Coaxial Indicator Problem

WY thanks for your question.
We do not need to use the indicator to see if it reads as advertised just push the feeler the correct amount and see if the dial agrees.

John. Yes the coax is indicating the null. The point is how wide is the null. On my indicator when the short feeler is used the dial is pushed by a Class One leaver of about 5 to1 ratio. so even when the in it's best mode. at zer0 diameter with the effort at 90° the accuracy is degraded by that amount.The longer the feeler the worse the result is
Brian
 
I am still not sure I understand, if a 5 to 1 ratio than .0005 would equal .0025 of linear movement, is that correct ?

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Yes correct. sorry to cut you loose but it's one in the morning and I am off to bed. see you later
Brian.
 
I kind of hate to step in this , but my understanding of these coax indicators is, they are not for measuring, they are for centering only. That meaning they are strictly for centering on a ID or OD of a part or centering on a hole, in which case the numbers are for reference only. I know I have a Best Test indicator with a long and short arm. With the short arm , the numbers are accurate, but if I use the long arm the numbers are off by a factor of 2. They tell you this in the literature and the long arm is not for measuring but more for lining up on a hole or OD where it is for convenience. I understood, and I could be wrong, but a coaxial indicator is not for measuring ( that is why I don't own one now). That is my opinion.
 
As I understand it BRIAN thinks he has an error with his co-ax indicator and was using a linear measurement to verify if there was an error or not , I was trying to understand the process he was using.

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Hi Mark . thank you for joining the conversation, all contributions are welcome.
WY you have it right I was trying to establish if the resolution of the indicator was as stated under the best conditions. Short feeler . Zero diameter. effort at 90°. I do not use the indicator to "measure".
But the thread took off down another path .
The point is my indicator has a resolution 5 times worse than is stated in the instructions and on the dial.
I am interested to see if other (Quality) brands have the same difference. so is any one prepared to do this simple test that takes all of 10 minutes, Or do we just say Bad resolution is not a problem.
Brian.
 
Well I set things up the same as your pictures, my dro and dial have been checked with a known accurate test indicator and I ran the same test as described about 5 times and the dro averaged .0072 . I didn't use an indicator to measure movement at the end of the arm like you did, not sure it matters? My co-ax is by SPI , if that helps, I have used it for other set-ups and it was always accurate for my needs. You may need more accuracy than I do.

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Hi WY
You are correct the second test is not relevant, thank you for running the test
So using the short feeler moving the Coax one division takes .0072 movement of the cross slide
Thank you for your time and interest.
Any others willing .
Brian
 
Small comment here. I see someone put the Blake video up. Do not try to compare the Blake with any other Coax. Most are not anywhere near the accuracy and quality of the Blake. If you really want to test them you need both a Blake and an off brand. Yes I am a tad biased on this, I have used many and the Blake is the winner hands down in my opinion.

I can understand the tests and reasons for them. In the end, the indicator with the finest resolution will be the winner It's hard to use something when it is not to spec.

I wish you good luck in resolving this issue Brian.

"Billy G"
 
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