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Default Mechanically polishing brass that's pitted?


"Vet Tech" wrote in message
...
I've got items of door furniture (letter box, knocker etc) that are
made of solid brass but they've not been polished for years so they're
pitted and looking very tired.

I've tried Brasso and lots of elbow grease but I'm just not getting
down to a level where it would make a difference.

So I'm looking for the best way to get them all buffed up by using
something that I can attached to my drill.

Any guidance would be much appreciated.

VT


Put a magnet on it first, and feel the weight... Lots of 'brass' these days
turns out to be plate when you get it (Screwfix for example did solid brass
electric sockets for a while, but continued advertising them as the same
when they were made of plate.). The pits are often holes that go down to
the iron underneath on old stuff, and, on new stuff ally, and you don't want
to rub the plate away getting down to the bottom of the pit.

Assuming it is solid brass then you may first need to go over it with
nitromors as it is often lacquered, and even if it isn't this will get off
the ground in skin and grease too. If you do adopt chemical or heat methods
watch out for the core metal of some of the old knobs: I got a shock when
the grey metal (presumably zinc/magnesium) that took the square turning rod
of one of mine melted and ran out - took a lot of fiddling to make a
replacement - when I was trying to hurry old lacquer off...

Then as TNP says, there really isn't much option but to choose the minimum
grade of emery/wet or dry, that will enable you to rub down past the pits.
Deep ones you may even have to start off with riffler files. Keep the
scratches all going the same way with the first grade, then rub these
scratches away by going at right angles with the next grade down; then at
right angles again, and so down through the grades. When you have got down
to 600 or 1200 - 1400 - depending on how much of a perfectionist you are -
T-cut or similar metal polish in a circular motion will rub out the fine
scratches that are left. If your pieces are easily detachable you may find
it easier to polish with wet and dry under the tap with a dash of wash-up
liquid now and again. In preparing metals for microscopic examination a
polishing sloping surface with water running over several grades of wet or
dry was used, followed by a final burnish on a diamond lapping wheel.

Brasso and Autosolve and similar products don't really polish: they just
fill in the finer scratches: which you can prove for yourself by wiping a so
'polished' surface with paraffin, which wipes the 'shine' back off. It is
better to polish properly - by reducing scratches to the minimum acceptable
size - and then oil your product, rather than go for a brilliant finish that
will mark and pit after the first fingerprint or raindrop.

For a real brilliant finish you will need a proper polishing mop or buffing
wheel, for which you can get several grades of cutting 'soap' and jewellers
rouge. But it would still be best to wipe the surface with an oily rag
regularly afterwards. (Oh and it'll get v hot on a buffer so leather gloves
are in order.)

The irregular shape of your knocker would probably be best tackled with
various grades of brass brush wheel, but you will need (as with the buffing
wheels) to find a way to clamp your drill securely, or get a bench
grinder/buffer - which is always worth having. Once you have cleaned it
with the brush wheel, then you go on to the polishing soaps on the buffing
wheel again. Keep different mops for different grades of buffing soap.
*Don't* whatever you do, be tempted to use an iron brush wheel.

If you don't want to tackle the mops and such, you can achieve a fair bit on
irregular surfaces with, say, strips of towelling or bootlaces. and various
grades of grinding paste. Hold the knocker in soft vice jaws and work the
strips of cloth 'shoe shine boy fashion' through it with one end in each
hand: you may actually find this easier than a pukka buffer in fact.

Sounds hard, but it is actually satisfying producing a good polish: rather
like getting that perfect sharp edge on a chisel or scythe.

S