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Tool Time Let's talk shop. Equipment, Tips & Tricks, Safety issues - Post it here.

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  #1  
Old 08-12-2003, 06:37 AM
Frank J Warner Frank J Warner is offline
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Location: Lompoc, California
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Dropped my dial caliper

Onto a concrete floor. Now it won't zero out at all. Is it toast, or is there a way to reset the thing back to zero?

BTW, these are just cheap Chinese calipers from Harbor Freight, so I'm only out $20 or so.

-Frank J Warner
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  #2  
Old 08-12-2003, 07:15 AM
Mail4Tim Mail4Tim is offline
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I think you should consider it toast. In my expierence it is difficult to impossible to repair even a quality, high dollar unit. If you do get it to re-zero the chances are it won't be accurate. I wouldn't trust it. Just my opnion.

Tim
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  #3  
Old 08-12-2003, 08:20 AM
Frank J Warner Frank J Warner is offline
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That's what I thought.

I once watched my father drop an expensive German micrometer on the floor. Without a word (not even a "drat!"), he picked the thing up and tossed it in the trash can. I asked him why and he said, "It'll never read right again. Even if it did, I couldn't trust it."

-FJW
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  #4  
Old 08-12-2003, 01:35 PM
R. Mark Lee R. Mark Lee is offline
 
Join Date: Oct 2002
Location: Dallas, Tx
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Hello Frank,

I worked in a machine shop for a few years, so I'll give you some options based on my experience. I've dropped, bumped, bounced calipers before and have then not read zero. Now in the shop I was in we had standards that came with the micrometers so I would verify that the calipers were reading correctly with the added offset, if so I would take a special tool made from some thin shim stock and insert it between the rack and gear behind the dial and move the gear to get it back to zero. This tool is easy to make with some siccors and shim stock, just cut the shim stock narrow enough to fit on top of the gear rack. You can also just move the dail to reset it to zero. Remeasure some standards (pick anthing) several times to see if it reads repeatably, if so your back in business. Hope this helps. By the way, if you drop your micrometer, they also can be adjusted (somewhat)to read zero again.

Mark
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  #5  
Old 08-12-2003, 01:44 PM
Frank J Warner Frank J Warner is offline
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Quote:
You can also just move the dail to reset it to zero.
Not with this damage. The reading is never the same when I close the calipers. Sometimes it's close to zero, sometimes it's way, way off. I think I killed it.

-FJW
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  #6  
Old 08-12-2003, 01:52 PM
R. Mark Lee R. Mark Lee is offline
 
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Location: Dallas, Tx
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Hi Frank,

Sounds like you could have killed it! One last thing to check, I had a pair do this as well and there was something wedged in the small rack so that everytime the gear ran across it it show a different number.

Mark
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  #7  
Old 08-12-2003, 08:18 PM
Mail4Tim Mail4Tim is offline
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Frank,

I've been working with and around machine tools for the last 20 plus years. Over that time I've seen a lot of calipers and dial indicators get dropped so I?m familiar with both examples that Mark has described. If it is a simple off set issue where the tool is always a set amount off then they can sometimes be corrected. That is provided the tool is one of the better quality units and not the cheaper type you described. If it is one of the ones that can?t be adjusted you could always just mark them and try to remember that you have to add or subtract X amount from the reading. I wouldn't recommend this, it's a bad habit to start and it?s just asking for problems down the road.

If as you said the readings are never the same then take Mark's advice and check the rack and see if something got stuck in it. You may get lucky! Most likely the pinion gear that rides in the rack has been knocked out of alignment. If this is the case you are better off tossing the thing and buying another. $20 for another unit is a small price for accuracy and peace of mind.

Tim
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  #8  
Old 08-13-2003, 07:13 AM
Rob Frink Rob Frink is offline
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No problem...it an honest mistake that happens daily in industry. Check your local yellow pages for an instrument repair shop....they rebuild/repair and certify instruments. Where ever there is industry...you'll probably be able to find on of these shops. They can typically certify instruments as well. My local shop charges a flat rate of ...approx 30% of the replacement value regardless of the condition. Calipers notoriously need the jaws squared and re-lapped. I take mine in yearly.


Here is a link to the shop that I use here in Columbus, Ohio:

http://www.idealprec.com/

I don't know if I would pursue repairing the chinese thingy....but maybe it is time to make an heirloom investment on a new set.

Good luck Frank.



Sincerely,
Rob


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  #9  
Old 08-13-2003, 07:51 AM
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Don Robinson Don Robinson is offline
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Frank, remove the little screws that hold the dial together. You may need to pry the dial face off. Carefully pry the indicator hand off.

You will find a very tiny rack gear inside held by a spring. The shock of dropping the caliper caused the spring to release the tension on the gear enough to let the gear turn and get out of time with the hand on the dial. Clean the whole caliper except for the dial face (plastic), or any other plastic, in acetone, make sure everything is clean, reset the jaws to zero, reset the rack gear in time with the indicator hand and put it back together.

You might need to do this a few times to get the hang of it, but it can be done. I know a replacement is cheap, but sometimes there's a little sentimental value in saving an old faithful tool.
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  #10  
Old 08-13-2003, 01:06 PM
Frank J Warner Frank J Warner is offline
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To Don,

I was able to disassemble the entire unit EXCEPT for the dial. I got the bezel and the crystal off, but the hands are on there for keeps. I'm afraid to pull any harder for fear of warping them beyond recognition.

To Rob,

I ordered a boxed Mitutoyo machinist's tool kit from MSC yesterday Comes with dial calipers, micrometer, 6" rule and a couple of other goodies. If I drop any of those on a concrete floor, SWMBO says a dead caliper will be the least of my worries.

-FJW
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  #11  
Old 08-14-2003, 08:51 AM
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Geno Geno is offline
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A few years ago a friend brought me some carpets to put out in my shop. These have saved many tools over the years.
I have a large one where I sit and build.
It has saved calipers, mic's, pearl handle material,ect...
It does not go in the forging area or the spark centers, but it saves broken stuff and makes your legs and back feel better at the end of the day.
Take it from an old man, it is worth the hassles.
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  #12  
Old 08-14-2003, 11:22 AM
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Jeff Higgins Jeff Higgins is offline
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I have those rubber back-saver floor mats in front of my mill and my lathe, which is where I use my measuring tools mostly anyway. Good idea on the carpeting though.


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