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HF's Digital Calipers

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  • MaxxLagg
    replied
    I have a nice Mitutoyo that I keep for nicer stuff. Three or four years ago I bought a 4 and 6 inch from HF. They are the older Cen-Tech versions. They are both smooth and reliable for measuring things that you should be measuring with calipers. The only problem is with the 4 incher. You HAVE to take the battery out of it when not in use. It will eat it overnight. The 6 incher lasts months.

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  • PStechPaul
    replied
    Just this evening I was rummaging through my piles of junk and treasure, and I found my second set of Harbor Freight calipers. They were in a box in my other house which is unheated and terribly damp, so much so that there is condensation on almost everything, especially on rainy cold days like today. So of course the SR44 battery was dead but at least not corroded, so I installed a new one (LR44), and it showed a garbled display. This was the reason I had bought this second pair years ago. I had been able to fix the first pair by taking it apart and cleaning the conductive rubber connection from the LCD to the PCB, and also messing with the battery connector and squeezing the "head", but eventually it just refused to work, and recently I bought a new pair for $10 on sale. It was the newer Pittsburgh version (although still the same #47257), and clearly of lesser quality, but it does the job and I'm satisfied with it.

    So, I decided to open up the calipers I just found to see if I could get them working. I was able to locate the four screw holes on the back so I did not need to remove the label covering them, and I took it completely apart. I cleaned the conductive strip and the PCB with alcohol followed by scrubbing with detergent and fresh water, and finally a blast with a heat gun to dry everything. When I reassembled it, at first it refused to work, but then after a few rounds of "fiddling" with it I was able to get it to work. Hooray!

    Encouraged by my success, I decided to once again "fiddle" with the original calipers that I had given up on but saved the parts. After some messing around I was able to get a flash of digits on the display, briefly, so I reassembled it, and it appeared to work intermittently, needing pressure on the battery to do anything. I measured the battery and it was low, and it seemed like it might have been shorting out because of my battery holder repairs. So I insulated the part that seemed to be giving trouble, and I added a few layers of tape on the top of the battery so the battery holder would exert more pressure on the contacts. Abracadabra and Shazaam! It works a treat. So now I have three working calipers.

    If anyone has one of these and wants to attempt a repair, let me know, and I'll provide more details. Here is the thing taken apart:

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  • flutedchamber
    replied
    Originally posted by jhe.1973 View Post
    dp: Thank you so much for including these links here. I missed your first posting on the capacitor conversion and found it so valuable I took the time to cut, paste & save it to a Word doc. in case it is removed from the web.



    flutedchamber:

    I too buy my batteries in bulk online but hadn't thought of the cool (pun intended) storage method. Thanks for that!

    Don't forget to leave them in their protective sleeves...

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  • jhe.1973
    replied
    Originally posted by dp View Post
    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/
    dp: Thank you so much for including these links here. I missed your first posting on the capacitor conversion and found it so valuable I took the time to cut, paste & save it to a Word doc. in case it is removed from the web.

    Originally posted by flutedchamber View Post
    ............. I buy them online for about half the price the store charges, and keep them in the fridge in a old medication bottle to keep them fresh.
    flutedchamber:

    I too buy my batteries in bulk online but hadn't thought of the cool (pun intended) storage method. Thanks for that!

    Leave a comment:


  • tlfamm
    replied
    One notch up in the "affordable caliper" spectrum is this Z-Limit product sold by LMS:

    http://www.littlemachineshop.com/pro...ProductID=4251

    It uses a coin battery; I'm not sure how they compare to SR44 in terms of battery life?

    Leave a comment:


  • Steve Steven
    replied
    I have one cheap Chinese digital caliper that SHUTS OFF entirely, and does not retain any memory and does not turn back on when moved. You have to hit the "on/off" button to get it to read, and it reads 0.000 when turned on, no matter where it is. You have to either move it to closed then turn on, or move it to closed after turning on and re-zero it.

    Looks like someone heard about battery life complaints and changed the circuitry.

    Steve

    Leave a comment:


  • J Tiers
    replied
    Originally posted by PStechPaul View Post

    I also got a free multimeter. I am actually impressed with this as well as the older yellow ones of which I have several.
    It might be as well to avoid measuring any circuit above 24V or capable of more than 50watts with that meter.... cheap meters have zero protection, and can erupt into fire in your hand at higher voltages. Not being an elitist here. There were, I think, some links posted here demonstrating what can happen to some of those meters if voltages etc are not quite as expected.

    Leave a comment:


  • PStechPaul
    replied
    I just went to HF and bought one of the Pittsburgh 6" calipers on sale for $9.99. It definitely has a cheaper feel than the Cen-Tech version that I was unable to fix. The reading head appears to be identical, so it might be possible to swap it onto the old caliper. But, really, the difference in quality is not enough to go through that trouble and risk.

    While I was there, I also looked at the inch/metric/fraction version, but the quality was rather poor and frankly the fractional display does not seem too useful, and it is harder to read. Not worth the $20 sale price. They also had dial calipers, for about $19, but they seemed rather flimsy, so I thought I might as well just use my plastic ones, since I have the digital for more accurate work, and my old Starrett 203-F for smaller work that needs better accuracy.

    They also had a set of parallels for $30. I don't have a set but I'm not sure I really need them. However, I've only just recently learned what they are for, and maybe I'll spring for them. I have several 25% off coupons, and for $22.50 they may be worth having. The one review was pretty good:
    http://www.harborfreight.com/catalog...ult?q=parallel

    I also got a free multimeter. I am actually impressed with this as well as the older yellow ones of which I have several.

    Leave a comment:


  • flutedchamber
    replied
    I use my HF caliper for rough measuring and have used it for years. It's the 6 inch CenTech brand. Use the good batteries in it, not the cheap alkaline batteries. I get 8-9 months of frequent use out of the good batteries. I buy them online for about half the price the store charges, and keep them in the fridge in a old medication bottle to keep them fresh.

    Leave a comment:


  • Paul Alciatore
    replied
    I have a bunch of import, digital calipers, several 6" ones, an 8", a 12", and one that does fractions. I have had good luck with all of them. But they are not the same quality level as Starrett or other name brands that sell for $100 and up.

    One of the six inch ones is a 6", Cen-Tec brand from HF and I keep it at my electronic bench. I purchased it about 2 years ago and it still has the original, Chinese LR-4 battery. The caliper has an auto-OFF function so the battery does not run out while I am not using it. I have not yet checked it against my shop blocks so I can not comment on the accuracy, but I have no reason to check it. It does run smoothly and has no more problems from cocking than any of the other imports that I have.

    My one complaint about it is it re-zeros itself when power is turned on so I always have to recheck the zero before use. But then, I should do that anyway so no real loss there.

    I did not try out a bunch of them at the store, so I may have been lucky.

    I can not say anything about the Pittsburgh brand calipers.

    Leave a comment:


  • J Tiers
    replied
    I have a bunch of dial calipers, mostly dual metric/english.

    I have one older digital caliper, which is probably cen-tech. No gravel in it.... (aside from the discolored silicon that runs it)

    For measuring capability, all are about the same, except that some of the non-metric calipers are two tenths per rev, and can't be read closely. The digital checks out against the others, and against gage blocks as well as any.

    The digital do have one problem, they have an "on/off" button. one push for on, a second for off, IIRC(I don't use them much). Since I have them at work for use by the "uninitiated", I find them "on" quite a bit. But the battery is still fine.

    As for the old saw about "it's the workman and not the tools"; that's true so long as the workman measures with the same instrument always. It wouldn't matter if his inches were 30mm long.

    But as soon as that workman has to make something that must fit some other thing which he hasn't seen, then it can't be hand-fitted, and the measuring tool is suddenly as important as his skill. All his skill cannot make the part to 3.643" +- 0.0005 unless he can measure it with inches which are the same size as the customer's inches.
    Last edited by J Tiers; 11-23-2013, 06:01 PM.

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  • dp
    replied
    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/
    Last edited by dp; 11-23-2013, 12:17 PM.

    Leave a comment:


  • cwolfs69
    replied
    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.

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  • David Powell
    replied
    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.

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  • Mike Burch
    replied
    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.
    Last edited by Mike Burch; 11-07-2013, 09:46 PM.

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