How to heat small part

[MattH]

I need to harden a small turned part made out of silver steel.
The part is a short tube about an inch wide and three long.
I need to get it cherry red and then quench in water to harden it.

I only have a couple of handheld torches but I have a large propane bottle.
If I bought a propane torch to go on this bottle do you think it would be hot enough to heat the part?

 

[brightspark]

it will be well hot enough try and pick a second hand torch hose and regulator up they only normaly fetch 15 quid at bootsales

 

[ford34/2]

definatly YES, just did some bits just over a week ago used copper wire as the support to hold it. can you not borrow a torch off some one. Must be a Bristol member with propane torch. Even carbon pencils in the welder will heat that up. Any friendly garages with oxy or "blacksmith metalworkers" in the area.

Stan

 

[MattH]

Cheers for the replies guys. I'm not bothered about buying one, it'll be there the next time then
I've only seen this done with Oxy/act so I just wanted to check before any outlay.

 

[brightspark]

Cheers for the replies guys. I'm not bothered about buying one, it'll be there the next time then
I've only seen this done with Oxy/act so I just wanted to check before any outlay.

if u have small torches u can crush some grey breezeblock or firebricks up and pack it round the job and it will retain the heat

 

[hareng]

Propane that might take about 10mins to heat up depending on bore.

 

[scott0031]

You should quench in oil and not water.

 

[MattH]

You should quench in oil and not water.

I was under the impression that Silver Steel aka drill rod is a water hardening steel.

 

[optima21]

thought you should be ok for quencing in water, it produces a harder but more brittle part than quenching in oil though (or thats what I was told years ago). also to allow enough heat soak you should maintain the part at the hardening or tempering temperature for an hour per inch of thickness

 

[MattH]

None of this is super critical guys. It's a adapter sleeve to allow me to fit a power feed onto my Bridgport. The sleeve adapts the 5/8ths leadscrew journal to ride in the 24mm needle bearing of the power feed unit. I just want a hardened surface to ride against the needle bearing rollers.

 

[Bill Edwards]

Bricking it up with bricks that are safe to handle heat will make a vast difference, make it small, shove the torch so the tip of the cone is touching the piece and it won't take long, and you won't need a second torch.

I don't know about silver steel, but 'ordinary' stuff should be held at temperature and is in theory usually best done in oil.
But for rough work, it's normally just fine to heat until it's cherry then quench in water, it does for non critical applications.

You probably need to temper it afterwards though (I'm not talking about silver steel again though, so do check first) as anything that has been hardened may not withstand being inserted in place if it's a tight fit anywhere, untempered metal is extremely brittle.

 

[CRB]

?How do you quench evenly something like that? A thin walled long tube, something has to give, or distort.

Asking because I do not know, but would like to.

 

[brightspark]

plunge it in fast

 

[Maker]

TechnicAl, what's your word on quenching in oil or water?

 

[MattF]

Oil is used because it doesn't boil/flash off like water, so you don't end up with an irregular surface quench. Least that's what I was always told.

 

[Maker]

Oil is used because it doesn't boil/flash off like water, so you don't end up with an irregular surface quench. Least that's what I was always told.

I've heard all sorts of crap, including "use used engine oil because it contains more carbon which will get into the surface and increase the carbon content".

 

[TechnicAl]

TechnicAl, what's your word on quenching in oil or water?

MattF is right. Oil quenchs better than Water. It matters with some steels when they need to quench really quickly. I dont think silver steel falls into that category.
There are colloids (whatever they are) that are better than oil
PS its special oil not old engine oil,,,,,,,,,,I think

 

[Fastfingaz]

Piece that small you could probably do it in coals,, the ol fashion way!

 

[Screwdriver]

11:30 in. Chap hardens a cutting tool.

S.

 

[Maker]

There are colloids (whatever they are)

Is that the same as a colloid in paint - A very fine insoluble powder that stays suspended in a liquid?

This is from "Caxton engineering workshop practice"

"Quenching tanks. When steel tools and small parts are to be hardened by oil quenching, it is usual for the bath to comprise a metal tank containing water in the lower part and oil in the upper part. The steel is heated to its correct hardening temperature and then withdrawn from the furnace and slowly immersed in the upper oil layer, which, for tool hardening purposes, should be about 3" deep.
The part should go through the oil at a sufficiently slow speed to to cause the red-hot metal to "flare" the oil, and then lowered into the water beneath. The effect of the oil is to form a partly non-conducting layer on the surface of the steel so that it delays the cooling in the water. This results in a certain amount of tempering of the metal, which would not be obtained by quenching direct in water alone.
The temperature of the water will rise with repeated use, so that after a time it will become necessary to allow the water to cool. A better plan is to fit a tap so the warm water can be drawn off and replaced without agitating the oil by pouring cold water through the funnel and pipe seen on the fight hand side of the tank."

There's a lot more information in there about heat treating, hardening, tempering, annealing and normalising.