Anybody seen anything like this?

K

Ken H>

Joined
Dec 31, 2011
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Hello all - got an interesting visual here. Take a look at this blade I'm sanding.


Notice the "eyes" in the blade? I'm not at all sure what's causing that. I'm sanding with 30 wt oil and 400 grit wet/dry paper. Now, when I wipe the oil away the eyes go away.


I can not see them at all - and it's not just a reflection, I can change lighting to vary reflection and the eyes are there with sanding oil/grit, but when oil/grit wiped away I can not see eyes even with blade moved around in lighting. Now, look at other side. The eyes are still there in same place, but opposite side. Eyes go away when the oil/grit is wiped away. Ever heard/seen anything like that before?




Well, I think I might have the answer. That blade was ground using the magnetic chuck for the surface grinder. While the blade didn't seem to have any magnetic properties, the blade didn't show any attraction to iron pin, etc I suspect there were magnetic artifacts left from the magnetic chuck. I placed blade on a demagnetizer and that took care of the problem - no more eyes. The oil/steel particles simulated a ferro-fluid that is really sensitive to magnetic field.

Comments from ya'll - does my thinking make sense?

Ken H>
 
That sure is strange. I have had little lines or waves that only showed up with oil/water on the blade when hand sanding before but not eyes! :eek:
Maybe same thing just yours looks a bit more weird!

Not sure what it is.
 
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Not uncommon to notice the shape of the magnets in your blade holder when hand sanding. Mine usually appears as 2 - 1" long parallel lines. I keep wanting to buy an old degaussing coil to demagnetize them.
 
Atlas - I did not realize it was somewhat common. First time for me. The magnets in my chuck are parallel bars, not sure where the circles came from. You're right, the demagnetizing did get rid of them.
 
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