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So I made a 3/8 copper billet to be a bolster on a knife. And while I was drilling through it, I snapped a drill bit!! How the blankety blank do you drill copper??? This was the grabbist crap I've ever worked with!!! I now have to make up another billet, but until I have a plan on getting through this stuff it seems a waste of time.

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I'm not a pro machinist, but sometimes I act like one.

 

Flatter angled drills, or slightly duller drills seems to help.  Slow drill speed, and frequent pecking also help.

 

Copper and lead are two materials I do not enjoy drilling.

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I use a hand drill on copper and silver for that very reason.  An eggbeater-type hand-powered drill, not a handheld electric drill.  No downfeed pressure, very sharp drills, just let it cut with its own weight.  Turn the crank at around 60 rpm.  If you try to force it it will grab and snap the bit, even hand-powered, up to 1/8" bits, anyway.  

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Induce a negative rake on the bit and you'll drill both Copper and Acrylic much nicer.  With a negative rake and slower speed you can drill mirrored holes in Acrylic.  You are essentially scraping the hole rather than cutting it.

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So...if I understand you, sharpen against the cutting edge of the drill. Make it lean back away from the flutes? Create a grinding bit instead of a cutting bit.

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Posted (edited)

More like scraping? Something like 90 degrees to the material being cut.

I do a lot of work with brass, and usually grind a small facet on the drill lip pretty much in line with the length of the bit.

 

For the billet the drill broke off in, if the bit's still stuck in there, and you want it out, putting it in a heated solution of alum and water will rust the broken off bit to dust.

Old watch-maker's trick. I've...  certainly never used it on, say, broken 2-56 taps. (A lot of grocery stores will have alum in the spice section)

Edited by Stuart Samuel

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1 hour ago, Brian Myers said:

So...if I understand you, sharpen against the cutting edge of the drill. Make it lean back away from the flutes? Create a grinding bit instead of a cutting bit.

 

"Lean back"?  Only very slightly.  I used to take a small diamond paddle and put it to the edge of each flute of the drill and file in about 2 degrees backwards from being in line with the bit's shank.  Basically you turn it into a sharp scraper.

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To dissolve drill bits, jewelry pickle/sodium bisulfate which is also in a number of swimming pool acids.

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Do a Google search for drilling brass. There's a good video on modifying your bit for drilling softer metals.

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Thanks, Garry, that's exactly the point I was trying to convey.  Believe me, it works.

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Yeah I like clickspring! He is why I asked about spade bits. I saw him make some once for drilling brass. Thanks!!!

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49 minutes ago, Chris Christenberry said:

Thanks, Garry, that's exactly the point I was trying to convey.  Believe me, it works.

Wish I'd known about that when I was making pipes!  Polishing the bore of a translucent acrylic pipestem is time-consuming.  

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Posted (edited)

Alan, my family used to own a plastic manufacturing company and one of the jobs I started out with in the company was doing the plastic fabrication.  I learned a lot of tricks..............many on my own and that was one of them.  I made the first artificial heart pump used in that new-fangled procedure, open heart surgery back in the 70's.   And as expensive as my product was, it only made sense it was to be beautiful as well as functional.  The medical establishment marveled at my mirror polished drilled holes because there was less room for bacteria propagation.  It was a closely guarded secret for years before I started telling folks how I did it.  I also tossed the 12" carbide tipped table saw blades I was told were the "best" to use.  I went to my saw sharpening guy and took him a 6" plywood blade and asked him to cut it down to 5" and put the same type negative blade angle on it I was using with my drill bits.  It didn't give a mirror polished edge, but it virtually stopped all chipping, so it made for a whole lot less sanding in preparation for polishing.

Edited by Chris Christenberry

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That's pretty cool, Chris!  

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I was really honored when the "Heart Team" from O.U. Medical Center came to my office and said they wanted me to work with them on the heart pump.  The "revolutionary" idea (at the time) was to keep the patient alive while the heart was taken out of the body, laid on an operating table and repaired before being put back into the body and retaking it's designed function.  I almost didn't believe them when they told me what they wanted me to build and what they wanted it for.  Our company was also involved in making the first pressurize suit for open heart surgery on dogs back in the middle 60's............which was part of the same project, obviously.

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