[TheForge] Bush Hog Blades 5160 vs S7

[David E. Smucker]

It is easy to judge the difference between 5160 and S7 if you think that 
these are the only two steel an item might be.  5160 is an oil hardening 
steel and S7 is air hardening.  Take a sample of the steel, 1/2 to 3/4 inch 
in dia. or square and heat it to above critical.  For S7 this 1750 F, so it 
is above an orange color.  5160 critical is lower but you need to heat the 
sample as if it is S7 since that is the higher temperature.  Now take the 
hot steel and set it on a fire brick or the edge of you forge and just let 
it air cool.

If it is 5160 or a similar oil hardening steel it will be hard but you 
should still be able to "cut it with a new file".  It will not file easily 
but it will just cut.  If it is S7 it will as my Dad use to say, "harder 
than a whore's heart".  It will not cut or grab with a brand new sharp 
file -- the file will just skate on the steel.  The best way to learn this 
test it to do it with some known material.  Some purchased S7 and a cut for 
a truck leaf spring for example.  Then you can run a similar test any time 
you want.

You should also be aware that many of the oil hardening steel will still get 
hard enough with an air quench to be rather hard.  I know, having worked 
some 4340 in the forge, let it air cool and then proceeding to take the 
teeth off my band saw blade trying to cut it.  That is what the chop saw is 
for or hot cut hardie.

I would by the way be surprised (I am surprised all the time) to find bush 
hog blades of S7.  S7 is too expensives for the application by my judgement.

Dave Smucker

----- Original Message ----- 
From: "David Childress" <trollkeep at gmail.com>
To: "Sponsored by ABANA" <theforge at mailman.qth.net>
Sent: Wednesday, October 04, 2006 10:23 AM
Subject: Re: [TheForge] Lawn Mower Blade also Bush Hog Blades


>A couple of years ago our club had several bush hog blades donated by
> the local International dealer.  He claimed they were S7.  I do not
> know how to tell for sure.
>
> David Childress
> Rocky Forge Blacksmith Guild
>
> On 10/4/06, David E. Smucker <davesmucker at hotmail.com> wrote:
>> > Speaking of which, what are bush hog blades? 5160?
>>
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