Fine Centering Scope

    [ ... ]


    I believe that Laser diodes turn off below a certain current, unlike LEDs which simply get dimmer. And the "knob to vary the intensity" would either waste power in a series resistor, or require active circuitry to control the current (a better but more expensive solution).
    You might be able to reduce the apparent intensity by PWM (Pulse Width Modulation) -- though I'm not sure that this would eliminate the appearance of the Airy ring.
    [ ... horizontal spindle mill ... ]

    I guess so -- except that the camera module would still probably be put on on a long arm to maintain the maximum sensitivity.
    Enjoy,         DoN.
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snipped-for-privacy@d-and-d.com (DoN. Nichols) wrote:

True enough, but lasers are linear above threshold, so all that's necessary is an offset, so zero on the pot is near the lasing threshold, and max on the pot is at max allowed current. (Or duty cycle, if using PWM; discussed below.)

I think that most laser pointers and modules made today have a little IC in them, not just a resistor. PWM would certainly work. Perhaps the ICs already work that way.
The Airy ring disappears simply because it becomes too dim to see with the unaided eye, especially in a well-lit shop, not because it isn't there.

Depends on the camera lens. One would expect that what is being used is a low-power microscope objective lens.
Joe Gwinn
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    [ ... ]

    O.K. One difference between this and the earlier ones is that it has an adjustment for the particular spindle in which you are mounting it. Put it in the spindle, move it up or down until you have a sharp image of a scribed line under it, crank the table until the line matches the hairline in the scope, then rotate the spindle 180 degrees, and check whether the hairline is still on the scribed line. If it is not, adjust it half-way to meet the line, and repeat the test. Once you can rotate the spindle 180 degrees with no obvious change, it is calibrated to that spindle and collet, and you have the center of rotation directly over the scribed line. So zero the dial on that axis, then rotate it 90 degrees, and zero the other axis to a scribed line at right angles to the first.
    Of course -- this does not correct for any errors in concentricity when you remove the scope and install the milling cutter, which may exhibit runout of its own, thus changing the width of the cut. But you are at least zeroed to the axis of rotation of the spindle.
    Oh yes -- the "focal length 5/8" part of the specs shows that you have to add 5/8" to the length extending beyond the collet. At a rough guess, that would be about 3-1/2 inches if the shank is fully inside the collet.
    Enjoy,         DoN.
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snipped-for-privacy@d-and-d.com (DoN. Nichols) wrote:

If this is what the expensive unit does, what does the $170 unit do? I thought it used the same 180 degree moves and difference splitting.

Yep.
And the quill travel is 4", so knee motion will be required.
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    [ ... ]

    The URL for that one is gone, so I can't re-check it, but as I remember, it did not have the knob which is visible in the flexbar unit (opposite and a bit above the eyepiece tube's joining point). So, I think that those cheaper ones do not have this adjustment, and perhaps also have less magnification, so there is less need for the correction -- unless you drop it, of course. :-)
    [ ... ]

    Unless you are using endmill holders of similar extension instead of collets..
    Enjoy,         DoN.
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snipped-for-privacy@d-and-d.com (DoN. Nichols) wrote:

here it is: <http://www.use-enco.com/CGI/INSRIT?PMAKA$0-0404&PMPXNOH22227&PARTPGINLMK3>.
It's Enco model number 240-0404.
All it has is the knurled rubber knob at the bottom. Now that I think about it, I think that Billy Hiebert said that this knob moves the reticle line. I assume that the knurl at the eyepiece does the focusing.
Here is the 20 July 2007 (or the day before) posting:

End of posting.

Good point. So far, I've used only R8 collets to hold endmills.
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    [ ... ]

    O.K. It is pretty much as I remembered.

    "Moves the reticle line" is the same as adjusting the centering to compensate for slightly off-center collets or spindles. If it does that, then it does everything that the other does.

    It only does the focusing of your eye to the hairline to make it good and sharp. Focusing of the image of the scribe line would be done by Z-axis motion -- either the quill or the knee -- whichever is easier and gives sufficient range.
    I must admit that I had originally though that the bottom knurled ring (just above the objective lens) was for fine focusing of the objective, so you don't have to tweak the Z axis as closely.

    O.K. Though I don't think that there *is* "another hair" -- you only need one to do what the scope is for. You rotate it 90 degrees to do the other axis, once you've zeroed it for the axis which lets you swing the eyepiece both ways. As mentioned above, you can't do the zeroing with the Y axis because you can't get your head between the eyepiece and the column -- though one with a TV camera built in and a TV monitor on a shelf nearby would allow that as well.

    I note that the Enco one says the length is 3" (which I suspect means from the step at the bottom of the shank to the end of the lens), and the lens then needs an additional inch to focus (working distance).
    It looks to me as though the eyepiece tube on that one is closer to six inches long, if the end of shank to lens tip is three inches.
    Enjoy,         DoN.
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snipped-for-privacy@d-and-d.com (DoN. Nichols) wrote:

So it would appear.

Billy Hiebert said that the lens to target distance needs to be about 1", constant.

I'm hoping for a crosshair.
I read about the calibrated TV cameras. Seemed like far too much trouble.

Well, I ordered one. When I get it and have used it a bit, I'll post a report.
Joe Gwinn
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