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hardening and tempering

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edwood05/02/2011 20:39:04
12 forum posts
hi
a trick i read years ago in a gunsmiths book. when try ing to heat up a job say a reamer you have made that goes to a very fine point and you burn the end off trying to heat it evenley. heat a tin of lead lower the job in it will heat it evenly ready for quenching .hope this is of use to someone
regards ed
ps lets have a few more tips theres thousands outthere .and they make life a bit easier
Nobby05/02/2011 22:08:30
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587 forum posts
113 photos
Hi
In the home workshop After hardening if you want an even colour when tempering . Place components in on a tray of sand with burner underneath . Make sure components are clean (shiny) and free from grease and oil . you get a nice even colour ie straw , light straw ect before quencing . Dont forget workshop safety precations
Regards Nobby
DMB23/10/2011 17:43:38
1585 forum posts
1 photos
Hi,
 
I seem to remember seeing on this forum or perhaps it was madmodders, something was said about no need to heat carbon steel to a full red heat and quench to harden, preparatory to tempering. The recommendation as I remember, was to heat to a colour indicating a higher temp than the tempering colour, quench, clean up then re-heat to actual tempering colour.
Can anyone please confirm this?
Regards John
Nicholas Farr23/10/2011 19:06:37
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Hi John, as far as I'm aware, carbon steel has to be in the Austenite condition to be able to be hardened, that is from around 700 to 900 plus degrees C depending on carbon content percentage, red hot range.
 
Regards Nick.

Edited By Nicholas Farr on 23/10/2011 19:08:24

JohnF24/10/2011 15:18:31
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Hi all, going back to the original question/comment regarding tempering with lead, yes it can be used for tempering but not a reamer.
 
It is often used to temper springs, it melts at about 327 deg C and springs are best tempered at around 330 to 340 deg C but your reamer or cutting tools would be tempered at a pale straw 230 deg C.
 
If you do use lead you need a high temp thermometer and you also need to make sure the lead does not stick--like solder--to your tool, if you have just hardened in oil leave it black, if you have cleaned it up then coat it with powdered chalk mixed with water or meths. VIP IF YOU USE WATER MAKE 100% SURE IT IS DRY BEFORE YOU PUT IT IN THE LEAD *******OTHERWISE SERIOUSE INJURY WILL OCCUR--HEALTH AND SAFETY !!!! ALWAYS USE A FACE MASK GLOVES ETC.
 
Hardening you need to have the steel above the uper critical point--i.e. in an austenitic condition as Nick says. This varies depending on the steel but as a rough guide silver steel and high carbon steel a dull red [in subdued light] is about 730/750 C quench in oil. For say EN9 you need a bright cherry red about 850 C to harden but it is always best to check in the makers spec sheet for heat treatment.
 
This is only a "potted" response heat treatment is very involved and to obtain specific results needs very careful treatment for each steel specification.
 
Best of luck
John.

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