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post #1 of (permalink) Old 02-18-2007, 06:54 PM Thread Starter
 
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Working with hardened steel

I'm trying to make some bumper brackets out of 1/2" plate steel. The steel is from an ATM machine (yes it was acquired legally) and it's been a pain to cut with a torch. Is there an easy way to drill and tap it? If there isn't i'll scratch this bracket iead and build them out of something else.
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post #2 of (permalink) Old 02-18-2007, 07:11 PM
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Re: Working with hardened steel

A torch doesnt care if its hard or not once its hot it will spray. I wonder if you have something that isnt steel. If it is hard, you dont want it for a bracket. Hardened steel cracks easy.

If you think its something odd ball scrap it.
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post #3 of (permalink) Old 02-18-2007, 08:25 PM
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Re: Working with hardened steel

Might be Stainless ,,, did you try a magnet on it ,,,A torch will not cut Stainless very good,,, I tryed a old welders trick one time buy putting a peice of mild steel on top of stainless & the torch cut it ,, I was told stainless dosent have carbon in it ,,,
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post #4 of (permalink) Old 02-18-2007, 09:09 PM
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Re: Working with hardened steel

[ QUOTE ]
Might be Stainless ,,, did you try a magnet on it ,,,A torch will not cut Stainless very good,,, I tryed a old welders trick one time buy putting a peice of mild steel on top of stainless & the torch cut it ,, I was told stainless dosent have carbon in it ,,,

[/ QUOTE ]

Stainless has carbon, just not a lot of it. The reason it doesn't cut well with a torch is mostly because of the chrome content. Chrome has a pretty high melting point. There can be a slew of other things in stainless steel that might have an effect but chrome is the one I know of.
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post #5 of (permalink) Old 02-19-2007, 08:48 AM
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Re: Working with hardened steel

Interesting -

It sounds reasonable that from an ATM machine it would be stainless - as it's much more difficult to cut. Thieves would need specialized equipment.

You guys got my curiosity up.
Found this: http://www.askzn.co.za/tech/tech_fab_cut.htm

I tried the trick about putting carbon steel on top of stainless with oxy/acet - it worked! Still not a nice cut but it did blow through it.

My plasma cutter cut it fine with a decent edge, but it's much higher heat.
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post #6 of (permalink) Old 02-19-2007, 09:10 AM
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Re: Working with hardened steel

Definitly pilot holes. Cobalt drill bits. And only cobalt drill bits. Several cobalt drill bits. Depending on the condition and quality of the bits it may take a couple per hole. Plenty of lube. Can be thread cutting oil. Some people like plain old water. If the bit doesn't start cutting right at the start or when the bit quits cutting STOP and get a new bit. If you don't cut the metal at the bottom of the hole you will "work harden" it. This can happen real quick and make it even more difficult to drill. If the bit stops cutting get a new one. Even if it means stopping the operation and going to the store. Use the correct size for the tap. Low r.p.m.s. Medium pressure. Taps. An industrial grade quality if you can purchase one. Again plenty of lube. I like cutting oil. Keep tap handle straight and apply medium pressure while turning. Once it starts cutting stop and back up to remove burrs often. Progress may be solw. Real slow. Plenty of lube. Good Luck.
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post #7 of (permalink) Old 02-19-2007, 10:30 AM
 
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Re: Working with hardened steel

You guys know what kind of bits and angles to use to drill and countersink carbon fibre? HSS just doesn't seem to cut it.
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post #8 of (permalink) Old 02-19-2007, 10:34 AM
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Re: Working with hardened steel

A bunch of good tips there!

But, Andy, is this really a good idea? First, half inch is too thick for bumper brackets unless you're building them for a D6. There's no point in putting more steel in the bracket than there is in the frame; it's just useless extra weight. And a good argument can be made that the bumpers and brackets should be slightly weaker than the frame: You want them to give way before the frame bends.

Second, not knowing what you really have there means that it could be brittle or fatigue-prone, could take special equipment or technique to weld properly, or may not weld to other materials you're using. Ever see magnesium TIG welded with aluminum filler? The weld looks perfect but you can pull the bead out with an icepick.

Better to stick with materials you know. You wouldn't want a bumper falling off on the road.
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post #9 of (permalink) Old 02-19-2007, 01:30 PM Thread Starter
 
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Re: Working with hardened steel

I guess it could be stainless, it's painted on both sides, i ground off paint on the side, I laid out and started the cut on the clean side. The cuts don't look too bad but there's a ton of slag and it's real hard to keep the cut going. I've got some mild 1/2" or 3/4" tonight i'll see If it's a lot easier to cut. The brackets are also d-ring brackets and the actual bumper goes though the middle. I'm thinking i'm going to re-design the bracket using something I know is mild steel.
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