A moan – steel of mysterious composition

[CirclipParticipant @circlip]

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.

[Nick HulmeParticipant @nickhulme30114]

Posted by charadam on 29/06/2017 21:58:54:

I volunteer with REMAP and was recently modifying a fully-adjustable bariatric bed.

The modification required drilling a couple of clearance holes for 10mm bolts in the 13mm trunnions for the bed actuators.

The holes had to be drilled with hand held tools as the bed is large and unwieldy.

The pilot holes at 5mm and 7mm went well using HSS bits.

When the 10.5 mm HSS drill was tried in the first hole it smeared and raised a large burr on the surface, as well as wandering off centre by a good 3mm.

Edited By charadam on 29/06/2017 22:03:13

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.

[Martin ConnellyParticipant @martinconnelly55370]

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

[charadamParticipant @charadam]

"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).

[MuzzerParticipant @muzzer]

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

[John ReeseParticipant @johnreese12848]

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.

[John ReeseParticipant @johnreese12848]

An added note:

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

[MWParticipant @mw27036]

Posted by Muzzer on 20/07/2017 16:13:59:

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

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

Michael W

[charadamParticipant @charadam]

Deleted – posted in error.

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

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