Any Gate manufacturer will have 12mm sq black bar.its dirt cheap look for a local place and call in

Chris

I remember you asking about how to machine the I beam in another post.

Something that may not have been mentioned before to reduce the banana effect when machining is to normalise the steel beforehand. Get it red hot let, let it soak at the red heat and allow it to cool slowly. At this time of the year, you could put the steel in your fire while it is good and hot and leave it there overnight.

Dave
The Emerald Isle

Best to use hot rolled black steel. It won't go banana shaped when machined. Black steel is usually slightly over nominal size, to allow for the corners not being square.

I've got some 16mm square hot rolled in stock – as it's way cheaper to buy the standard 6m length than mess about buying shorter lengths. Whereabouts are you?

Andrew

Even if you did come across 1/2" black bar it will likely have rounded corners so as I said in the other post mill it out of the next size up which is 16mm.

It is probably not quite so nice to machine as bright but is still best for the job.

Don't know if you saw my post yesterday in teh workshop progress thread but I showed some parts that are 5mm finish thickness, I cut them from a mixture of old 1/4" and new 6mm black bar that I had in stock. I also had 5mm black bar but chose the thicker material. They have not moved.

The black scale can be a bit abrasive on tools so is best removed before machining.

I use "brick cleaner" from the local builders merchant, a soak in that for about 1/2hr is usually enough to cause the scale to flake off, maybe a bit longer if the scale is very heavy or the acid getting old. Quick rub with a small wire brush can also help.

Once the scale is off rinse in water to remove any acid, dry and give a quick spray of WD40 so it won't start rusting.

It is also good as a pickle to remove the oxide after silver soldering and will also shift Tenacity/HT flux.

Don't do it inside as any fumes can make other metal rust.

Hi Chris, you may be able to do a little less machining by getting some 16 x 10mm bar for your "I" beam. These people do it and you can have some cut to length if you don't what a full 4.1M of it. **LINK** Just select cut to size in the select box and click on add enquiry. I don't know if they only do a minimum order value though, but it may be worth an inquiry.

Regards Nick.

I am firmly in the camp of those recommending hot rolled (black) bar. Attempting to use cold finished (bright) bar and anneal it is unnecessarily complicated and expensive. If you have a cutter with carbide inserts, I would not bother pickling the bar to remove rust. I suspect the brick cleaner mentioned is hydrochloric acid. Its fumes will corrode any steel nearby. For a source of hot rolled bar check out the shops doing ornamental iron work. They might have some drop about the right size and would save cutting charges.

Cannot see any problem getting 1/2 square m/s regular ME suppliers stock it, forget about black steel its blacksmith material,not all mild steel bananas when cut on all sides it varies batch to batch,rectangular seems to be worse than square particularly key steel, just anneal by heating to red and cool slowly. Another approach where there is a wider selection of available material specs is to machine round bar to the shape required ,leaded en 1A produces a super finish,or if a tougher material is required then free cutting en8 is just the job, with virtually no distortion , i remember reading in Model Engineer back in the 1970s of a exhibition winning model engineer who liked stainless steel motion on locomotives, his approach was to machine it from stainless round as it machined easier than rectangular section and had a wide choice of free cutting s/ steel specs, getting it right takes longer and more patience but worth it in the end.