Well, I suppose the most important question would be where else can I
ask these questions? Any good forums to recommend?
See, even the definition of lapping is still not clear to me. 3M makes
lapping films I can buy on eBay. What's the relationship to the rouge
the other poster mentionned? Particle size?
I wish to machine some ferrite transformer cores so they can slide
apart but still complete a magnetic circuit when simply pressed
together with light finger-type pressure.
This already exists so it's definitely doable.
However, I wish to do this at home with a minimum of expense.
I figure a 5.25 full height hard disk has the necessary flatness on
the platters for a good lapping surface. I'm not looking for the
ultimate polished finish like a gage block. Just good enough.
I figure putting the lapping film on the platter and making a jog to
hold the work piece steady ought to do it.
I need to know what to do! How to ensure dust doesn't mar the finish.
Textbooks about these processes are quite expensive. Any
I'm going to the library later.
Thanks. I was wondering about the granite cutting slabs you see in
kitchen supply stores. They're all shiny and stuff, but are they
(I don't mean an entire counter top, just a cutting board-sized
I guess there's a difference between "locally" flat and overall
As for the frequency range, it's DC to 50MHz. I already have parts to
do this, the Hall sensor is a thin film somehow bonded to ferrite
As for the accuracy I need, I was surprised to see the existing parts
were actually pretty sloppy. One of the pieces actually rocked back
and forth (barely so, but still perceptible) on my HD platter.
I didn't even need my micrometer to measure it either. One end of the
thing is 1 mil lower than the other, over a total of 176 mils.
So if I manually lap on a granite slab with a 3M lapping film, well,
how do I insure the work piece is not going to "rock" back and forth
as I move it?
A LONG time ago, I assembled FC fiber optic terminations. Once the
epoxy set, you put the FC connector in a steel puck and just rubbed
the FC/puck combo over a lapping film.
I would need suck a puck that fits my parts.
Is there a name for such a thing? The bottom of the puck was very
Truer words were never spoken. It is really common to establish air
gaps in transformer cores, for specific functions. He'd be better off
finding out if "lapping" were necessary first...
David A. Smith
I've put down the espressos and started to relax a bit.
I went to a kitchen supply store. No granite, but I bought a marble,
or something claiming to be marble, cheese cutting block. It's large
enough, and at any rate it was only 7$.
It certainly seems flat enough, I placed two of them shiny face
together and got that fun "vacuum cement" effect or whatever. There
was an airtight seal between the two.
I already have 600 grit sandpaper from my model rocket days.
We'll see as I go along what happens...
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