On 23/04/2014 22:02, Stephen wrote:
On 23/04/2014 21:50, Nightjar wrote:
On 23/04/2014 21:03, Andrew Mawson wrote:
...
As far as I'm concerned after something like 56 years doing it (*) there
is:

'soldering' - using lead based filler or now the 'lead free' dreadful
stuff
'silver soldering' - using a silver bearing filler

Devil's Advocate Mode On

Continuation of Devil's advocate mode on :-)


You can get silver / tin soft solders. We used them for medical devices,
both because they did not contain lead and because the melting point was
high enough to resist autoclaving.

Incidentally most plumbers solder now is lead free (to prevent water
being contaminated by lead and people ingesting it....)

A very low probability that only is relevant in some areas. I grew up in
a house with lead pipes and a nice hard layer of deposits on the inside,
which isolated the lead from the water.

This is 96S silver solder which is 96% tin and 4% silver.... so
following your so called definition,

Not mine, Andrew's.

its not "soldering" as theres no
lead and and so plumbers are now "silver soldering" copper tube?

That was rather the point I was making about the soft solder we used for
medical devices.


Additionally copper tube is malleable (otherwise it would not bend with
a pipe bender/spring). yet you can buy half hard copper tube and this
stuff can be bent......


Devil's Advocate Mode Off

'brazing' - using a basically brass based filler

That, to me, is the difference between brazing and hard soldering or
silver soldering. The latter don't contain brass and have a white
colour, which makes them more cosmetically suitable for some jobs.

silver soldering is not a hard solder, you can use emery paper on it
easily.

I hope that, at some point, you will grasp the fact that the hardness of
the solder is not what defines hard soldering. It is simply a widely
accepted alternative name for brazing or for silver soldering. As I
said, I believe it derives from it being a technique for joining hard
metals and that is also a loose definition, which does not actually need
them to be hard.

Colin Bignell

On 23/04/2014 21:36, Andrew Mawson wrote:
"Nightjar" wrote in message
...

On 23/04/2014 20:54, Stephen wrote:

You sound like an academic. In the real world, hard soldering and soft
soldering are well known and well understood terms. I suspect the
derivation has more to do with the metals that they are used on, than
the alloys used for joining them: another 'old fashioned' bit of
engineering terminology is to call people who work in steel hard metal
workers and those who work in copper alloys soft metal workers.


nope, not an academic... I'm a materials technologist.

That sounds like a very academic discipline to me.


Could just be the storeman who says 'nah - not EN8, I'd use a bit of
brass, mate '

Do I detect a certain amount of cynicism about modern job titles?

Colin Bignell

stanhvac1 wrote:
replying to meow2222 , stanhvac1 wrote:
meow2222 wrote:

No need to be snotty, the man's trying to help NT


Thank you. I don't guess he ever accidentaly mispelled a word, ie: typo.
Sometimes I don't hit the keys just right and fail to post the letter.
Anyway, this is not a spelling class, it's about trying to help someone
out.

AS far as I know mapp gas is not made any more, the new stuff is mapp
plus or some such thing and is slightly different.

On 23/04/2014 22:28, Andrew Mawson wrote:
"Stephen" wrote in message ...

Incidentally most plumbers solder now is lead free (to prevent water
being contaminated by lead and people ingesting it....)

Oh yes we know no pasty state for making wiped joints and it fails by
crystalisation if vibrated - dreadful stuff.

"pasty solders" are non-eutectic solders. They do not have a distinct
melting point as such but have whats called solidus and liquidus
temperatures. The pasty range sits between the solidus temperature and
the liquidus temperature.

Solders that have no "pasty" aspect to them have a very distinct melting
point and are called eutectic solders.

Another one to watch with lead-free solders is Tin Pest (which involves
allotropy) and Tin Whiskers....... I'll leave that for another day!


silver soldering is not a hard solder, you can use emery paper on it
easily.

Now where does emery sit on Moh's hardness scale ? 7-9 if my memory (as
a non materials scientist) serves, and diamond is 10 so pretty hard
isn't it !!!!!!!


Andrew

On Thu, 24 Apr 2014 07:15:44 +0100, Stephen wrote:

On 23/04/2014 22:28, Andrew Mawson wrote:
"Stephen" wrote in message ...

Incidentally most plumbers solder now is lead free (to prevent water
being contaminated by lead and people ingesting it....)

Oh yes we know no pasty state for making wiped joints and it fails by
crystalisation if vibrated - dreadful stuff.

"pasty solders" are non-eutectic solders. They do not have a distinct
melting point as such but have whats called solidus and liquidus
temperatures. The pasty range sits between the solidus temperature and
the liquidus temperature.

Solders that have no "pasty" aspect to them have a very distinct melting
point and are called eutectic solders.

Now we know the real reason why tin-lead was banned for water - it was panic
over the pasty tax.
--
Peter.
The gods will stay away
whilst religions hold sway

On Wed, 23 Apr 2014 21:29:38 +0100, Vir Campestris wrote:

On 23/04/2014 20:38, Fredxxx wrote:
On 23/04/2014 10:37, Huge wrote:
On 2014-04-23, Chris J Dixon wrote:
Nightjar wrote:

I think the Model 30 here was the device:

http://www.hswalsh.com/categories/micro-flame

It will be cheaper to keep replacing the kettles, if that is your only
use for it. :-)

Cheaper still to select a different kettle.

Quite possibly, but we do not select items simply on the single criterion
of cheapness.

One that has spots falling off hardly sounds value for money?

Ah, I hadn't realised the problem was an infection. It sounds a little
like leprosy, but I didn't know spots were one of the symptoms

Andy

Only in Dalmatia.
--
Peter.
The gods will stay away
whilst religions hold sway

"Nightjar" wrote in message
...



nope, not an academic... I'm a materials technologist.

That sounds like a very academic discipline to me.


Could just be the storeman who says 'nah - not EN8, I'd use a bit of
brass, mate '

Do I detect a certain amount of cynicism about modern job titles?

Colin Bignell


Oh yes !
It started when Dustmen became 'Cleansing Operatives' then arty farty types
get together for 'workshops' and countless other examples of avoiding
calling a spade a spade

Andrew

"Stephen" wrote in message ...

On 23/04/2014 22:28, Andrew Mawson wrote:
"Stephen" wrote in message ...

Incidentally most plumbers solder now is lead free (to prevent water
being contaminated by lead and people ingesting it....)

Oh yes we know no pasty state for making wiped joints and it fails by
crystalisation if vibrated - dreadful stuff.

"pasty solders" are non-eutectic solders. They do not have a distinct
melting point as such but have whats called solidus and liquidus
temperatures. The pasty range sits between the solidus temperature and the
liquidus temperature.

Yes we actually know this, but are using terms others can be familiar with.

I echo Collins comments about lead pipes. Lead oxide, as you will
undoubtedly know as a Materials Technologist, in pretty well insoluble in
water. Lead nitrate and lead acetate are the only two salts of lead that are
soluble, so you need a particular type of water containing other trace
elements to cause a problem.

Like Colin I was brought up in a house, as were most people a few years
back, that was supplied with water through lead pipes. Though I accept you
could advance the argument that I'm as I am 'cos of this

Andrew

On 22/04/2014 23:47, Cursitor Doom wrote:
Sometimes I need to join a couple of pieces of metal that are too much
for solder yet too delicate for arc welding. For those odd times,
brazing would be useful, but the standard propane torch I use for
plumbing is hopeless; the flame just isn't precise enough.
Can anyone recommend a brazing torch that would meet my requirements?
Something I could find in BnQ ideally. And should I be using propane,
butane, or some other gas? The 'metal' concerned is typically some
form of steel - mild, stainless, HT or HSS.

Cheers,

cd.

I used to get told off by Welding Instructors ... and told the correct
term is bronze welding

--
UK SelfBuild: http://uk.groups.yahoo.com/group/UK_Selfbuild/

On 24/04/2014 08:20, Andrew Mawson wrote:
"Stephen" wrote in message ...

On 23/04/2014 22:28, Andrew Mawson wrote:
"Stephen" wrote in message ...

Incidentally most plumbers solder now is lead free (to prevent water
being contaminated by lead and people ingesting it....)

Oh yes we know no pasty state for making wiped joints and it fails by
crystalisation if vibrated - dreadful stuff.

"pasty solders" are non-eutectic solders. They do not have a distinct
melting point as such but have whats called solidus and liquidus
temperatures. The pasty range sits between the solidus temperature and
the liquidus temperature.

Yes we actually know this, but are using terms others can be familiar with.

I echo Collins comments about lead pipes. Lead oxide, as you will
undoubtedly know as a Materials Technologist, in pretty well insoluble
in water. Lead nitrate and lead acetate are the only two salts of lead
that are soluble, so you need a particular type of water containing
other trace elements to cause a problem.

Like Colin I was brought up in a house, as were most people a few years
back, that was supplied with water through lead pipes. Though I accept
you could advance the argument that I'm as I am 'cos of this

Here in the south east (hard water) lead was pretty much a non issue.
Any pipe you cut open had nice orange or yellow oxide coating on the
inside so that the water never contacted the lead!



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 24/04/2014 20:46, mike wrote:
On Thu, 24 Apr 2014 19:55:49 +0100, Rick Hughes
wrote:

On 22/04/2014 23:47, Cursitor Doom wrote:
Sometimes I need to join a couple of pieces of metal that are too much
for solder yet too delicate for arc welding. For those odd times,
brazing would be useful, but the standard propane torch I use for
plumbing is hopeless; the flame just isn't precise enough.
Can anyone recommend a brazing torch that would meet my requirements?
Something I could find in BnQ ideally. And should I be using propane,
butane, or some other gas? The 'metal' concerned is typically some
form of steel - mild, stainless, HT or HSS.

Cheers,

cd.

I used to get told off by Welding Instructors ... and told the correct
term is bronze welding

Told off! Good grief, they needed something to do. Nothing wrong with
"brazing", like 99% of the diy world would understand it anyway. (No I
havn't done a survey) :-)


Yes, brazing is a universally understood generic term. But it also
happens to be a specific process too, one which has been completely
superseded by silver soldering.

In article , Andrew Mawson
scribeth thus
"Nightjar" wrote in message
m...



nope, not an academic... I'm a materials technologist.

That sounds like a very academic discipline to me.


Could just be the storeman who says 'nah - not EN8, I'd use a bit of
brass, mate '

Do I detect a certain amount of cynicism about modern job titles?

Colin Bignell


Oh yes !
It started when Dustmen became 'Cleansing Operatives' then arty farty types
get together for 'workshops' and countless other examples of avoiding
calling a spade a spade

Noo!,

Thats an "Earth inverting horticultural implement" !

And what's wrong with calling my missus the,

.... "Comestible procurement executive" ...



--
Tony Sayer

In article , Andrew Mawson
scribeth thus
"Nightjar" wrote in message
m...

On 23/04/2014 17:55, Stephen wrote:
On 23/04/2014 08:38, Nightjar wrote:
On 23/04/2014 07:03, Stephen wrote:
...
The only difference between soldering and brazing is that if the
temperature of the joining process is below 450°C its called soldering.
If the temperature is above 450°C, its called brazing....

Hardness or softeness does not come into it....

Apart, of course, from the fact that hard soldering is a common
alternative name for brazing (aka silver soldering, particularly when
non-copper alloys are used).

well "hard soldering" may well be the old fashioned name for brazing but
I can assure you that the difference between brazing and soldering
relates to the process temperature rather than the hardness of the
filler metal.


You sound like an academic. In the real world, hard soldering and soft
soldering are well known and well understood terms. I suspect the
derivation has more to do with the metals that they are used on, than the
alloys used for joining them: another 'old fashioned' bit of engineering
terminology is to call people who work in steel hard metal workers and
those who work in copper alloys soft metal workers.

Colin Bignell

Stephen,

I endorse Colin's comments. I find it is frequently the case that academic
teachings are a world away from every day life. It is necessary to use terms
in this context that will be understood by the vast majority of people
actually experienced and 'hands on' in industry.

As far as I'm concerned after something like 56 years doing it (*) there is:

'soldering' - using lead based filler or now the 'lead free' dreadful stuff
'silver soldering' - using a silver bearing filler
'brazing' - using a basically brass based filler


'welding' - using any filler compatible with the metals being welded

Shouldn't that really have "Ferric" in it somewhere;?...


These terms will be fully understood by most who have actually 'been there
and worn the tee shirt' but they may not sit easily with teaching on a
material sciences course

Andrew

(* my first soldering was using a copper bit heated on the gas ring making a
crystal set when I was 9, and yes it did work )

Close to an MF TX then as mine didn't;(..



--
Tony Sayer

On 24/04/2014 21:38, tony sayer wrote:
....
'welding' - using any filler compatible with the metals being welded

Shouldn't that really have "Ferric" in it somewhere;?...

Not if you are welding aluminium, or titanium or plastic.

To follow the theme of this thread, we could also mention friction
welding, which is actually a type of forging.

Colin Bignell

"tony sayer" wrote in message ...

'welding' - using any filler compatible with the metals being welded

Shouldn't that really have "Ferric" in it somewhere;?...



No, virtually all metals can be welded. Aluminium is very commonly. Lead can
be welded, but the accepted term is 'lead burning' despite the fact you try
to avoid it oxidising! Disimilar metals can, and are commonly welded, the
wires of a thermocouple being a common example. (Though no filler is used
usually).

I actually managed to spot weld brass mesh to galvanised sheet in a recent
project, and it was surprisingly successful.

Andrew

On 24/04/2014 08:08, Andrew Mawson wrote:
"Nightjar" wrote in message
...



nope, not an academic... I'm a materials technologist.

That sounds like a very academic discipline to me.


Could just be the storeman who says 'nah - not EN8, I'd use a bit of
brass, mate '

Do I detect a certain amount of cynicism about modern job titles?



Oh yes !
It started when Dustmen became 'Cleansing Operatives' then arty farty
types get together for 'workshops' and countless other examples of
avoiding calling a spade a spade

I don't think that is considered politically correct these days. :-)

Colin Bignell

On 25/04/2014 07:56, Andrew Mawson wrote:
"tony sayer" wrote in message ...

'welding' - using any filler compatible with the metals being welded

Shouldn't that really have "Ferric" in it somewhere;?...



No, virtually all metals can be welded. Aluminium is very commonly.

Aluminium forms a very tenacious nanometres thick aluminium oxide
(Al2O3) layer on the surface. You need to remove and prevent the
formation of this Al2O3 layer in order to succeed in welding it.

Titanium can be difficult to weld and so is stainless steels.


Lead
can be welded, but the accepted term is 'lead burning' despite the fact
you try to avoid it oxidising! Disimilar metals can, and are commonly
welded, the wires of a thermocouple being a common example. (Though no
filler is used usually).

Thermocouple junctions are in fact created using electrodischarge
welding. You charge up a capacitor bank to a couple of hundred volts,
attach one of the thermocouple wires to one end of teh capacitor, the
other wire is attached to the other end of of the capacitor. The other
two ends of the two wires are then brought together and allowed to make
contact. This results in a sudden discharge of the capacitor, with a
nice big fat spark and the two wires then spot weld forming the
thermoelectric junction.


I actually managed to spot weld brass mesh to galvanised sheet in a
recent project, and it was surprisingly successful.

Andrew

On 25/04/2014 08:18, Stephen wrote:
On 25/04/2014 07:56, Andrew Mawson wrote:
"tony sayer" wrote in message ...

'welding' - using any filler compatible with the metals being welded

Shouldn't that really have "Ferric" in it somewhere;?...



No, virtually all metals can be welded. Aluminium is very commonly.

Aluminium forms a very tenacious nanometres thick aluminium oxide
(Al2O3) layer on the surface. You need to remove and prevent the
formation of this Al2O3 layer in order to succeed in welding it...

Which does not stop it being a commonly used technique. There was lots
of aluminium being welded when I walked around the QE2 while she was
building and the very successful American M113 APC, which dates back
more than half a century, uses welded rolled aluminium armour.

Colin Bignell

"Stephen" wrote in message ...

On 25/04/2014 07:56, Andrew Mawson wrote:

Thermocouple junctions are in fact created using electrodischarge welding.
You charge up a capacitor bank to a couple of hundred volts, attach one of
the thermocouple wires to one end of teh capacitor, the other wire is
attached to the other end of of the capacitor. The other two ends of the
two wires are then brought together and allowed to make contact. This
results in a sudden discharge of the capacitor, with a nice big fat spark
and the two wires then spot weld forming the thermoelectric junction.

Well I've done them by spark discharge of a capacitor in the past, but tend
now to use oxy-acetylene nowadays as you can form a much neater end.

Andrew

In article ,
"Andrew Mawson" writes:
"tony sayer" wrote in message ...

'welding' - using any filler compatible with the metals being welded

Shouldn't that really have "Ferric" in it somewhere;?...



No, virtually all metals can be welded. Aluminium is very commonly. Lead can
be welded, but the accepted term is 'lead burning' despite the fact you try
to avoid it oxidising! Disimilar metals can, and are commonly welded, the
wires of a thermocouple being a common example. (Though no filler is used
usually).

I actually managed to spot weld brass mesh to galvanised sheet in a recent
project, and it was surprisingly successful.

How easy is ni-chrome wire to spot-weld?
I often find myself repairing toasters from around the family and
friends, and I currently crimp it with small high temperature crimps,
but I keep thinking about getting a spot welder (not just for this;-).
I presume you would have to do a few spot-welds in parallel, so that
one didn't become a hot-spot when the element is running?

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

"Nightjar" wrote in message
...

On 25/04/2014 08:18, Stephen wrote:
On 25/04/2014 07:56, Andrew Mawson wrote:
"tony sayer" wrote in message ...

'welding' - using any filler compatible with the metals being welded

Shouldn't that really have "Ferric" in it somewhere;?...



No, virtually all metals can be welded. Aluminium is very commonly.

Aluminium forms a very tenacious nanometres thick aluminium oxide
(Al2O3) layer on the surface. You need to remove and prevent the
formation of this Al2O3 layer in order to succeed in welding it...

Which does not stop it being a commonly used technique. There was lots of
aluminium being welded when I walked around the QE2 while she was building
and the very successful American M113 APC, which dates back more than half
a century, uses welded rolled aluminium armour.

Colin Bignell

Colin,

I didn't know that you had been involved in the QE2 ! We (Ferranti) had an
Argus 400 process control computer (*) on board monitoring the turbines
following that initial problem that they had with them. It was always a sort
after call out when she docked at Southampton, as if a job was unfinished
before she left you HAD to sail with her - great hardship

Andrew

(* lots of thermocouples there Stephen along with isothermal planes for the
interfaces )

"Andrew Gabriel" wrote in message ...



How easy is ni-chrome wire to spot-weld?
I often find myself repairing toasters from around the family and
friends, and I currently crimp it with small high temperature crimps,
but I keep thinking about getting a spot welder (not just for this;-).
I presume you would have to do a few spot-welds in parallel, so that
one didn't become a hot-spot when the element is running?


The problem with Ni-Chrome wire is that it gets very brittle in use.
Example - the old radiant 1kW heater elements could easily be unwound and
re-deployed before use. Get one that's been in service for a while and the
wire will break as you unwind it. Not sure why this is as it is being
annealed every time it's switched on. Perhaps out Material Technologist
friend can expound on this curiosity? I expect its an oxidisation effect.

So coming to the point of your question, clean soft ni-chrome can easily be
spot welded. A used toaster element may be more of a challenge as the
surface needs cleaning, and the spot welding pressure will reduce the cross
section and form a 'hot spot' in use.

Andrew

On 25/04/2014 09:42, Andrew Mawson wrote:
"Nightjar" wrote in message
...

On 25/04/2014 08:18, Stephen wrote:
On 25/04/2014 07:56, Andrew Mawson wrote:
"tony sayer" wrote in message ...

'welding' - using any filler compatible with the metals being welded

Shouldn't that really have "Ferric" in it somewhere;?...



No, virtually all metals can be welded. Aluminium is very commonly.

Aluminium forms a very tenacious nanometres thick aluminium oxide
(Al2O3) layer on the surface. You need to remove and prevent the
formation of this Al2O3 layer in order to succeed in welding it...

Which does not stop it being a commonly used technique. There was lots
of aluminium being welded when I walked around the QE2 while she was
building and the very successful American M113 APC, which dates back
more than half a century, uses welded rolled aluminium armour.


Colin,

I didn't know that you had been involved in the QE2!

I wasn't actually involved with building the ship, but Glasgow
University had close links with the shipyards and, as a member of the GU
Engineering Society, I was one of the only group allowed aboard her
during building. We also got to go around when she was finished and open
to the general public, but she looked a lot smaller inside once all the
furnishings were in.

We (Ferranti) had
an Argus 400 process control computer (*) on board monitoring the
turbines following that initial problem that they had with them. It was
always a sort after call out when she docked at Southampton, as if a job
was unfinished before she left you HAD to sail with her - great hardship

I'll bet.



(* lots of thermocouples there Stephen along with isothermal planes for
the interfaces )

:-)

Colin

On 25/04/2014 10:26, Nightjar wrote:


We (Ferranti) had
an Argus 400 process control computer (*) on board monitoring the
turbines following that initial problem that they had with them. It was
always a sort after call out when she docked at Southampton, as if a job
was unfinished before she left you HAD to sail with her - great
hardship

I'll bet.


An old mate of mine gets out on trips on the new cruise ships with
podded propulsion systems, to monitor their tribology problems.

In article ,
"Andrew Mawson" writes:
"Andrew Gabriel" wrote in message ...



How easy is ni-chrome wire to spot-weld?
I often find myself repairing toasters from around the family and
friends, and I currently crimp it with small high temperature crimps,
but I keep thinking about getting a spot welder (not just for this;-).
I presume you would have to do a few spot-welds in parallel, so that
one didn't become a hot-spot when the element is running?


The problem with Ni-Chrome wire is that it gets very brittle in use.
Example - the old radiant 1kW heater elements could easily be unwound and
re-deployed before use. Get one that's been in service for a while and the
wire will break as you unwind it. Not sure why this is as it is being
annealed every time it's switched on. Perhaps out Material Technologist
friend can expound on this curiosity? I expect its an oxidisation effect.

So coming to the point of your question, clean soft ni-chrome can easily be
spot welded. A used toaster element may be more of a challenge as the
surface needs cleaning, and the spot welding pressure will reduce the cross
section and form a 'hot spot' in use.

Thanks.
Toaster elements are almost always a ribbon rather than circular profile
wire. I'm always careful bending it, but it seems to bend across the
ribbon just fine. I scrape the surface shiny where it will make contact
in the crimp.

BTW, I'm assuming it's ni-chrome, but I could be wrong.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article ,
Nightjar wrote:
Aluminium forms a very tenacious nanometres thick aluminium oxide
(Al2O3) layer on the surface. You need to remove and prevent the
formation of this Al2O3 layer in order to succeed in welding it...

Which does not stop it being a commonly used technique. There was lots
of aluminium being welded when I walked around the QE2 while she was
building and the very successful American M113 APC, which dates back
more than half a century, uses welded rolled aluminium armour.

I've MIG welded ally at home successfully. It wasn't a critical weld, but
works and looks ok. Use a stainless steel wire brush to clean it just
before welding.

--
*I'll try being nicer if you'll try being smarter

Dave Plowman London SW
To e-mail, change noise into sound.

On 25/04/2014 10:43, Dave Plowman (News) wrote:
In article ,
Nightjar wrote:
Aluminium forms a very tenacious nanometres thick aluminium oxide
(Al2O3) layer on the surface. You need to remove and prevent the
formation of this Al2O3 layer in order to succeed in welding it...

Which does not stop it being a commonly used technique. There was lots
of aluminium being welded when I walked around the QE2 while she was
building and the very successful American M113 APC, which dates back
more than half a century, uses welded rolled aluminium armour.

I've MIG welded ally at home successfully. It wasn't a critical weld, but
works and looks ok. Use a stainless steel wire brush to clean it just
before welding.

The use of inert gas helps to shield the now newly exposed aluminium
from oxygen thus preventing the formation of the Al203 layer.

Incidentally, pure aluminium is actually extremely reactive. It is this
oxide layer that makes aluminium appear to be sd passive chemically
speaking.

On 25/04/2014 10:38, Andrew Gabriel wrote:
In article ,
"Andrew Mawson" writes:
"Andrew Gabriel" wrote in message ...



How easy is ni-chrome wire to spot-weld?
I often find myself repairing toasters from around the family and
friends, and I currently crimp it with small high temperature crimps,
but I keep thinking about getting a spot welder (not just for this;-).
I presume you would have to do a few spot-welds in parallel, so that
one didn't become a hot-spot when the element is running?


The problem with Ni-Chrome wire is that it gets very brittle in use.
Example - the old radiant 1kW heater elements could easily be unwound and
re-deployed before use. Get one that's been in service for a while and the
wire will break as you unwind it. Not sure why this is as it is being
annealed every time it's switched on. Perhaps out Material Technologist
friend can expound on this curiosity? I expect its an oxidisation effect.

So coming to the point of your question, clean soft ni-chrome can easily be
spot welded. A used toaster element may be more of a challenge as the
surface needs cleaning, and the spot welding pressure will reduce the cross
section and form a 'hot spot' in use.

Thanks.
Toaster elements are almost always a ribbon rather than circular profile
wire. I'm always careful bending it, but it seems to bend across the
ribbon just fine. I scrape the surface shiny where it will make contact
in the crimp.

BTW, I'm assuming it's ni-chrome, but I could be wrong.


it could be Kanthal or cupronickel instead.

On 25/04/2014 10:38, newshound wrote:
On 25/04/2014 10:26, Nightjar wrote:


We (Ferranti) had
an Argus 400 process control computer (*) on board monitoring the
turbines following that initial problem that they had with them. It was
always a sort after call out when she docked at Southampton, as if a job
was unfinished before she left you HAD to sail with her - great
hardship

I'll bet.


An old mate of mine gets out on trips on the new cruise ships with
podded propulsion systems, to monitor their tribology problems.

I must get new glasses. I read trilobyte.

Colin Bignell

In article ,
Stephen writes:
On 25/04/2014 10:43, Dave Plowman (News) wrote:
In article ,
Nightjar wrote:
Aluminium forms a very tenacious nanometres thick aluminium oxide
(Al2O3) layer on the surface. You need to remove and prevent the
formation of this Al2O3 layer in order to succeed in welding it...

Which does not stop it being a commonly used technique. There was lots
of aluminium being welded when I walked around the QE2 while she was
building and the very successful American M113 APC, which dates back
more than half a century, uses welded rolled aluminium armour.

I've MIG welded ally at home successfully. It wasn't a critical weld, but
works and looks ok. Use a stainless steel wire brush to clean it just
before welding.

The use of inert gas helps to shield the now newly exposed aluminium
from oxygen thus preventing the formation of the Al203 layer.

Incidentally, pure aluminium is actually extremely reactive. It is this
oxide layer that makes aluminium appear to be sd passive chemically
speaking.

and it's hard and a good insulator.

I was breadboarding a circuit on the bench which used a pair of power
MOSFETs to switch a mains heating load. I temporarily used a bulldog
clip to hold the MOSFET onto a piece of aluminium for a heatsink,
making a mental note not to touch the live heatsink. Circuit was
working OK so far, and I added the second MOSFET, also clipped onto
same piece of aluminium. All worked OK.

As I was disassembling it to build the final unit, which had proper
insulating kits between the MOSFETs and the heatsink, it suddenly
occured to me that the two MOSFETs actually had 240VAC between their
heatsink tabs, and it was only the aluminium oxide layer which had
stopped them going bang during the breadboarding.

This can also be an issue when you are trying to make an earth
connection to an aluminium case.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 25/04/2014 11:25, Andrew Gabriel wrote:
In article ,
Stephen writes:
On 25/04/2014 10:43, Dave Plowman (News) wrote:
In article ,
Nightjar wrote:
Aluminium forms a very tenacious nanometres thick aluminium oxide
(Al2O3) layer on the surface. You need to remove and prevent the
formation of this Al2O3 layer in order to succeed in welding it...

Which does not stop it being a commonly used technique. There was lots
of aluminium being welded when I walked around the QE2 while she was
building and the very successful American M113 APC, which dates back
more than half a century, uses welded rolled aluminium armour.

I've MIG welded ally at home successfully. It wasn't a critical weld, but
works and looks ok. Use a stainless steel wire brush to clean it just
before welding.

The use of inert gas helps to shield the now newly exposed aluminium
from oxygen thus preventing the formation of the Al203 layer.

Incidentally, pure aluminium is actually extremely reactive. It is this
oxide layer that makes aluminium appear to be sd passive chemically
speaking.

and it's hard and a good insulator.

I was breadboarding a circuit on the bench which used a pair of power
MOSFETs to switch a mains heating load. I temporarily used a bulldog
clip to hold the MOSFET onto a piece of aluminium for a heatsink,
making a mental note not to touch the live heatsink. Circuit was
working OK so far, and I added the second MOSFET, also clipped onto
same piece of aluminium. All worked OK.

As I was disassembling it to build the final unit, which had proper
insulating kits between the MOSFETs and the heatsink, it suddenly
occured to me that the two MOSFETs actually had 240VAC between their
heatsink tabs, and it was only the aluminium oxide layer which had
stopped them going bang during the breadboarding.

This can also be an issue when you are trying to make an earth
connection to an aluminium case.



yes that Al2O3 is also known as alumina, which is a ceramic.... and
ceramics are hard and electrically insulating materials as well as
chemically inert......

On 25/04/2014 11:40, Stephen wrote:
On 25/04/2014 11:25, Andrew Gabriel wrote:
....
and it's hard and a good insulator.

I was breadboarding a circuit on the bench which used a pair of power
MOSFETs to switch a mains heating load. I temporarily used a bulldog
clip to hold the MOSFET onto a piece of aluminium for a heatsink,
making a mental note not to touch the live heatsink. Circuit was
working OK so far, and I added the second MOSFET, also clipped onto
same piece of aluminium. All worked OK.

As I was disassembling it to build the final unit, which had proper
insulating kits between the MOSFETs and the heatsink, it suddenly
occured to me that the two MOSFETs actually had 240VAC between their
heatsink tabs, and it was only the aluminium oxide layer which had
stopped them going bang during the breadboarding.

This can also be an issue when you are trying to make an earth
connection to an aluminium case.


yes that Al2O3 is also known as alumina, which is a ceramic.... and
ceramics are hard and electrically insulating materials as well as
chemically inert......

Why do I have this mental image of a grandmother with a basket of eggs?

Colin Bignell

On 25/04/2014 08:18, Stephen wrote:

No, virtually all metals can be welded. Aluminium is very commonly.

Aluminium forms a very tenacious nanometres thick aluminium oxide
(Al2O3) layer on the surface. You need to remove and prevent the
formation of this Al2O3 layer in order to succeed in welding it.

And despite this aluminium is still very commonly welded - normally TIG
I believe.

In article , Nightjar
scribeth thus
On 24/04/2014 21:38, tony sayer wrote:
...
'welding' - using any filler compatible with the metals being welded

Shouldn't that really have "Ferric" in it somewhere;?...

Not if you are welding aluminium, or titanium or plastic.

To follow the theme of this thread, we could also mention friction
welding, which is actually a type of forging.

Colin Bignell


Ah!, Well thats what the hoi polli will assume when "welding" is
mentioned in most circles;-!...

--
Tony Sayer

On 25/04/2014 09:42, Andrew Mawson wrote:

I didn't know that you had been involved in the QE2 ! We (Ferranti) had
an Argus 400 process control computer (*) on board monitoring the
turbines following that initial problem that they had with them. It was
always a sort after call out when she docked at Southampton, as if a job
was unfinished before she left you HAD to sail with her - great hardship

Were they the engines which subsequently got replaced by 9 MAN diesels?

"Clive George" wrote in message
o.uk...

On 25/04/2014 09:42, Andrew Mawson wrote:

I didn't know that you had been involved in the QE2 ! We (Ferranti) had
an Argus 400 process control computer (*) on board monitoring the
turbines following that initial problem that they had with them. It was
always a sort after call out when she docked at Southampton, as if a job
was unfinished before she left you HAD to sail with her - great hardship


Were they the engines which subsequently got replaced by 9 MAN diesels?

My memory is a bit hazy after all these years but iirc the original turbines
had problems on the first few voyages due to uneven expansion and the system
monitored those engines at a vast number of points so that they could ensure
the situation didn't get out of hand. I have no knowledge regarding their
replacement by Mann diesels but wiki tells me that happened in 1986 which
makes me feel even older

some more info he

http://trid.trb.org/view.aspx?id=1311

In article ,
Andrew Gabriel wrote:
Incidentally, pure aluminium is actually extremely reactive. It is this
oxide layer that makes aluminium appear to be sd passive chemically
speaking.

and it's hard and a good insulator.

I was breadboarding a circuit on the bench which used a pair of power
MOSFETs to switch a mains heating load. I temporarily used a bulldog
clip to hold the MOSFET onto a piece of aluminium for a heatsink,
making a mental note not to touch the live heatsink. Circuit was
working OK so far, and I added the second MOSFET, also clipped onto
same piece of aluminium. All worked OK.

As I was disassembling it to build the final unit, which had proper
insulating kits between the MOSFETs and the heatsink, it suddenly
occured to me that the two MOSFETs actually had 240VAC between their
heatsink tabs, and it was only the aluminium oxide layer which had
stopped them going bang during the breadboarding.


I've just taken a bit of 1/4" plate ally from the scrap box and measured
it with the sides of the meter probes gently applied. Reads a dead short.
;-)

--
*Red meat is not bad for you. Fuzzy green meat is bad for you.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Clive George wrote:
Aluminium forms a very tenacious nanometres thick aluminium oxide
(Al2O3) layer on the surface. You need to remove and prevent the
formation of this Al2O3 layer in order to succeed in welding it.

And despite this aluminium is still very commonly welded - normally TIG
I believe.

Argon arc was the first common way. A MIG will work too.

--
*If horrific means to make horrible, does terrific mean to make terrible?

Dave Plowman London SW
To e-mail, change noise into sound.

There is also a very primitive form of welding which basically
involves beating the living **** out of two bits of metal until they
have no alternative but to fuse together. You don't need a filler for
this process; just arms like Popeye.

"Cursitor Doom" wrote in message
...

There is also a very primitive form of welding which basically
involves beating the living **** out of two bits of metal until they
have no alternative but to fuse together. You don't need a filler for
this process; just arms like Popeye.


It's called 'Hammer Welding'. Heat to white heat, sprinkle silver sand on
one piece as a flux, overlay them, then working from one end hammer them
into fusion progressively working to the other end. This forces the slag out
of the join keeping inclusions to a minimum.

I have a Blacksmiths Power Hammer, which is brilliant for this, and also
drawing down large sections. However as part of my major clear out the Power
Hammer will be featuring on eBay when I can get close enough to take photos


Another process that is largely similar is 'explosive welding'. The two
metals are forced together literally by means of an explosion. Often used to
fuse sheets of steel and aluminium as an interstitial layer between two
parts of a structure to avoid electrolytic corrosion. Many modern warships
have a steel lower hull and aluminium upper works, and use this bimetal to
make the union.

Andrew