Thumb Safeties

[Jammer Six]

Okay, Tuner, Fuff, Wichaka, here we go again.

Practiced on an old thumb safety I had lying around, and now I'm chewing on the one you sent me, 'Fuff. It's the real one, the one I want to keep.

I have it in, and it clicks nice.

New sear, first time fitting this thumb safety.

Smoking it up shows that the angle is good, I think. Nice, even contact across then entire width of the end of the contact surface.

So far, so good.

Hammer doesn't fall, clicks on, clicks off.

The problem is Tuner and his damn dial indicator.

Setting it up in the vise, fully assembled, cocked and unlocked, and setting the dial indicator to the hammer, with a small amount of pressure on the dial indicator, shows the following:

When you depress the grip safety, and engage the thumb safety, the hammer overcocks by about two thousandths.

Messing with the trigger at that point will result in the hammer moving forward, uncocking, by about one thousandth.

Releasing the safety returns the dial indicator to within a thousandth of where it started.

Now...

If it's locked up tight, which seems to be the case, if the safety is wedging itself up against the sear, how can it then allow sear (and therefore hammer) movement, as indicated by the dial indicator?

I was thinking that I'd actually LIKE to see a thousandth (or less) overcocking when the safety was engaged, because then you'd know that the thumb safety was making positive contact with the sear, and that there is absolutely no play between the sear and the safety.

But how can the hammer uncock, if the safety is in positive contact? Is the safety moving?

Enquiring Minds Want To Know!

This would all be so much simpler if I'd never bought the dial indicator, then I'd just run the safety checks, and head for the range...

 

[1911Tuner]

Much Ado

Only you, Jammer...Only you.

If the sear is moving, the safety isn't fully blocking it....BUT...if you pull on the trigger hard enough, things can flex. If you pull on it really hard, you can bend the trigger stirrup and even damage the disconnect. The safety is designed to prevent sear movement if the trigger should be unintentionally
pulled with about the same amount of force to cause the gun to fire if the safety were off.

Forget the dial indicator for now. Does it pass the "Click Test"?
Safety on...Pull trigger with about 10 pounds of force...or roughly double the normal amount that you'd use to fire the gun. Hold the left side of the gun up to your ear, right on top of the safety. Overcock the hammer slowly and listen for a light click. If you hear it, the sear has rotated away from the bottom of the hooks. If you don't, either it didn't rotate or the hooks pulled the sear back to the bottom when you released the trigger...which is why I like slightly undersquare hooks on carry guns.

Technically, the sear shouldn't move, but if your hooks haven't been chopped off to less than .023-.025 inch, a thousandth or two won't let the gun fire with the safety engaged. I like .025-.027 inch hooks, incidentally...but that's just me.

Standin' by...

 

[Jammer Six]

Well, there you go.

It's all good, then.

The problem with the click test is that I have trouble hearing my Old Lady yell at me from across the kitchen, there's no way I'll ever hear a click made by such tiny parts...

It's why I liked the dial indicator.

I can SEE it. As long as I'm using the BIG one...

 

[Old Fuff]

SOB!!!

What have you done to my poor genuine USGI safety???

Actually, Tuner is right again. The 1911 was designed to be a service pistol, and if the parts are made to blueprint specification, safety locks (manual safeties) can be interchanged without fitting and work most, if not all of the time. This presumes that the hammer hooks have not been shortened (something military armorers never did) and all of the meaningful angles on the hooks and sear nose are correct. Under these circumstances a little wiggle involving .001" +.002"/-.0005" will make no practical difference.

The problems come when someone makes a mess of the trigger pull by "adjusting" the hammer and sear, and/or new aftermarket parts don't come close to original specifications and dimensions. If you are one of those folks that want to carry the piece cocked & locked and have reduced the trigger pull to under 4 pounds (especially if it's "crisp, with no creep) there had better be zip play between the sear and safety lock when the safety is engaged. Otherwise you're good to go.

 

[Jim K]

OEM and GI Hammer notches are (or should be) cut at an angle so that moving the sear is done partly against the tension of the mainspring. This is not only for safety but also to ensure sear reset. If the trigger is released before the sear disengages, the angle of the notch will let the mainspring force the sear back into full engagement rather than leaving it part way out of the notch. Most "trigger jobs" involve changing that angle to lighten the pull, making the pistol a little less safe.

With a GI hammer, having the sear move it past full cock is normal, for the reason given above. The movement was slight, meaning the safety was doing its work, and the sear appears to have reset properly once trigger pressure was let up.

Jim

 

[Jammer Six]

Is there another field test, one for those of us who are deaf in one ear and can't hear out of the other?

I didn't do much to it, 'Fuff.

I used a dremel, then I finished it with a stone, then I stretched it back out with peening, polished it down with the dremel with a craytex bit, soldered an extension back on, and now I'm using a belt sander to get it just right.

Dremels are JUST the thing for working on safeties, but they're not quite as fast as a good, strong belt sander running some good belts. If you crank the speed up, it takes the material right off. Very efficient, and quite a bit of control over the angle.

I mean, as long as you can have a few thousandths of play when you're done...

 

[Old Fuff]

Your good words will be passed on to the Old Fuff by the EMT's who are trying to revive him ...

 

[1911Tuner]

Test for the Deaf

Yup...What Fuff and Jim K said. If the angles are right, the hooks tend to pull the sear back to the bottom. A couple thou movement won't make a difference, 'cause the sear will either reset, or it won't go any further...but it oughta reset. If the angles have been changed and the hooks shortened to...oh about .018 or so...all bets are off.

If ya can't hear the click...Let Miz Jammer listen for it. Most women have ears like a miniature sonar systems.. That's how they can hear what you're talkin' about to your neighbor clean out in the back yard...while they've got the TV on...and the dishwasher goin'...with the baby hollerin'...and they're on the phone...and watchin' dialin' for dollars.

Make double-sure the thing's unloaded first though...

 

[Jammer Six]

'Fuff, whattayabet that Tuner likes his click test because he hasn't been able to hear glass break since 1997, and he hasn't heard a sear click since five years before that...

I mean, given his advanced years...

I bet he thinks ALL his safeties are good to go...

"Nope! Didn't hear a thing!"

 

[Old Fuff]

WHAT YOU SAY BOY ???? I CAN'T HEAR YOU ....

But yes, I too suspect that his safety's work at least as well as mine ...

And ya' don't have too worry ... If you don't hear the click, the BANG!! that follows will get your attention.

 

[1911Tuner]

Click?

I can hear the click. I just have a problem hearing a telephone ring if I'm not in the same room with it due to the constant ringing, though...and there ain't a thing the docs can do about it. The other thing I have a problem with is most female voices, which can actually be a good thing sometimes...

 

[Jammer Six]

It's sopranos that I can't hear. I can hear altos just fine.

It's the chirpers that I annoy.