I bought a Marvel sear jig from Al Marvel himself (Very nice guy and what a setup for gunsmithing! WOW! He had literally every tool a person could ever want, it was truly awesome!) and I when I got the jig home I admired the craftsmanship, turning it in my hands, turning the sear adjustment screw a very small bit... Oops!
After reading the documentation that came with the jig I noticed that the screw is specifically set to properly stone the primary and secondary angles. I didn't turn it much (you need an allen wrench to turn it!) but enough that I am unsure where it was originally set.
I tried calling Mr. Marvel but I believe he went out for the evening. The machine shop that makes the jigs for him apparently adjusts the screw so there has to be an easy way to calibrate/set the screw back to it's original position.
How many of you guys own the Marvel sear jig? How many of you haven't moved the set screw? Finally, can anyone help me restore my jig to its original setting?
Guess that's what I get for tinkering before reading the directions. Who would have thought there wasn't some sort of return mark so the user can return to the original setting? Once I get it back to the original setting I'm going to mark the set screw. The jig is very solidly made and looks like it will last a lifetime.
The screw is set to an "average" angle that's in the middle of the tolerance band for normally built 1911's. There is no one magic setting...
Take a sear, stone it, do the black magic marker thing and see how mates with a proper hammer. Adjust the little screw until the stoned sear mates 100% with the hammer.
Spoke with Al Marvel today... He said the distance from the end of the set screw to the opposite inside wall should be .336 for the primary sear angle to be correctly set.
I did almost exactly the same thing with my first Marvel jig.
Actually, what I did was worse - I changed the screw setting after I had read the directions
Nice to know there's someone else out there a smidgin' dumber than me! (just kidding)
What I'm surprised about is that there isn't some sort of a mark or return system on the jig just in case a person fools around with the set screw. The jig is apparently built so a person can experiment with different primary angles. If this isn't true then why would there be a set screw in the first place? All in all the jig is very well built... overbuilt, which is how I like my tools to be made.
So... Have you had good luck using the jig? If you keep the primary angle the way Al Marvel has it set up and stone the sear, does it give you a nice trigger pull? I understand that you still have to polish the engagement areas and round off the sharp point between the two angles, but other than that... Has the jig worked well for you?
In fact the fixture is set up so you adjust it to match the setup you have. There is no single setting that's right on all pistols. If you are going to really get things right you adjust it for each trigger you do.
You're right Bob, But the way it comes pre-adjusted from Marvel is .336. Even the directions that come with the jig explain that the set screw shouldn't be moved. Since all guns aren't created equal I guess slight adjustment might be in order. I'm curioius though... How would you go about adjusting the jig yourself Bob?
Setup:
Stone the sear
"Paint" it with magic marker
Run it past the hammer
See which direction the fixture needs to go.
If it's hitting only on the "front" edge you go one way, if it's hitting only on the "back" edge you go the other way. When it's set right, you take off marker over the entire surface of the sear.
The real trick is that none of this takes much adjustment or stoning. You are working with *very* small amounts of metal removal. Do not go crazy pulling metal off. One pass with a fine stone may be to much.
The stoning and adjustment take very little time. Getting the sear and hammer back in the pistol to check is where all the time is. You really can't check it any other way though.
The adjuster is also so that you can cut the sear so that the area of contact on the hammer is full, as Bob describes, or minimal, as some fanatics prefer in order to try to eliminate all creep and make the disengagement break suddenly only when the desired pressure is applied... essentially setting the sear "on edge" so that the main effect that is overcome when pressing the trigger is the force applied by the sear spring countered by the force applied by the mainspring/hammer spring.
It's a jig for all seasons.
Thanks Bob, that helps a lot, same to you Hill, makes good sense to me. Didn't know that one pass with a stone is all it takes though. Glad I only fooled around with a cheap sear so far! I thought the secondary angle helped to eliminate creep also, though I've read that the secondary is to help clear the hammer, but that's a bit hard to believe. Seems like the rotation of the sear from the trigger bow would be enough to keep the sear out of the way of the hammer coming down.
The secondary angle serves a couple of purposes:
It allows for a certain amount of "crud" at the junction of the sear and hammer. It also keeps the "active" edge away what ever roughness is in the same area. You can cut the hooks with a slight bit of "round" down there and still get away with it.
The secondary angle also makes the active edge on the sear stronger. It's better supported and it's not going to wear as fast. It lets you set the active edge "square" without going crazy on the back side of the sear.
It's really a pretty neat idea...
No doubt. Lots of very subtle reasons to have the secondary, but not so "the hammer can clear the sear as it falls" right Bob?
Quote:
No doubt. Lots of very subtle reasons to have the secondary, but not so
"the hammer can clear the sear as it falls" right Bob?
Take a look at two cases:
1) Sear with no secondary
2) Sear with secondary
As the hammer starts down in the first case the sear "sits there" and may rub the hammer. It all depends on the shape of the back of the sear.
In the second case, as the hammer hits the secondary - it pushes (accelerates) the sear out of the way. Essentially the sear "flies" away from the hooks. It's out in mid air as the hooks go by.
You are trying to protect the edge of the hammer hooks.
Thanks... so there is truth to what I heard/read. but there are better reasons for the secondary, or rather, other reasons.
If you make a pair of pins that fit the sear and hammer pin holes in the frame snugly (Brownell's sells a set if you don't have a lathe) you can use them to see the relationship between the two parts through their range of movement by having them mocked up outside the frame. You won't be able feel how the trigger will break but you can compare their setup to the available drawings and begin to be able to see when you've got them the way you want them.
Quote:
What I'm surprised about is that there isn't some sort of a mark or return
system on the jig just in case a person fools around with the set screw.
Maybe they intend it as a learning device for folks like us!
Quote:
So... Have you had good luck using the jig? Has the jig worked well for
you?
I bought the jig to give myself a little more control and guidance in my first steps in fire control work. It has certainly given me that. I've used it on three different pistols (one SA .45 Milspec and two dedicated 1911 .22's I built using Ciener units) utilizing the "standard" sear angle setting. The results function very well and they're not dangerous!
With more skill, and some use of that extra adjustability on the jig, however, I'm sure I could do a better job on all of them. So it looks like I'll be playing around with that adjustment screw again sometime - a little less cluelessly this time, I hope.
How many "strokes" of the stone does it take to get the primary angle cut? Do you use a medium India stone first, and then go to a fine India stone for a final finish? I've also heard of people using Arkansas stones as opposed to the India stones... Would you know what the difference between these two types of stones are?
And finally... How was your trigger job... better than factory? Was it smooth and what poundage did it come out out... 3.5# -4.5#?
Most factory sears start out running on one leg, or one part of one leg only. They also vary quite a bit in hardness.
The amount of stoning needed to get things started is highly variable. If you have a really hard sear that's got a real slope to it, you may crank on it for a while. It's still a stroke and check sort of thing though. You can see how you are doing as the magic marker is ground off.
Getting the hammer hook angles right and the hook faces polished is just as important as taking care of the sear. Before you do *anything* on the sear make very sure the hammer is right...
Since you brought up hammer hooks and such, I've got a question you could probably answer for me:
I've got a Springfield stock hammer off of a G.I. pistol... strange thing is, it has a third step above the half cock notch... what is this extra step/notch and what does it do? Is it proprietary to Springfield pistols?
I don't know what The extra bump you are describing would be for.
Quote:
Is it proprietary to Springfield pistols?
Yes, as per this forum.
I use a medium India stone and a fine ceramic. I think the number of strokes will vary somewhat depending on what kind of sear you're working on. I was using el cheapo MIM parts and for that reason I probably had to work them a little more than you would a quality machined bar-stock part. The way I approached it was to watch carefully how much metal I was removing. Good magnification really helps here. I believe the jig instruction suggest something like 2/3 primary angle and 1/3 relief (??check me on this -- I did this work a year ago). I go just as far as necessary and then STOP and assemble and try it out.
The nice thing about the jig is that it helps you be in a little more control, so you can concentrate on your stoning. The only metal that comes off is what you remove, so go slow, keep track of your progress, and you'll be fine.
Quote:
And finally... How was your trigger job... better than factory? Was it
smooth and what poundage did it come out out... 3.5# -4.5#?
I don't know the pounds - I don't have a scale.
I'm happy with the triggers I got on my 1911 .22's. Smooth and light and you can do good shooting with them. After doing those two, however, I was a little leery of such light results on a carry .45. So I only used a Medium stone on those surfaces and actually undercut the hammer hooks a tiny bit so I really had to pull the trigger to make it fire.
That's why my next attempt will include greater attention to optimum sear/hammer contact by using the sear angle adjustment on the jig. This thread has a lot of great info on how to accomplish that!
It's incredibly easy to create a very light trigger. You may or may not have it do odd things when you do. Even if the trigger runs perfectly, I still believe that outside a special purpose range pistol they have no real use.