Machining Cast Bronze

[Bernd]

Ok rleete and I both are doing the coke bottle engine. Mine is cast bronze and his is cast iron.

Now the question. Seems this bronze is quite hard. A file will touch it but it's almost like filing HSS. Which brings me to the next thing. Since I'm using the Sherline to do the project I don't think carbide would work very good in this machine. Not ridge enough to withstand the forces. I'm using HSS lathe tools. They seem to cut rather hard. Seems like I realy need to twist the cranks with some effort to get the tool to cut. This now leads to the question I have. What should the angles be on the lathe tool to cut bronze casting? Same as one would use for brass?

I'm sure I'm going to get many answers. So fire away.

Bernd

[sbwhart]

Hi Bernd

I've machined quite a few Phosphor Bronze casting I take it we're talking about the same stuff.  I've used both TC tip tools and HSS tools with cutting angles the same as for brass, I've found that its just the skin thats hard, it may sound daft but you need to take a good deep cut, to get under the skin not less than 0.25mm or even more depending what your machine will take, light cuts will only rub over the surface.

One thing with P/Bronze is that it will tend to grab at the tools particularly if the tools too sharp, this is noticable when drilling and the drill breaks through.

Good
 
luck

Stew

[sbwhart]

Ian

I'd agree about ally bronze not only is it a b****r to machine but near on imposible to silver solder tried it failed learn't the lesson.

Stew

 

[Darren]

I don't have any trouble machining ally bronze? In fact I didn't notice that it was any more difficult than leaded.

I was making bearings with it, about 30 units or so 1/2" bore.......

I'm confused,,not difficult I know ....

[bogstandard]

There are so many different versions of bronze (maybe thousands), unless you know the exact makeup of the material for a specific job, then you just can't generalise over machineability.

I have some stock of hex ali bronze, and it machines very well indeed. But that is just one version of it, another one might be like trying to turn pure tungsten, and I have come across that sort of stuff before. But both are classed in general terms as ali bronze.

Unless you are used to turning all versions (and I am not) and as previously stated, the makeup, then most people will have machining problems of one sort or another.

Where we usually obtain our materials from (castouts, scrap yards, bar ends) you just have to try to machine it the best you can, as they will all most probably require some sort of special machining solutions.

I am just machining up some Colphos (purchased from a supplier because the drawings called for it), and it machines as easy as normal yellow brass, but with slight curls on the chips. This is the first time I have ever used it, but now, because it is only slightly more expensive than PB102, it will definitely be used again. Purely because I know I won't have any trouble machining it.

http://www.columbiametals.co.uk/products/details/?id=88&trademark=colphos

So really, in our small world of engineering, you just have to suck it, and see what happens.

John

[rleete]

I tried doing a skim cut on the inside of the smaller flywheel.  Not very concentric, so it was an inturrupted cut, but it seemed to cut okay.

Haven't done any of the other parts yet.

[Bernd]

It's definatly harder than some of the bronze I've turned before. If you do take a bit of a deeper cut it does cut better. I noticed that with the end mill. But it's still harder than hard brass.

So I'll be using angles normally used for brass and carry on. Also I don't think my tool was sharp enough.

Carbide on this small lathe might not work good unless it is of a very sharp edge. So HSS will be used for now. Although one of these days I'm going to have to look through some of those big catalogs and see what I can find in carbide cutting tips.

Bernd