Electronic Edge Finder

[Quadramaster]

I'm a newbie to machining, but I'm having a blast! Does anyone have any experience with this edge finder?

Wildhorse Innovations - Econo-Probe 3D Probe & Tool Height Setter

Or for that matter, any edge finders? I've just finished constructing a ShumaTech DRO-550, for my Shopmaster 2000, and this looks like an interesting addition.

Mark -

[TomB]

I don't know anything about the electronic ones but I live by the cheap mechanical ones.

Enco - Guaranteed Lowest Prices on Machinery, Measuring Tools, Cutting Tools and Shop Supplies

However they will not do everything shown in the electronic one's pictures. There are two distinct operations shown, edge finding and surface finding. The latter is important if you need to set the mill's distance above the top. I rarely need that operation. To set a mill so that I can cut a specified depth groove I just bring the mill down until it just touches the surface then I zero my DRO at that point. If I need to set it better I make a shallow cut then use a depth measuring micrometer to see where I am. Put that number back in the DRO and go at it.

Actual edge finding is for me way more critical. I often need to center the mill over an existing hole to establish the part dimensional origin or to set up a boring tool for hole enlargement. In the latter case the error in centering is very obvious. Center then bring the boring tool down to enlarge the hole by 10 or 20 thou. Let the cutter just touch down and pull it back up. Visually you can see how concentric the new cut is to the old and probably anyone can see misalignments of less than .001 at this point. I find that I can consistently center to where the error is too small to see with my technique and a relatively cheap mechanical edge finder.

I center in four steps. (1) Bring the center finders tip into the hole and touch off on any edge. Let that point define the east side for the purpose of explanation. Set the DRO to 0 and move the edge finder to the west side. That measures the length of a chord in the hole. (It may be close to the diameter chord but since you don’t know the center you don’t know how close.) (2) Divide that number in half via the DRO and move back to where the DRO reads 0. That puts the mill axis over the NS diameter chord. (3) Move the edge finder to the north side and zero the other axis of the DRO. Move to the south side to measure the diameter. (4) Use the DRO to divide that number in half then move the table to zero the second DRO. At that point the DRO 0/0 will be on the holes center point. People have told me that there is a slight bias in mechanical edge finders but I think the fact that this method uses two edges i.e. east/west once then north/south second means that the bias cancels.

[Kiwi]

Originally Posted by TomB ......People have told me that there is a slight bias in mechanical edge finders.........

To counter any bias, rotate CW on one side and CCW on the opposite.

[Quadramaster]

Thanks for the replies, I obviously have more to learn than I know... I'm not so interested in tool height measuring as I am in finding hole centers and edges. Perhaps a mechanical center finder would work as well for what I want, I need to do more research, and digest what you have said... Tks for the input...

Mark -

[Quadramaster]

So TomB, I went to that Enco link you posted and found a whole bunch of edge/center finders, different sizes and shapes. So do you use an assortment of them for different diameter holes, edges, and scribed lines? Or would you recommend one that is more universally useful? I see they sell a four piece set too...

Tks...

Mark -

[TomB]

I have an assortment of 4. Two come with dual ends and two with single ends. They all fit in a 3/8" collet. They have two type tips, 1/8" cylinder and 3/8 to 0 diameter cone. I don't remember it I bought my set from Enco or Grizzly, probably Grizzly as I wander into the PA store periodically. While shopping I pick up things wonder it it would work and buy to try. In this case the test was very successful.

The link to Enco I provdied was to the same thing from Starrett. That is probably a higher quality unit than I have but they all look the same.

Finally I've found no advantage for the cylinder style compared with the cone style. Obviousily if one was trying to find the center of a hole that was on an plane that angled with respect to the mill axis one would have to use the cylinder type. But mostly I use the cone unit to find the center of holes or edges in plate steel clampted to my table.

I was happy I could give you some thought you appreciated.

Tom

[Quadramaster]

As I continue my research about mechanical edgefinders, I have found that they sell ones that have an audible click when it kicks. Is that an advantage? I find as I get older my eye sight has gotten worse, but then again, so has my hearing. So I could use all the help I can get. Do you think the audible ones are worth trying?

Mark -

[Kiwi]

The parts shown in the attached picture are the only parts I've ever used in the set I have.
A mechanical ball end will find the edge on straight or curved faces good enough for all I require.
I dial in increments of 0.001mm (0.00004in) until the ball runs off.
I'm sure the surface finish and flatness affects the reading but this has been good enough for the work that I'm doing.

[Quadramaster]

So how does a wiggler work? I think I understand how the other edge finders work, by running in the spindle at around 1K RPM and moving slowly up to the edge and waiting for it to stop wobbling. Does the wiggler work the same way, or is it a different kind of tool?

Thanks for helping out a noobie...

[Kiwi]

Originally Posted by Quadramaster So how does a wiggler work?.....

This may help.
YouTube - Using a Wiggler

[Quadramaster]

Well, THAT was very cool, and helpful... Thanks.