RKM556

Unbelievable issues when attempting to drill holes...

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I've got a woefully inadequate drill press when it comes to drilling holes any larger than 1/4" in steel, and since I mostly work with tool steels I have had to learn how to sharpen bits (saved me a fortune!). Regrindin the normal hss twist bits certainly makes them cut better (and faster), assuming that you sharpen them properly. I've not gotten around to trying cobalt drills, but have recently picked up tct tipped ones when a normal jobber drill won't cut it. The main problem I've had with the tipped ones is that a little too much pressure and the tips shear straight off!  :(   But get it right and they cut hardened steel like nothing else I've used.

 

On a side track, slightly.  Due to the girly machine, I've discovered the easiest way to drill holes over 1/4 (or even smaller holes in hardened steel before I found the tct tips) is to regrind a masonry bit. I regrind the double beveled edge into a scraping edge and use higher revs than normal and they work a treat, less resistance in the material and the hard cutting edge. I don't know why the tct twist bits I have arn't constructed the same way as the masonary bits because I've not managed to strip them in the same way?

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Ryan: 100rpm max. 1/4" pilot hole then to 1/2". No drilling in really small increments is NOT a good thing, no less than 1/3rd increase i diameter or you'll chip out the outsides of the edges. With a little proper technique you can drill as quenched hardened 5160 with a cobalt bit.

100 rpm .... I run my little press at its lowest rpm range, but I know its several times higher than that.



The key to drilling is not only speed but feed as well. For instance: 154 CPM work hardens really fast. If I am drilling and let off on the downforce a little bit the bit is not drilling and heats the contact area enough to harden it...that bit will not get through the hard spot.

Another great tidbit of info I did not know.

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I agree, 460 rpm is way too fast for a 1/2" bit in hard steel. My drill press goes down to 60 rpm which is what I do most of my drilling at. Smaller bits like a little higher speed though so 460 is about ideal for around a 3/16" bit.

Also I always pilot drill large holes. 1/4" then 1/2" then 1" then 2". It may sound like more work but it goes quicker when the center of the drill isn't doing all the  work. Its the outside corners of the bit that does all the work anyway. That's why I don't like too small of a step up in size. You end up just breaking off the corner of the drill and drilling back on the flutes which just burns things up.

If 460 is as low as your press will go (hmm, must be a woodworker drill press) then you might consider using a large hand drill. The larger ones usually turn slow enough to work and your bit will tend to follow the pilot hole. You'll have to be careful to keep everything perpendicular to the hole but I've had good success with hand drilling large holes in the field. What you might do to keep the drill from wandering is to clamp a plate with a 1/2" hole already in it to the top of the piece you want to drill so that it follows the hole and keeps things in line. And you'll still want to pilot drill a 1/4" hole.

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I have trouble with a steel (110WCrV5) that is hard even after normalizing. This steel hardens if you look at it sideways. Thin sections, I guess.

I'm afraid what I do is just drill the holes when the material is at a dark red or black heat. I use standard "waster" drill bits for this. I get a bunch and just get used to the idea of sharpening them and get used to thinking of them as consumables.

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I hate drilling hard steel or work hardening steel.  Usually, I will just hot punch it.  There are two ways that have been successful for me.  First, sub-critical anneal, a propane torch is sufficient.  Second, using a big 3/4" drill that only runs at a few hundred RPM rigged up as an "old man".  The 2x3 lever and chain makes more difference than the RPM.  There are two tricks that I haven't tried, since I just bought a drill press (my first one!).  Try drilling with a piece of mild steel or a bad drill bit until the hole gets real hot.  Then let it cool and use a regular bit.  I am sure that this will work, since I have an antique carbon steel drill bit that got hot, and it just mangled the tip.  Since it was a garage sale bit, I did not figure it out until I did a spark test.  Oh well, it will be the bit of a hatchet or hardy tool now.  The second trick is to use an Artu drill.  I have never seen one of these work in person, but there are videos.  Basically, you run it hot and fast with a lot of pressure and no lube.  The brazing on the carbide will give way at about 1000 degrees, but the sales guy said that the steel will will be toast by then.  Has anybody else tried this?  It seems that it should work.

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for hard stuff I try to keep both the metal and the drill cool, low speed, and power feed on, release the feed and you lose your bite so the drill has to start again but this time oner the entire cutting face rather than just the center point ( I dont often use pilot holes ) also you sometimes get some swarf on the chisel point preventing it from cutting.

if you can do it in one go it will work most of the time until your drill get just a little blunt

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for a cheap fix of the hole buy a masonry drill bit & resharpen the carbide brazed in bit to the geometry of a normal drill bit ( for hard steels 135 deg to 140 deg  angle and thin the web) flood with coolant to keep it down at the tip of the drill bit. Make sure the job is secure on the drill press table so you can  keep the deep up on it. DON'T forget to use good PPE. I have drilled out broken taps & drill bits with this method.

Biggest problem I have seen when people drill harden  & or material that work hardens is they let the cutting tool rub. the heat generated by the friction of it rubbing will harden the spot almost instantly. For you problem I would try to drill from the other side & drill back through.

 

Just a few tips hope it helps. A lot of good points in other posts also. Have fun with your build.

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