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Long Reach Dial Test Indicator

Armourer

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#1
I am in the market for a long reach test indicator, it will be used to centre rifle barrels in my 4 jaw chuck. I have done some research and have found that long island indicator lists a Interapid with a 2.75" stylus which would be great, how ever the price isn't! I was wondering if there was any Mitutoyo indicators with a stylus that long, or a Starrett one? Anyone else have any other ideas??

BTW it would have to be a .0001 indicator as well. Thanks all
 

Bob Korves

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#2
Stylus tips are interchangeable. If you are only dialing in the barrels to center them, and not needing to hit a particular number, just buy a longer stylus and put it on any tenths indicator. Just make sure to get the correct thread. Actually, DTI's are not that good at hitting a specific dimension anyway, because of the cosine error caused by the stylus angle to the work.
 
Last edited:

dlane

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#4
image.jpg image.jpg
Good ones are e pricey, I have a super accurate veneer.yard stick, 3' been wanting to mount it on something
Who ever made it did good

Pic's gone goofy
 
Last edited:

Armourer

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#5
Stylus tips are interchangeable. If you are only dialing in the barrels to center them, and not needing to hit a particular number, just buy a longer stylus and put it on any tenths indicator. Just make sure to get the correct thread. Actually, DTI's are not that good at hitting a specific dimension anyway, because of the cosine error caused by the stylus angle to the work.

Just out of curiosity, do you happen to know the current size and thread pitch of the new Mitutoyo indicators? All I have found for them is they are a M1.7, but don't give a thread pitch. Thanks!
 

Tony Wells

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#6
Beware. Changing the contact point length from what it came with changes the ratio of movement at the tip and movement of the dial. Your tenths indicator will not read tenths if you put a long contact on it. What movement you see on the dial will be smaller than the actual error you are reading. Buy the indicator with the contact point length you need. And the trig error referred to is not that hard to negate. As long as the actual arc of contact movement has a vertex at the pivot point at the end of the indicator body, there is no error. And the line described by the center of that arc of movement and the pivot must be parallel with the surface you are measuring, or perpendicular to the anticipated movement of the object under test, depending on just what you are measuring. At least the error is minuscule with those factors taken care of. Further to correct for it, some mfg offer a "pear" shaped contact, but the difference it makes is really only observable in the practical world on indicators with larger travels, such as 0.0600. And there aren't that many of them.