shim question

[Kevin1]

If it's a dial type micrometer, close the jaws and turn the dial to read zero. Then measure the shims again.

[wengr]

Isn't there a "zero" button on the micrometer?

the on\off button doubles as the zero button. what seems to be happening is that when zeroed it then measures more accurately, but each time it's closed and reopened it's drifting off more, showing a result smaller than actual. should you have to zero it for each measurement? there is no mention of this in the instructions.

[wengr]

If it's a dial type micrometer, close the jaws and turn the dial to read zero. Then measure the shims again.

Kevin, it's one with a digital readout.

[kilrwail]

Sounds like a design/quality flaw. For $25 or less, you should be able to get a real one with a button. I'd return it for a refund.

[wengr]

Sounds like a design/quality flaw. For $25 or less, you should be able to get a real one with a button. I'd return it for a refund.

Yeah I agree, I wanted the basic one as I could not imagine what type component inside could take the physical reading and convert it to an electronic signal. wondered how acurate it would be now and in the future. however it was the only type they had, and to add insult to injury it's more money.

[manoa matt]

A good way to check the accuracy is to use the claiper measure the blades of a feeler gauge. Also when resetting to 0 or closing the jaws, make sure there are no impurties or debris stuck to the jaws or to will not read true 0.

[joelbert2k]

The only thing I trust for measuring. No batteries required.



Joel

[wengr]

The only thing I trust for measuring. No batteries required.



Joel

yeah that's what i wanted but all they had was the digital crap. Alvon if you are out there - as soon as you said that a shim should be at least as thick as a quarter and a dime, and that the coins together measure about 1.25 mm, I knew it could'nt be anything but a bad micrometer. and sure enough that's all it is. better than needing more machine work. thanks alot and thanks to everyone for thier helpful advice.

[ventura ace]

Glad you got it figured out. I keep a pair of digital calipers (about $15) and non-digital micrometers (about $35) -- 2 of the handiest tools I own. Especially the calipers. I use them all the time for checking dimensions. Both are from Harbor Freight (sorry Mike), and they've always worked great. It's nice to have both, since it's easy to make a mistake adding numbers together in you head for the micrometers -- each turn of the mic barrel is .025", so .144" actually reads '19' on the mics (19 + 25 = 44, and it's past the .100" mark). I usually use the digital calipers to give myself a ballpark number to keep in mind (accurate to .001"), and use the mics to get the most accurate measurement down to the closest .0001". The mics have a nice 'click' feature, so you know that you are always measuring with the same 'load' on the part that you are measuring.

And, like someone said, always start by checking the zero. I usually put a clean piece of paper betwen the meausuring faces, close the tool on the paper, and slide the paper back and forth a little bit to clean the face. Then pull the paper out, and check zero. This removes the slightest bit of oil or dust that will affect the measurement. And make sure that the part you are measuring is clean also.

The electronic feature on the digital calipers is very handy for converting between metric and inches. I use the calipers for almost everything, since they give a good accurate measurement down to .001". They have one more decimal place that toggles at .0005", so you might say it is accurate to that level, but there's always the question if you have closed the calipers with the same force repeatedly, if you are taking the same type measurements of many different parts. That's where the 'click' feature of the mics is valuable, since it assures you of measuring with the same force each time.

I hope all this rambling makes sense!

A

[engineerted]

Time to get a new Mic, you can also use a Caliperfor measuring. From you photos I see that you have one shim with 435 stamped on it, that shim is 4.35mm ~ 0.171" Use this to test your measuring skills.

Ted

[alexGS]

Excellent post Alvon - the rambling made perfect sense to me, at least

I use a Mitutoyo micrometer that's about 30 years old - and metric. Like most Japanese instruments seem to be, it's as good today as the day it was made, probably because of the proper case that it came with. My father taught me not to rely on the 'click' feature and to exercise a gentle touch instead, but usually I click it anyway.

However I certainly understood the reference to low-cost poor-quality stuff from China. Of course there is good-quality stuff somewhere in China too, but at the end of the day, I think you usually get what you pay for.

Anyway the point I wanted to suggest was that if buying a mechanical micrometer or calipers, surely it would be worth getting one with metric calibrations? Converting from 'thou' to metric or vice versa does my head in , I suppose because I've never worked in inches before and suddenly find it in old manuals. The target clearances are always round figures in mm, and the shims run in 0.05mm intervals. Yet the Haynes manual (English, of course) for the 124 insists on inches (for everything else, too) and doesn't give the metric measurements. For example, to set the brake compensator, I have to either try and find a ruler with inches on it (!) or convert the measurements to mm.

I'm thinking of buying some electronic calipers for the convenience factor - after all, they're so much cheaper than they used to be - but for accuracy I doubt they'll beat the old Mitutoyo, except if the latter is mis-read (which is less likely when it's metric, I reckon )

[Kevin1]

Starret has a line of micrometers that offers the best of both worlds, Digital readout, but in a completely mechanical device. No batteries, no digital anything, no errors from misreading. They aren't cheap but like alexGS said, you pretty much get what you pay for. When it comes to measuring, Starrett is about as good as it gets.

http://catalog.starrett.com/catalog/cat ... roupID=218