Breaking drill bits in cast iron

I got some cast iron from Metal Express and milled a small cube, about an inch in each dimension. Then I tried to drill a 1/8 inch hole through it. Just as the bit was emerging, it broke. So I tried it again, this time with lubrication, and the same thing happened. I do not understand this. The cast iron is soft and easily drilled.

What is causing this, and what can I do about it?

Thanks,

Will

Reply to
Will Self
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You may find, Mike, that quicker than locking the quill and using the knee to feed is to use the quill lock to put enough drag on the quill so that the drill can't self feed the last bit. I do this all the time. ERS

Reply to
Eric R Snow

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