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273555 Richard Wilson <yorkshireman@y...> 2021‑05‑03 Re: home made sanding compound?
Fascinating question for a Monday morning...

> On 3 May 2021, at 02:47, John  wrote:
> 

>  I need to make a round sanding device.  About 2" -3" in diameter to sand the
inside of a sphere.  So I am thinking of finding a material to add a grit to,
that will break down as using, to continually expose new sanding grit to sand a
spherical inside shape.

- snippety snip - 


You don’t mention whether this is indeed the inside of a sphere - as in, say an
easter egg, with a spherical outer, or, say a mortar, with a spherical
depression in an otherwise substantial object.

Why would that help?
because the one is likely to be on a pole lathe, or otherwise a spinning
workholder, and the other is not.   Abrasive use demands thqat one or other is
moving, and the quicker the better, so a stationary abrasive  and spinning
workpiece works.   And a stationary object and spinning abrasive works.

Case1 - the spinning workpiece.  Make up a curved something to the size of the
interior, less thickness of abrasive.  Glue abrasive to holder - present to
spinning workpiece.  Do not be tempted to make your tool over long and cover a
full quarter of the sphere, unless it is trivial.  It will grab and end in
tears.
If trivial then make up the full spherical size, as per ..


Case 2 - the spherical depression in a lump of something.   Make up a suitable
size sperically domed end stick.  Coat with hide glue.  Dip in abrasive grit.
Repeat several times .  This is a time tested means of making up abrasive
formers.  As the grit is used, the glue will release due to heat softening, and
more abrasive is brought into use.  I can’t give actual experience of using this
this, so the precise degree of undersizing and amount of grit that can be
embedded will be a bit of trial and error.   Making the full spherical shaped
thing is of course, to equalise the pressure as you spin the thing - maybe in a
breast drill, as we were talking of them recently.  If you are pressing into the
dome, then the base will be receiving pressure and the sides will not.

A template, and some practice on a sacrificial trial is called for.

Or, of course, depending on the accuracy needed, you could emulate the above by
gluing up small bits of abrasive paper around the spherical master.


How many to do?
How accurate must it be?
How strong is the substrate?
How good a finish is needed?


I DO hoe you tell us how it all works out.


Richard Wilson
Yorkshireman Galoot
in Northumberland, where the weather forecast is for a decent rain, as it’s a
public holiday.




-- 
Yorkshireman Galoot
in the most northerly county, farther north even than Yorkshire
IT #300

Recent Bios FAQ