Straighten a bent edge finder?

U

Unlogic

H-M Supporter - Gold Member
H-M Supporter Gold Member
Joined
Dec 28, 2020
Messages
164
I messed up and manage to bend my edge finder...


Is there chance it could be straightened again and in that case what's the best way to do it?

Nevermind the white tape on it. It's there to lower the volume of the beep which is way too loud otherwise.
 
Are those thousandths?
So it's running out about 8 thousandths, which would be 0.004 each side of the axis.

These are my (speculative) first thoughts. I have never done this, but one day, I might have to. I do own one just like it that is still in it's box.
If it got bent by too hard a sideways shove, it maybe can be shoved back by setting against the same surface that bent it, and shoving back, but in a very controlled way. There has to be some plastic resilience somewhere, and also, you might first get curious about in which part the bend really is. Might it be somewhere within that nylon looking bit?

Anyway - with not much more to lose, leave the indicator on it, and shove with the vise from it's "bent" maximum back by 0.004" and then un-shove it, and see if it returns back to maximum bend. Then shove again, maybe 0.006, exploring just how far you need to go to start affecting it. You might have to shove a whole lot, but once you know where it's yield point is, go careful, checking where it returns to.

There is much to go wrong here, and other stuff can happen on the way. If you get lucky, you might return it to within a few microns concentric
 
aliva said:
Scrap that one a buy one of these, cheap, accurate and no batteries required and hard to bend out of shape
Click to expand...
One of those I also happen to have is the reason the electronic beeper type has not yet even been tried out. I am sure they are great, (when not bent), but the slip-aside happened to be in the box I opened first, and the other required I tangled with a little battery. I had thought that electronic type would be the way to signal a CNC controller to take measurements

The slip-aside principle is damn clever. When there is no more room to keep spinning up against an edge, there is no place to go except way to the side. I love it!
 
Those edge finders can be made even more sensitive by grinding a small flat on the diameter of the probe. I use them by shining a light at the back side so I can see the eccentricity of the gap, when no light can be seen, I'm there; I think that to make the probe move sideways you would have slightly over traveled.
 
You could set up 2 ball bearings and with a spindle spinning, bring the edge finder into contact and use the 2 ball bearings to gently push out the defection.

But the easier course of action is to scrap it an use an edge finder that will last 4 generations as shown above.
 
I really understand those that prefer the mechanical edge finders but these electrical ones are extremely time efficient to use as they give off both a sound and a light signal as soon as it makes the slightest contact (the downside is that they only work with conductive materials).

I managed to straighten the shaft of the edge finder to within 4 hundreds of a millimeter but I later found out that the pocket for the spring loaded ball at the bottom was also damaged so the ball wouldn't stay centered anymore, it was all over the place. The ball isn't really supposed to move during measuring it's just a built in safety so to prevent the whole thing from bending if it's pushed too hard against a surface. I destroyed mine by lowering it straight down into 40 mm steel pipe and the the poor thing was never meant to survive such abuse.

So I bit the bullet and bought a new one today from the local tool store.


That runout is probably as good as it's going to get given the setup I'm using with a long stickout and a rather cheap collet holders. It should also be noted that these edge finders are not supposed to be spun when in use, I'm only doing it here to check the runout.
 
aliva said:
Suburban tools compare various edge finders
Click to expand...
Like so many of his videos he is completely wrong regarding the indicator / collet / magnetic fixture demonstration at 5:25 to 6:15.
If the collet runs out with a dial indicator in it, there is no error. The stylus tip still rotates concentrically around the spindle axis and will always find the true centre of the magnetic fixture. The same can be said for finding the centre of holes, an indicator does not have to run true.
 
You must log in or register to reply here.
Back
Top