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Polishing Brass

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ian voller05/04/2022 21:42:05
21 forum posts
5 photos

While I wait for some tools I decided to polish some of the brass work in the Congreve Rolling Ball clock, like the ball plate in the clock, this is 1/16" engraving brass and needs a high polish, I was thinking of using my belt sander with suitable belts so can anyone give me an idea of the type to use and the method?

Bizibilder05/04/2022 21:50:19
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126 forum posts
7 photos

Not a belt sander! It's the last thing you should use. File the edges of the brass using fine files (No4 or No6 cut).  Then polish use diminishing grades of emery paper - start at 400 or 600 grit and follow with 600, 800 then 1200. After that you can use a micro polishing paper ( i think its called 3000 grade?) (or best of all crocus paper if you can still get it). Lastly use Solvol Autosol polish (its a paste that comes in a tube).

Lots of patience and you will get a mirror polish. Remember to never go to a finer grade of paper until you have removed all the scratches from the previous one.

Edited By Bizibilder on 05/04/2022 21:51:51

Edited By Bizibilder on 05/04/2022 21:52:56

Edited By Bizibilder on 05/04/2022 21:53:26

Bezzer06/04/2022 16:07:45
172 forum posts
16 photos

Quickest and best method is with a polishing mop, cheap enough to get a mop and mandrel to fit it on a bench grinder. Light blue or white polishing compound (lighter the compound colour the finer "grit" it is) does it to a mirror finish quickly.

noel shelley06/04/2022 16:31:25
1444 forum posts
23 photos

AS Bezzer, but a few warnings ! BE VERY careful not to let the metal dig in to the mop, always work towards an edge not away from it and keep the work CONSTANTLY on the move, or grooves will be cut at any edges if you dwell. IT is a VERY dirty job ! For materials Etc, try the polishing shop. Good Luck, Noel.

bernard towers06/04/2022 17:02:01
691 forum posts
141 photos

shouldn't the plate be polished first, then the groove machined withe a protective film on it otherwise the polishing operation is likely to tear the sharp edges.

ian voller06/04/2022 18:44:01
21 forum posts
5 photos

The ball plate is made in individual sections 1/16" thick brass instead of a solid plate as in the picture.

My thoughts on the belt sander were that I can mount it upside down in my vice so its easy to use, as i can alter the speed it will also be safer. I can get many different types of belts in many grades including just felt so I don't see any problems using it apart from the price of the belts, around for £40 for ten of each grade. crook

pxl_20220305_104956865.jpg

roy entwistle06/04/2022 19:28:50
1551 forum posts

You will not polish the brass on a belt sander

Harry Wilkes06/04/2022 21:24:36
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1371 forum posts
66 photos

Take a look at clickspring on youtube he gets greats results

H

Paul Lousick06/04/2022 22:27:18
2078 forum posts
727 photos

I use a felt disk on an angle grinder for polishing brass. Grinder held in vice and metal polish as the cutting compound. (ps. don't touch the wheel with your hand unless you want a friction burn)

felt disk.jpg

Robin Graham06/04/2022 23:31:58
957 forum posts
297 photos

Ian. I have spent many hours polishing brass trying various methods including belt sanding. I agree with others that belt sanding is not the way to go. There are various problems with this approach. One is that it as you go through the grades, it is necessary to turn the work at angle of at least 45 degrees (preferably 90) between grades so you can see that all the scratches from the previous grade have been eliminated. In your case (unless you have have a linisher with a very wide belt!) this will involve running the work across the belt at right angles. It is pretty much impossible to do that without getting 'dig ins' when the work crosses the edges of the belt. Even if you have a massive belt you won't be able to hold those slender strips down on the belt with consistent pressure. You may also find that even at low belt speed the the work runs away from you - there's a lot of friction and with such thin material you don't have much to hold on to. By all means give it a go, and if you have success please report back - I have never got this method to work despite numerous attempts.

What I do now is old school wet 'n' dry up to 3000 grit then polishing compounds/mops. - I use mops and the Menzerna compounds from The Polishing Shop where you will find information about the various types of mops and compounds available.

Autosol is OK from maybe 1200 or 2000 grit if you're not too fussy. It won't give a true mirror finish on brass though - you will still see scratches if you look hard enough. If you want a specular finish (which I aim for) it's polishing compound, elbow grease and meticulous hygiene - you need to be sure that not a single particle of grit or compound from the previous stage is anywhere near. A flea can jump about 160 times it's body length, a grit particle would laugh scornfully at that.

Obviously I'm a bit obsessive about this, you may be less so!

Robin.

Edited By Robin Graham on 06/04/2022 23:33:41

CHAS LIPSCOMBE06/04/2022 23:33:15
35 forum posts
3 photos

The choice of method has to depend on the job. Bizibuilder's method will give perfect results at the expense of a lot of time. Use of any kind of polishing mop carries the risk of removing sharp edges, losing detail e.g. lettering (if present) and "dragging" holes. Unless the pressure on the mop is kept light, there is also a risk of getting "drag" marks on the job.It is the usual case of horses for courses, but I would have thought that fine work like clock-making would require the slow method. Clock cases, support pillars would be fine on a polishing mop but clock internals??

Michael Gilligan07/04/2022 09:35:45
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20289 forum posts
1064 photos

To see the ‘appropriate’ level of finish … it’s worth looking here: **LINK**

https://www.bonhams.com/auctions/18836/lot/269/

MichaelG.

John Haine07/04/2022 10:04:58
4718 forum posts
273 photos

Personally I hate highly polished brasswork on clocks. i see them as 3D moving sculptures, polish makes it very hard to see the details. There was a US clockmaker called Smith whose clocks have grained brass, and a recnt series on Clocks as Works of Art in HJ also described this. Much more appropriate I think.

Michael Gilligan07/04/2022 11:30:29
avatar
20289 forum posts
1064 photos
Posted by John Haine on 07/04/2022 10:04:58:

Personally I hate highly polished brasswork on clocks. i see them as 3D moving sculptures …

.

Agreed … But the Congreve barely qualifies as a time-keeper, so it’s best seen as an interesting display piece.

The example linked is Wilding’s original … and hence ‘appropriate’

MichaelG.

Phil H107/04/2022 16:42:57
459 forum posts
60 photos

I am with John Haine on this subject.

Only the cheap looking, nasty, over polished, horrible clocks that they used to sell in jewellers (but with a high price tag) have a highly polished surface with all the edges completely ruined because they are rounded over.

They should be a nice finish but still look flat with beautiful clean edges.

Just my opinion. Over polishing is simply ruining all the hard work.

Phil H

Michael Gilligan07/04/2022 20:03:06
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20289 forum posts
1064 photos

Regardless of the degree of polish … there is no need or justification for ‘rounded edges’ if they should be square.

MichaelG.

.

Have a look at the 3-legged bridge for the balance wheel of this watch:

 https://frodsham.com/wristwatch/index.php

It is roughed-out by CNC machining, and then profiled and polished by hand.

… He rests the piece on a bottle-cork and then sets-to with a file !!

Edited By Michael Gilligan on 07/04/2022 20:19:41

ian voller22/04/2022 20:15:44
21 forum posts
5 photos

Thanks for all the advice guys but after some thought I think I will go with a brushed finish.

I am building this as an engineering project for my own personal satisfaction, not as a public display item so while I want it to look smart I don't think a brilliant shiny finish is a necessity.

david bennett 822/04/2022 21:32:34
76 forum posts

 

I finished my last clock plates on ever finer wet and dry emery paper (wet), backed by a flat surface, moving the plates in small circles, finally using Vim scouring powder (wet) on the smooth side of a sheet of emery paper.

Edited By david bennett 8 on 22/04/2022 21:33:22

Edited By david bennett 8 on 22/04/2022 21:35:10

bernard towers22/04/2022 23:54:46
691 forum posts
141 photos

18 mm mdf sheet and coat with rouge as a finishing.Or you could try 3M micro polishing sheets.

Edited By bernard towers on 22/04/2022 23:59:06

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