Author Topic: Bits for drilling blanks  (Read 963 times)

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Offline downstream

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Bits for drilling blanks
« on: January 11, 2018, 02:57:25 PM »
I'm trying to bore out a 5/32nd hole to an 11/64th in a 3/32nd Russell blank.  I've used a cobalt bit in a drill press and managed to drill one out with much smoke and sparks. There must be a better bit.  Suggestions?  Thank you for your time.
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Offline xj35s

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Re: Bits for drilling blanks
« Reply #1 on: January 11, 2018, 04:27:31 PM »
use cutting oil. go easy. not much better than cobalt bits, maybe a plasma cutter? lol!
pessimist complain about the wind. optimist expect the wind to change. realist adjusts the sails.

Offline wsdstan

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Re: Bits for drilling blanks
« Reply #2 on: January 11, 2018, 05:24:38 PM »
Ditto on what xj said.  Smoke and sparks means you are drilling hardened steel way too fast.  Cutting oil, slow, and the correct drill speed.  Since you are using a drill press it is easy to set the speed.
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Offline downstream

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Re: Bits for drilling blanks
« Reply #3 on: January 11, 2018, 06:26:40 PM »
I had the belt set for a woodworking speed. The highest for the bit size.  I was using oil but the steel got so hot the oil would flow away from the bit.
I'll slow things down tomorrow.
Thanks for the common sense answers.
You're never late until you get there.

Offline wolfy

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Re: Bits for drilling blanks
« Reply #4 on: January 11, 2018, 07:24:27 PM »
We ran into a very similar problem trying to bore a hole to a larger size in a planer blade.  Those things are harder than woodpecker lips! :shocked:   Carbide-tipped masonry bits work real well for this type of job, but it was a weekend, we don't have a decent hardware store in town...and we didn't want to drive to Sioux City just to buy a cheap drill bit.  :-\

We took a broken 3/8" twist-drill bit and chucked it, upside down, in the drill press chuck & clamped the planer blade in the drill press vise.  Then we centered it where we wanted to drill the 5/16" hole.  We then started the press on a medium speed and held the flat end of the bit (with no lubricant) against the blade until it started turning red, stopped the press, but continued to hold the bit in contact with the blade.  As the bit cooled, we started the press again, and again and again, in the same manner....that transferred the heat to the area we wished to drill in a controlled manner....and in a very small portion of the hardened blade.  After a while the hole itself started turning red, also.  That was the time to bury the blade in a small pile of wood ash, which insulated the annealed portion and prevented it from cooling too quickly.  Result: Retained hardness in the rest of the blade, but a small, soft spot that we could easily drill with even a cheap Chinese bit off the bargain table at Harbor Freight.  It helps to have an old retired machinist around town that has run into almost every metal-related problem at one time or another to ask about such things.......like we did. :P :P

EDIT: ing auto-correct :soap:
« Last Edit: January 11, 2018, 07:49:52 PM by wolfy »
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Offline hayshaker

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Re: Bits for drilling blanks
« Reply #5 on: January 12, 2018, 05:04:08 AM »
try the black/gold bits that Fastnal store sell work really well.
another thing you could do is wrap a wet cloth around the piece and heat up the area of where you wish to drill with a torch till its herry red then drill.

Offline xj35s

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Re: Bits for drilling blanks
« Reply #6 on: January 12, 2018, 10:05:44 AM »
I can't explain the magic but there is a huge difference between CUTTING oil and motor oil, wd-40, 3-in-1, or anything else. I don't think I'll ever drill another hole without it.
pessimist complain about the wind. optimist expect the wind to change. realist adjusts the sails.

Offline downstream

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Re: Bits for drilling blanks
« Reply #7 on: January 20, 2018, 07:17:44 PM »
Come to find out the double nuts that hold the shaft straight when you pull down the handle had loosened so the bit wasn't being held straight. After those were tightened and the speed reduced to 525 things went smoother.  Very very light pressure and a few drops of 3 in 1 every so often got the job done.  I've got three blanks drilled out now.  Thanks for all you input.
You're never late until you get there.