Posted: 3/2/2014 1:54:32 PM EDT
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A couple members asked me to post up on fitting a 1911 thumb safety. This is by no means an all inclusive essay on fitting a safety, as there are a lot of additional considerations for getting a perfect feel. For this post, I'll assume the reader can detail strip a 1911. There are plenty of tutorials easily found if that's not the case. I realize this has been done before, but someone asked, and I'm happy to do it.
I'm going to go over fitting a Wilson Combat ambi safety. For the most part this post will apply to just about any 1911 safety out there, but I chose an ambi for some additional considerations. I'll address function, form, and feel. First off, let's examine the part itself. The primary area of fitting is the sear block, where there is an over sized ledge that will require cutting. This is the part that actually blocks the rearward movement of the sear. It can wear several thousandths of an inch after fitting and not be an issue, but your goal is to get a perfect fit. The arrow shows the area we'll be fitting. You can fit this area a variety of ways. I like to use an old worn out 1911 locking lug file, since it cuts very smooth and efficiently, and lends itself to leaning the file one way or another during cutting. Some people use a stone, such as coarse or medium India stone. If you use a file, it's best to use something with a very fine cut. The choice is yours. 
The area of the sear that is blocked by this ledge is highlighted here. These two sears are an STI on the left and a stock Springfield on the right, by the way. More on that later. 
Before we get too involved, I want to discuss an area of potential trouble. I rarely see this appear as an issue, and I never see anyone mention it. However, I thought it best to include this. I've only ever seen this while fitting Ed Brown safeties. The area in this picture above the sear block ledge is hollowed out for a reason. It's a relief cut for sear movement when the safety is in the off or down position. It's highlighted in the third picture. On some Ed Browns this area can be almost non existent. It's something that can lead to incomplete sear movement, resulting in anything from a failure to drop the hammer to the hammer hooks rubbing the sear face when the trigger is pulled. The latter can be disastrous with a Series 70 hammer, as the half cock notch can shear and disable the gun. I had this exact issue with one of my first 1911s when I failed to address this area back in 1987. If you don't have enough in this area, send your safety back, or hog it out. I use a carbide cutter on a Dremel or on a milling machine, depending on my mood. 
This shot shows a previously fit safety in the down position, with plenty of space for the sear to move back into: 
Another area of concern is a relief cut on the underside of the internal lug. This relief cut allows the safety to be depressed once assembled to the frame. On occasion a frame can be wide at the safety lug cut out. Also, the relief cut can be too low, or too thin. If it's too thin, you won't get the safety to move much in the way of downward movement once it slips into the frame. If it's too low, or shallow, then you will have limited downward movement, resulting in a safety that sits too high when disengaged. That can be a cosmetic issue, or it can lead to incomplete disengagement. It can also mean that the detent relief in the face of the safety sits too high, resulting in a mushy feel or a safety that bumps on too easily or accidentally. Trial fit the left side paddle into a disassembled frame with no detent or fire control parts present. Check for complete up and down movement. Again, I usually only see this with Ed Brown safeties, as their lug seems to be more oversized than most. To deepen or widen the relief cut, you'll need a safe sided file, or a really keen eye and steady hands. Be sure to maintain the original lines of the relief cut and watch for the lug itself as it's easy to hit with the file. Here's the relief cut I'm talking about: 
Before going further, disassemble the frame, remove the fire control parts and safety/slide stop detent, and reassemble with the sear spring, grip safety, and mainspring housing in place. Keep in mind if fitting an ambi, you will also want to trim your sear and hammer pins flush with the frame. Failure to do so will can result in a sloppier feel with the right side lever. Also, the lever will tend to walk out and partially disassemble easier. When building a gun for someone else I trim my pins on a lathe if it's a detail oriented build. However, you can grind them down a variety of ways and trial fit them. The goal is to get them flush to the frame. In this particular gun I had spare pins from another gun. They're actually too narrow, but it's my kid's gun so it's not an issue to us. Also note the potential interference point with the top of the grip. If this becomes an issue after fitting the safety, trim the top of the grip. Our goal at this point is to check for freedom of movement up and down. We want to see how the joint between the ambi levers fit too. Ideally it will be tight, rather than loose, but not so tight as to preclude easy removal. The choice is yours on how to get a perfect fit between the joints. I can go into that further if someone wants advice, but that's a long issue to address. The thing to be cautious of is that tightening can break the female tab(s), especially if the safety you're using is MIM. A small note on removing the off side, or right side lever. If you have a hard plastic faced hammer, one of the easiest ways to remove a tight right side lever is to rap the frame on the right side, just under the safety or just in front of the top grip screw bushing if the grip is removed. While we're here, check for smooth up and down movement. Make sure the face of the left side lever where the detent cut out is does not interfere with the cut out in the slide. Every once in awhile you have to dress the front in order to allow an interference free fit into the slide. Also make sure the top corner of the safety isn't too sharp for the cut out in the slide. Finally, check for binding of the grip safety. If you have a tightly fit beavertail in place, and the pin on the previous safety was smaller, you might get binding. Make sure your grip safety still engages and blocks the trigger, and that it swings freely up and down. If it's tight but still engages, it might not disengage and be held in place by the trigger once assembled. If things are too tight, open up the safety pin hole in the grip safety, or dress the rear of the frame tangs. 
Now that we have that out of the way, let's get started on the fitting aspect. Disassemble your frame, remove the grip safety, as well as the safety/slide stop detents, and reassemble. I swung my hammer strut out of the way for the purposes of photographing the sear and safety engagement. Assemble yours with the hammer strut in place, as you need tension on the hammer to keep the sear in the right relationship to the safety. Our goal here is just to get the grip safety out of the way so you can see the engagement between the sear and the safety block. Note the ledge I mentioned in the beginning. Here it's shown blocking that bottom portion of the sear. This is a Wilson stainless ambi safety that has already been fit. It's in the up, or engaged position. 
Here's the same shot with the blued Wilson ambi that is uncut. It's very hard to see in this picture, but the ledge is too large to allow the safety into the gun. 
You're going to cut that ledge a small amount at a time, and trial fit in your gun. Once you make a small cut, check your work often. Try to make sure you keep your cut parallel to the face of the ledge. You can't always judge by the actual ledge itself, as some safeties come from the factory with a crooked ledge. Most of your quality after market safeties are pretty squared up on the face of the ledge though. Some considerations on cutting the ledge are how to hold the safety, as well as angles. I place my safeties in a padded vise. I like to use leather lined vise jaws. I do most of my work at a friend's gunsmithing shop, but since I'm at home, here's my jury rigged set up with rubber vise jaws and a lame vise on my reloading bench. 
Again, when making the cuts, try to keep the face of the file perpendicular to the safety paddle, as you want a squared up ledge against the back of your sear. A crooked ledge can result in a fit that is initially tight but wears out prematurely, leading to failure of your safety. Also, note the angle of my file. In case anyone with a sharp eye notices at this point, the file I'm using here has safe sides, and the cutting edge is shown up. I didn't want to mar my uncut safety, so I didn't put the cutting edge against the safety. Sorry for any confusion. 
If you reference the rear of the sear relief cutout on the lug, there's a face I highlighted in red. It's okay to go up to parallel with this face, but it's better to open up the angle a little bit. What I have pictured isn't an exact science. You can ink your ledge with a permanent marker when fitting once you can barely get it in the gun, and then perfect your angle and engagement. 
Keep fitting until you barely get the ability to move the safety up into place. When you're getting close, you'll want to check the fit with the slide on. Resist the temptation to simply line the slide up without the slide stop in place and without tension from the recoil spring. You want everything as it will be when assembled. Your goal is a tight but consistent lockup. If it starts up into the relief cut in the slide but gets tight towards the fully engaged, all the way up position, ink it and look at where it needs to be cut. Go very slowly at this point. A hard Arkansas stone might be appropriate. You can take metal off too quickly, and once gone, you're in a pickle (if you do go too far, don't fret, as the fix won't necessarily be a new safety). Once you do get the sear blocking ledge properly fit, then it's time to try it out with the detents back in place. Flick it on and off. It should slide up and down fully into place. Do this without the grips on the frame. If the feel is mushy, now is the time to address that. How crisp it feels is dependent on the angle shown here, as well as how high the bottom curve is behind that corner. If the safety, while in the up or fully engaged position, doesn't flick off with a crisp "snick", then you need to look at the detent. If the bottom curve behind that highlighted corner is too high, the detent will be too depressed, and lead to a safety that has too little spring engagement. If the corner is too rounded, you get too spongy a feel. Adjust accordingly. I raise that bottom radius using a carbide cutter on a Dremel. I make the corner sharper using a file against the face. It's a matter of finesse though, as you want to remove only a little bit of material. If you choose to remove metal from the face to sharpen up the corner, realize you will likely have to deepen the detent cut out. You'll need a small ball cutter on a Dremel, or better yet, a detent cutter as sold by Brownells. 
Hopefully we now have a safety that blocks the sear when engaged, has enough relief when disengaged to allow complete rear movement of the sear, a safety that has a satisfying on and off "snick", and if it's an ambi, one that has a slop free joint that feels as nice when operating the right side as it does on the left side. We need to make sure that the right side grip doesn't interfere with the downward movement of the right side safety, and the same on the left. If you didn't trim your pins before, now is the time to do that too. Trim your grips if needed. Also, make sure the underside of the left lever, if extended, doesn't rub against the plunger tube. Finally, if you are installing an ambi and it has the traditional Swenson style tab this Wilson does, you need to relieve the underside of the right grip panel for freedom of movement.
Once we're all back together, consider this part. The curve on the underside of the left lever won't match up with the contour of the grip frame. You can cut the contour on a Dremel. If you do, realize that you will have a finish that no longer looks professional. You will need a refinish of some sort if that bothers you. Also, if you do use a Dremel or something similar, remember to address the back side, as you will now have a small raised bur that will continually scratch your frame. A small round needle file or a scraper can take care of that quick. Ed Brown's have next to no contour in this area, and it's intentional. If you contour this area, and engage your safety up, you will likely see the hole in the frame where the sear blocking lug fits through. Most of the time an Ed Brown will cover this area. Up to you if you want to cut on an Ed Brown. 
Remember to address the opposite lever too, as the corner may be sharp. Again, you can address this in a number of ways, such as a buffer, files, stones, sandpaper, or Dremel. It's up to you. Now it's time to function check, with an unloaded gun of course. Pretty simple, just make sure it flicks on and off, make sure your plunger tube is snug so that your detent doesn't walk out over your left safety binding it up, make sure it blocks the sear in the up position. With the safety engaged, pull the trigger firmly, then slowly push down on the top of the hammer to check for a click. If there's a click you over cut the sear blocking ledge. If you did everything correctly earlier, you shouldn't get a click. If you did over cut, don't worry. You can get a new safety, or perhaps a cheaper alternative would be a larger sear. This is what I was referring to at the beginning. An STI sear has more material at the rear base of the sear, which means an otherwise overcut safety can often be salvaged with an STI sear. An STI sear will be cheaper than a new ambi safety, or most single side safeties. A final note on the safety. If you have hamhocks for hands, you can inadvertently push the bottom of the safety up when the gun is hammer down, slide shut. Doing this while trying to rack the slide can result in the top of the safety moving up enough for the corner to engage the slide. Most smiths will dress this corner slightly, as a 1911 safety has a little free movement when the gun is hammer down. Some will round the corner, others cut a bevel. I usually round the corner slightly, but on this gun the free movement was a bit much. I had to cut quite a bevel on this gun to alleviate this potential issue. The corner of the safety that can be an issue is highlighted. 
While this is a long post, there's actually a lot I'm leaving out. Good luck to those who asked for this, and if you have any questions feel free to contact me. |
| Good post. It'd be nice to get this copied into the 1911 Resource Page |
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Thanks, but I think that Brazos Custom page is pretty good. I didn't even know there was a 1911 resource page. |
