calipers

[Jeff Bartley]

I have a caliper that seems to have issues. In use I usually zero it first and then go about using it. The problem is that if you zero it and then open and close it ten times it's off and needs to be zero'd again.
It's the $50 fractional woodcraft branded model. And in full disclosure--it has hit the floor once!
Thoughts?
Jeff

[Cary Falk]

If it doesn't require a battery then you probably knocked something loose and time to get a new one. Otherwise replace the battery and shee what happens. I have a cheap battery operated HF one and I have not dropped it yet but won't cry if I do.

[Rich Engelhardt]

All three of my cheap HF ones do the same thing even with new batteries.

I'm kind of ata loss here since setting them to zero is such an easy and fast thing to do, why does it matter?

My SOP is to zero - measure, then zero - measure a second time ( or third or fourth) ala "measure twice cut once".

[John Coloccia]

If you can't trust your precision measuring tools, then who can you trust? Seriously. I wouldn't have a ruler in my shop that I had to re-calibrate every measurement, and I certainly wouldn't have calipers like that! How far off are you? All of my calipers, even my cheap ones, are good to <.001" repeatability. I always check them before I use them but I rarely have to zero my nice ones. I have to zero the cheap ones maybe a couple of times a day. Certainly not every measurement.

If you end up replacing them, I've had great luck with RCBS calipers. I don't know who they're importing them from, but whoever it is makes a decent caliper. If I wanted to step up from there, I'd grab a Mitutoyo. They're available in the $120 range.

I've owned lots of cheap calipers from Harbor Freight and others on the theory that it's a wood shop and I don't want precision equipment subjected to that kind of treatment. Bah. The cheap ones all frustrate me eventually. The nicer ones just keep going.

[Lee Schierer]

I have two HF digital calipers bought several years apart. I can take repeated measurements without rezeroing. I just ran the set on my desk from closed to full open and closed again over 2 dozen times. It still read zero when I closed it all the way. If the reading changes less than +/-.001 why worry about it, it is wood you know!

[John Coloccia]

I have two HF digital calipers bought several years apart. I can take repeated measurements without rezeroing. I just ran the set on my desk from closed to full open and closed again over 2 dozen times. It still read zero when I closed it all the way. If the reading changes less than +/-.001 why worry about it, it is wood you know!

My HF don't frustrate me because of that. They frustrate me because the jaws loosen up and make it difficult to get a precise measurement when they've worn. But as you say, maintaing zero just doesn't really seem to be a problem even with the cheap ones, so it makes me wonder what's going on.

[Alan Schaffter]

You must be careful you don't move the sensors on these capacitive strip type measuring devices too fast. If you do or if the sensor head is too loose they can skip a few lines on the strip and lose calibration.

[Mike Barney Sr]

After reading this I just had to go to my shop and find out the brand name of my calipers; I couldn't remember. I have used General dial calipers and the Fowler digital caliper I use at work for my woodworking. The Fowlers read in thousands and I had to convert to fractions; the General, in 64ths, but not very accurate. I have seen fractional digital and was curious, so when there were a set of Darson fractional digital calipers at my local woodworking store, Johnson's Workbench, a Rockler affiliate, I decided to try them out. They were only 30 something $, so I wouldn't be out much. I was impressed, I must say. Unlike others they read to 1/128th of an inch. My Makita planer adjusts 5/64" per revolution of the crank, so I am able top move it half a mark, or 1/128th of an inch. I do some cold bent laminations and my accuracy has improved that after making the final pass I can stack up my laminations and they will measure the final thickness - exactly. They automatically turn off. Just by moving the jaws they turn back on again and even if you don't close them they still are zeroed out at the closed position. I keep checking them by closing the jaws and they always read zero. I have never had to recalibrate them. I have to re-zero my $280 Fowlers at work every time I use them, but not these. I definately would reccomend them to anyone who wants accuracy.

Oh, and yes, I have dropped them. Several times.

[Jeff Bartley]

Thanks for all the responses and recommendations! The one that I have is a dial type, not digital, which is zero'd by loosening a screw on the face of the dial and rotating the glass with the etched reference line. I think something must be loose because it gets further out of adjustment the more it's opened and closed.
I'll likely keep on zeroing it 'cause as was pointed out it is just wood. I like to use a caliper after rough milling parts to make sure the joinery goes smoothly. I've found that taking that step eliminates headaches later in a project.
One of these days I'll buy a good one but it's at the end of my long list of hand-planes!
Thanks again and if I figure out what's causing this problem I'll be sure to post!

[Lee Schierer]

If I recall correctly on some dial types the needle is just stuck on a tapered drive shaft, sort of like a jacobs taper chuck. If you can pop off the lens you might be able to push it onto the shaft better. YMMV.

As far as buying, a HF digital model generally sells for $20 or less and doesn't develop problems from saw dust getting into the works and for wood purposes, will be accurate enough.

[Mike Davis NC]

I have a Starrett Master Precision vernier caliper that i bought at an estate sale for $40. It never has missed the mark. Lucky find, I know.

But, If I lost it I would replace it with the same no matter the cost. Once you know what precision really is you don't want to go back.

[Mike Barney Sr]

Ooops! Brain fart! I forgot to mention that the main trouble with using a dial caliper in a woodworking shop is the dust. This was the main reason I looked for a digital caliper. Mechanical movements are not sealed well enough for a dirty environment. I used to work in a foundry in maintenance and we always bought digital calipers because of the sand and dust. Mechanical movements on dial calipers are prone to failure because of this and digital calipers are immune. Old timers will say that digital are not as accurate but pretty much they are equal. Anything more accurate would be a micrometer. Anyways, get a digital for your shop. You won't have to worry about the dust causing it to fail.