How is this edge finder an "audible" indicator?

[ChazzC]

Honestly, this has become my go to for simple center punch pickup.

A coworker showed me his method years back and I really couldn't grasp it and didn't like it flailing around and having to reset it every time.

I've developed my own method where I run it at roughly 140rpm and I have good success.

The key to running it that slow if to lift it off of the spot quickly.

The wiggler with the pointed attachment is only rotating while you set the pointer to align with the spindle; then you turn the spindle off and use the long pointer to line up the spindle with the pinch mark. Even at slow speeds the needle point can open you up.

 

[woodchucker]

I continue to run the spindle when using the pointer. That way when I am off a little, it will not be running true. I keep lifting and truing the pointer, then stick the pointer in to the mark. Static does not clearly indicate it.

 

[ChazzC]

I continue to run the spindle when using the pointer. That way when I am off a little, it will not be running true. I keep lifting and truing the pointer, then stick the pointer in to the mark. Static does not clearly indicate it.

Can't find the video I was looking for (shows what can happen if you bump into the probe as it is turning – not pretty. But here is a clean, easy to follow video without any glitz.

 

[RaisedByWolves]

I continue to run the spindle when using the pointer. That way when I am off a little, it will not be running true. I keep lifting and truing the pointer, then stick the pointer in to the mark. Static does not clearly indicate it.

What speed?

I found low speeds to work better for me.

I usually get everything close and put the pointer in the punch mark and look across both axes for any gross misalignment and dial that out.

Then start the spindle and quickly lift the quill and look for runout which at this point there will be some.

I then look at the circle the pointer is transcribing and further adjust the X-Y, then repeat

Usually on the 2nd or 3rd attempt the pointer will run true enough it will go back into the punch mark on its own, then I adjust until it no longer shows movement.

The trick is to very rapidly raise the quill and with this method I’m well within .002-.003.

Plenty good enough for picking up screw holes, for finer work I break out the co-ax.

 

[woodchucker]

What speed?

I found low speeds to work better for me.

I usually get everything close and put the pointer in the punch mark and look across both axes for any gross misalignment and dial that out.

Then start the spindle and quickly lift the quill and look for runout which at this point there will be some.

I then look at the circle the pointer is transcribing and further adjust the X-Y, then repeat

Usually on the 2nd or 3rd attempt the pointer will run true enough it will go back into the punch mark on its own, then I adjust until it no longer shows movement.

The trick is to very rapidly raise the quill and with this method I’m well within .002-.003.

Plenty good enough for picking up screw holes, for finer work I break out the co-ax.

I don't have a way of telling with the VFD, but if I remember with out the VFD it was about 800 or 1100. I do quick dives into the mark as well. I don't dawdle. I find the wiggler is the fastest acting of the edge finders.

 

[RJSakowski]

Center punches are usually made by punching the intersection of two scribed lines. This is a visual process. In that regard, I don't believe that one can reliably locate the center punch to better than ten thousandths. Even if one can find the intersection, if the punch is not perfectly perpendicular to the surface, there is a good chance of drift. For those reasons, I don't consider locating a center punch mark as needing a precision operation. If drilling on the drill press, I will usually allow the workpiece to move and let the drill find the center of the punch mark. In a situation where the work is clamped, I have a sharp point mounted in a TTS chuck, similar to what @ChazzC uses that I visually align with the punch mark. However, if I have a workpiece clamped on my mill table, I am most likely performing other operations, in which case, I use offsets with my DRO for precise location of a hole.

 

[woodchucker]

I agree with you. The center prick is not that accurate, not as accurate as working from a known datum.

 

[RaisedByWolves]

Center punches are usually made by punching the intersection of two scribed lines. This is a visual process. In that regard, I don't believe that one can reliably locate the center punch to better than ten thousandths. Even if one can find the intersection, if the punch is not perfectly perpendicular to the surface, there is a good chance of drift. For those reasons, I don't consider locating a center punch mark as needing a precision operation. If drilling on the drill press, I will usually allow the workpiece to move and let the drill find the center of the punch mark. In a situation where the work is clamped, I have a sharp point mounted in a TTS chuck, similar to what @ChazzC uses that I visually align with the punch mark. However, if I have a workpiece clamped on my mill table, I am most likely performing other operations, in which case, I use offsets with my DRO for precise location of a hole.

Dave ticehurst does a good explanation of how to best pick up the intersection of two scribed lines.

4:00 mark

 

[ChazzC]

Center punches are usually made by punching the intersection of two scribed lines. This is a visual process. In that regard, I don't believe that one can reliably locate the center punch to better than ten thousandths. Even if one can find the intersection, if the punch is not perfectly perpendicular to the surface, there is a good chance of drift. For those reasons, I don't consider locating a center punch mark as needing a precision operation. If drilling on the drill press, I will usually allow the workpiece to move and let the drill find the center of the punch mark. In a situation where the work is clamped, I have a sharp point mounted in a TTS chuck, similar to what @ChazzC uses that I visually align with the punch mark. However, if I have a workpiece clamped on my mill table, I am most likely performing other operations, in which case, I use offsets with my DRO for precise location of a hole.

The point is also good if you are picking up a scribed line or intersection (can get vey close with a loupe), then use DRO for subsequent locations.

I mostly use center-punched locations to help keep the drill from wandering (like when mounting something on a machine).

 

[RJSakowski]

Dave ticehurst does a good explanation of how to best pick up the intersection of two scribed lines.

4:00 mark

I am aware of that method of locating the intersection and use it myself. In my experience, even the lightest scribe line is multiple thousandths wide. When he says perfectly located, what does that mean? He verifies with a loupe. I had done some work in the past where I needed to visually verify position to better than a thousandth with a 50X microscope and that was difficult enough.

However, a good R&R study would demonstrate just how accurate that or any other method was. For my part, I have a 300X microscope that I can mount in the spindle of my mill and in conjunction with the DRO, I can verify positions of features to +/- .0001". I would scribe a series of intersecting lines and center punch the them. The I would locate the coordinates of the scribed lines and the center punch marks and compare.