From: "Frank Q" 
To: "Dwight K. Elvey" ,
        
Reply-To: "Frank Q" 


Hi All

In answer to the question (below) regarding grit sizes, the numbers relate
(historically at least) to the size of the grid (in inches) used to
separate the various grit sizes. Consequently, grade 2500 means that the
size of the grains is 1/2500 inch.

Using simple arithmetic, we have

1 inch  = 25.4E-3 metres
so for grade 2500 grit, we have
25.4E-3 / 2500 = 1E-5m = 10E-6m = 10 microns

and for grade 1000, we have

25.4E-3/1000 = 25.4E-6 = 25 microns

Unfortunately, I can't help anyone with the emery classification. I have at
home a few jars of M303 and M305 and have no idea how these numbers relate
to grit sizes. I have been told they're about equivalent to grade 1000 or
thereabouts.

I would greatly appreciate it if someone on the list could post the
relevant information.

Cheers

Frank Q


>
> >From: "Scott Berfield" 
> >
> >Hi,
> >
> >After another bout of scratch removal (don't ask -- it involves the
> >spouse being "helpful" and we don't want to go there) 
Any opinions?
> >
> >Also, I have some grits labeled 1000 and 2500. How would these (grayish
> >colored) relate size-wise to the 15, 9, and 5 micron aluminum oxide
> >grits?
> >
> >-sb
>
> Hi
>  My understanding is that 2500 is about 10 micron. You may
> find that the 10 micron aluminum oxide produces a smoother
> finish because the carbide is made of sharper chuncks.
>  I've seen little difference in time from 10 micron to
> polished for going to 5 micron first and then polish, compared
> with just the 10 and then polish. The risk of scratching
> is much greater with 5 micron as well.
> Dwight
>
>

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