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Indicator needle

What brand? Since you are aware that adding a longer point decreases the resolution , not makes it less accurate, you can say add a 1.75" point to a .0001 indicator and get an indicator that reads .00023 or so per division. ( iirc someone on Practical machinist did the math a while back so the actual figure may be different, anyway it's worked for me) Still better that a .0005 indicator designed for that long point, but not as good as an interapid with a .0005 but cheaper.
 
There are accuracy tolerances/guarantees that come with each piece of measuring equipment. They are not 0.00000". Interapid tenth indicators have .0001" accuracy. Add the long 2.675" long stylus and you increased that to .000411".
 
DaveTooley said:
There are accuracy tolerances/guarantees that come with each piece of measuring equipment. They are not 0.00000". Interapid tenth indicators have .0001" accuracy. Add the long 2.675" long stylus and you increased that to .000411".
Click to expand...
Dave, I have gotten into this conversation to many times, they just don't get it. so here we go again ALL dial indicators have a working tolerance call hysteresis this would be the allowable backlash in the indicator this tolerance is 10% of the resolution ie. ,001 is .0001 allowable backlash. so when you change probe you have changed the pivot length thus changing resolution. some indicator designs are more tolerant than others but they ALL have error. All the years I spent in a gage lab calibrating .0001 indicators around 10 % were good or in tolerance....
 
Layman's translation, you are magnifying the SLOP in the indicator. Example: Install longer stem, set it at zero, rotate lathe 180 degrees, longer stem now indicates a number that could be plus or minus .0005 from what is showing on the dial instead of plus or minus .0001 with the shorter stem.
 
Sorry I used the wrong term when I said not as accurate. I think caleb85 new what I was saying. I do know that putting a 2.75 piont on a .0001 Interapid gave me repeatability problems. So I just got the right indacator and was done.
 
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My thought, if the indicator only reads .001" from the minor to the major diameter. Then that should tell you if your indicator is right or not. To me, it should read the difference. Say.0035"
 
Even if the indicator was perfectly accurate and had zero backlash the longer tip changes the reading of the indicator based on the changed geometry.

Say where you once had .003 run out with a .500 long tip when you install a 1.5 long tip the actual run out will still be .003. But the indicator will say the run out is .001.

The difference is due to the fact that the indicator contact is part of a pivoting geometry. The longer contact does not create as sharp an angle with it is displaced. So it lies to you.

If you want a long contact buy an indicator that came from the factory with it.
 
You have to do a rough dial in of the barrel and make a hole before using the Mitutoyo. That means doing the same work multiple times before preceding with turning and chambering. Time is money.
 
DaveTooley said:
You have to do a rough dial in of the barrel and make a hole before using the Mitutoyo. That means doing the same work multiple times before preceding with turning and chambering. Time is money.
Click to expand...
Yes, definitely. Depending on your method doesn't necessarily mean an extra step. I indicate, twist drill undersized then indicate again at throat and deeper fore and aft. The drilled hole allows me to reach in further. Then I'm on my merry way of boring, turning and so on. So either way.... Interapid or mitutoyo won't save me a step. I can care less about an extra step...

Just simply pointing out there are other options than a $300 long stem Interapid. Me personally, I have the correct long stem Interapid.
 
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