NEW BROWNELLS 1911 SEAR STONING FIXTURE OUT OF SPEC???

[EngineerEli]

Hey All,

 

First post in like a year, glad to be back!

 

So I was shooting my backup limited gun, an STI Apiro,  at the range the other day and it started doubling on me, looking at the sear it look somewhat rounded, the sear leaf of the spring was a little loose too so I tightened that. I wanted to put a fresh primary and secondary cut on the sear face so I bought the Brownells 1911 sear stoning fixture. (linked below) The gun still has the original STI sear and hammer in it, to the best of my knowledge, though it was purchased used.

 

Problem is after adding loctite and setting the set screw as they instruct in the directions, the tip of the sear does not appear to be ending up in the correct position, this is making me think the dimensions on my particular fixture are out of whack.... Can anyone see something I am doing wrong, or does it look like I need Brownells to send me out a replacement stoning fixture? Would someone be willing to measure theirs, and post the correct dimensions I could check against mine? I believe this one and the Ed Brown one should be dimensionally similar.

 

 

https://www.brownells.com/gunsmith-tools-supplies/handgun-tools/trigger-tools/1911-sear-stoning-fixture-prod27288.aspx

 

Thanks,

Eli

[Vmax606]

There is nothing wrong with the jig, it's the STI sear that gives you problem . Anyway, you can confirm that by putting a Wilson or EB sears in there.

 

Also, I do not  loctite the set screw, I adjust the set screw to get the correct angle depends on the sear.

 

 STI fits the sear to the thumb safety, not the TS to the sear and that is why the blocking part on the sear is not resting on the set screw because it was filed down.

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Edited June 22, 2018 by Vmax606

[EngineerEli]

Interesting... So is there a method I could use to establish proper sear angel and set screw length for my given sear to use it on this jig.

 

Thanks!

[Vmax606]

Turn the screw out until the face of the sear is 90* with the line drawn straight up from the center of the pin, after the cut you can fine tune it by turning the screw in or out 1/8 turn at a time.

 

Turning the screw in will lighten the pull, but if you go too far then the sear can trip itself.

 

In your case right now, color the face of the sear with magic marker, turn the screw out until the face is about 90* to the line, run the stone over LIGHTLY and adjust the screw until the ink on the whole face is removed when the stone is run over, not just the front or back part of the face.

 

Now turn the screw out another 1/8 of a turn and do the cut, that should put a little positive angle on the sear , after the cut and if you can live with that trigger break I would leave it right there, do the secondary cut and then do the safety test.

 

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Edited June 22, 2018 by Vmax606

[EngineerEli]

Perfect, sounds pretty straight forward. Just to make sure I'm thinking about it right, you say perpendicular to the line drawn straight up from the center of the pin, would that not be the same as having the sear face parallel to the top of the tool? Just seems like an easier way to think about it. Then yea, just gently touch it with a stone to figure out where I need to be. Given the sear face is a little rounded at the moment, I guess I just need to find the position where I am only removing material from the center of whats left of the primary sear surface, right?

[EngineerEli]

OK, now that I'm thinking about, wouldn't turning the screw out the last 1/8th turn cause the engagement to go further negative? (first image below) Is this what you meant? If I'm understanding correctly, going perpendicular to the line straight up from the pin axis would already result in a somewhat negative engagement, (second image below) is it desirable for competitive shooting to go even a little further, or is that getting risky? I want a crisp light trigger, but I want the trigger job to last and be relatively safe.

[Vmax606]

Turning the screw out will put a Positive angle on the sear, that will make it safer and the sear lasts longer. 

 

Also about the 90* line up, that is the starting point ,because it varies with each sear due to the length of the sears and the angle of the stone.

 

I could not see the pics because the computer I have (at work) sucks !

 

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Edited June 22, 2018 by Vmax606

[EngineerEli]

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Edited June 22, 2018 by EngineerEli

[38super]

Helps to have a pin jig that positions the hammer and sear, jeweler's loupe is very handy.

 

edit: get extra GI hammers n sears from sarco, beat up the cheap stuff before working on spendy parts.

Edited June 24, 2018 by 38super

[mike cyrwus]

Sears have specs too. FYI. Not hard to burn em up playing w angles. 

[Vmax606]

The sear he has already fitted to the gun, it has been working fine until now because the tip is rounded off from use.

 

All it needs now is lining up to the previous angle and give it a clean shave, and maybe add a little more positive angle to it and makes it last a little longer.

 

It's NOT that hard to do. Just have to grow some **** and do it.

[EngineerEli]

So I finished my first attempt with the sear last night, and I'm less than thrilled... It is perfectly crisp, and no creep, but the trigger went up from 2# 9oz to 3# 12oz... I made no other adjustments, does this mean I need to go back and turn the screw in an eighth, or a quarter and put a new primary edge on the sear? Seems like maybe my current sear surface is too positive? I did also take my fine white ceramic stone and just shined up (and squared up)the hammer hooks. I stoned the sear first with a medium fine India stone, then with the white extra fine ceramic stone. Lastly I polished all the contact surfaces with mothers polish on the end of a cut in half q-tip. (hard cardboard stick, not the cotton end)

 

What should I try next? This gun is for competition / range use only, never self defense. It is the back up for my Infinity limited gun that has an incredible 1# 13oz trigger. So I would like it as close to that as reasonably possible. Honestly the 2.5 lbs it was before was acceptable, just need it to stop doubling, and I did want it a little more crisp. In retrospect, the doubling could have been from sear spring adjustment, which has since been corrected...

Edited June 27, 2018 by EngineerEli

[Vmax606]

How much pressure is on the left finger of the sear spring right now ?  With a good clean surface and a positive angle on the sear, it does not require that much pressure at all.

 

Bend the left finger backward a little at a time and see how low you can bring the trigger down, you want to keep hearing a clean "Click" when you thumb the hammer back,  and if that still does not make the trigger light enough then bend the middle finger also, but bending the middle finger back will make the trigger returns slower.

 

If all that does not give you what you want, then turn the screw in 1/8 turn and recut the sear, just a few strokes is all it takes. The thing is, if you remove the positive angle then the trigger break will no longer be crisp, it will become a rolled trigger, it depends on the individual taste of the shooters, some like the snappy break and some like the rolled.

[Don_B]

I suspect the sear was not worn as you thought. It is common

practice to slightly round the point between the primary and secondary angle. It does not require much, just break the sharp angle and it will improve the trigger pull. 

 

So so you could well be correct that the sear spring just needed adjusted. 

[EngineerEli]

Well, I went back and adjusted the center and left legs of the spring to mirror my SV, which helped a bit. I checked pull required to make the trigger start moving in the first stage ~6 oz , then I held the hammer to the rear and checked the pull required to make the trigger start moving into the second stage ~14-15 oz (move the sear) I then went back and rounded the edge between the primary and secondary angles of my sear with my white extra fine stone. and polished with mothers and a q tip stick.

 

Result is 2 lb 15 oz. Its an improvement, but I think when time permits, I need to go back and turn the screw in 1-8th turn and re-set my primary sear angle a tiny bit. Its still exceptionally crisp. (too crisp?) Difference between first stage and second stage (break) is too great.

[joelpend]

I use as a rule 2/3 of the total pull weight on the sear and 1/3 on the trigger return. Seems to work very reliably for me.

[EngineerEli]

Hmmm, I like that idea, very linear...

Edited July 6, 2018 by EngineerEli

[EngineerEli]

I found some time and went back and re-faced the primary sear edge with the screw in an 1/8th turn. Re polished everything and broke the edge between the two sear surfaces with the white stone. Trigger pull dropped to 2 lb 10 oz, and this is with the first stage increased to about 9 oz, which feels much better. I think I'll leave it here for a little while, haven't had the chance to go test it out at the range yet, but I have not been able to educe any malfunctions manually. I'm wondering if as the trigger job sets in a little more if the pull will drop slightly more... Is that common? Thanks for the help everyone!