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Author Topic: Drill bit for hardened steel  (Read 210 times)

spclark

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Drill bit for hardened steel
« on: December 21, 2016, 03:51:08 PM »
I make hammers for the Marauder.  The most recent one is being made out of some sort of 1.25" axle shaft.  I turned it down to diameter on the lathe with no issues, and drilled thru for the striker hole and spring counter bore with no problem.  When I went to cross drill it for 8-32 and 10-32 tapped holes, the cobalt drill wouldn't touch it.  What type of drill bit do i need to drill this HARD steel?



Alan

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Re: Drill bit for hardened steel
« Reply #1 on: December 21, 2016, 04:42:47 PM »
They are case hardened, so I suspect a diamond drill.
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rsterne

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Re: Drill bit for hardened steel
« Reply #2 on: December 21, 2016, 04:43:29 PM »
I would try a Carbide bit.... or anneal the hammer by heating red hot and allowing to cool slowly....

Bob
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Madmullet

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Re: Drill bit for hardened steel
« Reply #3 on: December 22, 2016, 05:02:31 AM »
I dabble in knife making and a few times I have had to drill a blade after it has been harden and heat treated to 60-61 rockwell.  The only thing I found that worked was Pure carbide drills from a company called Drill America.  They are not cheap about 20 to 150 bucks each and very brittle so use them in a drill press on low speed or in a trusty Ol bridgeport.  I cant see a axle being supper hard I would look in to a set of HSS drills first. 
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spclark

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Re: Drill bit for hardened steel
« Reply #4 on: December 23, 2016, 04:06:57 PM »
are HSS bits 'better' than cobalt for hard steel? 

marmot_militia

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Re: Drill bit for hardened steel
« Reply #5 on: December 24, 2016, 06:31:54 AM »
You will have to anneal it.  If you think drilling is hard, wait till you try to tap it.

As noted above, heat the area to red hot and let it cool slowly.

Jim