What did I do? Hardened Iron

Hi Guys, Once in a blue moon welder here. I made two brackets with 3/16" x 1-1/2" angle iron. All went well, I drilled some holes and checked fit, then
when I went to drill the holes larger, it seems like the iron is hardened and I can't drill it. I did water cool it after welding, but it seems like my first set of holes drilled ok. When I went to redrill, it was to hard to drill. I tried heating the whole thing up to dull cherry red and let it cool slow, but I still can't drill my holes larger. What is going on? I need to know before the next blue moon :-)
MikeK
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Dull drill?
Seriously though, one frequently drills a hole with a smaller drill and all goes well. then tries a larger drill and it doan work! Usually a matter of cutting speed.
Cheers,
John B. (johnbslocombatgmaildotcom)
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Welding and plasma does a number on steel and if it can harden it will.
If I need nice holes, I drill them. If the holes are nor drill size I use my cnc plasma to cut them. But I learned not to punch pilot holes for a drill press - the metal hardens nicely.
A grindstone - like a cone might grind the holes a bit larger and then a drill can take over. Or if sheet - try a cone drill.
I'd drill the holes before welding and if not - use a cone drill - or get a round file and open the hole up a bit then try a drill.
If stainless - drill first no matter what. Chrome oxides are tough!
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net "Our Republic and the Press will Rise or Fall Together": Joseph Pulitzer TSRA: Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal. NRA Second Amendment Task Force Originator & Charter Founder IHMSA and NRA Metallic Silhouette maker & member. http://lufkinced.com /
On 8/8/2010 7:05 PM, John B. slocomb wrote:

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