Heat treatment?

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The Medway Handyman

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Jul 4, 2012, 6:38:00 AM7/4/12
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I have a pry bar like this
http://www.wickes.co.uk/red-plastic-wallplugs/invt/167371/

No idea why the address says red plastic plugs :-)

Anywho, it's basically a piece of flat section steel strip bent to
shape, then heat treated [?] in some way so it stays that shape.

I want to make up something similar to assist with installing awnings.

I can get the steel strip, I can bend it to the shape I want - how do I
heat treat it?



--
Dave - The Medway Handyman www.medwayhandyman.co.uk

NT

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Jul 4, 2012, 6:40:06 AM7/4/12
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On Jul 4, 11:38 am, The Medway Handyman <davidl...@blueyonder.co.uk>
wrote:
> I have a pry bar like thishttp://www.wickes.co.uk/red-plastic-wallplugs/invt/167371/
>
> No idea why the address says red plastic plugs :-)
>
> Anywho, it's basically a piece of flat section steel strip bent to
> shape, then heat treated [?] in some way so it stays that shape.
>
> I want to make up something similar to assist with installing awnings.
>
> I can get the steel strip, I can bend it to the shape I want - how do I
> heat treat it?
>

Heat is excessively hot, drop into water to quench it. Heat it up
again to exactly the right temperature, which is determined by colour
changes on the metal, then drop it back in the water.


NT

Andrew Mawson

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Jul 4, 2012, 7:10:50 AM7/4/12
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"The Medway Handyman" wrote in message
news:f2VIr.476148$C_6.1...@fx28.am4...
>
>I have a pry bar like this
>http://www.wickes.co.uk/red-plastic-wallplugs/invt/167371/
>
>No idea why the address says red plastic plugs :-)
>
>Anywho, it's basically a piece of flat section steel strip bent to shape,
>then heat treated [?] in some way so it stays that shape.
>
>I want to make up something similar to assist with installing awnings.
>
>I can get the steel strip, I can bend it to the shape I want - how do I
>heat treat it?
>
>
>

It will be something somewhat stronger than mild steel, so wen you say you
can get the steel, are you sure? It needs probably to be an alloy steel (ie
chromium and molybdenum as well as carbon)

AWEM

Nick Odell

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Jul 4, 2012, 7:19:40 AM7/4/12
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On Wed, 04 Jul 2012 11:38:00 +0100, The Medway Handyman
<davi...@blueyonder.co.uk> wrote:

>I have a pry bar like this
>http://www.wickes.co.uk/red-plastic-wallplugs/invt/167371/
>
>No idea why the address says red plastic plugs :-)
>
>Anywho, it's basically a piece of flat section steel strip bent to
>shape, then heat treated [?] in some way so it stays that shape.
>
>I want to make up something similar to assist with installing awnings.
>
>I can get the steel strip, I can bend it to the shape I want - how do I
>heat treat it?

If you've got a piece of mild steel to begin with, at the end of the
treatment all you have is a piece of heat-treated mild steel. If you
have a piece of steel with a higher carbon content then you'll likely
break it before you bend it to shape. There are two possible ways out
of this.

One is to take your higher carbon steel and anneal it before you bend
it. Heat it up to cherry-red then let it cool slowly and it should be
more maleable; follow NTs heat treatment plan to get the hardness back
again.

The other is to use mild steel and case-harden it. An amateur way of
doing this without having to buy difficult-to-explain chemicals is to
shape it and bend it and hone it then heat it up to cherry red and
cover it up with flour (or some say sawdust) so the carbon produced
from the heat has a chance to bond into the surface of the steel as it
slowly cools. You might want to do this several times. Then follow the
NT heat treatment plan to temper it. This will never be as strong as
using high carbon steel but it will be slightly stronger overall than
untreated mild steel and the edges will be more resistant against wear
and tear.

We were taught to do this in O Level metalwork classes about 45 years
ago so my apologies if I may have misremembered details.

Nick

Nightjar

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Jul 4, 2012, 7:48:23 AM7/4/12
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On 04/07/2012 11:38, The Medway Handyman wrote:
> I have a pry bar like this
> http://www.wickes.co.uk/red-plastic-wallplugs/invt/167371/
>
> No idea why the address says red plastic plugs :-)
>
> Anywho, it's basically a piece of flat section steel strip bent to
> shape, then heat treated [?] in some way so it stays that shape.
>
> I want to make up something similar to assist with installing awnings.
>
> I can get the steel strip,

You need a medium carbon hardening steel - O1 ought to work and is
readily available from most steel stockists.

> I can bend it to the shape I want - how do I
> heat treat it?

If you don't already know, I recommend finding a company that does heat
treatment and getting them to do it for you. Tell them what you want to
use it for and they will sort out exactly what treatment it needs.

Colin Bignell


Nightjar

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Jul 4, 2012, 7:50:18 AM7/4/12
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It depends upon the steel. Some are oil hardening, rather than water
hardening.

Colin Bignell


John Rumm

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Jul 4, 2012, 9:00:23 AM7/4/12
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Do you not also need to maintain the temperature for a period of time
before quenching?


--
Cheers,

John.

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


Nightjar

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Jul 4, 2012, 9:25:11 AM7/4/12
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On 04/07/2012 14:00, John Rumm wrote:
> On 04/07/2012 12:50, Nightjar wrote:
>> On 04/07/2012 11:40, NT wrote:
>>> On Jul 4, 11:38 am, The Medway Handyman <davidl...@blueyonder.co.uk>
>>> wrote:
>>>> I have a pry bar like
>>>> thishttp://www.wickes.co.uk/red-plastic-wallplugs/invt/167371/
>>>>
>>>> No idea why the address says red plastic plugs :-)
>>>>
>>>> Anywho, it's basically a piece of flat section steel strip bent to
>>>> shape, then heat treated [?] in some way so it stays that shape.
>>>>
>>>> I want to make up something similar to assist with installing awnings.
>>>>
>>>> I can get the steel strip, I can bend it to the shape I want - how do I
>>>> heat treat it?
>>>>
>>>
>>> Heat is excessively hot, drop into water to quench it. Heat it up
>>> again to exactly the right temperature, which is determined by colour
>>> changes on the metal, then drop it back in the water.
>>
>> It depends upon the steel. Some are oil hardening, rather than water
>> hardening.

> Do you not also need to maintain the temperature for a period of time
> before quenching?

The important thing is to get all the steel to above the upper critical
temperature before quenching. If you heat to cherry red, which is only
just hot enough, then you do need to hold it there for a while, to allow
the heat to soak through. If you heat to yellow, then many pieces will
be hot enough right through to quench immediately.

Colin Bignell

newshound

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Jul 4, 2012, 9:45:15 AM7/4/12
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While none of the other posts are incorrect, you basically need steel
with a sufficiently high carbon content: mild steel will not do. (Case
hardening is fine for something like a cold chisel, but not for
something to resist bending like a pry bar, for which you need hardness
all the way through).

Amateur blacksmiths often start with material from scrap-yards, for
example drive shafts for round stock or leaf springs for flat stock (in
the good old days when everything had leaf springs).

If the Wickes pry bar is almost right but needs adjustment, you might
consider starting with one of these. Heat to red heat with a big propane
torch, using something like bricks or firebricks or vermiculite
insulation blocks (readily available on the net) to prevent heat loss.
When it's red hot you can forge it by hitting it with a hammer on an
anvil or something sufficiently solid, or even bend it in a vice. If you
let it cool slowly, it will end up "soft" like mild steel. Re-heat to
red heat and drop in water or oil and this will harden it. Very high
carbon stuff like chisels will end up brittle, you need to temper them.
Loads of info on the web about tempering. My guess is that you wouldn't
need to temper a pry bar but YMMV.

For something like a pry bar you can probably forge and then harden one
end while holding the other in your hand or at most a welding glove.
Only the really hot bit gets softened.

Know any friendly blacksmiths or metallurgy lecturers?

Olav M

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Jul 4, 2012, 10:22:45 AM7/4/12
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--
OlavM
Overlooking the Clyde where it meets the Sea
> You need a medium carbon hardening steel - O1 ought to work and is If you
> don't already know, I recommend finding a company that does heat treatment
> and getting them to do it for you. Tell them what you want to use it for
> and they will sort out exactly what treatment it needs.
>
> Colin Bignell
I agree totally, with above good advice.
I've made some of my own hand tools in the past, when training...eg. chisels
for wood and steel. These you Harden by heating cherry red, and quenching to
lock in the hard crystalline structure, Then you Temper by heating the
remote(from cutting edge) end in a (blacksmiths) furnace and watching the
colours of rainbow progress towards cutting edge. When your chosen colour
reaches cutting edge, quickly quench until COLD. Colour at cutting edge
decides hardness. From memory ..blue for steel, straw for wood, but look it
up. And clean up a line along tool using emery cloth, before tempering, so
you can see colours.
BUT none of this helps OP because you want the same hardness/tempering
throughout the bar, hence advice to go to a specialist is correct.
PS. Case hardening would not help you. The surface is made hard to resist
wear and abrasion but 20 thou below surface the old steel is still there.


Dave Baker

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Jul 4, 2012, 2:36:46 PM7/4/12
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The Medway Handyman wrote:
> I have a pry bar like this
> http://www.wickes.co.uk/red-plastic-wallplugs/invt/167371/
>
> No idea why the address says red plastic plugs :-)
>
> Anywho, it's basically a piece of flat section steel strip bent to
> shape, then heat treated [?] in some way so it stays that shape.
>
> I want to make up something similar to assist with installing awnings.
>
> I can get the steel strip, I can bend it to the shape I want - how do
> I heat treat it?

Pretty much answered already but some things have not been mentioned. Heat
treatment achieves two things.

1) It increases the tensile strength of steels that are designed to take it
by a factor of two or more.
2) It increases the hardness and durability of the steel by potentially an
order of magnitude.

However, you only need to do this if the component is too weak or too soft
in the untreated state which is obviously a function of the section
thickness and the loadings it will encounter and the type of steel you make
it from.

Ordinary mild steel only has a tensile strength of 30 tons/square inch or
so - no more than high tensile aluminium alloy and it can't be "through"
heat treated, only case hardened.

However even mild steel may suffice for your purpose if the loadings are low
and the steel doesn't need to be hardened because it's being used against
soft materials (you indicate plastic awnings).

Heat treatable steels contain higher levels of carbon and/or other alloying
elements to increase both strength and heat treatability. EN8 or EN16 are
common examples and ideal for general purpose low duty tool making. More
specialised alloy steels are stronger still.

http://www.westyorkssteel.com/carbon_and_alloy_steel.html

A pry bar, or a claw hammer for example, needs to be both strong and hard.
Mild steel would be useless for pulling nails out with any sort of service
life. However for what you intend to do, which is not completely clear, it
may suffice or perhaps a stronger grade of steel, still without heat
treatment, might.

uk.rec.models.engineering is where the people who can help you best tend to
lurk and someone will almost certainly have a strip of something lying about
that will do you nicely for a couple of beer tokens.
--
Dave Baker


Andy Burns

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Jul 5, 2012, 2:54:58 PM7/5/12
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The Medway Handyman wrote:

> I have a pry bar like this
> http://www.wickes.co.uk/red-plastic-wallplugs/invt/167371/
> No idea why the address says red plastic plugs :-)

It's all search engine optimisatiob bollox, the address could say
anything you like, and still work, e.g.

http://www.wickes.co.uk/blue-rubber-bananas/invt/167371/

Andy Dingley

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Jul 7, 2012, 6:32:08 AM7/7/12
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On Jul 4, 11:38 am, The Medway Handyman <davidl...@blueyonder.co.uk>
wrote:
> I can get the steel strip, I can bend it to the shape I want - how do I
> heat treat it?

Best thing is to get a 1950s textbook for either school metalwork
lessons, or else a better handbook for engineering apprentices. In the
1950s, pretty much everything possible was still at the level where it
could be understood by the DIY worker, and most of it could still be
done over the kitchen sink. It's a useful generation for practical
textbooks (unless they have numbers in, in which case you want a
metric / SI one).

Then fins the right piece of steel. You just can't heat treat most
steel, it needs to have an adequate carbon content before it will
respond. So forget random bits of steel, forget new mild steel,
forget case hardening. What you need is old leafspring, so find a van
or truck scrappie. Don't use coilsprings, those alloys are really
awkward to handle.

The usual process is to harden (make it too hard, pretty much as hard
as you can), then temper it (soften it in a more controlled manner, to
reduce brittleness).

You harden by heating and rapid cooling. Heating is a big gas
blowtorch, or a coal fire (charcoal won't have the heat, unless blown)
and then a quench by a rapid dunk into oil (old engine oil) or maybe
water (not IMHO, unless I'm making edged tools). Leave it in the
quench tank until cold enough to handle. BTW - oil may well ignite on
quenching, so use a big fireproof tank and have a lid ready to shut
over it and just leave it to its own devices. My tank is a big ammo
box. Heat until it reaches its Curie point - when a magnet on a bit
of coathanger wire stops being attracted to it - or just a bright red
is close enough for jazz. It needs to be hot throughout (at least on
the hard bits), but doesn't need to soak very long at this
temperature.

Quenching involves polishing the surface up afterwards, then gently
heating from the middle (softer) part of your tool and watching the
temper colours travel towards the brittle edges. When the right colour
gets there, then quench again (probably in water). The colour you want
is up to you and your uses - but blue or purple is about right for a
crowbar.

Afterwards, test before use. Also don't trust the thing (until you're
good at making them) and expect bits to chip and fly off. You really
do want eye protection here!

It's cheap to buy leafsprings, once you've found them. So get several
and make a number of tools. You'll break some to start with.

Otherwise (both better and simpler) is to have a blacksmith make it
for you, to order. Best of all is to apprentice to a smith for an
afternoon and make it yourself, under their supervision.

There are also a number of US cutlery books like "$50 knife shop" that
are cheap and useful.
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