Machining Cast Aluminum
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  1. #1
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    Default Machining Cast Aluminum

    I've got a job coming in for a bid this week in cast aluminum (customer didn't specify what type or alloy). I've never machined any type of cast aluminum so I have some very basic questions:

    Do you run coolant with cast AL?
    When tapping is it recommended to use a cut tap or a form tap?

    Any other tips/suggestions/precautions would be appreciated. Thanks.

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    I don't know that the questions can be answered with any accuracy without knowing the alloy and condition.

    Coolant use won't cause an issue with any alloy. Not using coolant will work with some but not others. Some high silicon alloys won't form tap IME.

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    Quote Originally Posted by biglord4ever View Post
    I've got a job coming in for a bid this week in cast aluminum (customer didn't specify what type or alloy). I've never machined any type of cast aluminum so I have some very basic questions:

    Do you run coolant with cast AL?
    When tapping is it recommended to use a cut tap or a form tap?

    Any other tips/suggestions/precautions would be appreciated. Thanks.
    Coolant - yes
    Form or cut tap - people swear by both methods.

    What type of aluminum?
    You need to give some more info.

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    Another for running coolant. I don't really see a reason not to.

    You should be able to do either. We machine a lot of A356-T6 and haven't had an issue either way, but our customer typically requires cut taps.

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    Sand cast A356 can be a little rough on tooling, bear that in mind as you quote the job. The age of the casting makes a difference as well. The newer the casting the more gummy the material. Chip welding is not uncommon. I found that I needed aggressive coolant with a slightly higher concentration for castings in the machining involved slotting or tapping. I use cut taps on castings, and preferably spiral tip straight flute unless the geo absolutely precluded their use. On certain castings, I had to use a cutting oil rather than flood for tapping.

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    I do a fair amount of work with cast automotive parts.
    Use mql or coolant. Some of these parts are pretty gummy. Without it you can weld up the cutter pretty quick when rough cutting.
    Form tap works on some and is a disaster on others. Cast doesn't like to deform.
    As a result I cut tap and more often single flute machine them.
    I suggest some experimenting with the form tap on the cast you get before assuming it works.

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    Comments regarding cast aluminum has everything to do with alloy and temper. As cast can be a bitch regardless of alloy. A good T6 in 356 machines almost as well as bar stock so. . . . . . . be aware.


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