Steel plate distorting when machining surface

[JasonBModerator @jasonb]

Citric would take a very long time. I use Feb Brick Cleaner which is Hydrocloric solution. If used neat the scale will have just dropped off in about 1/2hr and left a grey surface. I then rince in water, dry and spray with WD40 as like a shot blasted surface the clean metal will want to start rusting. Also very good for cleaning steel and brass/bronze after silver soldering and takes HT5 flux off easily.

Use it outside and preferably store outside the workshop as fumes will make things rust.

This is a bit of 10×200 black flat bar after cleaning and no trace of scale

Our old friend JS posted about this, he used to produce dividing plates in batches of 50 or so if he did not pickle them his drills did not last very long.

Carbide should fair a bit better than HSS but it will not last as long as if it did not have to cut through the scale, your shallow cuts would really not have helped with cutter life hear as the first one would just be rubbing against the scale and then you have lost the edge for the rest of teh job.

[JonParticipant @jon]

Spot on Mike and Colin it happens on pretty much every material i have come across from various MS, bdms, aluminiums, different spring steels annealed to plastics and woods.

Exactly right Colin we had an apprentice grind underside of an old spring steel then horizontal machine 1/2" x 5/16" x 8" in specialist vice jaws with coolant down to 130 thou ish. Soon as vice opened they bent like a banana whether taken in 1 or 4 passes made no odds. Few seconds each to straighten out.
Same applied when manually vertically milled the strips but less so, luckily end product filed tapered both ends 75 thou and 125 thou in middle.

[Men IfrParticipant @menifr84251]

So to recap, If I have steel with the rough black surface it's best to pickle it in brick cleaner (hydrochloric acid) and then machine.

When the steel is ready to machine (or with bright steel bar with no preparation) what would be the best way to machine? I used parallels in the vice so I can machine one surface in one go (top f the bar is proud of the top of the jaws and held by the thin side in the jaws) but if I machine one surface it bends so if I turn it over and do the other I need to take a lot off and then the 1st surface will now be bent..

Maybe it would be best to do 4 passes with a smaller cutter after one turn it over and do the other side so the warping is kept to a minimum then after the 4 passes on each side do each surface in one pass to get them flat and parallel.. thoughts?

Also how much depth would I need to take off so they will not bend with further machining?

Or just buy ground stock…

[richardandtracyParticipant @richardandtracy]

Wildly off topic I know, but many anti-limescale toilet cleaners use HCl too. I've usefully used brick cleaner in the toilet and neat toilet cleaner (domestos) for mill scale removal. Having an 'Ocean Spray' scent in the workshop was odd, but the effect was overpowered by a quick squirt of WD40.

Regards

Richard.

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