hole mapping

[MartinUsher]

As the title says, i have a project where i need to drill a small hole (.25") offcentre in a diameter bar approx 40" deep.
mapping this hole has given me a few headaches, using ultrasound i can only find the hole and its proximity to the wall or outside diameter, single axis only.
what id like to do is measure its deviation and positional error from its programmed path in two axis to project the absolute position at the end of the drilled hole.
does anyone have any ideas as to where i should look for equipment to do such an operation, your opinions and suggestions would be appreciated.
thanks,
Martin.

 

[redpicker]

Use polar coordinates to do your mapping.

Index the end of the bar where the hole starts with 0 degrees being with the hole nearest the surface. For every inch (or half-inch, if you wish) along the length, find the shallowest depth the hole is below the surface and record both that and the angular rotation of the index. Once you have all the distances and angles, it would be rather simple to convert them to Cartesian coordinates.

rp

 

[MartinUsher]

understood, but i am looking for a more accurate and quicker method, something an operator can do on the fly with the drill at cut, or in a retract position say .025" of the cut face.
using a phased array in two positions could work but i am not that familiar with the operation.
two single point sensors at equidistance from a pivot point over the outside diameter could be configured with simple math equations, but i am in theory right now, im not sure about the practise side.

any thoughts guys.
Martin.