Heat treat?

[Scota4570]

The tumbler is O-1 round bar.  The sear is automotive leaf spring.  I was planning on heating to orange, quench in canola oil.  Then draw to 750*F in a lead bath for both parts.  Sound good? 

This is the lock I put together with a mix of L/R parts and my own.  I made the plate, tumbler, sear and an oversized sear screw.  I am happy enough that I actually stamped my initials on it.  I want to get the heat treat right the first time. 

[rich pierce]

Can’t give specific temps for O1 but I want sear nose and tumbler harder than spring temper which can be cut with a new file.

[44-henry]

Your temps are too high for O1, that would get you in the low 50's on the Rockwell scale, too soft. The few replacement tumblers I have turned from O1 were tempered at 450 which gets you a more suitable 58 RC.

[Scota4570]

I went with 550 for about 10 min. in lead alloy.  The tumbler does not cut with a random needle file.   If I notice any wear I will try a lower temp.  I have had parts break when I made them too hard.  Wear I can fix, broken I start again. 

I have seen a chart someplace for draw temperatures.  I can not find it in my reference books or on line.  Anyone? 

[Bob Roller]

Can’t give specific temps for O1 but I want sear nose and tumbler harder than spring temper which can be cut with a new file.

I use a method that goes back to antiquity and I for it from George Killen who
was a gunsmith here.On 0-1 after it was hardened I would polish it bright all
over and then using a Bernz-O-Matic* torch and carefully heat it and watch  the color
change,It will start into a very light yellow and when it starts into a deeper yellow or
amber,stop and watch it if it starts to get darker drop it into the oil and stop that action.
I made sears from 0-1 for decades and used this method and started the draw by holing the sear by
the front and walking the colors into a deep blue and when it approached the area that  engages
the tumbler I would watch the color start to change and when it started into amber I drop it
into the oil.I have NO idea about the truck spring material your sear is made from.
All the locks I have made used the method I described here and in spite of many critics saying
it won't work,over 50 years of success says it does.
* The Bernz-O-Matic has an adapter I made to concentrate the flame into an area of about 1/4"
in diameter and I use it daily oin tempering the springs on the triggers I am now making.

Bob Roller

[Scota4570]

According to Roy Dunlap's book like you are in the 450-475* range. 
 

[Elnathan]

Heat Treat Info for

O-1
http://www.cashenblades.com/steel/o1.html

5160 (my best guess as to what your leaf spring was)
https://i.pinimg.com/736x/2f/84/f1/2f84f1f30ab18560bc6882ed8f625449.jpg

You have two different steels there, likely with quite different carbon contents, which will likely require different temperatures to get the same hardness.

[jerrywh]

Don't need to heat .01 to an orange heat to harden. A bright rred is good enough. If quenched too hot it might crack. Quench in light oil . like trans fluid. Then use the lead bath. 725°F is perfect in my opinion. I've done hundreds of them.  I would draw the internals to a  blue or purple for 5 to 10 minutes. Let cool normally.
 Don't matter what the leaf spring is it will heat treat the same as the other springs. Technically it might be different but the difference is so slight it won't matter.

[smart dog]

Hi,
I've made quite a few locks and heat treated many internal lock parts and forged many springs.  Often the tumbler and sear were O-1 steel.  The tumbler and sear are best tempered to 600.  Temper them together so they are exactly the same.  For springs I temper them for 1 hour at 750 degrees.  You need to be careul about the tumble and sear being too hard because the lip on the half cock notch and the tip of the sear are fragile areas prone to chipping and breaking.

dave   

[Scota4570]

"Don't need to heat .01 to an orange heat to harden."

Color is subjective.  I work inside with florescent light.  I use two map gas torches and heat until the part is a blood orange color to my eye.  I then check with a magnet.  IF it does not stick the temp is about right. 

[Bob Roller]

I used 0-1 for sears and flys and on rare occasions set triggers but don't recall
ever making a tumbler from it.1144 to me is the ideal material and it machines
easy as 12L14 and hardens like 0-1.Actually MAKING a gun lock IS labor intensive
and there is no reason to make it more than need be. That is the reason I decided
that we can get along without the lock work and these triggers are as much as I
will make.I hope some one will offer an upgraded caplock to those who prefer them.

Bob Roller