[bevinp]

While I would love to buy the Tormach probe, the cost is above my budget. So I am looking to buy an electronic edge finder and would love to hear any pros/cons about the current offerings from the credible manufacturers - Fowler, Borite, Pec, SPI and other brands.

And if anyone has the opinion that the electronic edge finders with a spring mounted contact ball do not produce consistent readings, please tell everyone your story.

Thanks,
Bevin

[tobyaxis]

I use a Mechanical Edge Finder from Brown & Sharp (10years old), and used one electronic.
The electronic will break easily even if dropped 12" onto a wooden table.

[bevinp]

Toby,
Yes I have a mechanical one that I could never get to work properly, until I saw a Youtube of one working correctly. I realised that mine is poor quality and on closer examination I found that the .200" dia end is not square to the body and has significant runout at its end. Also it is out of round by about 0.0005". I thought it was a little cheap when I bought it!!!!

I am hoping that an electronic edge finder (a good one) will be easier to use (not require spindle running).

Did you use yours much before it broke? What brand was it? Did it have the overrun protection?
Bevin

[MichaelHenry]

Here's a real nice mechanical edge finder:

https://www.hschmidt.com/productcart...&idproduct=148

Mike

[BobWarfield]

I have both Starrett mechanicals and a Fowler electronic (LED) edgefinder. The Starrets work fine, but I found the Fowler faster and easier.

I did eventually manage to break it, but only after I had CNC'd my mill and jogged a bit too far and fast. LOL, I have broken a 1/2" endmill doing same while it was running--stuff happens!

In other words, I haven't found them too delicate. The best news, is I took the Fowler apart and I'm able to convert it for use as a touchprobe talking to Mach3. It works reliably with an ohmeter, so I just need to wire it up to Mach and set up the screens.

Really handy little gadgets to have.

Cheers,

BW

[zephyr9900]

... Fowler electronic (LED) edgefinder.

Bob, is it this one? I'll be very interested to hear about your Mach probing results.

Randy

[BobWarfield]

Yes, exactly.

I'll eventually get a chance to fool with it and get it working, at which point I will document on the web site. I haven't gone further than to hook it up to the ohmeter and try it. Frankly, I needed it one day and was annoyed when my jogging broke it (LED stayed permanently on and I never did figure out why).

Here's the deal. If you unscrew the battery compartment, there is a battery, and below that there is a little LED assembly in a plastic tube that just drops out.

I took the little plastic tube a 3/16" endmill arrived in and discovered it fits nicely into the edgefinder. I drilled the end and stuck a wire down it and out the hole in the bottom of the plastic tube. Stuck a 1/4" dowel pin into the top of the endmill holder to wedge the wire in place and drilled a hole in the side of the edgefinder at top for the wire to come out. I needed a little heavier spring between this assembly and the battery cap to reliably hold it in place, but that's all there is to it.

You get a contact closure between the body of the edgefinder and the wire, which connects to the tip inside the black insulated area just by rubbing against it, whenever the edgefinder contacts the workpiece.

Refer to Hoss and others to see how to set up the screens and such for Mach3 to use this as an edgefinding probe.

For those that have broken their edgefinder, this may provide interesting new life for it.

Cheers,

BW

[zephyr9900]

Bob, since the Tormach version of Mach3 is already set up for probing I'm imagining that, assuming your edgefinder mod works electrically (and why shouldn't it? ), it would literally be "plug and play" with the appropriate connector. It would definitely be worth buying a new one and hacking it.

Randy

[silverfoxx03]

www.haimer-usa.com

go to the sensors--the best of the best there. Quite a variety and priced well.

[benji2505]

.... I am hoping that an electronic edge finder (a good one) will be easier to use (not require spindle running).

...
Bevin

Bevin,

I have the Fowler LED solution as well. He only difference to the mechanical edge finder is the LED/ battery gismo. You will have to turn on the spindle and move until you get a full LED-on. Before that you have an on-off signal that comes from the runout of the edge finder.

I frequently use the electronic edge finder to check the travel in x and y direction with some gage blocks. If you know the shortcomings they work well.

99% of the LED edge finders that I have seen/wrecked/shot through the room have a runout. The shaft that holds the contact area is flexible and bends easily. Use a collet holder.

That fact throws some wrinkles on my forehead concerning the probe solution addressed earlier.

Expect the tip to be between 0.199X and 0.200X. Pretty sad for a precision instrument, but it is what it is. I am adjusting for it in the tool table.

Have fun.

Benji

[Superman]

We use a SPI 3D Alignment indicator
on some of our smaller CNCs that don't have autogauging

-allows for a fair bit of travel
-the actual stems can be fragile ( ceramic base ?), They are sacrificial ( they break before anything else )

[R.DesJardin]

I had always used a mechanical Starret edge finger until I bought my Tormach. I then tried out a Electronic one and found for the accuracy most of us need it is faster and easier to use plus I also use it for my T0-Z0 setting.

[kevperro]

Anyone using the laser?

http://littlemachineshop.com/product...2604&category=

[keen]

Hi - I now only use rotating mechanical edge finders -The Starrett one is good - and a paper feeler for the Z. . On my elecronic height setter - sometimes I would get a persistant micro 'hair' of conductive material that gave false readings. Too dangerous for very accurate work.

[bevinp]

Thanks Guys, that was good information. After following the tips and links I will probably go for an electronic with overrun protection. But might buy both.

That mechanical one from H Schmidt looks very good and and seems to have a better design than the Starrett so should perform at least the same. Thanks Michael.

I found the debate (elsewhere in CNC) about exactly when the mechanical edge finders are indicating the correct position, to be a little confusing. The description provided by Starrett is a little ambiguous and probably gives rise to the two differing opinions. One is that the correct position is where the tip snaps into running true and the other is where the continued movement snaps the tip out of true. I am inclined to think it should be the mid position between those two points, with a bias towards the first. And the width of that gap would depend on the friction of the edgefinder tip to body (and spring pressure) and the friction of the tip rubbing against the workpiece. All of which would vary between edge finders, RPM, workpiece material and any lubrication. But I assume the gap would be small and therefore satisfactory for my needs.

No doubt the expensive ($500+) 3D sensors would be excellent but too expensive for me.

And the electronic finders seem to be fragile and most without reasonable cost of repair (but good for salvaging for other purposes!). But their apparent ease of use and consistency of errors that can be accommodated, makes me favour their mid price solution. Now all I have to do is chose the brand and the supplier.

SPI told me their electronics don't have overrun protection. Fowler ads say theirs do and I am investigating the other common names.

Thanks for the help.
Bevin

[bevinp]

Anyone using the laser?

http://littlemachineshop.com/product...2604&category=

Yes I have the $50 laser and use it for woodwork or bench drilling but it is not accurate enough for mill work. The beam diameter appears too large and because it is a laser, you get the strong reflections which makes it hard to assess when you are on the correct point. Even when I try to align a centre punch mark I get reflections from the side of the indentation and I can't "see" to centre the beam. Hence the manufacturer's advice to paint the surface blue to reduce the reflections and make the beam just illuminate not dazzle. The dimmer (polariser) does reduce the diam/dazzle somewhat but reflection still occurs... it is the nature of a laser beam.

It works better on a sharp edge with a clean vertical surface as this splits the beam into two and makes it easier to assess equal reflections from top to bottom surfaces.

But it certainly does not provide accuracy within a few thou.

[kevperro]

Yes I have the $50 laser and use it for woodwork or bench drilling but it is not accurate enough for mill work. The beam diameter appears too large and because it is a laser, you get the strong reflections which makes it hard to assess when you are on the correct point. Even when I try to align a centre punch mark I get reflections from the side of the indentation and I can't "see" to centre the beam. Hence the manufacturer's advice to paint the surface blue to reduce the reflections and make the beam just illuminate not dazzle. The dimmer (polariser) does reduce the diam/dazzle somewhat but reflection still occurs... it is the nature of a laser beam.

It works better on a sharp edge with a clean vertical surface as this splits the beam into two and makes it easier to assess equal reflections from top to bottom surfaces.

But it certainly does not provide accuracy within a few thou.

That is good input. I'm using an el-cheapo SPI manual edge finder now. I can get repeatable results. I don't know how accurate they are but I suspect they are +/- 0.001

The laser would have the advantage of not needing a turning spindle.

I found directions somewhere on the web that suggested a 1000 RPM spindle speed as the "right" speed for the mechanical edge finder. Tormach says the transition between center & offset is zero. If the part isn't perfectly smooth or if you have an angled surface that probably throws you off more than any error you make judging what to call centered. I've been using the step before it pops out as my reference.

[bevinp]

[QUOTE=kevperro;615304]
The laser would have the advantage of not needing a turning spindle.
QUOTE]

You are right when you say that but since I find it difficult to see exactly where the centre of the beam is, I am not confident that when adjusted, it does not have an error. Consequently when I do use it, I am probably doubling the error.

I do need to wear glasses so perhaps that may be adding to the dazzle. Others may not find the same problem.

[keen]

"I found the debate (elsewhere in CNC) about exactly when the mechanical edge finders are indicating the correct position, to be a little confusing. The description provided by Starrett is a little ambiguous and probably gives rise to the two differing opinions. One is that the correct position is where the tip snaps into running true and the other is where the continued movement snaps the tip out of true. I am inclined to think it should be the mid position between those two points, with a bias towards the first. And the width of that gap would depend on the friction of the edgefinder tip to body (and spring pressure) and the friction of the tip rubbing against the workpiece. All of which would vary between edge finders, RPM, workpiece material and any lubrication. But I assume the gap would be small and therefore satisfactory for my needs."

The best way to obtain high accuracy is to make the cad/cam X/Y axis the part centre line, not the edge. and set the work or stock up central. that means you zero on wobbler spin "out' and do the same on the opposite side, It is very repeatable. and enter half the value in that axis dro - same for other axis. This is very accurate - you can be in position better than a half thou.

[bevinp]

"The best way to obtain high accuracy is to make the cad/cam X/Y axis the part centre line, not the edge. and set the work or stock up central. that means you zero on wobbler spin "out' and do the same on the opposite side, It is very repeatable. and enter half the value in that axis dro - same for other axis. This is very accurate - you can be in position better than a half thou."

That sounds good. Since you are doing two opposing contacts you are automatically compensating for the diameter of the contact pin as well as for any consistent error in the technique. And if you can accurately measure by micrometer the actual width of the workpiece then you will be able to determine the actual allowance you need to make for those occasions when you can only contact one edge. As we say is Australia.. "Bloody good mate".

And the more times you do the two side contact and check the actual measurement, the better average allowance you can determine, even get differing average allowances for different materials. And as the edge finder gets older and has altered characteristics, the two side technique will continue to compensate. As my kids would say.. "Cool".

And sometime when I was a kid I think we would say "Keen".