Once metal has been heated and quenched, is it possible to reheat it and let it cool slowly to make it less hard? The reason I ask: I off-center drilled a hole in a part and had to fill it with weld. Being impatient, I quenched the part and proceeded to break two drill bits on it. I'd like to salvage the part if possible and figured someone on here might have some info. on this prior to my destroying the rest of my bits. Thanks.
yes your right i went to college for welding just dont concentrate all of the heat in one spot spread it around and heat evenly
...that should work, but if it doesn't just by some carbide drill bits. They're a great investment that you'll find other uses for anyway.
Heating and cooling works fine to anneal the metal back to a softer state. Get it up to a orange-ish red in a shaded area, just past a dull red and let it cool out of the wind. Shaded defined as daytime, garage door open and lights off. You should then be able to drill with no probs. If need be, heat it back to the same color and quench it. I did that with a Hurst 4-speed shifter arm so I could file it out a touch to match a T-10. After filing, I did the heat and quench bit. Worked ok, but you're not gonna get back to exactly what it was hardness-wise. It can be a touch brittle too, but if it's a non-critical part it shouldn't be a problem. A spotting drill makes quick work of drilling on center when the part is crooked on the surface and a regular twist drill wants to wander. You can make a good one out of a broken center drill like machinists use. After the small tip is broken off, grind the drill to a point without damaging the short fluted area. These drills are short to start with and the stiffness keeps them from wandering. Most times you don't need to center-punch the surface prior to starting the pilot hole with the spotting drill. A small trick to accurate drilling on flat stock is; after hitting the metal with a center punch, file the uplifted cratered area flush with the surface of the workpiece. You still have a cratered area for the drill to start in, but it won't try to wander up and out due to no crater edges. And . . . if you're not drilling critical or large holes with a pilot drill . . . there's your problem. ~~~~~~~~~~~~~~~~~~~~~ You probably know this, but here it is anyway; if you center punch off center - where you don't want to drill - just stick the center punch in the crater, tip it toward the direction you want to move and make a medium force hammer strike and when the crater is moved into position straighten the center punch to vertical and give it one more smack. It helps to use an automatic center punch for the first strike. The small crater helps guide the regular center punch when you use it. If the automatic center punch is off from the mark, you can tip it and fire it again to move the crater as was done above with a regular center punch.
First don't nobody get offended here okay! This kind of question is why guys (I mean people) should take shop classes. The people that run schools today probably don't even know what a shop class is but... Computers and that kinda' tech have their place, but where are they showin' anybody which end 'o' the monkey wrench to grab when 'ya got frozen nuts?
if you can get dry sand, not the humid stuff, heat it up and stick it in the sand overnight, it'll cool super slowly.
Use a autocenter drill bitt to start your hole. They are available at machiene shop supplyers. USE patientance while drilling.
Excellent advice, but shop classes are no longer available in many areas. Many schools closed shop classes down and converted the area to computer classrooms.
That was EXACTLY my point! This debate goes round and round, it has for a looooong time. My dad was a mechanic and tinkerer, I took shop classes, did well, still tinker. Where do 'younguns get this knowledge? If it isn't taught in schools who teaches it? Is it up to those of us that have some skill to pass it on by word of mouth as was done before we became a world of communicators that don't talk to anyone? Who would have thought hot-rodding would have socially redeeming values, but; well, there 'ya go!
heating to above the transformation temperature (1335 degrees F) and slow cooling in air is annealing, after your work on the part, it can be re-heated and quenched in the appropriate media (oil) and tempered, and you should be able to use as previous, do not omit the tempering operation, as it should relieve brittleness issues
auto shop is still available at the school i went to (when i went ) but most of the surrounding schools shops are closed... i asked about that a while ago, a guy i grew up with taught small engines in a high school before they closed that class down,.. he told me, its all about gettin sued. yep lawsuits are slowly shuttin em all down, mixed with a bit of throw away mentality and there is your answer.
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