Electronic edge-finder for Acu-rite VRO300M dro - generic ones work?

JasonPAtkins · Jul 19, 2018

Hi folks, I just emailed acu-rite but expect to get the company line in response, lol. The DRO can accept input from an electronic edge finder. I'd like to add this for the mill the dro is installed on, if I can find one for cheap. The dro manual doesn't specify a model number, but googling shows the KT130. Are electronic edge finder generic though, can I use anything from 3rd part mfg's, or do I need the acu-rite model? A quick search shows ones that flash a light but have no cable for output, which this would need.

Here's one on ebay that looks compatible - are there many others?

Thanks to anyone who has some knowledge in this area!

Forrest Addy · Jul 19, 2018

Electronic edgefinders and part probes are nothing more than glorified limit switches. Nudge the part and it opens a circuit. The wired ones are no more complicated than a doorbell. The wireless ones same deal except the wireless part where protocol and paring add to the fun.

An electronic edgefinder depends on the electrical conductivity of the part. Contacting the work closes the circuit and lights the LED. An additional concern may be the return current via the sliding elements and machine structure can be less that certain. However, the sensing current is very small: so long as the part is conductive you should get crisp consistant indications. If you're machining plastic or other insulating material, an electronic edgefinder won't work.

Part probes - touch probes - work in the opposite sense: they have a built-in switch that opens on deflection of the stylus. You can probe anything, insulator or conductor, and get positive readings.

Those of you fascinated by how stuff works might find the internal construction of a touch probe interesting. Some are so sensitive they change state with deflections measured in millionths of an inch and do so consistently.

JasonPAtkins · Jul 19, 2018

So really in the most basic form you could wrap a wire around a chucked dowel pin, plug that wire in, and then when the dowel pin touched the part, the edge detect would go off on the DRO?

If it's really that simple in basic operation, it seems like I could ground the table to the DRO, then turn a simple self-centering edge finder, to give the probe some "give" to keep it from being damaged by being rapided into a part, then wire a connection from there to the DRO edge detector input?

bw_4000 · Jul 19, 2018

I've "dicked" with the electronic edge finder in my past out of curiosity. Save your time and money. Use a standard edge finder, zero the DRO, move half of your edge finder diameter into the part (with the "Z" up over the part) and zero your DRO again. Easy peasy.

SamH · Jul 19, 2018

I have that acu-rite D200 DRO, and the electronic edge finder you pictured. If I had it to do over, would have probably spend the money on a 3D taster. To Forrest's point, it is just a glorified limit switch. As far as zeroing, you still have to do the offset. Where it can be handy is running the canned function of finding the Center Line of something.

David J. · Jul 19, 2018

Not to totally derail the thread..... for those that use a 3D taster in manual mills do they
usually repeat pretty well as the holder is swapped in and out of the mill?
Say on a manual knee mill R8 tool holders I mark a dedicated holder to the taster and add
a witness mark where the holder goes in the spindle, will I usually repeat say plus/minus
.001? The time savings of the taster would be eaten up if I had to re-indicate every time
it went in and out of the mill.
Thinking on the x and y axis.
Ideas?
Thanks
David

moonlight machine · Jul 20, 2018

JasonPAtkins said:
Hi folks, I just emailed acu-rite but expect to get the company line in response, lol. The DRO can accept input from an electronic edge finder. I'd like to add this for the mill the dro is installed on, if I can find one for cheap. The dro manual doesn't specify a model number, but googling shows the KT130. Are electronic edge finder generic though, can I use anything from 3rd part mfg's, or do I need the acu-rite model? A quick search shows ones that flash a light but have no cable for output, which this would need.

Here's one on ebay that looks compatible - are there many others?

Thanks to anyone who has some knowledge in this area!

I have a genuine Acu-Rite electronic edge finder. I bought it new with the DRO. Total waste of money, you can find an edge, usually within .010 or so but it does not repeat. If that's close enough go for it.

Limy Sami · Jul 20, 2018

IME - Electronic edge finders don't work too well on plastics either.

machtool · Jul 20, 2018

Limy Sami said:
IME - Electronic edge finders don't work too well on plastics either.

Shouldn't you be on "Light Duty" When they discharged you. Did they happen to mention, anything that would bring your heart rate up?

Regards Phil.

Limy Sami · Jul 20, 2018

machtool said:
Shouldn't you be on "Light Duty" When they discharged you. Did they happen to mention, anything that would bring your heart rate up?

Regards Phil.

Very very light Phil, as for heart rate, I can think of worse ways of going than LMAO at some of the PM squit

JasonPAtkins · Jul 20, 2018

bw_4000 said:
I've "dicked" with the electronic edge finder in my past out of curiosity. Save your time and money. Use a standard edge finder, zero the DRO, move half of your edge finder diameter into the part (with the "Z" up over the part) and zero your DRO again. Easy peasy.

Ok all, thanks for paying the price of my mistake for me so I don't have to. It just seems like such a handy gadget, but I will trust the collective wisdom.

On this DRO, the process is even easier, because you don't have to move after the first zero - when you hit the zero you can just directly put the diameter of the center finder into the dro and you're set. I'll stick with that method. Thanks!

bw_4000 · Jul 20, 2018

Sounds like you are all set :cheers:

KMoffett · Oct 8, 2018

The KT130 isn't a even a switch. It's a flexible contact that completes the circuit to a grounded part. I had an ACU-RITE DRO on my previous mill. The probe plugged into the back of the DRO. As I remember, touching the probe to the edge of the vise/part automatically zeroed the axis plus half the probe's diameter. I kept the probe, but it doesn't work with the new CNC mill. I added an electronic circuit with an LED and buzzer, and still can use it. The fact that it doesn't work with non-conductive parts is a big down side.

Ken

Gordon Heaton · Oct 8, 2018

KMoffett said:
The KT130 isn't a even a switch. . . The fact that it doesn't work with non-conductive parts is a big down side. . .

Odd, Acu-rite says it will: "The KT 130 is a 3-D triggering edge finder. This means it can also be used for nonconducting materials."

KMoffett · Oct 8, 2018

Yes 3D. It will make electrical contact in all three axes. No, it will not work on insulated surfaces.

Ken

Gordon Heaton · Oct 8, 2018

If you say so, this is a direct quote from Acu-Rite: The KT 130 is a 3-D triggering edge finder. This means it can also be used for nonconducting materials. The stylus is deflected when it contacts the workpiece, and the edge finder sends a triggering signal over the connecting cable to the 200S or 300S digital readout.

Perhaps the signal generated is only readable by the 200S & 300S. Those units are specifically mentioned in the quote above.
That would work for me, since I use the 200S. What doesn't work for me is the $900+ pricetag.

KMoffett · Oct 9, 2018

OK. A google search for KT3D (my probe) or KT130 brought up the same page: ACU-RITE Edge Finder - KT3D - Penn Tool Co., Inc
My probe has a single pin socket on the side of the body that connects to the probe. From Penn's KT3D web page it appears that the KT130 has a screw-on connector. So I think you're right. Like other 3D probes it probably has internal contacts that are broken on probe movement. If I didn't already have it, I would not buy one. It would cost me $$$$ to purchase the software and hardware for 3D probing for my mill.

Ken

AlfaGTA · Oct 9, 2018

Better choice would be a dedicated tool holder and a good quality "3'D Taster".
Don't see any real advantage to the electronic edge finder....A probe, yes but only if you have a machine that uses a probe cycle (CNC) that produces a repeatable approach to the work.
The analog Taster gives a moving dial as you approach the target ("0") so you don't overshoot (something that always happens using digital or electronic edge indicators)
Also the Taster compensates for the probe end diameter so no adding or subtracting is done..Zero is the edge directly....
These are true 3-D indicators that work approaching from any direction.

Cheers Ross

Electronic edge-finder for Acu-rite VRO300M dro - generic ones work?

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