Wiggler or edge finder?

DavidR8

DavidR8

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In yesterday's drawer cleaning I came across a complete Starrett S828HZ wiggler set in perfect condition.
I see people using the type of centre finder that spins until on the edge and then goes off to indicate the edge. Are these type more useful than the Starrett set?
 
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I also find the edge finder totally reliable, repeatable and accurate. I got a 10mm wide finder, which works perfectly with my mill having 5mm leadscrews. Makes it super easy - one turn to get to the edge from where I picked up with the edge finder. I find less thinking on simple ops like that is a definite advantage. I don't think I'd get anywhere near the same accuracy with a wiggler, but I'm sure very useful in some situations where edges aren't easily picked up with an edge finder.
 
I have been told that if you grind a small flat on an edge finder that it increases it's sensitivity, I did it to mine; I have always thought that if you advance until the edge finder goes off, that you went a bit too far, I go until no light gap can be seen with a strong back lighting. I use both an edge finder and wiggler, mostly the sharp point for picking up prick punch marks or center lines, they are both useful., also the wiggler set can be used to mount a Last Word style indicator.
 
Could someone please explain exactly why (not how) an edge finder works?
 
The only thing I use my wiggler set for is picking up a hole that I want to drill with the head kicked on an angle.

I will spot the hole/ holes with the mill squared up, then set the head angle. Use edge finder to find Y zero. Then, pointy wiggler tip finds spot center for X.

I use my edge finder every day, to pick up edges or find center of a round part, wiggler set maybe use it once a month.
 
An edge finder works because the tip is fictionally bound to the shaft, and it takes just enough pressure on the tip to overcome this friction for the tip to walk/move off center. This side "pressure" versus the tiny amounts of friction eliminates tiny particles, liquid films, and the like from giving false readings.

I use edge finders for finding edges, I use wigglers for finding centers. They both have <different> purposes.
 
They both have their uses. The majority of the time I use the edge finder. But there are times the wiggler is very useful. The disc is useful when you have to pick up the edge in a confined area. The point for picking up lines and center punch marks. It’s worth having both in your tool box.
 
The way I use the edge finder is to approach the edge relatively quickly to get an idea as to the location. Then I back it off ad nudge the tip wihn my finger nail to run true and approach the edge at around .0002"/sec. as determined by my DRO. what this does is it allows the tip to become perfectly centered on the spindle axis. As you continue the approach at some point the perfectly centered tip will contact the edge and the tip will deflect to the side at which point the edge is offset by the radius of the tip.

Approaching too quickly can cause one of two errors. Too fast an approach can cause an overshoot because of a delayed personal reaction. On the other hand if approached too quickly, the top may not center and it can deflect prematurely. Slowing the approach prevents both of these issues. If you have a DRO you can easily check your positioning ability by finding the opposite sides of a known block. A 1-2-3 block is a good candidate. Find two opposite sides and compare the DRO readings to a miked value.

Different materials react slightly differently as do ifferent surface textures. Hard, smooth surfaces provide the best accuracy while softer materials or those with rougher surfaces can cause slight errors. Surfaces should be clean and dry. A liquid film can cause viscous drag which will deflect the tip prematurely. I apply a light oil between the tip and shank and wipe it dry with a clean cloth. This leaves a very light film on the surface which enhances the deflection.
 
I definitely get more use out of my edge finder, but a few times I've used the wiggler. The wiggler is useful for finding a punched point, a scribed line, or centering on a small hole (where the coax indicator isn't going to work).

I'm glad I have both, and for a few bucks they are worth having in a drawer for when you need it.
 
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