Re: [Harp-L] Flat sanding problems

[Boris Plotnikov <ploboris@xxxxxxxxx>]

Thanks guys for responce. Just for experiment I just tried to flat sand
wood 1847 comb. The same crap, borders is thinner than center. I'll buy
coarser sandpaper tomorrow and will try again.


2012/12/26 Vern <jevern@xxxxxxx>

> Your problem is that the comb is small and flexible so you will sand away
> more material where you are holding it and the downward force is the
> greatest. Bear in mind that it is very difficult to apply even pressure
> with your hands and that you must use extreme care to avoid rounding off
> the sides and ends.
>
> You are trying to reduce the thickness by .5 mm and not just to flatten
> it. This may lead you to press too hard.  It is very difficult to remove .5
> mm with 800 sandpaper
>
> You should:
> - Use wet sandpaper for plastic combs.
> - Hold it at different places, ends, middle, etc.
> - Press down from the top with your whole hand, don't put your fingers on
> the front, back, or sides.
> - Turn it in different directions with respect to your hand.
> - Hold it with right and left hands.
> - Stroke in different directions, along the length, across. at a 45 deg
> angle, in small circles, etc.
> - Use different areas of a whole sheet of sandpaper.
> - Press gently.
> - Use coarser sandpaper instead of more strokes while removing material to
> change thickness.
>
> Frequently hold the comb against a reference flat and up to a bright
> backlight.  Peek along the surface of the reference flat to see the high
> places and use a little extra pressure there.
>
>
>
> This is a skill that requires practice to acquire.  Start with junk combs
> until you can get it right.
>
> The flexible reedplate can bend to conform to a uniform gentle curve along
> the long dimension.  However, a curve across the short dimension is
> unacceptable.
>
> I have flattened many Hands-Free-Chromatic combs and mouthpieces to .001"
>  or .03 mm using the above techniques.
>
> Vern
>
>
>
>
> On Dec 26, 2012, at 6:17 AM, Boris Plotnikov wrote:
>
> > Hi to all!
> >
> > I'm not happy with my flat sanding job. Usually I get stock combs and
> > polish them with 2000 sandpaper and it's ok for me and my customers. I'm
> > trying to turn standart 1847 silver comb (6 mm) into thinner comb (5.5
> mm)
> > and it looks flat, but actually leaks, as central of comb is thicker than
> > borders. I follow ElkRiver instructions, use 800 sandpaper on a mirror,
> > extra comb under to support and minimum pressure, marker lines to look
> > where it works, but anyway they're not flat. What am I doing wrong?
> > --
> > Thanks, Boris Plotnikov
> > http://borisplotnikov.ru
>
>
>


-- 
Thanks, Boris Plotnikov
http://borisplotnikov.ru