1911 Safety fitting question??? Need help

[Bushman15]

I there folks....newbie here to this forum, not new to gun building.

I'm working on a do-it-yourself 1911 project right now. Taking a stock 1911A1 and cut in beavertail safety and adding ambi thumb safety.

I have also bought and Ed Brown hardcore hammer and STI - S7 sear. The thumb safety is also an STI unit.

Doing the fitting tonight and see that the safety will not go in....here is what I'm seeing.

It's obvious that something has to give......the sear or the safety....before I start gringing and ruining parts what do you say?

Thanks much for any input you can offer.

Chuck

 

[gunjunky]

Don't grind

Welcome to the board. Looks like you have a fun project going on. Working on your own pistol is a lot of fun and very gratifying. It all pays off when you shoot it the first time and everything works like you want.

Now to your safety. Do not file the sear. You will have to remove small amounts of material from the thumb safety, right where it contacts the sear. If you look around the board I am sure you can find a detailed post with pictures to help. Go slow with lots of file/check and it will go in easier than you think.

Good luck and enjoy.

 

[highorder]

yes, fit the safety to the sear, not vice versa.

 

[jrhines]

Look at the top sticky in this forum

It has some great pics of what you want to do

 

[Bushman15]

Thanks guys...I'm gonna work the safety stub unitl it fits snug.....I don't want anymore that .005" of sear movement witht the safety on and squeezing the trigger.

 

[HammerBite]

Look at the top sticky in this forum

That sticky is great for showing the relationship of the parts, however, in my opinion, the gun has a poorly fitted thumb safety. In the top picture there is a considerable gap between the safety stud and the sear. It looks to me as if pulling the trigger would almost move the sear enough to drop the hammer. That could lead to a dangerous situation when the safety is subsequently switched off.

The safety stud should fit lightly snug against the sear.

Notice how Bushman15's picture very nicely shows the function of the sear spring legs: Left one on the sear, middle one on the disconnector and the right one sticking out ready to tension the grip safety.

 

[brickeyee]

"I don't want anymore that .005" of sear movement witht the safety on and squeezing the trigger."

When correctly done there should be ZERO.
The sear is ~0.020 deep.
Allowing 0.005 movement is 25%.

NO MOVEMENT

 

[BBBBill]

First things first. Have you done the "trigger job", i.e. are the hammer and sear final fit to each other? No more work planned there? If so, proceed. If not, stop right now! This must be completed first.
Second. Did you check fit of the thumb safety to the bare frame (no hammer/sear) to insure that it will fit flush and move through its arc unimpeded? You don't want to be confused and confounded by resistance from one place and go filing somewhere else.
I see that you are using reversed hammer and sear pins. Are these the pins that you will be using with the gun? Pins and holes are sometimes tapered (not good, replace/ream as needed with the proper tools). And be sure that either end is not protruding from the frame enough to keep the safety from fitting flush.
There is more to it than that to get a "premium" level of fit, but that will get you started towards a safe installation.

 

[Bushman15]

All good stuff...thanks to all who have replied.

I would agree that "zero" sear movement would be ideal, however, I have checked several very "tight" guns and have found nerry a one that had "zero" sear movement.

And frankly that would require an interference fit between the two components...I'm just learning about this 1911 smithing business, but that sounds darn near impossible to achieve, and still have the safety function properly.

Has any smith out there put an intererence fit on their safety work???

I have poured over Jerry Kuhnhausens Shop Manual and he does not mention any allowable movement of the sear???? Just that depot rebuild specs called for replacement if the sear moved more than .005" when the trigger was firmly squeezed with the safety engaged (on).

At any rate, intereference +/- .001" is a real tight fit for this part...very careful filing required!

Also, the trigger job is complete, hammer and sear are mated with proper sear 45 degree breakaway clearance cut etc. I have not final polished the trigger legs, disconnector top, spring contact points etc. Those items should not effect the sear fitting though.

I'll let you know how this turns out. Thanks for the input.

 

[Bushman15]

Saved for pictures

 

[brickeyee]

"And frankly that would require an interference fit between the two components...I'm just learning about this 1911 smithing business, but that sounds darn near impossible to achieve, and still have the safety function properly.

Has any smith out there put an intererence fit on their safety work???"

All the time.
You switch to stones for the last bit of fitting on the safety.
The thumb safety travel to the on position is stopped by the sear.
You remove enough metal from the thumb safety so it still stops with ZERO clearance on the sear, and far enough upwards to be caught by the plunger and held.

 

[BBBBill]

... I have checked several very "tight" guns and have found nerry a one that had "zero" sear movement...

Then they are misfit.

...And frankly that would require an interference fit between the two components... but that sounds darn near impossible to achieve, and still have the safety function properly...

Not nearly as hard as you think. brickeyee explained it well. For a GI spec gun, .005" may be acceptible (not to me). What you must understand is that you have huge engagement surfaces on GI guns compared to a tuned gun. Hammer hooks cut to .020", sear relief angle cut to 1/3 of the engagement face, leaves you with ~.013-.015" actual engagement. Add that .005" safety slack and you've only got .008-.010" actual bearing surface. Highly polished hammer hooks and sear face to eliminate crunch/creep also means no drag/friction such as you would have on GI spec guns, making it much easier for the sear to move. Then let's hope that you got neutral or very slightly captive angle on your slick hammer hooks and sear face so that the sear isn't being force out from under the hammer hooks by the force of the hammer spring, dropping the hammer as you swipe off the safety. ZERO movement is the only acceptible answer. The fact that you are asking questions/seeking advice/input is good. Good luck.

 

[Bushman15]

"The fact that you are asking questions/seeking advice/input is good."

Well...thanks so much for your honest input....I'm old enough to know that if I'm gonna do this that it has to be right....no sense in doing it wrong and having an unsafe situation, or ruining a part.

If zero sear movement is the gold standard on a tuned gun then I'm gonna strive to achieve it....it may take me a week of stoning, but that's what I'm gonna do....you guys say it can be done...so that gives me the info that I need to make it happen also.

I will let you know how the job goes! And thanks to all....I'm learning!

 

[Walkalong]

If you go slow and check often, it is possible to get a very "snug" fit which will allow virtually no sear movement. It needs to have enough clearence to slip off safety easily as well. You will know when it is right. File until it is a tight fit (no play. It will go in and "on safe", but is to tight) then polish down until it is just right. Slow and easy, be patient, you can't put metal back on.

Cylinder & Slide posts a good Safety Check for 1911's on their website.

 

[Bushman15]

SUCCESS....I took everyones advise and just went real slow...like over 3hours to file and stone the safety engagement until it was just right.

The sear to hammer engagement looked like this.

Thanks for everything...I have sure learned alot doing all this.

 

[Bushman15]

SUCCESS....I took everyones advise and just went real slow...like over 3hours to file and stone the safety engagement until it was just right.

The sear to hammer engagement looked like this.

Thanks for everything...I have sure learned alot doing all this.