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Old 02-12-2018, 10:03 PM   #1
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Default Drilling hardened rods , masonry drill

Here's something I think is worth sharing .
I needed to cross drill and tap 16mm hardened rods , wich will
eventually be the lineair rails for the router I'm building .

Only the outer skin , maybe 1mm is hardened , the core is reasonably soft .
These are not the chinese rails found on ebay , but german made by FAG , abt 20 years ago . They're HARD allright .

So I heard and read about using masonry drill bits to drill hard steel .
You can even drill out broken taps this way
Never really believed it , but I decided to give it a try as I had no off the shelve alternatives .

I must say , I'm speechless .
This actually works , and it works very good .
I was able to drill 2.5mm trough the hard skin , and then continue with a smaller regular tap size drill .

First thing I did was sharpen the drill bit like I would sharpen a "normal" drill bit for steel .
A diamond disk is needed . Mine is pretty coarse , but it's all I have .
The sharpened drill point looks a bit odd , as the spade blade isn't really shaped like a twist drill So my initial scepticism grew ....

Then some cutting oil , light feed and rpm of 350-ish .
Did a test on a piece of scrap from a previous project .
Cuts it like butter ,

So I set up everuthing in the mill , drilled 14 holes without any problem and the bit is still as sharp as it was .
Chips are blue-ish and very fine , almost like steel wool .
It makes a squeeking noise when drilling , and it stops making that noise once the hardened skin is cleared .


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Old 02-12-2018, 10:51 PM   #2
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I saw a demo at a show many years ago and they were drilling thru files
Probably come a long way since then

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Old 02-12-2018, 11:17 PM   #3
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If you want the same profile as a normal twist drill, then these are the things to get, used by locksmiths to drill out hardened locks.

If you don't try it, you will never know if you can do it!!
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Old 02-13-2018, 07:47 AM   #4
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The simple test for anything is to simply rub one thing against another---- and see what happens. If something rubs off, that's it.

It's been going on since the World was created.

As far as the present situation which has just been discovered( ho-HO), one simply tries scratching a bit of hard steel with something possibly harder.
All one is doing here is changing the cutting angle to a perhaps more suitable angle on a cheap thruway masonry drill on something harder i.e. a diamond.

We finally reach 'Diamond cuts diamond' and 'That's it, folks'

In practical terms, a scrap carbide drill CAN be converted into to all sorts of cutting tools- to do all sorts of tasks far removed from from battering a hole in a stone or brick.

Perhaps the only caution which I would offer is 'Don't use your wife's diamond ring'. but the first Queen Elizabeth did use hers to write on glass.

I'm going back to bed.
-- Good night all

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Old 02-13-2018, 08:18 PM   #5
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Hi Guys,

At the end of the day carbide is one of the hardest materials you could use for cutting metal. I believe that ceramic is harder but far more fragile. I've reground and used carbide masonry drills to do all sorts of things, not just drilling holes. Carbide router bits make good form tools.

If you think about it, in regrinding a carbide tool bit, you have probably used something harder, like CBN or Diamond to do it.

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