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VernonCooney

Cobalt driĺl bits and hardend steel

13 posts in this topic

I bought some Bosch cobalt drill bits and tried to drill thru my 1084 partially heat treated knife handle. It clearly did not work. It worked on part of the handle that was not heat treated just fine. Anyone with similar problems?

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most people don't drill threw hardened metal, some bits can get threw it but you'll run threw em like crazy. i own a set of milwaukee cobalt bits (the cheapest i could find) and they have been great, lasting a lot of blades but i only drill threw annealed steel, and you should also use some kind of lube when drilling. hope this helps!

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yup seems conmen issue, dont drill in harden or air hardening steel (i made a bubu there) , alternative is diamond if you can afford. I would advice to anneal again if that is the case. 

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Try carbide, it will drill hardened steel.

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Don't harden your tang, I don't know why people do that. I stopped when one of my blades broke at the tang when I tried to straighten it. I know some people have heat treatment ovens that will heat the whole knife but hard steel is a huge pain in the butt so anneal your tang if it gets hard, you only need to harden the edge of a knife. if you had a weak tang you might benefit from a hardening it, some swords and probably daggers have hardened tangs as well.

 

every time I read about hardened tangs it reminds me of that miniature katana I broke.

could you imagine the tang just coming off of your precious blade and there's nothing you can do about it? Like if you swung your hammer and the head came off and just floated into the sky.  Jeez I might have been traumatized a bit...

 

also, not many people try to burn tangs into their handles anymore but you can harden parts of your tang with wood, so if anyone does that be weary. And while I'm getting off topic, the trick to burning a tang into a handle is figuring out the right temperature for your tang but more importantly you have to tap the handle on something so the blade gets knocked in, like when your hammer is loose and you tap the handle on your anvil to tighten it. Otherwise the blade won't go through as easy, or at all, and it will burn a big nasty hollow in your handle. (Sorry but I love finding random stuff like this here)

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2 hours ago, steven smith said:

Don't harden your tang, I don't know why people do that. I stopped when one of my blades broke at the tang when I tried to straighten it. I know some people have heat treatment ovens that will heat the whole knife but hard steel is a huge pain in the butt so anneal your tang if it gets hard, you only need to harden the edge of a knife. if you had a weak tang you might benefit from a hardening it, some swords and probably daggers have hardened tangs as well.

 

Actually, most historic swords had soft tangs, and very often made from a separate piece of iron forge-welded on. If the tang's wide enough at the base there's no reason to harden and many not to.

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I was building a trailer and found out some the old bed iron I welded to the frame for mounting floor boards too, the bed irons were air hardened after the heat of welding. After burning up several bits and only had a few of the holes i needed to drill done, I decided I had to try something else!

 I went to an old machinist friend with my problem. He went to his shop and takes an old 1/4" masonry bit out and fires up his grinder. Free handing the bit he re-bevels the carbide tip. He told me run it as fast you can and put all the pressure on it you can without snapping!

I wish I had paid more attention to what he actually did to the bit. He had cancer and was dead three months after this incident and I never got to pick his brain on exactly how he changed the point. I will say this I drilled probably 60 holes with that one bit and never had a problem from the bit he had sharpened!!

One thing he did was he changed the angle of the  point!

The following is a quote from Wikipedia:

  • The point angle, or the angle formed at the tip of the bit, is determined by the material the bit will be operating in. Harder materials require a larger point angle, and softer materials require a sharper angle. The correct point angle for the hardness of the material influences wandering, chatter, hole shape, and wear rate.

The other thing he did was sharpen the cutting carbide. When using the bit in concrete, the bit doesn't really need to have a crisp cutting edge. However when using the bit in steel, the cutter/carbide needs and edge. Its like the principle of cutter for a metal lathe!

I have tried to duplicate this with small diameter bits. but it is hard to get it just right, and at best on hardened steel they didn't last long!! About the best I was able to do was about 3-4 holes with one bit of 1/8" diameter!!

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Tried HSS, titanium and cobalt bits and nothing works with 1080 and 01 tool steel. Steel is not hardened. Suggestions??

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24 minutes ago, VernonCooney said:

Tried HSS, titanium and cobalt bits and nothing works with 1080 and 01 tool steel. Steel is not hardened. Suggestions??

Carbide tips and cutting oil should get you through this, are you running your drill press at too slow / high of a speed?

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20 minutes ago, VernonCooney said:

1720rpm and 3 in one oil 3/16 bit

tool steel grade you need to go lower, like into the 6-800 rpm range

Edited by rickmanb

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I use carbide tipped bits, drill press running @ 625 rpm, with 3 in 1 oil. I've drilled through hardened steel and hot rolled without issue. Try a  pilot hole with a 1/8" bit first. Light to moderate pressure, go in a little, back it out, another drop of oil, then a little more, and so forth.

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