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Joined: Sat Apr 09, 2011 5:34 am
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Location: Glendale,AZ

Post Posted: Fri Apr 29, 2011 5:58 pm 
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I've been reading all the post and threads I could find on multiple sites. There is lots of discussion on terms and geometry. I've been trying to break all the theories and standards from prints and pictures down into a simple idea. That may be the wrong thing to do because of the complexity involved in a quality and safe trigger.

I copied this quote from a post by log man on another forum: Unless you are after an exceptionally hard trigger pull the sear primary angle should always be neutral, or square to a line which touches the tip and passes through the center. And the hammer hook face when extended towards the hammer pivot should be above center from mid way to the edge of the hole. If the hooks are then cut to .020" or so the tips will land first, but due to the sears neutral geometry the hammer will not lift or lower before being released. Just as the neutral sear with a hammer whose face is in line with the center hole.

It would be my understanding that you would end up with a hammer/sear relation similar to the right picture? The sear would move out from under the hammer hooks with out the hammer lifting or lowering which would cause creep?
http://i258.photobucket.com/albums/hh26 ... ement3.png

Or do you want the hammer and sear to mate as pictured in the left drawing?

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Last edited by azpoolguy on Fri Apr 29, 2011 11:00 pm, edited 1 time in total.
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Post Posted: Fri Apr 29, 2011 6:21 pm 
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My preferred technique most closely resembles the illustation shown on the right.

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Post Posted: Fri Apr 29, 2011 8:57 pm 
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On Jerry's thread about grinding hammer hooks I had asked about using a dial indicator on the back of the hammer to test hammer/sear engagement. If you pull the trigger very slowly and watch the indicator, you can see what movement the hammer has prior to the sear releasing. I find that this is helpful for some people to understand the differences between negative, neutral and positive sear engagement angles.

Negative: the hammer will move forward before the sear releases.
Neutral: the hammer does not move before the sear releases.
Positive: the hammer moves rearward before the sear releases.

I usually aim for a neutral to slightly positive sear engagement with the dial indicator showing that the hammer moves to the rear from zero to about .0005 - .001 before it drops. There is a lot more to the trigger job than this but it seems helpful when trying to adjust the sear fixture to stone the primary sear angle.

I was curious if anyone else has tested their trigger work this way. If so, what does yours look like?

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Post Posted: Fri Apr 29, 2011 9:19 pm 
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Dave,
I tried......a little. The results were inconclusive and very, very minor.
Rather than refine my procedure in using the indicator, I elected to use what has been working and working
well for me for many years.
My success with my trigger jobs is VERY dependent upon hammer geometry though.
Wilson and Colt hammers are my choice and I refuse trigger work on those hammers such as Kimber and Extreme Engineering
that incorporate an altered geometry.
Perhaps I could find success with those hammers by altering the sear angle, but I have spun my wheels trying to do
just that in the past.
No thanks.......life is short and Wilson and Colt hammers are easily obtained.

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Post Posted: Fri Apr 29, 2011 9:36 pm 
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Chuck, The Wilson hammer was my next question. You have posted before as to its design/geometry being correct and needing little work to get a good result.

Would this be the best route to go for a garage gunsmith without acces to milling machines to correct hammer hooks? Is it a good idea to mate that to a Wilson Ultra light trigger to obtain the best results? You have talked about using the lightest trigger possible to avoid trigger bounce and I believe you have posted pictures of your lightened trigger bows.

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Post Posted: Fri Apr 29, 2011 11:15 pm 
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Chuck is correct in the illustration on the right most nearly reflects most engagements, and illustrates the description that you quoted of mine. It is labeled positive, but is not. The position of the engagement flats of sear, and hammer to the pivot centers is unknown, so it is difficult to mentally rotate them in your mind.

My description that you quoted is said by me to be neutral, but that also isn't quite true, it is really a negative engagement if we note the hammer hook tips are landing on the sear primary face at a point that is higher/above the sear's primary face edge. The hammer doesn't drop before release however, because it releases from it's point of contact, and doesn't slip and slide down to the actual edge. The sear snaps out, no creep. How much higher? Pythagoras gave us the simple understanding of the right triangle to figure this out. Pretty close to .0001", the value of this is the sear can clear the hook tips cleanly. If when you are tuning the engagement, and you note the pull stacks, most likely the primary face is just slightly positive and you're feeling the sear slip to the point of pull, and then needs more, safe, but not a favored pull feeling. Either a clean crisp snap, or a smooth drop with the release point not being as defined. Assumptions are that the hooks are in the .018"-.022" range.

LOG

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Post Posted: Fri Apr 29, 2011 11:15 pm 
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pistolwrench wrote:
Dave,
I tried......a little. The results were inconclusive and very, very minor. ....


Yeah, my testing has not had consistent results other than being in the same range. Sometimes neutral feels crisp, sometimes it feels creepy. I'll get a trigger that feels right, put an indicator on the hammer and get one result. The next pistol will show show a slightly different result. It could be that there are many elements that affect the "feel" of the trigger pull. Or maybe it's due to the hammer geometry, which is what I'm playing around with now.

I was hoping that someone else had cracked the code on this.

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Post Posted: Fri Apr 29, 2011 11:25 pm 
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log man wrote:
...if we note the hammer hook tips are landing on the sear primary face at a point that is higher/above the sear's primary face edge....


Log - what are you defining as the "primary face edge?" Is that where the primary and secondary surfaces intersect?

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Post Posted: Fri Apr 29, 2011 11:34 pm 
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Dave B wrote:
log man wrote:
...if we note the hammer hook tips are landing on the sear primary face at a point that is higher/above the sear's primary face edge....


Log - what are you defining as the "primary face edge?" Is that where the primary and secondary surfaces intersect?

Yes, the escape edge. When we think about the sear primary face geometry as drawn, and described in the terms mentioned, it is easier, at least for me, to envision a circle with a line tangent touching it. From the center of this circle, to the point the line is touching the distance is the same as the circle radius, but as you go further away from the point you are further away from center. And the hammer hook tips land on this higher point.

LOG

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Post Posted: Mon May 09, 2011 5:49 am 
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log man wrote:

Pythagoras gave us the simple understanding of the right triangle to figure this out. Pretty close to .0001", the value of this is the sear can clear the hook tips cleanly. If when you are tuning the engagement,.....................

LOG


Thanks for this revelation, you opened my eyes! I changed my sear jig to do some experimenting.
Please excuse the bad photos and tool marks, my photo skills are found wanting and my Bridgeport needs new spindle bearings.
I bought the Marvel precision sear jig because it is like a surface grinder in use (the rollers are parallel within .0001" to the sear pin holes).
However the sear should be held as it is in the pistol for true hammer/sear mating surface contact, the tension should be on the pins. If you rely on the sear pin hole being perpendicular to its sides, then clamp the sear in the fixture, as in the original B. Marvel, A. Marvel, and R. Power holders, there may be some misalignment. The perpendicularity of the pin hole is controlled by the machinist who loads the plate into the EDM fixture.
This is the original sear holder minus the brass thumbscrew to lock the sear in place.
Image
I didn't like the sear holder, so I made revision 2. Held like the Wilson or Brown sear jigs.
Image

Here is the revision 3
Image
I modified the block to duplicate how the sear is tensioned in the frame by spring pressure. It can be adjusted using a depth micrometer to the dimensions suggested by Logman in his many posts.
Image
Image
Image
The sear nose height is adjusted using the pin OD and then add .055" to get the dimension suggested by Logman.
Image
Here is a jig I made to examine the hammer/sear in tensioned relationship under 40x magnification. The brass knobs slide on a shaft to release the sear.
Image
Image
Image
Thanks to all,
Wes


Last edited by Wes Lorenz on Mon May 09, 2011 5:50 pm, edited 1 time in total.
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