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  #1  
Old 05-05-2012, 12:17 AM
ggun ggun is offline
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mil-spec trigger job with original parts




Hello 1911 People!

I'm getting ready to do a trigger job on my Mil-Spec but want to use the original parts. I've only got 120 rounds on the gun so the parts are practically new, and although I changed the trigger and mainspring housing, I like the look of the spur hammer and was hoping that I could just lighten up the pull with the original parts except for lighter springs (main and sear). I've got all the tools I need (or are "in the mail"), but somewhere I read that I shouldn't expect to get down below 5# with the stock components and I just don't understand that. I'm hoping that is a misstatement since they also neglected to make any adjustment to the sear spring, so I'm thinking that is the hole in their claim.

My impression is that after all the polishing of parts, the sear spring should be able to be adjusted for practically whatever trigger pull is desired. Is this not true? I'm only aiming for between 4# and 4.25#. I did order a new sear spring to adjust so that if need be, I can always put the unmodified original spring back in.

[And I have read through the many posts regarding safety issues on this job, much appreciated.]

~Dan
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  #2  
Old 05-05-2012, 12:37 AM
skipsan skipsan is offline
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Springfield will do a trigger job using the original parts and get the trigger pull between 4 and 5 lbs. I don't know if they can hit a specific value in that range, or if "between 4 and 5 lbs" is as close as they will call it. The TRP line has a spec trigger pull of somewhere between 4 and 5 lbs and the fire control bits are all made from MIM.

If the owner wants less than 4 lbs, then SA insists on changing out the MIM to wrought parts and the price doubles to $200ish. Don't know whether the issue with MIM is hardness, surface finish, revenue generation or whatever.

I believe the price sheet on the website spells all this out.
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  #3  
Old 05-05-2012, 12:46 AM
ggun ggun is offline
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Thanks skipsan. I don't want below 4# and I am doing the job myself. I just want to know if my reasoning is correct, that I can make the final adjustment to ~4# with the sear spring.
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  #4  
Old 05-05-2012, 01:16 AM
mark2734 mark2734 is offline
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Quote:
Originally Posted by ggun View Post
Thanks skipsan. I don't want below 4# and I am doing the job myself. I just want to know if my reasoning is correct, that I can make the final adjustment to ~4# with the sear spring.
No.

Its not just polishing the parts but the angle of the sear and how it engages the hammer hooks. That requires exact stoning.

Once your got the sear/hammer interface down you can go pretty low.
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  #5  
Old 05-05-2012, 01:23 AM
ggun ggun is offline
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I've got Ed Brown's sear jig and intend to break the edge on the sear as well. Is there any reason to expect that I cannot obtain a 4# trigger pull with the stock parts then?
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  #6  
Old 05-05-2012, 04:47 AM
Jim Watson Jim Watson is online now
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I don't see why not, I have a stable 3.75 lb on MixMaster A and its factory MIM bits.
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  #7  
Old 05-05-2012, 05:00 AM
BBBBill BBBBill is online now
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Quote:
Originally Posted by ggun View Post
I've got Ed Brown's sear jig and intend to break the edge on the sear as well. Is there any reason to expect that I cannot obtain a 4# trigger pull with the stock parts then?
Depends. Have you ever done a trigger job before? Do you fully understand the 1911 fire controls? Do you grasp the subtleties of slight changes in angles and how those can either work to give you a great safe trigger job or one that will be dangerous if it functions at all? Do you know that the thumb safety will more than likely not block the sear after a trigger job on the existing parts? Do you know how to refit your existing thumb safety or fit a new one? Do you know how to check for proper operation of the thumb and grip safeties? If the answer to those questions are the right ones, you may succeed. If not.......... Only you can know that.
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  #8  
Old 05-05-2012, 07:31 AM
TTAC TTAC is offline
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I have pretty much given up trying trigger jobs on factory parts. Most factory parts are MIM injected and they can be only surfaced hardened.
You may get a good trigger pull, but it may not last.
I suggest something along the lines of Cylinder and Slides trigger kits. They are made out of good steel and each part comes hardness certified.
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  #9  
Old 05-05-2012, 07:54 AM
Jolly Rogers Jolly Rogers is offline
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MIM parts being surface hardened only is a fallacy. If you study how MIM is produced you will come to know that the sintering of the parts to bake out the plastic component creates the structures hardness. It is consistent throughout the part. Which may in part explain some of the breakage MIM parts experience.
Joe
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  #10  
Old 05-05-2012, 10:21 AM
ggun ggun is offline
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Thanks for the responses. I'm learning, like everyone else here, hopefully. And I appreciate all the cautionary advice and questions. "A man's got to know his limitations." And considering them, at some point you step out and do something that you've never done before and you have to decide when you're ready. I'm not ready just yet but I think I'm getting close and I've made the commitment to learn so that I can pull the trigger on that job someday soon. Coming to this forum is part of my learning process. I've had the gun completely apart numerous times and am grasping how the parts work together though I know there is still more to learn. So no, I have not done the job before and am learning about the subtleties. I was aware of the thumb safety potential to not function and am prepared to have that solved by my local gunsmith if I cannot solve it myself. I've got a lengthening list of safety checks that I will perform and will ask my local gunsmith to check my work if there is any lingering question or doubt. But I am doing this job whether I bring it to him in one piece or in a bag. Thanks again for all the thoughts.

Be safe. Be courageous.
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  #11  
Old 05-05-2012, 01:12 PM
GOVTMODEL GOVTMODEL is offline
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Quote:
Originally Posted by ggun View Post
Hello 1911 People!


My impression is that after all the polishing of parts, the sear spring should be able to be adjusted for practically whatever trigger pull is desired. Is this not true? I'm only aiming for between 4# and 4.25#. I did order a new sear spring to adjust so that if need be, I can always put the unmodified original spring back in.

[And I have read through the many posts regarding safety issues on this job, much appreciated.]

~Dan
See http://www.brownells.com/.aspx/lid=1...__Trigger_Pull

for details.
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  #12  
Old 05-05-2012, 05:02 PM
ggun ggun is offline
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Thank you Richard. That is an interesting article. I'll look at it again when I'm ready to go, but right now I'm puzzled by the sear spring adjustment. From the article:

"Adjust the spring pressure until you get a reading of 8 oz. Pull rearward on the trigger with the Trigger Pull Gauge only enough to cause the disconnector leg to move. If you pull it too far, you will also engage the sear spring leg and that will cause you to get a false reading on the gauge.

"Next, add in the sear to the limited assembly. Again, measure the spring pressure with the Trigger Pull Gauge. We now need a total of 16 oz. of spring pressure with both the disconnector and sear legs of the sear spring engaged. If you get a reading that is either more or less, bend the sear leg of the spring in or out until you get the 16 oz. reading. This is really the only variable I do to my trigger jobs. If I need a heavier weight trigger pull I adjust the tension of these two spring legs upward. Remember, both legs of the sear spring need to be adjusted equally. Here is an example for a 3 pound trigger pull:
Disconnector Spring Weight - 16 oz.
Sear Spring Weight - 32 oz."

My question with this is that it states to adjust sear and disconx legs equally, and demonstrates that in the first example (8 oz + 8 oz = 16 oz), but for the 3 1/2 lb pull example the sear spring weight is 2X the disconx weight. Is this a typo such that it should read "Disconx + Sear Weight -> 32 oz? or do you stop at 16 oz regardless for the disconx leg and finish the adjustment with the sear leg.

My guess is that it is a typo. And just to state what should be obvious, I assume that the remaining 1/2 lb (or 1 1/2 lbs if it was a typo) come from the totalage from the final assembly including the mainspring.

Thanks for pointing me to this very informative article.
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  #13  
Old 05-05-2012, 05:30 PM
broadus123 broadus123 is offline
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I have done trigger jobs on all my 1911s. I use the original parts and only replace the sear spring. I like c & s light sear springs. I have a ria that I picked up NIB and the trigger was over 7 lbs. I reduced it to 3.5 by stoning the internals and replacing the sear spring. It did require a lot of stoning ! I have several kimbers that I use in competition and have the triggers set at 2.5 lbs using the original internals and a sear spring.
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  #14  
Old 05-05-2012, 11:45 PM
Magnumite Magnumite is online now
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In the 1911 the mainspring typically contributes about 1 1/4 to 1 3/8 pounds of force to the pull weight. Hook and sear angles will effect that but we will negate that since we'll assume print angles and sear length.

So subtracting say 22 ounces (1 3/8 pound) from your 64 ounce target pull weight (4 pound pull) you get 44 ounces. Divide that by 2 and you get 22 ounces for both the sear and disconnector leg of the sear spring.

Obviously you should use a pull gauge or weights to do this.

Using your parts as they are, measure the pull weight with all parts in place. Remove the the gs and reassemble with the hammer strut up and not engaging the mainspring housing. Put the mainspring housing in so the pin holes line up. This puts pressure on the sear spring as it will be in the assembled pistol.

Now, cock the hammer and measure the pull weight to allow the hammer to just drop. I keep the pistol upside down at about a 45 degree angle to let gravity help me out. The resultant pull subtracted from the fully assembled pull will be what the mainspring with the angles on your pistol contribute to overall pull.
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Last edited by Magnumite; 05-06-2012 at 01:15 PM. Reason: grammar
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  #15  
Old 05-07-2012, 11:08 AM
ggun ggun is offline
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Thanks. I would still like to know if the partial weights of the sear and disconnector springs have an ideal ratio or not. Is it 1:1, 2:1 or other? Does anybody know this or at least what the range should be?
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  #16  
Old 05-07-2012, 11:53 AM
GOVTMODEL GOVTMODEL is offline
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Adjusting trigger pull

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Originally Posted by ggun View Post
Thanks. I would still like to know if the partial weights of the sear and disconnector springs have an ideal ratio or not. Is it 1:1, 2:1 or other? Does anybody know this or at least what the range should be?

Being a Bullseye shooter, all I ever did was 3.5 pounds for my wadcutter pistol and 4 pounds for my hardball gun.
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  #17  
Old 05-07-2012, 01:33 PM
Magnumite Magnumite is online now
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Shoukd be one to one. There are times where I opted to put a little more on the disconnector leaf if using a heavier trigger to prevent trigger bump.
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  #18  
Old 05-08-2012, 11:23 AM
ggun ggun is offline
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Thanks Magnumite. I woke up thinking about it. I think I'm figuring it out, but please correct me if I'm wrong. And forgive me for splitting sears here.

This is a simplistic example which is not likely to be completely accurate but I think makes the desired point. Let's say the goal on the two springs is 32 oz, like in the Brownell's example. First you engage the disconx leaf until just before the sear leaf engages for 16 oz. Then as you engage the sear leaf, both contribute (directly and indirectly) to trigger pull weight; if you add 8 oz to both the disconx leaf and the sear leaf for another 16 oz, you total 32 oz. 24 oz is now attributed to the disconx leaf and only 8 oz to the sear leaf for a 3:1 ratio.

Is that a fair line of reason?

Last edited by ggun; 05-08-2012 at 07:49 PM.
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  #19  
Old 05-09-2012, 01:03 AM
ggun ggun is offline
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I received the sear jig tonight so I started doing preliminary measurements. I have not received my pull gauge yet so I don't want to do any stoning until I can get the baseline trigger pull weight.

It looks like the hooks are hitting equally but it's pretty hard to tell because the sear is all black and there isn't enough wear on the nose for ink to show well. I could not see anything at all on the hooks. I'll have to check that again after I flatten out that surface. I didn't want to hunt down a bottle of dykem so I was just using a sharpie like I saw in another video.

The original parts have these measurements:

0.022" - nose protrudes above the sear jig surface
0.028" - nose length
0.030" - hammer hooks

I "assembled" the hammer and sear with their pins on the outside of the frame for line-up. It looks as though the engagement is neutral as I cannot perceive the hammer moving as the sear is moving.

The tips of the hammer hooks (obviously by the measurements) extend beyond the edge of the nose (by 0.002") so the whole nose is currently being used as far as I can tell.

My plan is to use the 0.020" shim and clean the nose on the jig with india and arkansas stones. I don't feel the need to reduce the length down to 0.020", but then that's why I'm posting here, to make sure that I'm not missing something. From what I've read on this forum that should be just fine.

My goal is for a 4.0-4.2# trigger pull. (I guessed that once I get anything under 4.2# dry with incremental leaf spring adjustments at the tail end of this job, adding oil may bring it down slightly. I don't think I want to end up below 4#.)

Assuming the length of the nose will remain at 0.028" after stoning, I should easily be able to cut the escape ramp to 1/3 of the face and still have ~0.019" of engagement surface remaining (0.015" target minimum).

Question 1: When stoning for the escape ramp, is it necessary to protect the curved back surface of the sear or can it take a little stoning while I'm concentrating on forming the escape ramp? From the nutnfancy video of a gunsmith at Impact Guns, it looked like he just rubbed the whole sear on the stone, and that should have touched the curved back of the sear body. I could put some foil down or a thin shim where it touches so that only the escape surface gets hit, but is that really necessary if I am careful not to butcher it?

Question 2: Will I be able to get away with the hammer hook height as-is (the hooks would extend even farther beyond the sear nose edge after the escape ramp is cut) or am I going to have to take them down so that the edges rest on the nose surface? If so, I think I'd have to take them down about 0.004" to just get on the nose surface, with 0.002" margin for error. (I'm expecting the answer to this is "yes or why do the trigger job at all?" If that is the case, what is the best way of taking those hooks down? I'm in my garage using hand tools only.)

Ok, I am starting to have fun now.

Last edited by ggun; 05-09-2012 at 01:25 AM.
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  #20  
Old 05-09-2012, 03:37 PM
Magnumite Magnumite is online now
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Your understanding on the leaf forces are correct.

For the sear and hammer engagement, you'll need longer pins which go through both sides of the frame for more stability. Then your final mark/check adjustments should be in the pistol since the pins are not the most stable checks. Excessive manipulation force tends to spread the pins apart.

As far as how far to go, you seem to be looking for a clean trigger and not a light race job. You've thought this out. A couple things to keep in mind as you work. This assumes stock angles and a starting sear length on the long side of spec.

- The more relief you put on the sear, the further it rotates into the hammer increasing the distance between the sear foot and the thumb safety lug;

- as you shorten the sear the distance between the sear foot and thumb safety lug closes up;

- if you set the sear into the hammer with relief, you will probably feel a 'hitch' or creep as the shortened sear nose sets into the hammer more then moves out from under the the ends of the hooks;

- shortening the hooks will make it doubly important you weld up the thumb safety lug or replace the thumb safety since there will be less hammer hook to compensate for space between the thumb safety lug and sear foot. The mil spec hook length will tolerate this clearance more than a tuned trigger. Do the "click" test before testing the pistol and fit the thumb safety as required.

You seem to approaching this intelligently, work slow, be safe. Others will probably chime in as well.
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  #21  
Old 05-09-2012, 04:58 PM
ggun ggun is offline
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Thanks for that information and comments. I'm a little nervous about having to make adjustments (weld and grind) on the thumb safety, but if it comes down to it, it shall be done. I would like to keep the stock safety so I may end up modifying it to get the job done.

A light just turned on. After cutting the escape ramp, the nose should go about 0.003" deeper into the hammer so that almost doubles the amount that needs to be removed from the hooks to 0.007". Now the worms are coming out of the can.

1. So the weld repair is likely if I take 0.007" off the hooks?

2. I do believe shortening the hooks is what I want to do for a crisp trigger. I've heard-tell there is such a thing as a hammer hook file. Do I need that or will medium india and hard arkansas stones be sufficient to remove this amount of material? (I got the three stone set from Brownells for $52.)

Last edited by ggun; 05-10-2012 at 12:44 PM. Reason: calculation change
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  #22  
Old 05-12-2012, 09:18 PM
ggun ggun is offline
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1. Any recommendations on how to take down the hook length by 0.007 evenly with hand tools. I'll probably take 'er down only 0.004" at first and then check engagement with the finished sear. Anyway, I've got stones and a vernier caliper. Am I on the right track?

2. Is there a maximum clearance that should exist between the ts lug and sear foot? or should it be that there is a minimum sear to hook engagement when the ts is engaged and the foot contacts the lug? (or maybe both; I can see that I'm not going to get out of a weld repair on the ts lug.) A spec like that would make more sense to me. I calculate that the foot/lug clearance is only going to increase by 0.003" but I can see that the engagement decreases with the hook length. I also surmise that it is not sufficient just to make sure that the ts functions as it may be on the verge of failure if there is not enough engagement when the trigger is pulled.

Last edited by ggun; 05-12-2012 at 11:12 PM.
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  #23  
Old 05-13-2012, 12:08 PM
GOVTMODEL GOVTMODEL is offline
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Stoning Hammer Hooks

Quote:
Originally Posted by ggun View Post
1. Any recommendations on how to take down the hook length by 0.007 evenly with hand tools. I'll probably take 'er down only 0.004" at first and then check engagement with the finished sear. Anyway, I've got stones and a vernier caliper. Am I on the right track?
Lay the stone and the hammer on a piece of glass or a mirror. Turn the hammer over every ~5 strokes until you're done.
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  #24  
Old 05-13-2012, 01:36 PM
ggun ggun is offline
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I like it, Richard, thank you. Now into the minutia...

I originally figured on cutting down the hooks first and then polishing the large side surface flats afterward. Your idea makes me think that it may be best to lightly polish the sides first and cut the hooks after, finishing up with final dressing of the cut edges.

That's the procedure that immediately comes to mind but I post here because of all the great ideas offered. I am a first-time triggerer and since we all like talking about these things, I usually find a better way of doing it or gain confidence in my method when pros like yourself offer their critique.
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  #25  
Old 05-13-2012, 03:25 PM
GOVTMODEL GOVTMODEL is offline
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Hammer Hooks

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Originally Posted by ggun View Post
I like it, Richard, thank you. Now into the minutia...

I originally figured on cutting down the hooks first and then polishing the large side surface flats afterward. Your idea makes me think that it may be best to lightly polish the sides first and cut the hooks after, finishing up with final dressing of the cut edges.

That's the procedure that immediately comes to mind but I post here because of all the great ideas offered. I am a first-time triggerer and since we all like talking about these things, I usually find a better way of doing it or gain confidence in my method when pros like yourself offer their critique.
Sounds like basically the same approach. Should work just fine.
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