Why Am I Unable To Plunge Cut A Bronze Casting

[tomw]

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.

I have tried 4 different end mills in two different sizes. All center cutting.

Any help will be much appreciated. This seems like an easy part to work on!

Cheers,

Tom

 

[Tony Wells]

If needed, punch a small hole with a drill right in the center of where you need to plunge.

 

[TommyD]

Are you sure they are center cutting? I have seen some cheap 2 flute endmills that LOOK to be center cutting but don't. As Tony said, maybe a pilot hole first.

Could be improperly ground also, too much 'land' on the cutting face.

 

[tomw]

TommyD,
I tried 4 different center cutting mills, both 2 and 4 flute. One was an unused mill from McMaster. I also just did a test on a chunk of aluminum. No problem plunge cutting that.

Tony,

I will try that. Thanks


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[mmcmdl]

If that bronze is hard , the center of your end mill has a very low surface speed compared to the OD of it . Wouldn't make that much difference on aluminum . The pilot hole would remedy that if it's the case or a carbide CC end mill would work .

 

[tomw]

I just ordered a carbide 1/8" end mill. Damn, their expensive!

Tried the pilot hole trick. Unfortunately, I still can't plunge below the drill tip angle, and I need a flat surface. Hopefully the carbide will help.

Thanks for the help.

Tom

 

[Tony Wells]

The face of an end mill is not truly square. You will have a bit of a inverted cone if you just straight plunge. If there is any pocket milling to do, this will pretty much eliminate that, and it may not be severe enough to worry about anyway, but you should be aware.

 

[tomw]

Thanks. It is a pocket that I am milling (a steam chest).


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[TOOLMASTER]

brass is kinda self lubricating....once is grabs watch out

 

[Metal]

Another thought might be to "slightly" tilt your milling head if that is allowed, letting the endmill have a slight leading edge and working into the material from its tip slower, this works really well with a cnc but would be a pain to do manually.

since its a casting, I'm thinking the outer surface might be denser then the inside of it depending how it was cast, once you break into the material your going may be much easier.