By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale Jan 24th

A moan - steel of mysterious composition

All Topics | Latest Posts

Search for:  in Thread Title in  
charadam29/06/2017 21:58:54
182 forum posts
6 photos

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.

A cobalt bit was tried next with no more success.

An end mill did not succeed.

I finally touched up a carbide tipped masonry drill on the green wheel and got through. Luckily the job did not require precision!

I talked to the bed manufacturers' representative who told me that the steel is notorious for unpredictable properties in his industry.

Must have been slag or stainless inclusions or what?

 

 

 

 

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

Hacksaw29/06/2017 22:54:53
428 forum posts
173 photos

Bed iron ! Arghh ! Try drilling really slow using a hand brace,a new drill bit and lots of pressure....It's hard..

jason udall30/06/2017 08:52:18
2026 forum posts
41 photos
I find it very surprising that that every component isn't documented down to the batch /cast of the steel.
But maybe the manufacturer didn't feel like shareing with you.

That said more interesting might be the apparent variation of hardness across the section....

Work hardening would be my explanation.
I don't expect any possible effect of radiation but repeated stress might be an intresting essay

Edited By jason udall on 30/06/2017 08:54:54

larry Phelan30/06/2017 08:57:32
avatar
544 forum posts
17 photos

I remember trying to drill bed irons many years ago and it nearly broke my heart,not to mention many drills. I thought it would be cheaper than buying angle iron [since there was plenty of it around ] Now I know why it was left around.I found too that the only way to get through it was with a hand brace and plenty of push. Take good advice and stay well away from it,no wonder it ends up in scrapheaps !

S.D.L.30/06/2017 09:32:24
219 forum posts
37 photos
Posted by jason udall on 30/06/2017 08:52:18:
I find it very surprising that that every component isn't documented down to the batch /cast of the steel.
But maybe the manufacturer didn't feel like shareing with you.

That said more interesting might be the apparent variation of hardness across the section....

Work hardening would be my explanation.
I don't expect any possible effect of radiation but repeated stress might be an intresting essay

Edited By jason udall on 30/06/2017 08:54:54

Why would it be documented to that level?

Its an adjustable bed i would expect most of the parts to be mild steel, might be modern equivalent of EN3 or EN1

Steve

KWIL30/06/2017 09:51:45
3286 forum posts
63 photos

Maybe just "good commercial quality" which is the code for we do not know the grade nor care.

SillyOldDuffer30/06/2017 11:51:28
Moderator
6168 forum posts
1334 photos
Posted by larry Phelan on 30/06/2017 08:57:32:

I remember trying to drill bed irons many years ago and it nearly broke my heart,not to mention many drills.

...

I recall reading that a lot of bed-iron was made of recycled tram-line. Huge amounts of it were lifted as motor transport replaced trams and light railways in quarries and factories etc.

If true it certainly explains why bed-iron is notorious. Rail steel has always been carefully formulated to maximise durability, stiffness and strength. And unlike mild-steel, a slice of old railway line makes a decent anvil!

Probably not what Chardam's bed is made of though!  That might be some species of stainless.

Dave

Edited By SillyOldDuffer on 30/06/2017 11:53:00

charadam30/06/2017 11:55:35
182 forum posts
6 photos

This is a modern bed costing thousands.

The trunnion I was drilling is 13mm thick and I can't see any good reason for it to be anything other than bog standard MS.

I am told that the steel is manufactured in Poland, as is the bed.

Maybe there is a "special recipe" for bed steel but why go to what must be additional cost?

Hacksaw30/06/2017 12:07:30
428 forum posts
173 photos

The 1" angle that temporary road signs are made of.... that's similar stuff ... !!

I don't bother nicking ones left behind anymore angry

Beds might well work harden. Kids use them as trampolines, grown ups give them a pounding every night and twice on Sundays...laugh

Howard Lewis30/06/2017 13:19:43
3536 forum posts
2 photos

Many years ago, made a trailer from bed angle iron (he could get lot of it for free). The quality varied greatly, from good (in drilling terms) to appalling. The supposedly household names were often the worst!

Almost on a par with rebar!

Howard

SillyOldDuffer30/06/2017 13:23:02
Moderator
6168 forum posts
1334 photos
Posted by charadam on 30/06/2017 11:55:35:

This is a modern bed costing thousands.

The trunnion I was drilling is 13mm thick and I can't see any good reason for it to be anything other than bog standard MS.

I am told that the steel is manufactured in Poland, as is the bed.

Maybe there is a "special recipe" for bed steel but why go to what must be additional cost?

Just a guess Charadam but being a medical bed could explain why it might be made of stainless steel.

Your description reminds me of bad experiences with work-hardening stainless which I now avoid like the plague! First a sharp fast drill cuts OK. Then, moving up to a bigger drill, the cutting edge starts to rub and the stainless steel hardens. That blunts the drill and the steel gets even harder; hard enough to immediately blunt a new drill. As the horrible stuff only hardens around the edge of the hole you can get a sort of burr as the soft metal underneath deforms under tool pressure.

Dave

larry Phelan30/06/2017 14:46:28
avatar
544 forum posts
17 photos

I can see where this subject is heading !

I never knew bed irons were made from old tram tracks,you learn something new every day.

Stainless steel is something I seldom have to deal with,but I know most drills dont like it,neither do guillotines.

Must look closer at the beds next time I,m at my local hospital,will help to pass the time if nothing else.

charadam30/06/2017 14:57:37
182 forum posts
6 photos

Dave,

I think you've cracked it.

I never considered that it might be stainless, but the symptoms were as you describe.

But why would the choose stainless with all the added cost, special welding, etc. And then powder coat it.

I suppose it helps justify the price!

Martin Cargill30/06/2017 18:50:22
139 forum posts

The angle iron used in the manufacture of beds (in the old days) was a form of spring steel. Those of us familiar with the stuff will recollect how thin it was, given its purpose. It was good for repair / strengthening brackets because it was considerably thinner and it tended to have a tighter angle internal than the round corner of angle iron.

Martin

Ian Skeldon 230/06/2017 19:30:24
487 forum posts
37 photos

Hi Charadam,

The reason they make em out of stainless is because of the exposure to bodily fluids which have a very corrosive effect, especially if left on the metal surface for a few hours, also the bed needs to be cleaned very stringently again using chlorine based cleaning products which are also corrosive.

The finish coating, which as well as being more estheticaly pleasing is also much easier for NHS staff to keep clean.

If the finished coating were to becomes porus, the stainless frame will not fail and end up in a law suite, the mild steel one probably would.

Edited By Ian Skeldon 2 on 30/06/2017 19:36:51

Neil Wyatt30/06/2017 20:04:53
avatar
Moderator
18099 forum posts
713 photos
77 articles

Tell then young people of today that your bed was made of iron girders with steel springs and they just won't believe you.

Having dealt with the results of modern youngsters using a bed as a trampoline...

Neil

duncan webster30/06/2017 21:10:23
avatar
2732 forum posts
40 photos
Posted by Martin Cargill on 30/06/2017 18:50:22:

The angle iron used in the manufacture of beds (in the old days) was a form of spring steel. Those of us familiar with the stuff will recollect how thin it was, given its purpose. It was good for repair / strengthening brackets because it was considerably thinner and it tended to have a tighter angle internal than the round corner of angle iron.

Martin

Not a good idea to weld this stuff, the heat affected zone can be very brittle. Weld gives way spectacularly just when you don't want it to.

vintagengineer30/06/2017 21:28:24
avatar
468 forum posts
6 photos

It is probably low grade cheap and nasty mild steel. When they recycle cars now they shred the whole car and this goes off to be made into new non structural steel and it contains boron,nickel, chrome and all sorts of exotic material!

Some of the steel I get cannot be drilled after it has been forged and can even shatter. Unless you buy structural grade mild steel now, you can end up with any old crap in it!

 

Ordinary hospital beds are made from mild steel then plastic coated. They are made to a price not a quality.

Edited By vintagengineer on 30/06/2017 21:31:10

Rick Kirkland 101/07/2017 08:34:57
avatar
175 forum posts

Posted by vintagengineer on 30/06/2017 21:28:24:

It is probably low grade cheap and nasty mild steel. When they recycle cars now they shred the whole car and this goes off to be made into new non structural steel and it contains boron,nickel, chrome and all sorts of exotic material!

Some of the steel I get cannot be drilled after it has been forged and can even shatter. Unless you buy structural grade mild steel now, you can end up with any old crap in it!

Ordinary hospital beds are made from mild steel then plastic coated. They are made to a price not a quality.

Edited By vintagengineer on 30/06/2017 21:31:10 You possibly haven't read the bit on the first line at the top of the page stating "Fully adjustable Bariatric bed". In addition you possibly missed the post stating "This is a modern bed costing thousands". I refer you to the post by Ian Skelden2. It contains a factual account. I shall add that I have experienced these problems whilst doing trial mods to these beds several years ago. Keep the term "Bariatric" in mind when considering the bed construction.

Antony Powell01/07/2017 11:59:39
avatar
147 forum posts
19 photos

I come from family of steel makers.......modern steel unless a "special steel" has a very high recycled content which can be any metal or mix of metals contained within the scrap used therefore unless a "special steel" no record is kept of its content and can be made up of just about anything.......

Tony

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Latest Forum Posts
Support Our Partners
Eccentric July 5 2018
Warco
emcomachinetools
cowells
EngineDIY
ChesterUK
Eccentric Engineering
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest