How to get a stunning finish on Brass

[AdeV]

I've been turning some brass the last couple of days, and had been getting very rough finishes using my new Glanze indexable tooling. A couple of weeks back, however, I'd bought a couple of inserts for aluminium cutting from Chronos: Linky thing. Figuring that brass is softer than steel, it had to be worth trying it out. And, like wow (as a Californian might say):

After a simple turning operation, the machine marks are almost invisible to the naked eye. This pic is after a 0.005" cut @ 400cuts/inch (2.5 thou per revolution - the best my lathe will do):


So then I tried a facing cut... I didn't quite cut all the way through the marks, but you can see the quality of finish:



Suitably impressed, I broke out another product I recently bought, having seen it on here:



After applying a smear on the end & letting the lathe spin it for maybe 30-40 seconds (any more an I lose patience), this is the result:


It was proving quite difficult to photograph with the flash (the light just bounces off & goes somewhere other than in the camera), so I tried one without:


OK, it's not quite as good as a bathroom mirror, but not half bad for 5 mins of turning & half that polishing....

[Bogstandard]

Ade,

If you want really superb finishes and a versatile tool as well, invest in a profile tool. They can cut in all directions.

I have been using one for years now, and they really are a good addition to your arsenal.

http://rdgtools.co.uk/acatalog/PROFILE_LATHE_TOOLS.html

The big plus is that when one area goes dull, you just turn the tip a few degrees and you have a nice new cutting edge. You can turn it say up to about 20 to 30 new edges before the tip needs replacing. If you are very careful, and a real cheapskate, you can in fact resharpen them for use with brass by just stroking the top face across a water wetted diamond lap. DAMHIK, and guess who's a cheapskate.


John

[Powder Keg]

You can also use some fine grits of Emery paper before you polish it up to help get rid of tool marks.

[John Hill]

Do not use a rag to apply polish to work in a lathe while it is running, in fact do not allow rags anywhere near rotating machinery!

Use small scraps of newspaper to apply the polish!  If it gets snagged on the work the news paper will tear and you will still have your fingers!  Besides, the paper fibres are rather hard and bring up a nice polish in no time at all.

[AdeV]

Bogs - I nearly bought one of those last time I bought some tooling, but didn't in the end as I was already spending more than I ought... but I will definitely get one next time. I guess the real point here, however, is that when cutting brass (or Ali), one needs an absolutely razor sharp tool, which most indexable tooling simply isn't.

Powder Keg - the machine marks simply aren't there (compared to every other bit of turning I've done). I expect a bit of 1000-1500 grit work would help, but I don't have any such paper... so it's straight to the polish for me.

John H - Fear not! I used a microfibre "pad" to apply the polish. Had it got caught in any way, it would simply rotate out of my hand, causing no injuries and only some minor cursing. In the event, it didn't even do that, so all was well. Nice idea about the newspaper though, I must try that out.

All good hint & tips chaps, keep 'em coming!

[raynerd]

I have one of those profiling tools that John linked to, it does give an excellent finish but because of its shape it obviously can`t get right into a shoulder. That use to be very frustrating having to swap tools but to be fair not such a big deal now I have my QCTP. Worth the £15-20 they cost!
Thanks for the post - I`ll order some of those tips when I have some cash!

Chris

[Bogstandard]

Actually Ade, it is the fact that it is round that gives the fine finishes.

In reality, after you have ground up your tool to a very sharp point, you should always knock the sharp tip off by swiping it round with a very fine stone. That should impart a slightly rounded tip to the cutting tool, which should improve finishes no end. CC tips are usually made with a tiny rounded nose during manufacture.

If you do your machining correctly, and deburr and countersink all holes correctly, the tiny rounded fillet produced by a rounded over tip (not the profile tool, that is too rounded) in the corner of the job should not cause problems. If you have a look at a ballrace, usually the inner race has a fairly large countersink and the outer a radius, that is to allow it to fit onto or into shouldered shafts or bored holes with that small fillet in the corners.


John

[Ned Ludd]

Hi Guys,
At last someone else has found that you don't need a zero rake tool for brass, despite what all the books say. I use a Tangential tool and for a fine finish I use it backwards which gives a shearing cut, well it works for me, and the backwards bit seems appropriate somehow.
Has anybody tried polishing with a piece of cardboard with some buffing compound on it. The card I use is from a cat biscuit box and is the thin-ish but dense variety. To use put a little compound, brass finishing type will do or you could use Solvol or Brasso, on the un-printed slightly rougher side and hold against the rotating work, but do keep it moving to prevent creating ridges.
You can use rag on the lathe, BUT NEVER EVER wrap it around your finger, small pieces held between finger and thumb will just pull out of your grip if things catch. If you wrap rags around your finger and things catch it might be more than the rag that goes flying.
Ned

[kwackers]

I use lolly sticks with solvite/brasso etc for polishing. They're cheap and make it easier to avoid polishing the corners off.

[bry1975]

Chaps,

Have you tried small pieces of micromesh sheet glue to a lolly stick, the finish should be AMAZING as you have grits down to 2microns.  

That's the stuff sadly not £6-£7 like I use to pay!

http://cgi.ebay.co.uk/Micro-Mesh-Abrasive-Cloth-Regular-mixed-grade-set-/220691469982?pt=UK_CPV_Aviation_SM&hash=item33623c969e


I wonder would paraffin improve the cutting and finish I like it does with Aluminium?

[Jonny]

Parafins good for colour hardening dip it after nice blue on steels and stainless.

Just got to learn to let go quick and grab/hold cutting paper or rags accordingly.

Got a Seco or Sandvic version of those round profiling tools never used since scrapped me Myford 11 years ago, lovely but too small for what i have now and the other coming tomorrow.
Can see facing off that brass its ripped it rather than cut, could be the Glanze flexing.

[Miner]

For anyone that is interested in obtaining the very best quality polished finish I highly recommend a book called Gunsmith Kinks avalible at www.brownells.com This is the first book in a series of 4. $29.95 at todays price. The polishing section is written from the perspective of a gunsmith polishing gun parts for very demanding customers and he may be working on some REAL expensive guns or parts. Without a doubt it's the very best artical I've ever read about the proper way to get a crisp and highly polished part without rounding over edges or the O.Ds of holes.

Pete

[rleete]

Does anyone have a link for the profile tools like Bogs listed above, but for the US?

[johnbaz]

I use this Wolf 1hp buffing machine, it returns a mirror finish (the workpiece usually burns your fingers though  )
Care has to be exercised too as it can grab the workpiece and sling it at your feet as i found out when i was polishing a Commando knife years ago



BTW, the 4" G cramps don't look too safe but it's never moved yet and it's easily moved out of the way

The wheel on the right is a leather dolly that i made from old aprons from work


John

[Xldevil]

Does anyone have a link for the profile tools like Bogs listed above, but for the US?

Hello.
You got to look for SRDCN holder and RCMT insert.
Ralph

[bry1975]

Arr oks Kool!