Author Topic: Sear bar vs trigger bar hardness  (Read 642 times)

Offline HighUintas

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Sear bar vs trigger bar hardness
« on: November 21, 2023, 11:08:43 PM »
When I built my rifle, I had to add some height to the trigger bar so that it reaches the sear bar correctly. I cut a piece of a flat need file off, polished it up and soldered it to the trigger bar using Solder It paste. I think the remelt temp of that paste is around 600F or maybe 650F.

Last time I had the lock out, I noticed some wear on the sear bar. Should I have heated up the piece of file I used to draw down the hardness a little bit? If so, to what color should I draw it back to? Maybe purplish? If I need to do that, I'm hoping it won't be above the solder remelt temp.

Thanks
« Last Edit: November 21, 2023, 11:13:59 PM by HighUintas »

Offline smylee grouch

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Re: Sear bar vs trigger bar hardness
« Reply #1 on: November 22, 2023, 12:25:38 AM »
An option. You could remove that file and solder\rivit a piece on to the trigger bar on the lock plate side that is just high enuf to take up the slak. Make the add on out of milder steel. A tiny bit closer to the lock plate might give you a bit smoother trigger pull.  :-\

Online Elnathan

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Re: Sear bar vs trigger bar hardness
« Reply #2 on: November 22, 2023, 12:42:37 AM »
"Purplish" should be somewhere in the 520-540F range per the color charts online, or about a 100F cooler than the melt temperature of your paste, so theoretically, with a careful hand, you could heat it up to purple without melting the solder. That said, how did you manage to solder the thing in the first place without drawing the temper to that 600-650F temperature cited? If you have already heated it to 650 to solder it, the only way to soften it further is to heat it hotter...

Assuming 1095 for the file and an even heat to 600-650 for soldering, the current hardness is probably already somewhere between 53-50 rockwell.
A man can never have too much red wine, too many books, or too much ammunition -  Rudyard Kipling

Offline HighUintas

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Re: Sear bar vs trigger bar hardness
« Reply #3 on: November 22, 2023, 01:44:08 AM »
An option. You could remove that file and solder\rivit a piece on to the trigger bar on the lock plate side that is just high enuf to take up the slak. Make the add on out of milder steel. A tiny bit closer to the lock plate might give you a bit smoother trigger pull.  :-\

That is what I did in the first place, but used a piece of needle file instead of mild steel and it now has almost now slack. It's maybe a 3lb pull.  When I decided to use the piece of needle file, I was under the impression that mild steel, even if hardened with kasenit, wouldn't be hard enough to use for a trigger bar extension.

So it sounds like you're recommending just removing the current piece and replacing it with a milder steel, correct?

"Purplish" should be somewhere in the 520-540F range per the color charts online, or about a 100F cooler than the melt temperature of your paste, so theoretically, with a careful hand, you could heat it up to purple without melting the solder. That said, how did you manage to solder the thing in the first place without drawing the temper to that 600-650F temperature cited? If you have already heated it to 650 to solder it, the only way to soften it further is to heat it hotter...

Assuming 1095 for the file and an even heat to 600-650 for soldering, the current hardness is probably already somewhere between 53-50 rockwell.

The Solder It paste I used initially melts at around 400F... Can't remember exactly. The remelting temperature is higher, 600-650F. I'm not sure how that works, but that's what the product says.

Offline rich pierce

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Re: Sear bar vs trigger bar hardness
« Reply #4 on: November 22, 2023, 03:21:24 AM »
Just joking here - you did grind the teeth off, right?  ;D
Andover, Vermont

Offline Bob Roller

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Re: Sear bar vs trigger bar hardness
« Reply #5 on: November 22, 2023, 04:40:37 PM »
The sears on my locks were hardened at the engagement end to where the sear spring contacts it.
Most of mine were used with double set triggers and single set triggers.
Bob Roller.

Offline HighUintas

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Re: Sear bar vs trigger bar hardness
« Reply #6 on: November 22, 2023, 06:12:47 PM »
Just joking here - you did grind the teeth off, right?  ;D

I guess that would have been a good thing to do! ;) Haha yes I did. Ground down and polished.


I did some inspection work last night and I found that it is actually the SET trigger bar (double set trigger) that is causing the wear. The front trigger has only produced a slight shiny spot. I didn't add any extension to the no set trigger. It is unmodified.

What it looks like is that the set trigger bar contact surface is at the wrong angle relative to the contact surface of the sear bar. So when it is released, it hits more on the corner of the sear bar than having a direct square contact. I will have to grind the set trigger bar a bit to correct that angle, and then all is well!

Offline kutter

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Re: Sear bar vs trigger bar hardness
« Reply #7 on: November 22, 2023, 06:20:07 PM »
The Solder-It paste you used (as you pointed out) flows and solders at around 430F.
Then if you heat it up again to undo it or adjust the position, etc, it takes around 650F to make the solder flow.

That according to the mfg'rs instructions.

I would clamp the join firmly together, a small vise grip works great.
Heat to betw purple and light blue.
That should draw the temper and still keep the temp lower than the flow temp of the joint.
Even if it does reach that point, being clamped and held in position, it should just remain soldered as it cools back down again.

Here's a steel temper color chart.
https://www.servicesteel.org/resources/steel-tempering-colors

If it all fails, I would remove the piece from the trigger all together and make the adjustment in height on the sear bar itself.
Use a piece of mild steel (a large dia nail/spike works).
File a flat on both the nail and the sear bar arm. Clamp together and (I would) Hi-Temp Hard Solder them together.
Protect the sear/sear nose itself by holding that portion in a vise as a heat sink.
Then file the assembly to shape removing un-needed matr'l. Then the final adjusmnet in height to get your trigger pull.


Offline P.W.Berkuta

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Re: Sear bar vs trigger bar hardness
« Reply #8 on: November 22, 2023, 07:39:49 PM »
Leave it alone it will outlast you ;).
"The person who says it cannot be done should not interrupt the person who is doing it." - Chinese proverb