Re: Edge Finder, DTI, Digitizer probe. Was Re: Help a confused newbie

Hi Caudlet,

Good description!

I see you've combined "squaring" the 'Y' axis along with zeroing it. I
am currently using a laborious procedure, somewhat similar to yours:

I use an ancient "Last Word" Starrett dial test indicator (DTI) to get
the stock square to the 'Y' axis (actually the fixed jaw of the vice).
Then I level the stock (in vice) with the DTI in 'Y'. Next I change to
a Starrett edge finder, and find the 'Y' and 'X' edges (set each axis to
0). Since the center finder has .2" dia disks, I then do a "G92 X-0.1
Y-0.1" to get "on the edge". I'd really like to COMBINE these operations
using the added accuracy of the DTI and edge finder. I'm taking more
then 5 minutes!

Better yet, I'd like to AUTOMATE the process and use my digitizer probe
to AUTOMATICALLY assist me in squaring an axis, and then finding the
edges. Due to the construction of my simple probe (a copy of MaxNC's),
I SURE I can't guarantee that the probe tip (.0625") is "spot on" on
center of the spindle, so that lets out edge finding (I think). I could
have it take a pair of edge readings, and help me get the stock square
(or level for that matter), however (offsets should be OK relative).

So I'm basically replacing the DTI, as far as I can see. OK for an
edge. How about a circle/hole? That would seem to require the probe
tip to be spot on, as far as I can see. Oh, you could get the diameter
accurately. Perhaps the probe could be "touched off" a known X, Y (and
Z?) "home" for it's calibration. This starts to sound like CM (computer
measuring?).

Alan KM6VV


caudlet wrote:

>
> <SNIP>
> To comment on Alan's observations. I normally layout a piece to cut
> on an oversized chunk of material. I will run the table to some
> point that "looks like zero" and zero my DRO/Controller indicator. I
> have a broken carbide mill that is exactly .249 inch in diameter. I
> put the mill/feeler in the chuck and move the head down so it's lower
> than the surface of the piece I need to cut. I gently slide the
> material against the "feeler" so the Y edge of the material touches
> it and lightly tighen the hold downs. I then jog the machine with
> the head retracted to the other end of the same Y edge and once again
> lower the feeler and touch it with the edge. Now I recheck the
> original stop and make any slight adjustments. At this point I have
> established two reference points paralle to the X axis travel. All
> you have to do then is raise the head, move more than the diameter of
> the feeler up the Y axis and use one last pint to establish the
> x "0". Now take your machine back to zero, zero and then move each
> axis exactly 1/2D of the feeler; in my case .1245". The center of
> the tool is now over the material zero. Reset your machine to 0,0
> and you can start your program. (set the z by putting in the tool you
> will use to cut with and moving the head down until a piece of thin
> paper placed on the material under the cutting tool has resistance
> from being pulled out. If you ever loose zero during a cut you can
> repeat the procedure to get things back in register. This works on a
> piece of material that has at least one staight edge.
>
> This looks more complicated than it really is. I can do the whole
> manouver in 5 minutes.
>