What size edge finder

[PixMan]

To repeat: Get A Good One. Anything less won't kick out as much or as reliably.

They seem to be quite sensitive to their condition. I've got a Starrett that I've had for years. One day it stopped vigorously kicking out and instead just sort of crept over. No idea why. I checked for any obvious problems, lubricated the junction with light machine oil, no help. Bought a new one, and it's fine. Physically, I can detect no difference between the two.

The most common failure of one of those edgefinders is a little damage that's almost undectable with the naked eye. I did it to one of mine over 20 years ago, and that's why I now have a spare.

What happened is that when I used it to pick up an edge, I accidentally rubbed the major diameter solid body up against the workpiece and by doing that created a tiny little "ridge" on the solid face. I could barely notice any bump, but it was there for sure. I trued taking it apart and lapping the surface flat again, but the tool was never the same again.

[firbikrhd1]

I like the old Schmidt edge finders, Fisher Machine is making one similar to it:

http://www.fishermachine.com/index.p...datecart&id=36

I don't know if this is the black body one that Lew complains about, but I've got a couple others from him (hat top ones to find an edge under and overhang) and they work quite well.

I have a SPI Edge finder that works OK but wouldn't mind having another. What is the difference between the Fisher Big Jump Edge Finder you gave the address to and the Fisher Model A which also has a 3/8" shank? From the pictures it appears the Big Jump has a longer shank and a step from 3/8" to a larger size before it gets to the business end.

[rkepler]

What is the difference between the Fisher Big Jump Edge Finder you gave the address to and the Fisher Model A which also has a 3/8" shank? From the pictures it appears the Big Jump has a longer shank and a step from 3/8" to a larger size before it gets to the business end.

With more surface between the tip and the body the 'jump' is greater. It really stands out when compared to the edges finders with the 3/8 body at the tip interface. The design is very similar to the Schmidt edge finders that are no longer made.

[firbikrhd1]

With more surface between the tip and the body the 'jump' is greater. It really stands out when compared to the edges finders with the 3/8 body at the tip interface. The design is very similar to the Schmidt edge finders that are no longer made.

First, I don't mean to hijack the OP's thread. Hopefully he will find my questions useful as he selects an edge finder for himself.

rkepler, thank you for your reply which is clear but brings to mind another question: If one were to get a 1/2" shank edge finder with .2 tip, like the Fisher Model B, rather than a 3/8" shank one, how would that differ from the Big Jump? Would the 1/2" shank Model B not show as much jump as the Big Jump? Am I missing something else here?
Thanks in advance.

[rkepler]

rkepler, thank you for your reply which is clear but brings to mind another question: If one were to get a 1/2" shank edge finder with .2 tip, like the Fisher Model B, rather than a 3/8" shank one, how would that differ from the Big Jump? Would the 1/2" shank Model B not show as much jump as the Big Jump? Am I missing something else here?
Thanks in advance.

Likely it would, I really don't know. I know that my 1/2 inch (all the way down) doesn't have a very significant jump, but then it's got a 1/2 inch 'tip' and I tend to run it a little bit slower than the .200" tip guys (1000 vs 1500 rpm at a guess).

[MaxxLagg]

I prefer the 3/8 with the .200 diameter tip for 90% of applications involving manual machines. One thing that the .500 diameter ones are better at is if you have largish round stock that you're trying to pick up on the diameter. Using a .200 tip, the 3/8 body, in some cases, is close to touching instead of the .200 diameter. A .500 version doesn't have this problem. For machining centers and such, I like electronic versions for stuff that is conductive.

[dalee100]

Hi,

After a while I found I needed several different edge finders. I have a Fisher 3/8" shank, a Starrett 1/2" double end with .200" end and a pointed end, a 1/2" Brown&Sharpe clicker, and a Fisher 3/8" ridged electronic, and a 3/4" shank electronic with a spring loaded .400" ball end.

I find myself using the electronics more and more. Since they are used with the spindles off, I don't need to fool with getting the right speed for the edge finder. The rigid Fisher is very sensitive, but perhaps a bit delicate. It won't last long with a hoof-handed operator. The spring loaded ball end works quite well also and is more forgiving with over travel like the spinners have. I think the electronics are better for use in a horizontal mill rather than spinners.

If I must use a spinner, I find I use the Brown & Sharpe clicker the most. I really like the click. Much easier for tired old eyes to use.

dalee

[whitis]

On a small machine, you may want or need a small edge finder. Small shank diameter and/or small amount of z-axis daylight consumed (a potential issue for those with round column mills, as well).

Fisher makes them down to 1/4" shank, which is hard to find.
http://www.fishermachine.com/
Supposed to be pretty well made and they start around $10.

It is possible that the bigger edge finders with a bigger jump also have more hysteresis before that jump occurs - i.e. less accuracy. There are also "audible" models.

For those who want to avoid changing collets, some have a stepped shank which may give you double the chances of fitting in the collet you are already using. Edge finders operate on the center of rotation so it shouldn't matter if the steps aren't perfectly concentric.

As far as theory of operation, if it is a little out of position that will be rectified as it approaches the work and gets bumped towards center. Once it is centered, though, when it touches the work it will rub against the work for a full rotation. Just as a rotating tire will try to take off when it hits the road, so will the tip of the edge finder. A little friction is needed. Without friction, it may not indicate until it is a little past center and running eccentric and getting trapped by the work.

[tdmidget]

What ever size you get, DON'T get the ones that have the body
shiny steel and the tip black. It makes seeing the kick much more difficult.
The school ones are like that and mine is all the polished
steel and the difference is amazing. I like the 1/2 body and the
0.200 tip but occasionally would like to have the 1/2 - 0.500 one when
trying to edge on a round with a large diameter.
...lew...

Now you're talkin'. That is one of the best situations for an edge finder. edge find both sides and split the difference. By doing both sides you cancel out any error . Works like a charm even with a Chink POS.

[gr8life]

I second or is it third on the Fisher. I have a 3/8 & 1/2 big jump and love them both.
thanks
ed

[gundog]

I like these. http://www.lasercenteredgefinder.com/ I have the other type as well but I find these faster and set-up my CNC machines with them. I also use the laser to tram in the vise it makes quick work of it. They are not super precision but good enough for most of my projects I will dig out more precision equipment if necessary. They don't work good for finding the edge of a round shaft though.

Mike

[tdmidget]

Hi,

After a while I found I needed several different edge finders. I have a Fisher 3/8" shank, a Starrett 1/2" double end with .200" end and a pointed end, a 1/2" Brown&Sharpe clicker, and a Fisher 3/8" ridged electronic, and a 3/4" shank electronic with a spring loaded .400" ball end.

I find myself using the electronics more and more. Since they are used with the spindles off, I don't need to fool with getting the right speed for the edge finder. The rigid Fisher is very sensitive, but perhaps a bit delicate. It won't last long with a hoof-handed operator. The spring loaded ball end works quite well also and is more forgiving with over travel like the spinners have. I think the electronics are better for use in a horizontal mill rather than spinners.

If I must use a spinner, I find I use the Brown & Sharpe clicker the most. I really like the click. Much easier for tired old eyes to use.

dalee

Your electronic does not compensate for spindle runout because it is not turning. The cheapest POS is therefore more accurate.

[dalee100]

Your electronic does not compensate for spindle runout because it is not turning. The cheapest POS is therefore more accurate.

Hi,

If you need to worry about that much runout in your spindle, buy better collets and get your mill fixed.

dalee

[rkepler]

If you need to worry about that much runout in your spindle, buy better collets and get your mill fixed.

Whether or not the runout matter should depend on the class of work that you're doing. If you need to relate a feature to a couple of edges to .0001" the runout on the non-moving edgefinder really matters. If you're drilling bolt clearance holes it doesn't matter so much. Most of the work that we do is somewhere in between those extremes, I use everything from jig boring setup techniques to running the tool to the edge and saying "that's about right".