Bright Mild Steel vs Black Mild Steel

Size does not come into it much. Like Andrew I machined some 5/16" sq section brass down to 1/4". Took 1/16" off one side and it bent really badly maybe 10mm of light shining through on a 300mm length.

I also leave things like those crank shafts for a few days after stitch drilling so that they settle and again after rough turning.

I suppose to some extent it will depend on how much the bar has cooled down as it goes through the last set of rollers.

Edited By JasonB on 06/07/2017 14:35:21

I needed to forge an item this morning and I wanted to make sure it wouldn't give any problems. So I decided to us BMS square bar, it turned out to be the worst piece of steel I have worked form years! It just fell apart with so much crap in the mix. I resorted to cutting up a new RSJ that I new was all new steel, it was the difference between chalk and cheese!

I took a millimetre off the full length of my test piece as Andrew suggested. No change.

This is an important result. If you want to prove that BMS warps when you machine it NOTHING HAPPENS.

These experiments prove that BMS only bends when it's vital that it doesn't. This is Sod's Law in action and the only rational explanation for it is supernatural. I have Gremlins.

Excellent news. Despite continual cock-ups suggesting I still have a lot to learn, I'm really a first-class craftsman...

Dave

LOL

The discussion is really about the difference between cold drawn materials and hot rolled, or formed, materials, not just Bright MS versus Black MS.

Out of idle curiosity I've just taken a 6" length of ½" square bright drawn mild steel and milled 1.4mm off one side. As far as I could tell the material was straight (rule and backlight) before I started. Afterwards it was clearly bowed away from the machined edge. The material was bowed about 5 thou at each end.

Andrew

I wonder if normalising the steel first will relieve the stresses?

Yes it does, Andrew also mentioned it earlier.

I often have wondered if the age of the material has any effect on this bowing characteristic inasmuch that over time any locked in stress has been able to work itself out. The majority of my material stock steel, brass, copper etc is in the order of 50 - 60 years old, the last stock I bought was some brass angle and that was at least 10 years ago.

I'm not a massive user of milled stock but it is an issue that personally I have not encountered but do recognise that it does happen.

Phil

often have wondered if the age of the material has any effect

Not sure about BMS, but certainly large engine castings were left to "weather" (often for several months(?)), back in the earlier decades of the last century.