Posted: 2/18/2008 10:31:14 PM EDT
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Ok, I started checking the valves on my bike, and all of the exhaust valves are out of spec! So I'm going to have to pull the shims and measure them to get the correct sized new ones. Looks like I'll need a micrometer, the shims are very small and I need .001 or better accuracy. The problem is, I've never used one before and really have no idea what to look for. I'd like to get a quality one, but keep it at $100 or less. Craftsman sells an electronic one for $100 that converts to metric and standard, but I don't know if electronic is the way to go or not. It would be much easier to read for sure! Anyway, thanks in advance for the help. |
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You can buy a regular mic pretty cheap and just convert the reading with your calculator. For readings < .001, an electronic one may be best for the untrained eye. otherwise with a little effort they are pretty easy to use. The conversion from standard to metric is take your standard measurement, for instance .005 (or 5 thousandths) and multiply it times 25.4, which gives you .127mm. Or for the other way its .127mm times .03937 which is .005. If you need to read a mic, I can see if I can find an instructional pic or two online. ETA: 
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It just crossed my mind, but what about a caliper? Do they make those precise enough to read something that small? Also, if I need to read accurately to .001(inches), do I need to get something that is good to .0001? Taking into account the amount of error and all. The clearance on this bike is .xxx +/- .001, so there isn't much room for error. |
Most digital calipers only read to .0005 (which is 1/2 a thousandth) and aren't really accurate to that, they just read to that. For <.001, you'll need mics. Check those Harbor Freight ones, measure what you need, lock the thimble and push the standard/metric button to convert. |
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check EBAY . lots of good used mics on there . to double check a 0-1" mic just run it down till both faces touch . it should read all zero's . cgi.ebay.com/FOWLER-NO-3921-0-1-MICROMETER_W0QQitemZ270212115725QQcmdZViewItem?hash=item270212115725 something like this . the digital and such while nice are not really nessacary. reading a mic is pretty easy , each revolution is .025" . the .0001" marks read a little differently but its a still easy. some of the 3-4 piece sets might be a good idea to get insted , that way you can measure stuff correctly. |
+1 Good calipers usually won't be as accurate as you want. Good micros usually will be more accurate than you need. Better to have it and not need it, than need it and not have it. |
Not trying to offend you,--------- but if you don't own and/or know how to properly use precision measuring devices,-------- do you think you can accurately adjust your valves...? |
| I prefer the mechanical mics, so I'm not dependent on batteries. But get whatever you like. If you find a good mic, that is not electronic go ahead and buy it. Dont worry about conversion, just remember "25.4" that is what you divide metric by to get a fractional tolerance. Also it works the opposite direction, you would multiply a fractional tolerance by" 25.4" to obtain a metric tolerance....until you memorize the metric/inch conversions the number 25.4 will be your best friend! |
Use an electronic, and do not force the caliper closed, it should gently touch the object. |
Get a micrometer with a force limiter, so that it will always apply the same amount of pressure to close every time. You'll never over tighten if you use one of those. |