A moan - steel of mysterious composition

But what constitutes "Non Special"? ALL should be to some sort of Spec. unless we're working to ROC mixes?

Regards Ian

Mild steel is very low carbon steel less than 0.25% contains all manner of recycled crap. Special steels are normally alloy steel for structural and engineering work.

Bariatric beds are no different from ordinary hospital beds other than being stronger to take the weight of grossly obese patients.

Agreed

Any quality steel producer will sample the scap going into the mix and alter the mix to suit,also sampling during the melting process to refine the steel. I doubt this is the case with most mild steel that enters the country from china.

All steel should have a data sheet which gives composition info

Working for a company which manufactures equipment for petrochemical and medical applications, the quality of material we use is generally proscribed by the end user, and we have to supply a detailed material record book which defines exactly what is used in manufacture.

For every ferrous and non ferrous material we utilise, we request from the supplier a certificate (see en 10204 on Google for details) which clearly determines the material through a series of traceability checks. In addition we also (for some clients) have to complete local PMI checks (Positive Material Identification - again see google).

These checks are needed to ensure that the end user gets a product that complies with internationally recognised standards. Do we need such documentation for most of what we model engineers manufacture - probably not. Does the purchaser of the hospital bed need it? Very unlikely - especially as every certificate has a significant cost associated with it.......

Grum

If I ordered EN42J or 316L I wouldn't expect to request a C of C to ensure the supplier sent what I ordered, and lets face it, how many Chinese test certs look remarkably similar despite the offerings being vastly different? Industry works to different parameters in that if what you ordered isn't what you received and someone is injured due to material failure, litigation follows cos where there's blame there's a claim. Recent events may explain why a material passed its test parameters but failed when subject to different tests obviously not required at the time.

Old school Muddle Ingineers have always managed to scavenge "Odd" materials and been able to utilise them, some machine well, others are pigs. Up to the individual to choose, want to make a shiny shelf queen?, leave the skips and tip finds alone.

Regards Ian.

If you'd gone straight from 5mm or better still 3mm to 10.5mm with low speed plenty of pressure and a bit of lube now and then it would probably have worked fine.

The odds are good that you hooped the flutes on the 10.5 and cooked the material at the same time, it's a common misconception that small steps up to the finished size are a good idea because that works most of the time with lots of easily machined materials.

This comment by Nick is linked to the thread on milling speeds by the Presto Counsellor book where on page 14 note 8 it states that pilot holes should be 1.5 times the chisel edge length. Do we need a table of chisel edge lengths now?

As an aside I have just ordered 40 3mm short drills and 40 5mm short drills for some pipe fitters. They only have to go through relatively thin sections and the short drills are much stiffer and so work well as pilot drills for stainless steel pipes.

Martin C

"If you'd gone straight from 5mm or better still 3mm to 10.5mm with low speed plenty of pressure and a bit of lube now and then it would probably have worked fine."

Well, there's always something to learn.

I didn't even consider going from a 3mm drill to the 10.5mm finished size as I was working with a heavy corded drill and very little wriggle room. Would have got hurt if the bit had jammed or hit an inclusion (as the intermediate drill did a couple of times).

A lot of lazy stereotypes and generalisations here, just for a change. My company sources large quantities of a variety of mild, carbon and stainless steels in China and always get a (free and genuine) CofC with each delivery. We have a team of local SQEs who regularly audit the supply chain to ensure no crap gets in, as do our own customers. Sure enough there are plenty of suppliers who would happily supply you with crap but if it actually matters to you, it's perfectly possible to avoid them. And you don't need to go to China to find them...

Murray

Back in the 1950's I visited a Republic Steel facility at Moline, Illinois. Their raw material was railroad rail. It was heated and passed through rollers that separated the head, web, and bottom flange. The individual parts were then rolled into fenceposts, reinforcing bar, and small angle iron. The angle was the size commonly used for bed rails. At that time the plant was nearing the end of its life. The facility was pretty old and obsolete. Incoming material was handled by a small steam powered locomotive crane (Brownhoist). Considering the raw material used I would expect the finished product to be pretty hard, especially if it was cooled too rapidly. Here in the US bed frames were notoriously hard to saw or drill, just like yours.

An added note:

China exports a lot of hospital beds. China does not have a great reputation for producing consistent quality steel.

Well they've had a lot of time to get used to steel making since Mao's disastrous "great leap forward".

Michael W

Deleted - posted in error.

Edited By charadam on 20/07/2017 18:42:17