine. never remember to turn off m(they do go off auto after some time) have not changed batteries in at least a year and they never fail.

[dp]

I posted this link here back in 2009 and it's still interesting: http://www.robotroom.com/CaliperCapacitor.html

Note that in this article the capacitor is not powering the instrument. It is a filter to cut noise from an external source for those devices that are set up as poor man's DRO encoders.

This, though, is the link I was looking for. Dave Hylands did a writeup on battery life here: http://davehylands.com/Machinist/Caliper-Batteries/