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Old 02-23-2017, 05:46 AM   #1
Naiveambition
 
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Default Drilling and tapping hardened steel

The project I'm working on requires two holes in hardened steel. May possibly be stainless but not sure. I don't have the option to anneal and reharden for multiple reasons so, I am looking into alternatives. When I first looked into this the drill bits were extremely exspensive ( 300$)for one Like that's gonna happen

The tapped hole is 6/32 if I can remember correctly and drilled hole is .125

I've ran across some YouTube videos that mention a sharpened masonry bit which is fine for the drilled hole, but for the tapped hole it will be important to have it sized for tapping, as most are standard sizes not related to tapping. I have a small area of flexibility I suppose on tapping a little larger hole.

Any suggestions


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Old 02-23-2017, 09:26 AM   #2
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Carbide drills are available but even if you drill the hole how will you tap it ?


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Old 02-23-2017, 10:05 AM   #3
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You could get somebody with an orbiting head on a EDM Machine to spark the thread. You just need a copper thread with the correct pitch but smaller diameter. They could also spark the hole to start with.
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Old 02-23-2017, 10:24 AM   #4
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It seems perfectly possible to reduce an oversize masonry drill to be a correctly sized carbide drill. There are pages and pages here and elsewhere of how to grind and how to make the appropriate tooling as diamond and carbide is so freely available and cheap. I recall years before this internet thing that we sharpened masonry drills on a worn out diamond wheel that had done service for cutting spectacle lens blanks.

As for tapping, there is seems to be no reason why the tap is cut with nothing more than a diamond nail file.

After all, if one looks at the gearing that was cut for the Gutenberg printing machine, it was done with a wood chisel.

Some clever arse is going to decry my comments but dear old Professor Chaddock made hardened steel ball bearings -in his home. workshop. Where he made bits for the first atomic bomb is unclear!

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Old 02-23-2017, 10:39 AM   #5
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The first question you should ask yourself is how hard is hard? You can buy carbide drills, usually single flute, that will drill through most materials. These aren't that expensive but you may need more than one.

At work i once had to pierce some hardened components and only had a small carbide drill. I used that to drill the initial hole and then followed up with a carbide end mill. The end mill of course couldn't handle the material and chip and eroded badly. In the end the end mill ground its way through.

Such an approach may disgust trained machinist but the overwhelming focus was getting a machine inline as fast as possible.

This doesn't solve your threading problem though. 6-32 is pretty small which makes me wonder what the application is. There may be alternatives to trying to tap threads that small in hard steel.

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Originally Posted by Naiveambition View Post
The project I'm working on requires two holes in hardened steel. May possibly be stainless but not sure. I don't have the option to anneal and reharden for multiple reasons so, I am looking into alternatives. When I first looked into this the drill bits were extremely exspensive ( 300$)for one Like that's gonna happen



The tapped hole is 6/32 if I can remember correctly and drilled hole is .125



I've ran across some YouTube videos that mention a sharpened masonry bit which is fine for the drilled hole, but for the tapped hole it will be important to have it sized for tapping, as most are standard sizes not related to tapping. I have a small area of flexibility I suppose on tapping a little larger hole.



Any suggestions
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Old 02-23-2017, 11:14 AM   #6
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I agree that you need to know how hard the material is, if you are talking 40 RC or less then it is do able. Anything harder that that will be VERY difficult to tap. Most hard materials I have tried to tap the tap froze in the material and would not back out. Orbiting EDM is the best chance for threading the material if over 45 RC

Mike
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Old 02-23-2017, 12:42 PM   #7
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With a CNC mill you could thread mill the holes.
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Old 02-23-2017, 04:30 PM   #8
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Hi

Drill hole a little oversize and ream for a tapered pin. loctite and drive pin into place. Drill and thread the pin.

Mark T
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Old 02-23-2017, 04:32 PM   #9
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Thread milling may be the way to go, depending on your job size you can mount it on a face plate and thread mill it on the lathe with a high speed spindle on the cross slide, it's just like single pointing a thread but with a spinning tool,

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Old 02-23-2017, 04:52 PM   #10
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Not many of us with milling spindles these days. It's a bit like finding hen's teeth amongst the rocking horse manure. We're a sort of dying breed( well, not yet)

Regards

Norm


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