Turning Phosphor Bronze

[WolfieParticipant @wolfie]

OK I am making a start on my next model and I have got a piece of phosphor bronze for the cylinder (how expensive???!).

OK so theres me thinking this is similar to brass so it will be easy peasy to turn. Once you have all picked yourselves up and stopped laughing, can anyone tell me why its so bloody hard? I was trying to use a tool that I have parted mild steel with and it started to slip before it cut into the metal grrr.

So how do I go about turning bronze (summat else to learn sigh)

[WolfieParticipant @wolfie]

[Michael FodenParticipant @michaelfoden39595]

I bought some phos. Bronze many years ago, (the Rolls Royce of bronzes ), & as far as I can recall it behaved no differently than brass. I did not have anything better than HSS tools in those days.

Maybe there are different grades of it, but I am no expert in these matters.

Mike.

[KWILParticipant @kwil]

Wolfie, see the last photo in album. 3.5" dia, parted with tool in background.

[Clive HartlandParticipant @clivehartland94829]

Wolfie, my way is to use a coolant and a tool with a slight top rake angle, I cannot tell you how much but re-grind till you get a good cut. Then keep that tool for the next lot of bronze work.

The tool should have a very small radius on the cutting edge.

When turning Phosphor Bronze it gets hot and the chips come off hot so take care.

Drilling, again take care as it will grip and bind so you need to grind off a bit of the cutting edge flat on both lips.

Only drill in small steps, backing out and clearing regularly.

Reaming, take care as it will grab and you will not get the reamer out unless you knock it out so only allow a very small amount for reaming to size.

Boring, rough turn, clearing chips and swarf as you go and then a fine cut for finishing.

Speeds, fairly fast for the outside but slower for drilling and boring and dead slow for reaming.

No doubt someone will have a different set of ideas.

Clive

[WolfieParticipant @wolfie]

I don't get it, My tool was bouncing off rather than cut. A tool I've used succesfully on mild steel.

Is it a skin thing perhaps?

[JasonBModerator @jasonb]

Like brass, bronze likes a very sharp tool also check you are not above centre height.

J

[ronan walshParticipant @ronanwalsh98054]

I was turning up some bushes for a bsa motorcycle gearbox yesterday ,a sharp hss tool walked through it easily, the drilling was the same , good and sharp but the fine swarf builds up and binds the drill bit in the hole so regular pecking to keep it clear.

[Clive HartlandParticipant @clivehartland94829]

Just a point here Wolfie, were you running the lathe backwards?

I had an expert turner who cussed and swore and stamped way saying the lathe was useless, he was running it backwards !

Clive

[Robert DoddsParticipant @robertdodds43397]

Wolfie,

Did you tell us what type of phosphor bronze you got? Sand cast bronzes especially can have a hard skin but all the bronzes tend to have a hard skin that needs to be attacked with a max cut for your machine and using a carbide tool.

Once through the skin you may, like so many others, get a better finish from a keenly sharpened HSS tool. It's your choice.

Bob D

[John Stevenson 1Participant @johnstevenson1]

Wolfie,

You haven't got a piece of Aluminium Bronze have you ?

Clive, couldn't been much of an expert if he was running it backwards.

John S.

[Michael GilliganParticipant @michaelgilligan61133]

John,

Etymology of the word Expert …

"X" is an unknown Factor

"Spurt" is a Drip under Pressure.

MichaelG.

[WolfieParticipant @wolfie]

I dunno what type it is exactly, I got it from Macc Models via ebay. It just looks like a piece sawn off a bar.

[Stewart HartParticipant @stewarthart90345]

Wolfie

Lot of good advice her, you may be being to gentle with it give it a good deep cut 1mm or more with a slow speed and course feed this will get under the hard skin,

Stew

[Ian S CParticipant @iansc]

One of the first jobs I took on with my new lathe was 16 radiator nuts for a Lanze Bulldog tractor, I used 2″ cast bar of Phosphor Bronze. I machined it with the HSS tools I used for mild steel. Had no troubles, used a parting tool made from a 12″ power hacksaw blade, it cut like a hot Knife through butter, 20yrs on the nuts look like new. Ian S C

[mickParticipant @mick65121]

PB is designed to be a good hard wearing material, that's why its used for bearing bushes and the like. To be hard wearing it has to be very dense material and will be tough to machine. If you have a tool that's cut high carbon steel, like sliver steel that will be the one to use. Plenty of coolant will help, drop the revs, but don't cut back on the feed, as the tool needs to bite. If the tool isn't cutting then its in the process of becoming blunt as all its doing is rubbing. I know its expensive, but for a couple of quid more you could get free cutting bronze, which has all the bearing qualities of PB but is a joy to machine. Talk to Viv at Milton Keynes Metal, they advertise on the forum.

[_Paul_Participant @_paul_]

Posted by Michael Gilligan on 16/08/2012 23:32:53:

John,

Etymology of the word Expert …

"X" is an unknown Factor

"Spurt" is a Drip under Pressure.

MichaelG.

Slight variation:

Ex = somthing past it's best

Spurt = Drip under pressure.

P

[NJHParticipant @njh]

I always thought it was :_

"X" Is a " Has been"

"Spurt" is a drip under pressure.

I've known a few " experts" in my time!

N

[Sub MandrelParticipant @submandrel]

Wolfie,

If your PB is small diameter it may be drawn rather than cast, which is a tad* harder to machine.

You need a tool with some top rake, not the flat topped tool oftyen recommended for brass.

I have only had problems drilling, not turning it. As it is tough and doesn't chip away like brass a lot of heat is generated when drilling. unlike steel it conducts heat quickly like brass or copper, and therefor iof you slow down it cools and can jam on the drill.

Neil

(*1 tad = 17 gnat's chuffs)

[JohnFParticipant @johnf59703]

Wolfie, turned a lot of the stuff in industry, lots already been said but I would suggest always a corner rad on your tool –say 0.020 minimum and a top rake of 7 – 10 deg. I would use HSS I am sure there are specific TCT tips for this material but I don't think the general grades would work well at all [not tried them] and on home machining I recon you will get better results with HSS — besides you can alter your tool geometry if you think it will improve the result–if it does not you can revert back — not with TCT's !!

Best flooded with coolant to keep cool but not always practical in a home shop so might be worth allowing a little "cooling time" now and then whilst working.

Drilling — I can already hear the shouting !!!— we often used to grind the drill a little off centre so it cuts big to help prevent binding then of course bore the hole to size or to straighten before reaming–lots of lube! works for copper as well.

Good luck—John

[_Paul_Participant @_paul_]

Posted by NJH on 17/08/2012 20:24:32:

I always thought it was :_

"X" Is a " Has been"

"Spurt" is a drip under pressure.

I've known a few " experts" in my time!

N

It always tickles me when I get the odd "herbert" introduce him/herself as an "ExSpurt" in something or other……….

It's hard to choke back the phrase "yes you probably are" ……….

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Expertise can have real and imagined parts therefore :

Expert = complex conjugate of nitwit .

Great Expert = complex nitwit cubed .

 

 

Edited By MICHAEL WILLIAMS on 18/08/2012 09:43:40

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Stub Mandrel on 17/08/2012 21:29:37:I have only had problems drilling, not turning it. As it is tough and doesn't chip away like brass a lot of heat is generated when drilling. unlike steel it conducts heat quickly like brass or copper, and therefor iof you slow down it cools and can jam on the drill.

Been there, done that, broken the drill!

Russell.

[Will RobertsonParticipant @willrobertson16447]

Hi Wolfie,

Thanks for starting this thread. Many thanks as well to everyone who's contributed – it's very interesting (haven't found any of this in the books). I'm planning drilling, boring and reaming chunks out of lumps of Rg7 bronze (gun metal) so this thread made very useful reading.

Just a quick question:

Do the difficulties described only happen with phosphor bronze or will they happen with Rg7 (gun metal) and other bronzes as well? I'd guessed that Rg7 (gun metal) behaved more like a free cutting bronze but I though I should check.

Some people seem to have found phosphor bronze very easy to work with and other seem to have had problems. I'm only guessing but I wondered if this might be down to the exact composition – some extra lead in a bronze might significantly improve its machining properties.

In mountaineering I long since learned the distinction between expert and a non-expert (a.k.a.dangerous fool). A dangerous fool thinks that he knows a great deal and that all his decisions are right, an expert is painfully aware of the gaps in his knowledge and that he often makes errors which have to be corrected before they kill him.

Just as well that the guy survived running the lathe backwards – might have been in for a very nasty surprise depending on exactly how the chuck was attached to the lathe…

[Thor 🇳🇴Participant @thor]

Hi Will,

gunmetal has a different composition from phosphor bronze, and subsequently machines differently. Most gunmetal I have come across contains a small amount of lead to make it easier to machine. The gunmetal I have machined has never presented any difficulty, so as you say it is fairly free cutting. The phosphor bronzes I have seen does not contain any lead (but some P) and are much harder and tougher.

 

Regards

Thor.

Edited By Thor on 05/02/2013 17:45:02

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