# Dial Test Indicator



## mclarenross (Feb 27, 2013)

Im in need of buying my first DTI and it needs to have a long stem on it for reaching up inside barrels for chambering in the headstock.  Unfortunantly as this is my hobby I cannot swing a long reach Interipid. My question is this, if I buy a cheaper DTI that has a standard length stem on it, and replace that stem with a ~2.5" one, will I affect the accuracy of the indicator being that the point is much farther from the pivot? Also, do all DTIs have removable points?


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## Tony Wells (Feb 27, 2013)

Answer to the first question is yes, it changes the ratio between the length of the stem and the actuator inside the body. If you can get a tenths reading DTI and find a long enough point, doing some calculations might give you accurate enough readings, but I'm not so sure about finding one 2.500" long. Most test indicators have replaceable points, always with the caveat that the length must remain original or the readings won't be accurate. One way to look at it though, is zero is zero. If you're showing absolutely no movement, then you are at zero. It's just that the further you reach, small movements become almost impossible to see on the needle. So you can't settle for 0.0005 TIR with a point that is 5 times the original length. That makes it more like 0.0025 TIR.


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## GaryK (Feb 27, 2013)

mclarenross said:


> Im in need of buying my first DTI and it needs to have a long stem on it for reaching up inside barrels for chambering in the headstock.  Unfortunantly as this is my hobby I cannot swing a long reach Interipid. My question is this, if I buy a cheaper DTI that has a standard length stem on it, and replace that stem with a ~2.5" one, will I affect the accuracy of the indicator being that the point is much farther from the pivot? Also, do all DTIs have removable points?



YES.

If you are just trying to get it centered and not measured then it may not matter. It all depends on how much accuracy you are looking for?

Gary


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## mclarenross (Feb 27, 2013)

Hmm. I was afraid of that. Ok so I found a DTI that measures in 0.0001" increments. It appears to me that the standard stem is about 0.5" long so if I put a 2.5" one on there it will be 5x as long as the standard so the increments would then be 0.0005"? I dont think I calculated that right...


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## GaryK (Feb 27, 2013)

mclarenross said:


> Hmm. I was afraid of that. Ok so I found a DTI that measures in 0.0001" increments. It appears to me that the standard stem is about 0.5" long so if I put a 2.5" one on there it will be 5x as long as the standard so the increments would then be 0.0005"? I dont think I calculated that right...



That sounds right to me. 0.0005"

Gary


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## mclarenross (Feb 27, 2013)

Sweet. So a +-0.004" indicator with 0.0001" accuracy becomes a +-0.020" indicator with 0.0005" accuracy upon addition of a 5x longer stem. I love it. Makes things simple. I appreciate it.


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