I finally obtained a set of 3/4" 3M radial discs and polished a few
things from the most abrasive right on through to the polishing step
and find that there are miniscule ridges here and there when I
finished. Has anyone had experience with that problem? I am
wondering if I pushed too hard on them ( I used from 4 -6 on the
mandrel with each grade). What would you recomend to rid an area of
the ridges? My reason for wanting these discs was to remove the
traces of firescale near bezels but I don’t want to add another
problem instead. By the way, I am a big fan of Pripp’s homemade
firescale retardant, (thanks, Peter R.) but it sometimes is not 100%
free of firescale when I finish. Another thought is: should I
omit using the yellow (most agressive) disc and just start with the
If anyone has some hints on this I would really welcome them.
Sue in VA on a beautiful, hot day.
Sue - I’ve recently started using the 3M radial brushes and haven’t
encountered the ridge problem that you have. Possibly I’m using to
fine a grit or yours is to heavy? They do work well though.
Another item I’m using fighting firescale is NO-OX from Rio. I’ve
tried the various methods mentioned on this board, they do work. So
far, I’m leaning towards NO-OX. It seems to be good stuff.
Operations Supervisor - Image Processing
Hi. I am a great fan of bristle discs, for all sorts of
applications. I like the shimmery finish from the red (medium) disc
and both the red and also the pink (fine) will clean up a surface
well. I use them with a very light touch and I haven’t had any
trouble with unwanted marks. The medium is the most versatile for me
and it eliminates the need to pick brass bristles out of my clothes,
hair, fingers, the cats fur &etc etc. Ruth.
I haven’t used them but maybe you need to move the piece from side
to side, as the brush is striking it. dp
Dear Sue, The 3 m discs are really quite useful, but I have
discovered that the small wheels should always be used three or four
at a time. The yellow discs are quite aggressive and one must use
them carefully. The small discs are best used in tight quarters. In
my opinion , these small versions are overpriced cosidering their
short usefull life span. I now use the larger wheels on a tapered
spivdle using my buffing motor at 3450 rpm. This approach is much
more serviceable…the wheels last fifty times longer. Ron at Mills
Gem. Los Osos, CA.
I think you may have leaned way too hard on the discs – the tips of
the bristles are what does the real work of polishing, and you can
change the way they contact the material by forcing them down too
firmly onto the piece. The discs’ round shape should not distort
during use – in other words, you don’t want to look at the spinning
stack of discs and see a flat-sided cylinder where they are in
contact with the metal. If you do, you’re pressing too hard. You
really don’t need to “push” on them at all – just like in sawing,
let the tool do the work. If you lean too hard on that sawblade:
ping Think of sweeping and stroking motions with the radial
bristlies, not scrubbing and rubbing.
I’ve been using the discs for years, as have my students, and none
of us have ever gotten ridges. If you look at a single radial
bristle disc edge on, you will see that the bristles are arranged in
a checkerboard pattern. This makes it extremely difficult for them
to plow a furrow, unlike solid cylinder silicone polishing wheels,
which are so good at digging troughs in your work. Even using the
brown and green wheels, which are more aggressive than the yellow
ones, I have not gotten the effect you describe. Is it possible the
marks were on the piece before you began and the polishing made them
more visible or exaggerated them?
Another possibility is that the end of the mandrel was too close to
the surface of the piece and made tiny nicks as it spun – this
would be very likely in the tight quarters around a bezel,
especially if you were really pressing hard. You might not even have
felt or heard it hitting over the regular sound of polishing. 3M has
made a cup bristle brush in three grits – they are available from
Rio – that uses the same neat abrasive-impregnated plastic as the
radial bristlies but in a form that covers the end of the mandrel so
you can get down inside things without risking damage from spinning
Sue, the 3M discs are fantastic and we have been using them for a
couple of years now. However, if you are creating ridges on your
work with them you are either bearing down too hard, using too course
of disc (perhaps yellow when not needed) or more likely, not changing
polishing direction continually as you must with any abrasive.
Silver is especially susceptible to surface damage due to its softer
nature. Start next time by eliminating the very course yellow disc
and continually change direction. We still use a lot of tripoli or
similar bobbing compound for pre polishing and find it the old
standby for silver and gold, but the 3M discs have their place. We
even still finish with red rouge or Zam, especially for silver. By
the way, Prips flux is always 100% dependable to guard against
firescale if properly mixed and applied. If you still have firescale
after applying Prips, something you are doing is incorrect.