Re-Bending a Sear Spring

[Rich Jakowski]

The sear spring on the 1803 HF lock I'm putting together needs to be shortened about 1/8 inch. The lock is a TRS parts set cast from an original lock, but the spring isn't a casting - it's made up from 1/4 X 0.043 inch spring stock.

Seems like a straight forward task to anneal and rebend the spring, but I'm wondering what the best technique would be to retemper. I know there's lot of ways to do this, just looking for a consensis on the simplist/most likely to succeed method for spring stock.

 

[J.D.]

I am wondering why you want to bend the spring?

The sear spring only puts enough pressure on the sear to engage the tumbler, so the pressure on the sear bar is minimal.

I would wait until everything is assembled, then test the sear engagement before bending the spring.

The end of the spring is supposed to engage the sear bar just behind the screw boss. The end of the spring should not contact the screw boss at full cock, so there needs to be 1/32 inch, or so,  clearance between the boss and the tip of the spring.

I mention this because the sear spring on many cheap locks rests on the sear bar about 1/3- 1/2 down the bar.

[Pete Allan]

There is no need to anneal and reheat treat. Spring steel will bend easily at the tempering temperature which is usually 6 to 700F or just as the steel turns blue. I just put 2 small pins in a vice to hold the spring and heat with a SMALL propane torch and bend with a small screw driver. Good luck

[Dphariss]

The sear spring on the 1803 HF lock I'm putting together needs to be shortened about 1/8 inch. The lock is a TRS parts set cast from an original lock, but the spring isn't a casting - it's made up from 1/4 X 0.043 inch spring stock.

Seems like a straight forward task to anneal and rebend the spring, but I'm wondering what the best technique would be to retemper. I know there's lot of ways to do this, just looking for a consensis on the simplist/most likely to succeed method for spring stock.

 

I bend them as Pete Allen recommends.
 
Polish and degrease so you can watch the color then use a metal wedge (round stock etc almost anything will often work) to spread to the desired contour. Now carefully heat to a nice even blue.
Carefully heat to a nice even blue and allow to air cool. Keep the heat moving to avoid hot spots.
This should work.
Many sheet metal springs can be bent with smooth jawed pliers and springs of this temper often give a mushy feel. This is generally not critical in a sear spring.
If it collapses back to its previous contour in use you need to reharden and temper to blue.

Dan

[Rich Jakowski]

In response to JD's question re: reason for wanting to re-bend the sear spring.

Assembling the TRS 1803 HF lock parts set was tricky since none of the original tumbler axle or bridle &  sear screw holes were evident on the lock plate casting I received. This resuted in my having to eyeball guess the postion of these components. Now that these parts are in place the sear spring I have gets cramped when cocking the lock which prevents the sear from engaging the notch on the tumbler. I'm hoping that reshaping the spring will remedy this, but perhaps I should be thinking of another solution. Would fileing the top portion of the sear bar accomplish the same thing?

Any thoughts on this?

[rich pierce]

Just shorten the working arm, see how that works.  If the rear of the spring is not extending beyond the plate, there should be no need to re-bend the spring.

[J.D.]

I would reduce the length of the working leg of the spring, as Rich suggests, and see how the sear works before bending anything.

Another thought. Since a shorter leg relates to increased weight, reducing the length of the working leg that much might cause increased pressure on the sear, which might increase the weight of the trigger pull.

If the spring needs to be shortened that much, it might be better to fill the screw hole and redrill in the correct location...if that is possible. 

Just kinda thinkn'...typn' out loud, so to speak....type.

God bless,
J.D.