Imperial Electronic Edge Finder

[JasonBModerator @jasonb]

Mine has lasted at least 10 years, I bought a spare not long after I got the finder but Have not needed it yet. Just make sure you don't leave it anywhere that may complete the circuit as that will probably flatten it.

[Brian HParticipant @brianh50089]

That's a very good point Jason. I have resolved to keep it in the box that it came in but I will now be careful where i leave it inbetween uses.

Brian

[Ron LadenParticipant @ronladen17547]

Would I be correct in thinking they are no more accurate than manual finders but easier to use.

I get on fine with my manual version so have not been tempted but if I am missing out on something I will reconsider.

Ron

[EmgeeParticipant @emgee]

Ron

Your assumption is just about correct IMO, but the electronic is much quicker and has excellent repeatability.

Emgee

[JasonBModerator @jasonb]

The Tormech video in the PEC link I posted suggets they are more accurate but probably more than we really need. I just use them as I find them quicker and easier to use.

Edited By JasonB on 14/03/2020 10:09:39

[Bill PhinnParticipant @billphinn90025]

Posted by Emgee on 13/03/2020 13:00:04:

New unit is PEC and identical to my previous one and as in Jason's picture, price was far less than shown in the link you have, inc pp £24.18

Emgee

Any chance of providing a link to your item?

I'm getting on OK with mechanical edge finders, but I do like the idea of the convenience of an electronic one. Since these are used without rotating the spindle, presumably your spindle/chuck/collet has to be very concentric for the finder to give completely dependable results. I notice the kind of 3D tester Andrew uses has adjustment screws to compensate for any run-out.

One last point: do I take it the z-axis edge finding function on these two different kinds of tester is for checking the flatness of a part rather than establishing a starting point for milling etc? I can't really see how it can be the latter unless the difference in z height between your cutting tool tip and the finder tip is somewhow readily calculable.

[JasonBModerator @jasonb]

Bill, you use them with the mill running. If you do want to use them without them stationary then touch off on one side of the part, move to the other side and turn the spindle 180deg so that the same part of the finder makes contact which will eliminate any run out issues. Video from my earlier PEC link

[Bill PhinnParticipant @billphinn90025]

Thanks, Jason. Good to know they can be used with the mill running. Also good to see from your photo how with a bit of thought you can still use them on non-conductive material.

What is the overshoot leeway on one of these? I notice some of the ball-ended types have up to 2mm. Presumably it's somewhat less on the PEC type we're discussing.

[JasonBModerator @jasonb]

Probably best to regard it as zero overrun, you could maybe get away with a few thou before it will take on a permanent bend.

Meant to say I have not found th eneed for using the end (Z) of it.

Edited By JasonB on 14/03/2020 13:07:37

[Ron LadenParticipant @ronladen17547]

Interesting but I think I will stick with my mechanical version, I cant see that I would save any time in using an electronic version. I tend to creep the finder in very very slowly looking for the instant it trips trying to avoid any over run and I can see I would do the same with an electronic one, so no benefit.

[Bill PhinnParticipant @billphinn90025]

Thanks for the clarification, Jason.

Ron, the advantage, as I see it, with the electronic one is that the instant a light comes on is less open to interpretation than the instant a shaft starts to slide sideways. This assumes the light works by being either on or off and doesn't, for example, start very dim and come on with increasing intensity the more firmly it contacts the edge. The only real disadvantage I can see is the need for extra care to avoid overrun in case you damage the tip.

[Harry WilkesParticipant @harrywilkes58467]

My PEC 4200-520 arrived from Chronos this morning had a quick appraisal (read play) seem a good bit of kit

H

[Enough!Participant @enough]

Posted by Bill Phinn on 14/03/2020 14:47:36:

..the advantage, as I see it, with the electronic one is that the instant a light comes on is less open to interpretation than the instant a shaft starts to slide sideways. This assumes the light works by being either on or off and doesn't, for example, start very dim and come on with increasing intensity the more firmly it contacts the edge. The only real disadvantage I can see is the need for extra care to avoid overrun in case you damage the tip.

One reason I prefer the ball-end type is that you can safely run in fast initially until it beeps (and the light comes on). Then back off 5 or 10 thou and go in carefully to get the exact point.

To each his own though of course.

[Brian HParticipant @brianh50089]

Interesting conversation this; I still have (and use) my Starrett wiggler but the electronic one has it's uses. Also interesting that Jason does not use the end indication.

Brian

[Clive FosterParticipant @clivefoster55965]

#2 to Jasons suggestion of touching off both sides of the workpiece and using the DRO 1/2 function to find the workpiece to get reasonably reliable accuracy.

One of the many reasons I prefer my Huffam "wiggler" is that its pretty obvious from the behaviour when you've messed up.

Too many unconstrained variables in the pure electric "touch conductive material" ones for my tastes. It would be prudent to spens an hour or two testing things out, getting a feel for real world accuracy and sorting out a reliable technique befor using in anger. Most especially including testing the effects of poor connections in the eklectronic side.

But my job included building and developing bespoke special purpose lab measurement kit when no commercial equipment was available. So my antennae may be a bit over sensitiveto potential issues.

Clive

[Pete.Participant @pete-2]

Posted by Emgee on 13/03/2020 13:00:04:

Hi Brian

Did you get your edge finder yet ? mine arrived today, replacement for the PEC unit I crashed which now needs a new body machining.
New unit is PEC and identical to my previous one and as in Jason's picture, price was far less than shown in the link you have, inc pp £24.18

Emgee

Where did you purchase yours from if you don't mind me asking?

[Brian HParticipant @brianh50089]

Hello Pete, mine came from a Chronos company called Linear Tools and is a PEC 4200-520. Cost was £24.18 including post and VAT.

Brian

[EmgeeParticipant @emgee]

Pete

Same for me as Brian above.

Emgee

[Pete.Participant @pete-2]

Thank you both, I found them on the chronos linear website, the imperial on is about £45, the metric £41, where did you find one for £24 posted?

[EmgeeParticipant @emgee]

Pete

I have just been back to the Linear/Chronos website and couldn't find the offer, only as you £45 price, either they had some old stock to move or have just increased the price.

Emgee

[Pete.Participant @pete-2]

Ok no problem, still a very useful tool so worth £40 if the comments about it on here are to go by,

Thanks again

[Ron LadenParticipant @ronladen17547]

This is right off the top of my head so feel free to shoot me down. Isn't an electronic finder only as accurate as the mount in the spindle..?

If for example the collet/chuck it's mounted in has runout the electronic finder won't compensate for it whereas a mechanical finder does as it finds its own centre regardless of how its mounted..?

Ron

[Ron LadenParticipant @ronladen17547]

Oops, should have read the thread fully, Bill mentioned this in his post.

[EmgeeParticipant @emgee]

Ron

Your statement re spindle runout is absolutely correct if using the electronic edge finder with a static spindle as recommended by PEC in the instructions.

However if the spindle is rotating slowly the runout will cause on/off of the diodes, this is not a problem if you want to position the spindle to the centre of a block/part by indicating one side and setting axis to zero then indicate the other side and divide the reading by 2 for the centre of the part.

If using to find the centre of a bore with the spindle off, indicate 1 side of the bore and and set zero, move tool away from bore surface and rotate the spindle 180 degrees so the opposite bore side is indicated with the tool in the same orientation as the first reading, divide reading by 2 for centre of bore. Move tool to centre found and set axis zero.

(Jason did mention this earlier but it is the method used by very expensive indicators and control systems in industry when setting spindles to the centre of bores).

Set the second axis in the same way, the dimensions may be different for each setting because the first position is not at the bore centreline, it is only estimated by eye or other means.

If using the electronic indicator on a manually operated axis that has any degree of backlash the advantage offered is that the edge will be found without reversing the axis handle to bring the mechanical indicator back inline.

Using a PEC to indicate front edge of a part and then the centre between 2 legs, video starts at 2:25

**LINK**

Emgee

[Ron LadenParticipant @ronladen17547]

Thanks Emgee, I missed Jasons explanation also, sorry guys.

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