Polishing Brass - or where to get P5000 paper

Thanks Michael, that's a really good learning point for me.

Steve

Well, the Autosol arrived today - ordered off Amazon about 5pm Saturday, and with me by Sunday noon! How do they do that? Anyhow, it's pretty good stuff - thanks for the recommendations. The scratches on my work are now shiny scratches! I think Bob Stevenson's caveats apply to me - trying to get a mirror finish in a dusty home workshop is unlikely to be successful because of cross contamination. It probably doesn't matter, the guy I'm doing this for is hardly likely take a microscope to the work and cancel the cheque because of a 5 micron scratch - but I've got a bee in my bonnet now.

Rob

Some really good info in the above posts. What can cause scratching and effect your finish is the polishing cloth you are using. Home paper towels are terrible at scratching. Lens wipes are very good and so is Hydraulic lint free wipes. Cotton cheese cloth that car polishers use is very good as well. Very soft balsa wood makes for a great lap and very fine polishing compound holder as well. A little bit of very fine diamond in balsa wood lasts a long time and works well. The hardest part of it all is to keep the contaminants away from one process to the other. You just can not ever be too clean when it comes to polishing. Cleaning is essential between grades . The finer the finish the more it is involved, especially at keeping the contour to form is definitely easier said than done. There are lots of little tricks to keep the form correct and each situation will use a combination of ways to achieve this. Like polishing in 2 directions to ensure you have the scratches from the previous grit fully removed before going to the next level, etc.

Neil

Hi Neil,

I'm not sure whether you know this site or not but there's a lot of good info and products here... **LINK**

I've no association with them, just a satisfied customer.

I use tripoli on wooden items but it's original purpose is as a first stage abrasive for brass polishing I believe.

HTH

Jon

A while since I started this thread I know, but as there was some interest I thought I should report on a recent discovery - a box of diamond pastes hidden in a drawer. I have no idea of why or when I bought them (from Arc Euro according to the labels), but the kit goes down to 0,5 microns - hand polishing down to that with those bog-standard yellow dusting cloths gives a very fine finish indeed. As an experiment I tried to further refine the surface with Autosol, using the same technique, but it was a retrograde step.

Rob.

Edited By Robin Graham on 28/09/2016 00:10:03

Very interesting, Robin ... Thanks for reporting back.

MichaelG.

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P.S. ... Don't tell John Stevenson [he doesn't believe microns exist].

Just seen this, a good polishing base is some Chamoi leather stretched over a piece of suitable wood and then apply polishing medium to the leather. Keep wet with medium used.

Clive

I spent my working life in Injection mould making where hardened steel moulds had to be polished to mirror like finishes. Think transparent plastic like spectacle lenses. Car door and lorry mirrors. I could never achieve the level of polish the polishing section could. They would make comments like "highly polished and deeply scratched"

After going through lots of abrasive grades diamond past was used with a special lubricant, paraffin would scratch the polished surface.

There are a number of polishing and lapping options around and on this page.

**LINK**

John

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Thanks for further replies. As I now have about 5 million (× 10^-6 orders for this shiny thing I'm making, it's been worth making some systematic experiments based on the info in this thread and in other places.

My aim was to polish the faces of two inch diameter brass discs as quickly as possible. I tried various methods - going through the grades of wet'n'dry on plate glass followed by tripoli and the blue compound on machine driven mops, going through the belts on a linisher, Autotosol on a mop at various stages etc etc - I tried many permutations.

It turned out (to my surprise) that I could take machining marks out in less than a minute per face using an A6 (roughly P2000) Trizact belt on the linisher without going through the grades - the belt was already on the machine,and laziness was the mother of this discovery for sure. Trizacts cut fast and don't seem to clog at all.

From there, Autosol on a machine driven G-type loose-leaf cotton mop gave about the same finish as Tripoli/blue compounds, on their individual G mops , but much faster. I had assumed that aggressive and coarse went together, but not so.

Final hand polishing with 2, 1, 0.5, 0.25 micron diamond pastes gives a specular surface - but if a fly coughs on it....

Rob.

Edited By Robin Graham on 04/10/2016 23:23:56

I think my Jovilabe is going to have an enclosed gearbox

Up to P7000

**LINK**

Had to google Jovilabe - wow, I want one.

Thanks for the link KWIL - duly ordered. An Amazon reviewer bought them for getting fine points on pencils - and I thought I was being obsessive/compulsive! A mild case it seems.

Rob.

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Robin,

I hope you found this excellent video **LINK**

http://brunelleschi.imss.fi.it/itineraries/multimedia/Jovilabe.html

MichaelG.

I must admit I am not getting a gold-medal finish on my gears...

But I am getting a reasonable polish (mirror-like with a few flaws) following this procedure:

Using wet and dry on a my granite 'surface plate' I am doing an initial run on 180 grit untill all machining marks disappear.

Then at 90-degrees with 280 grit.

Lastly circular movements with 400 grit until you can't see any straight lines, 30-40 seconds, perhaps.

The above takes 3-4 minutes for an average brass gear about 30mm diameter.

Final polish is with silver/brass liquid polish on a sheet of 1/16" ply - which goes jet black in seconds!

This certainly achieves a polish my mum would have approved off, if not a gold-medal result. I think another stage with 600 grit would probably be the way to go for that.

Foolish me made all the gears with a 1mm boss underneath, so I am not doing as through a job but these surfaces will only be visible as reflections in other gears anyway :-0

Neil