Edge finding for small mills and setting 0,0,0

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dorin
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Edge finding for small mills and setting 0,0,0

Postby dorin » Thu Apr 13, 2017 6:25 am

Looking at this article, it seems possible to make a 1/8 edge finder.

http://www.sherline.com/pages/tips/tip29.htm

So you grind some material out of an old drill bit or cutter and then listen for it wrapping against the part as you move it over.

My confusion is ... how do you know, when you hear the wrapping..that the center of the spindle is exactly 0.0625 from the edge of the work?
Would you not have to grind it exactly in the middle?

Thank you,
Mike

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SteveM
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Re: Edge finding for small mills and setting 0,0,0

Postby SteveM » Thu Apr 13, 2017 7:01 am

You aren't grinding a flat that has any meaning as far as dimensionally.

The flat is just a noisemaker. When you hear it rapping, that means that the edge finder is up against the part. You are hearing it rapidly making contact and then not (as it gets to the flat).

You would want to stop just as you hear the noise for best effect, just as you would stop just as the regular edge finder steps sideways.

At that point, the work is against the 1/8" diameter drill bit, the center of which is 1/16" away, so moving 1/16" gets the edge of the work under the center of the spindle.

Steve

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GlennW
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Re: Edge finding for small mills and setting 0,0,0

Postby GlennW » Thu Apr 13, 2017 8:06 am

The idea that is states that you would be "exactly .0625"" from the edge is where it all goes bad.

It would be subjective to spindle/chuck/edge finder runout, and the ability of one to hear exactly when it touches.

I'd consider it one of the more inaccurate ways to find an edge, but if being within two or three thousandths is good enough for your needs...
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

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ctwo
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Re: Edge finding for small mills and setting 0,0,0

Postby ctwo » Thu Apr 13, 2017 11:44 am

I made a "6-ball" type of touch probe. Instead of balls, I used button head hex screws. I've made several different tips too.
Attachments
touch-probe-20160215_181436.jpg
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SteveM
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Re: Edge finding for small mills and setting 0,0,0

Postby SteveM » Thu Apr 13, 2017 1:33 pm

ctwo wrote:I made a "6-ball" type of touch probe. Instead of balls, I used button head hex screws. I've made several different tips too.


Please explain how that works.

Steve

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Re: Edge finding for small mills and setting 0,0,0

Postby Harold_V » Thu Apr 13, 2017 3:51 pm

I'm not too keen on the device in question, as the degree of precision is totally reliant upon the piece running dead true, which isn't a likely scenario, especially if the edge finder is intended to be used in a drill chuck, as is generally done.

Here's the deal. An edge finder doesn't rely on the body being chucked true, nor does a wiggler. That's the beauty of each of those devices, and the reason they are so reliable.

Worthy of note. Drills are made with a taper, so the shank does NOT represent the size of the drill. The portion intended to be chucked is also not hardened, so it deforms with use, and would NOT be a good fit in a collet, in any case. A person would be far better served to choose a dowel pin if one of these simple devices was to be created. Dowel pins are dead straight, and sized a couple tenths over nominal. Best of all, the body is hardened and will withstand the intended use without being altered.

Harold
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dorin
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Re: Edge finding for small mills and setting 0,0,0

Postby dorin » Fri Apr 14, 2017 6:12 am

Hello,
I ended up using a dowel pin...I backed up the tool little by little until I could roll the pin between the flat stock for x and y.
For z I loosened the collet so the tool could move...then lowered the tool to the flat and tightened it up.

Our shop was way too noisy anyway to listen for the wrapping.

I then spot drilled about 160 holes into the aluminum plate.

All and all the process went ok..but I was pushing the spot drill to hard, I could hear the machine complain...
I need to practice with my software a bit more.

After that, I drilled the holes out completely in a drill press and one of the guys in the shop had an automatic tapping device...
I was able to tap all those holes in about 20 minutes!

EDIT: I added a picture of the result. It was made from a hunk of scrap aluminum plate.
Amazing how much one learns even from tiny projects!

-Mike
Attachments
20170413_200943.jpg

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ctwo
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Re: Edge finding for small mills and setting 0,0,0

Postby ctwo » Fri Apr 14, 2017 1:26 pm

SteveM wrote:
ctwo wrote:I made a "6-ball" type of touch probe. Instead of balls, I used button head hex screws. I've made several different tips too.


Please explain how that works.

Steve


Maybe I'll take it apart and illustrate in another thread. The basic operation is that steel pins (spokes) bridge the two balls. When the tip is moved, one pin moves off the balls and opens the circuit. The center shaft and tip is spring loaded.
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

Magicniner
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Re: Edge finding for small mills and setting 0,0,0

Postby Magicniner » Sun Aug 06, 2017 5:59 pm

I use an electronic LED indicator, I replaced the probe with a sprung ball to make it less prone to damage for rough work I use it with the mill off, for greater precision I use it with the mill running at "Jog" speed on the VFD and just look for even on/off LED timings.

- Nick


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