minding your P's and F's in grit sizes

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minding your P's and F's in grit sizes

Postby Chris A » Mon Feb 20, 2017 10:55 am

I'm obviously a bit thick, ignorant or both, I recently bought some silicon carbide powder F800 thinking it was similar in grade to P800 abrasive paper; it's not, its more like P3000! (about 8 microns, P800 paper being 22 microns).

F and P numbers are part of the FEPA European system: P for abrasive papers, F for abrasive powders; U.S. ANCI system numbers have no letter prefix; Japanese JIS system may use a J prefix.

In the past I've used terms like 600g for 600 grit - this seems to be nonsense.

Here is the best comparison chart (Russian) I could find which includes FEPA, ANSI, JIS, MICRONS, and other water stone types like Shapton etc. hope this is of help to other site users.
Best grid.png
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Re: minding your P's and F's in grit sizes

Postby Doug Sanders » Tue Feb 21, 2017 1:34 pm

That's a great chart. Thanks! Interesting to see my assumptions over the years between 3M micromesh, and conventional sandpapers are borne out.
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Re: minding your P's and F's in grit sizes

Postby Chris A » Sat Feb 25, 2017 7:50 am

Does anyone know where charcoal as used in polishing might be placed on this chart?
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Re: minding your P's and F's in grit sizes

Postby Steve » Sat Feb 25, 2017 2:47 pm

Chris A wrote:Does anyone know where charcoal as used in polishing might be placed on this chart?


Smudgey fingerprints around the margin?
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Re: minding your P's and F's in grit sizes

Postby Chris A » Sat Feb 25, 2017 5:25 pm

very funny :crackup:
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Re: minding your P's and F's in grit sizes

Postby Chris A » Mon Feb 27, 2017 5:14 pm

what I'm trying to do is learn about charcoal for polishing: is it a powder or a lump is it Magnolia or Paulownia ; what's the difference? where do you get it?

will another type of charcoal do? I presume it's an abrasive ?

I've searched the site but cannot find the answers.
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Re: minding your P's and F's in grit sizes

Postby Christoph K » Tue Feb 28, 2017 12:48 pm

Hi Chris,
if I remember correctly Ford did recommend this one as a substitute for magnolia charcoal https://www.amazon.de/dp/B006OD7E06/ref ... JOHDT5KC0A :-)
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Re: minding your P's and F's in grit sizes

Postby Chris A » Wed Mar 01, 2017 12:55 pm

Christoph, thank you for that ; have probably got something on the bbq shelf that would do ; I tend to get technical when in ignorance; feel the need to pin it down.

Was looking at your latest utsuchi yesterday though felt unqualified to critique; but have a suggestion so will make it later.
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Re: minding your P's and F's in grit sizes

Postby Albert R » Thu Jul 20, 2017 10:54 am

"I tend to get technical when in ignorance; feel the need to pin it down"
I know the feeling...

FYI old time Navy Chiefs used to use cigar ash to polish the mirror on the sextants.
Off the cuff guessing, but I bet the abrasive nature of a charcoal depends on the type of wood and its inherent silica content. I know some woods will eat up blades much quicker than others.

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Re: minding your P's and F's in grit sizes

Postby Jim J » Thu Jul 20, 2017 4:02 pm

Some time back I read an article on super polishing aluminum mirrors for scientific instruments.
I recall they actually used India ink as the final grit.
Assuming it would be the superfine carbon black in the ink doing the polishing.
Supposed to leave a superior flatness and reflectivity.

Then again, a chocolate bar and wrapper will polish an aluminum soda can enough to make a fire starter.

But, yeah the grit size changes get confusing at times.
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