I have been machining a 2'' round piece of cast iron into a finned barrel for an engine I am making.

Going between lathe and mill I have managed to produce a large amount of swarf and everything is covered in black dust, including me.

Not enjoying it and I have another three to do.

Will all this dust be a problem, do I need to strip down my equipment and wash everything off when I finish barrel no4.

I would, but you might be able to reduce clean-up effort by covering up as much of the machines as you can with paper and catching it.

Two reasons for cleaning up, cast-iron dust penetrates deep into the works and it can be abrasive. The main reason is it's filthy and it spreads. If you don't clean up it will transfer to you and everything you touch for yonks. And very little cast-iron goes a long, long way. Horrible mess. You can guess how I know...

Dave

I use a brush to sweep it off the bed as you generate it, it gives the bed wipers a much easier time and then clean it all up at the end of the job.

Brian

I would cover all exposed parts with old cloths / paper before starting & if possible rig up a shop vacuum near the cutting tool to collect dust. I have several bank coin bags that I put a neodymium magnet in & stick them onto the X slide & lathe ways to collect chips / dust, works well, when I'm done I hold the bag over the waste bin & take the magnet out, the chips & dust just fall off the bag, shake the bag then replace magnet & back onto machine.

George.

Cast iron dust , is it really that bad for lathe beds.

The simple answer is “YES”. Would you add cast iron dust to your car engine oil? Thought not.

Neither would I add steel, brass, aluminium, chocolate sprinkles or ice cream. The skin on castings can consist of chilled iron and moulding sand, both of which are harder than other swarfs and best cleaned up fairly quickly but the inside of an iron casting or meeanite are pretty benign. I just clear up and oil when the job is finished. My Myford is still accurate enough after 30 odd years of tool and model making.

Rod

Edited By Roderick Jenkins on 02/06/2019 17:38:38

Something that disturbs me is the idea that inverting the tool and running the lathe backwards prevents CI swarf from flying everywhere. That lifts the cross slide and top slide creating openings for swarf to enter.

A friend who knows far more about machining tells me that if you leave a pile of cast iron swarf on some steel it will go hard and metallurgically bond with the steel. I think time and some moisture is required. The consequences are too frightening to think about.

However it may be an old wives' tale.

JA

Same as Rod; I don't sweat over it and I've turned a lot of cast iron both as castings and meehanite. But the castings for my traction engine have been done properly, so they have very little skin and no hard spots. Plus I always fettle with angle grinder/files/wire brush before machining to get rid of dust and grit from the casting process.

Meehanite in particular is very soft, drop the part and it gets a ***** great dent, often resulting in scrapping the part. The black dirt contains a lot of free carbon, and since the allotrope isn't diamond, it's very soft,

Andrew

I doubt it is a metallurgical bond. I believe the rusted swaf forms a mechanical bond to the substrate. Steel swarf from grinders will do the same.

Try a scientific ( ish) approach. Take a piece of clean rag , dip it into some of the cast iron dust and rub it against some part of the lathe that is not critical ( At the far end of the bed behind the tailstock perhaps . . Examine that area of the lathe bed .

Brian C

I have worked in shops that ran a lot of cast iron parts. No special precautions were taken with the machinery. It is messy and because of that I don't like to machine it but I don't worry about damage to my machines.

I will give it a wipe over before I start barrel no2 then probably do a strip down when I get to no4.

I like to keep my machines clean anyway so I suppose a strip down will not do any harm.

Judging by how easy It is to machine I am guessing I have soft meehanite bar.

Apart from wiping up the soluble oil left from coolant nowt happened. But to be fair my lathe bed is induction hardened.

Andrew

Don't forget cast-iron isn't a single well-identified material. At one end of the scale are carefully made engineering alloys like Meehanite, at the other the worst kind of foundry waste imaginable. The latter is used to make sash weights, ornaments and other carp where machinability matters not one jot. Slag, inclusions, floor scrapings, sand, left overs and rubbish, casually melted, poured, and chilled by hosing down. No skill required. The cast-iron used to make street furniture like man-hole covers is a notch or two up, but it too might be a more-or-less random mix. Possibly this class of lower-end foundry work might include castings made for models.

The question's not if cast-iron dust in general damages machines, it's what's the risk with the cast-iron you're cutting? It can be nasty stuff. Traces of sand, hard-skin, inclusions or casting faults are alarm signals. Soft cast-iron that turns easily is unlikely to be a problem.

Often the worst is all in a thin outer skin and the inside is great. It may pay to shave the skin off with an angle grinder. (Ultra-messy!)

Dave

A major problem with small and thin-walled castings is chill. There isn't enough mass of metal to slow the cooling rate. The result is an extremely hard casting. A similar problem exists with larger castings that are dumped from the mold to early. The result there is an extrermely hard skin.

Might be more scientific(ish) if you took a block of oiled steel, dipped it into some cast iron dust and then rub it, under pressure, against some part of the lathe bed, repeatedly, for a few weeks?

But surely if it's got a lot of cr*p in it that's not cast iron? The original question was is cast iron swarf a problem? I'd be inclined to say no. But of course if one includes non-metallic components that may be associated with poor quality material that's a different story.

Andrew

Edited By Andrew Johnston on 02/06/2019 23:24:06

Cast Iron swarf is a total pain, if left on a machine that has had a water based coolant in use the swarf will fuse together and form a solid lump.

I speak through experience of having two Brigeport R8s written off because the apprentices didn't vacuum out the slideways properly on the knees.

If it gets down into the suds tank you have to chip it out with a chisel / screwdriver. and it bungs up the pump.

Regards

I'm of the Rod & Andrew school of thought and don't get stressed about it getting onto the machines. If it is a casting that I feel may have a harder surface then I might slip a sheet of paper on the bed between headstock and carrage but that is all.

A casting can be pure and but still be chilled so you will get harder swarf and induction beds are only hardened to a certain hardness, try running a scriber over the ways and it will leave a mark as they are not as hard as a cutting edge. Don't just think it is CI that can have hard spots, ever had a bronze or GM casting with pockets of phosphor oxides in it, may as well be cutting a grinding wheel!

There is also a wide variation in the quality of iron used in model castings, I've just totted up and have probably machined castings from over 20 different sources which ranged from beautiful high carbon content German castings to unpleasant UK castings that probably got done when some man hole covers were being poured. Not only do these produce different swarf some will leave your hands a lot blacker than others

I don't seem to get a lot of fine dust, only if doing fine detailed work where the cuts are small, on something like a finned IC cylinder I would hope to be making chips.

Edited By JasonB on 03/06/2019 07:32:05