Why Am I Unable To Plunge Cut A Bronze Casting

[Billh50]

There are many types of bronze. Some much harder to machine than others. Don't use too slow of feed as the cutter has to bite in to cut with bronze. Most types of bronze will cut fine with HSS tools with proper feeds. If the feed is too slow the tool will just rub and dull quickly. I have only turned bronze but do remember a friend bringing me a 1" square bar he wanted me to cut in half for him. Took the band saw with a new blade a little over an hour to cut it. That piece was tough. Good Luck!

 

[TommyD]

Just be careful drilling brass or bronze with a sharp drill, we used bronze castings for hinges on our compression molds and have seen more than one vice turn into a helicopter. You have to brace the vice and dub the cutting edges, soft metals like this like to grab the cutting edges when it starts to break through. Dubbing is squaring the cutting edges on the drill flutes.

 

[derf]

Bronze cuts better with zero or negative rake on the cutter.

 

[Wreck™Wreck]

Dear All,

I am working on a bronze cylinder casting from PM Research. I am trying to get the steam chest milled, which requires that I make plunge cuts. I have tried 2 and 4 flute center cutting mills, but they do NOT plunge! They just sort of buff the surface. I have done lots of plunge cutting in aluminum, CI, and brass. What the hell am I doing wrong.

Tom

My best guess is that the feed is way to slow and the spindle speed to high letting the tool rub rather then cut, many bronze alloys are rather hard and abrasive.

Also be aware that hard bronze chips will come off the tool like shards of very unfriendly glass,

 

[Flammable_Solid]

You might have a casting with a martensitic microstructure. A quick hardness check might allow you to heat treat it, otherwise you probably won't be abke to machine it.

 

[EmilioG]

Guhring makes an end mill called the diver that is supposed to make all types of cuts including plunge cuts.
The video looks amazing. Msc has them.

 

[Billh50]

Some bronze materials can be tough to machine. 9D aluminum bronze machines like 316 stainless. Not an easy to machine material sometimes. It is hard to give good advice without knowing what bronze alloy you are working with. So there may be a little trial and error before you find the right answer. I know you have had some good advice for most bronze alloys so far.

 

[TomS]

Some bronze materials can be tough to machine. 9D aluminum bronze machines like 316 stainless. Not an easy to machine material sometimes. It is hard to give good advice without knowing what bronze alloy you are working with. So there may be a little trial and error before you find the right answer. I know you have had some good advice for most bronze alloys so far.

Bill - my thoughts exactly. Many years ago I was given a job that required a specific type of bronze. For the life of me I can't remember the alloy designation but it ate up end mills quickly. Just because it's bronze doesn't mean it machines easily.

Tom S.

 

[tomw]

Thank you all for the advice on feeds, speeds and bronze in general. This stuff is hard, but also in places gummy! And it loves to eat 1/8" end mills. I have now dulled all of mine, and am awaiting some new ones.

The weird thing is that I had no problem on the lathe doing the bore and head surfaces. The chips were like sharp sand, but I got a nice surface.

But, I was using carbide cutters for the lathe work...

For the carbide end mills I have, what plunge (Z AXIS) feeds and what spindle speeds do you think I should try? They will 1/8" dia center-cutting 2 flute mills for roughing, 1/8" 4 flute mills for finishing. The machine is a 5400 Sherline mill, so no power Z AXIS feed, but I can try to regulate my manual cranking speed. Normally for plunging I go pretty slow, but this would appear to be bad. However, too fast and I risk breaking the end mill or crashing the mill.

Thank you all so much for your help on this problem. As a newbie, I bow at y'alls feet, tip my hat, and genuflect to your experience and wisdom.

Cheers,

Tom

p.s. Never thought I would use "genuflect" on a machinist forum.

 

[mmcmdl]

Any way you could post a picture of what you are machining ? Perhaps a sketch ? RPMs you are running ? Coolant . spray mist etc ? This may help with finding a solution . If you are milling a pocket , do you have to use a 1/8" for corner radius ? Just curious ?