Coaxial Indicator Problem

mark_f said:
That is what I am talking about. It does not say each division equals .0005" of movement. it says it is axis offset,:dunno: what ever that means. offset from what and where.
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Mark, that is the offset from the center of the hole (or pin) to the spindle centerline. Normally in use you don't worry about actual dimensions, just adjust X-Y position for minimum needle movement when centering on a part.
 
JimDawson said:
Mark, that is the offset from the center of the hole (or pin) to the spindle centerline. Normally in use you don't worry about actual dimensions, just adjust X-Y position for minimum needle movement when centering on a part.
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an expensive center finder......
 
Yes, we are all on the same page in understanding the authors question. And my Blake is doing the same thing? That means using a 2” feeler in about a 2” hole should give 0.0005” offset readings/div (manufactures recommendation), but it does not? It’s more like 0.0025” actual/div. What am I missing? Instead, the dial reading is the space from the bottom of the CO-AX case to a finger on the spinning feeler holder...Dave.
 
JimDawson said:
Mark, that is the offset from the center of the hole (or pin) to the spindle centerline. Normally in use you don't worry about actual dimensions, just adjust X-Y position for minimum needle movement when centering on a part.
Click to expand...
Yes, but that means my Blake that advertises 0.0005”/div or you could say its sensitivity or resolution is not as advertised. It’s actually not that sensitive now that I did findings on it today. It’s more like 0.0025”/div. It would be hard to true position anything with a Blake down to 0.0005”!!! Because you could not see that kind of needle movement on the dial! Or, am I missing something?
 
If you move the cross slide 2 divisions, how many divisions does the Blake move? This is no time to have a broken ankle. Dang it all

"Billy G"
 
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As an aside, here is an individuals plans to build a coaxial indicator.. just a FYI: https://drive.google.com/file/d/0BwXDcXKx2KzlaUVrZ0l6QU4yaTA/view

Also, statement from Long Island indicator repair, regarding Blake Coaxial indicators:

"Additionally, we have the following statement from the manufacturer :
The Blake Co-Ax indicator is a centering device. It requires a reading of both sides of the bore (or boss), in each axis, to arrive at center. Its sole function is to find center. It is never to be used as a measuring instrument.

You can not certify the Co-Ax on a surface plate. It must be put in the spindle of the machine in which it would normally be used and indicate a precision ring or plug. Then remove it and use a .0001" indicator to check that you are on center.

The Co-Ax indicator is made to be used under power. When checking the Co-Ax position with a test indicator the spindle should be rotated manually for both indicators due to the fact that spindle torque under power on some machines will give a different reading for center." - manufacturer's instructions
 
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This is correct. The resolution only allows you to see how close to center you actually are and the needle tells you which direction to move. It is all position, nothing else.

"Billy G"
 
Bill Gruby said:
If you move the cross slide 2 divisions, how many divisions does the Blake move? This is no time to have a broken ankle. Dang it all

"Billy G"
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If you move the cross slide 0.0025” the Blake will move 0.0005”. The Blake is fitted with a 2” feeler and 1” offset from datum centerline.
 
Then the Blake is correct in resolution. Resolution on a Coax indicator merely tells you how fine a movement (adjustment) you have. If the resolution was say .001 the movement would be coarse, .005 fine movement (adjustment). All you are seeking is absolute"0".

"Billy G"
 
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