Polishing Brass - or where to get P5000 paper

Normally when I want a brass summat to look shiny bright, I take it to P2500 then Brasso and it looks OK. But the other day I did that on a piece, then it caught a glancing light which showed a visible scratch pattern. OCD kicked in and I bought a polishing set which comprised a stitched wheel with 'brown compound' for preparation and a floppy wheel with 'blue compound' for finishing. It works OK, but it takes forevever for the 'brown compound' to get the P2500 scratches out, hence my wondering if there's anywhere to get P5000 at a reasonable price - a Google search turned up a source at about £4 a sheet but I'm not as mad as that!

Or is there a better way of getting a specular finish on brass? I realise that it's pretty pointless as you only have to touch the stuff with a less than forensically clean finger and it's scratched again, but I'm interested.

Rob.

Hi Robin,

On mostly plastics I've used a product called micromesh by Alclad. The stuff I had goes up to P12000 and is used to remove scratches from clear plastic, e.g. aircraft canopies). I think I remember seeing a while back, a chemical process to surface metal to a mirror finish, possibly on youtube.

Ed.

Have you tried optical polishing pads as used on telescope mirrors etc? they are disposable and work quite fast.
Otherwise the various optical 'grits' go down to cerium or tin oxide, or the old fashioned rouge. They can all be elutriated to get a finer finish.

Robin,

I recommend that you try using [previously Solvol] Autosol as your polish, after the abrasives.

... It has more 'cut' than Brasso, but is capable of producing a very high polish.

From your description, it sounds like you are 'polishing-up', rather than 'polishing-out', the micro-scratches.

MichaelG.

At Epping Forest Horology Club we tend to either be 'Autosol Men' or 'T-Cut People'...both have their adherents who prefer one or the other for various reason. Personally, i'm a T-Cut fancier, but not by much!

Most members of the club who are serious about polishing brass (and there are some who are VERY serious!) stop with the abrasive papers at around 3000 and graduate to 'microfinishing film' which are made both by 3M and also by some Swiss makers notably Graessner. These films are described in microns unlike abrasive paper.

We mostly aquire our films from the large horological supply houses, Walsh or Cousins...see here for Cousins finishing films........

https://www.cousinsuk.com/search?SearchTerm=finishing+film

A word of caution if you are going to get involved with finishing film,........it's not as easy as it looks and there are several pitfalls for the unwary. Contamination quickly becomes an issue...it's highly irritating to get a superb finish on a piece and suddenly find that the surface has efects due to microscopic contaminants. For this reason its quite easy to become an obbsessive before you realise it and you are suddenly looking at a forensic white overalls and turning the shower room into a laboratory.........You have been warned! Then there is the issue of keeping the films stored in utter cleanliness.......

Unless you are aiming at the very finest work it might be a plan to polish to 3000 or so using a sheet of plate glass to hold the paper to, and then use Liberon 0000 wire wool (which is super nice and fine to use) and then a CLEAN polishing mop in the lathe with just a touch of T-cut.....

I needed to polish some brass to a fine finish, and found a kit (by accident) in a local car spares shop used for polishing out scratches in car paint. It was two (small) tubes of white polish, apparently one finer than the other, meant to be used in succession. It did a good job, but I think in future I will stick to Solvol Autosol - seems to polish anything to any standard, depending on how long you use it!

I'd use some flour paper and then maybe a little bit of brasso, Incidentally, if you want to get a good finish with aluminium or stainless go for PEEK paste, works really well, slight ammonia smell to it though.

Michael W

Tooth paste ?

3M and others produce some films for both polishing and lapping that go down to a 1um grit size. There are also some discs of it around that are intended for polishing the ends of fibre optic cables - these will polish HSS and just plain water makes a decent lubricant to prevent clogging.

The best place I found to buy a sample pack of 3M's product was Cousins UK, watch and clock bits suppliers. Prices elsewhere were sometime a lot higher or the A4 sheets had been cut up.

The discs - RS or ebay.

John

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.

... In principle, probably O.K. but you would need to select a suitable product [many have all sorts of questionanble chemicals in them, and the abrasive content varies too].

Autosol is consistent in quality, and 'handles' nicely ... Given its modest price, I wouldn't bother experimenting.

MichaelG.

Been using Solvol Autosol on aluminium motorbike engine covers and the like for 40 years or more with very pleasing results.  The bit of brass I have used it on showed similar results.

Edited By Hopper on 30/07/2016 12:32:42

The most abrasive toothpaste I have come across was the stuff suppl;ied free on British Airways in the early 1980s. Used tooth paste to prepare steel samples for microscopic study when I was at school in 1963.

Ian S C

Good old fashioned newspaper (newsprint) works pretty well. Just a drop of Brasso for lubricant.

Mike

Very fine wire wool but make sure it doesn't grab your fingers. If you want to err on the side of safety, attach a wad to a wooden stick and use like that. then Autosol etc.
BobH

Forgive me if I am stating the obvious, but I think it worth mentioning:

Technique is just as important as the choice of abrasives and polishes ...

I went on a short course a few years ago, given by Buehler, on preparing metallurgical samples.

http://www.buehler.co.uk

They drummed it into us that each successive fineness of filing/abrasion/polishing should be done at right-angles to the last, and must be continued until all trace of the previous work is removed. ... If this is not done, then [as I mentioned earlier] you will end up 'polishing-up the scratches'.

MichaelG.

Thanks for all your replies - plenty of leads to follow up. Pro tem, I've ordered some Autosol as it seems to be generally recommended. If it's good enough for horologists (who I know can be - quite rightly IMO - a bit obsessive about finish) it'll probably be OK for what I want to achieve but I'll follow up the other suggestions as well.

MichaelG - the advice given to you by Buehler reminds me of what I was told in my first job after leaving school - I had to prepare metallurgical samples inter alia. Like every lad before and after me I expect, I thought that a tiny scratch in the wrong direction would yield to the next grade and save me some tedious work. But it never did of course.

Rob

Edited By Robin Graham on 30/07/2016 22:17:58

.

So we can safely assume that 'Granny knows how to suck eggs'

MichaelG.

Sorry if that came over wrong - this Granny certainly doesn't know how to suck eggs! T'was a long time ago and it sparked a memory,

.

Not wrong at all, Rob

MichaelG.

That's taken me back to the early 60's, something I'd forgotten about, Selvyt cloths and diamond paste polishing of steel samples for examination under the microscope, not one of my favourite jobs at work.

John