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PostPosted: Mon Oct 30, 2017 7:11 pm 
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Location: Eastern Townships
I'm building a trigger group (two actually), and I'd like to know to which Rockwell C hardness I should temper the sear. I'm using high-carbon tool steel, not quite sure of the grade since it's an old ('60) chainsaw bar, maybe O1 or 1095 according to what I found on the net. The original metal was 45 Rc, I annealed and re-hardened and tempered it as a test, but my tempering temperature was rather high at around 600°F, and I obtained 55 Rc hardness. I saw people using 400 to 450°F to get around 60 Rc hardness. Would that be good?


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PostPosted: Mon Oct 30, 2017 9:20 pm 
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Location: Coalmont BC
Depends entirely on the operation of the sear.... Drop sears like in an MRod or PRod work fine on a hammer made from MDS plastic.... because there is no sliding across a fine edge.... The sear either has tons of area under load, or drops out of the way....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
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PostPosted: Tue Oct 31, 2017 4:07 am 
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Location: Eastern Townships
Ah yes, forgot to tell on what kind of system it'll be :oops: . Same kind as a13xx/22xx, I'm actually using a 1377 hammer and spring, and same hammer stroke. I'm using an M4-177 tube and internals. It'll be a .22 cal. rifle.

Thanks for your time Bob :)


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PostPosted: Tue Oct 31, 2017 5:17 am 
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I'd say 45-50, but that sear doesn't see much stress so I'd imagine you could make it whatever you want.
I guess with nothing to go on I'd just make some sample pieces until you get as hard as possible but no longer brittle.
So are you making a copy of an oem sear, or something different? Pix when done plz ;)


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PostPosted: Tue Oct 31, 2017 4:34 pm 
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Location: Eastern Townships
Chevota wrote:
...So are you making a copy of an oem sear, or something different?...


Something different, built from scratch, but based on the Crosman/B19/Gamo trigger group. With adjustable two stage trigger, adjustable trigger weight and trigger stops. I could probably have used the 2260 trigger group, but I think the trigger guard is plastic and I don't want any plastic on that rifle, and I want a fully adjustable set-up 8) .


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PostPosted: Tue Oct 31, 2017 6:56 pm 
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Location: Lebanon, CT
60 on the Rockwell scale is a quite hard knife blade. RC


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PostPosted: Fri Nov 03, 2017 6:08 pm 
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Location: Eastern Townships
Preview of the still rough sear, sear lever and SS trigger blade:


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PostPosted: Sun Nov 05, 2017 5:33 pm 
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The finished sear and sear lever. Heated to a bright orange, quenched in 130°F canola oil and tempered at 430°F for an hour. I'll test them tomorrow on the hardness tester at work 8)


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PostPosted: Sun Nov 05, 2017 6:15 pm 
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Location: Coalmont BC
That looks like a drop sear design?.... ie when you pull the trigger, the sear drops out of the way of the hammer.... it is either fully engaged, or not engaged at all.... If so, hardening was not necessary, we use MDS plastic hammers in PRods and MRods all the time, with no wear problems where the sear catches them.... The only spot prone to wear is where the sear rubs on the sear lever, and the loads there are MUCH smaller, only vertical (and through leverage).... not the whole load of holding the hammer back....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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