April 23, 2012

Replace Flat Sear Springs With Coils

With apologies to Chet Atkins, a guitar string makes a fine substitute when you need a replacement spring in a hurry.

Before I moved from California to Texas, my son sent me his friend Mike’s old Hopkins & Allen double-action revolver to fix. Mike was displeased because it had no double-action unless it was pointed down. This nearly always indicates that the lifter spring—hands spring, if you prefer—is broken, but can be indicative of a few other maladies.

The material we’ll cover here can apply in a multitude of firearms situations, but I’d like to tell it as a narrative of a particular job because I learned a lesson about myself that changed my outlook on telling you “how to do this and that.” Having to really live “Back To The Basics” was an humbling experience that should help my writing.

By telling it as it happened, I can share with those of you just starting out the thought and decision-making process I go through when I approach a simple but borderline dollar-value job. I assume some of the same thoughts might go through the heads of novice gunsmiths and those with no shop to play in.

I had wanted to move back to my native Texas for several years or, more like it, move out of California with its many restrictions, high prices and cold attitude of business. About the only thing I’ll miss about California will be a few really good friends and the gun shows. California shows seem to be full of knowledgable gun fanciers despite some of the stiffest firearms laws and fewest shooting places of any place in the country.

Caught up in interviewing, accepting a dream job, and moving to an apartment in Austin until our house sold in the depressed California real estate market, I postponed working on the gun until I got settled. With my wife Arlene remaining in the San Diego area to sell the house (and shop), I was alone and without a shop for the first time in more than 19 years. This put me off doing the promised work on Mike’s gun even though I had some time on my hands. When I faced reality, I procrastinated because I didn’t want to do the work without all my toys and machines. Boy, had I gotten spoiled.

When I finally got ashamed of keeping the gun so long for such a simple task, I looked through my catalogs to see if parts were still available for that model of Hopkins & Allen. If not, I decided to make one because the time involved in finding one would far exceed the value of the gun.

The Hopkins & Allen I was working was a solid frame, removable cylinder pin, double-action revolver with about 50 percent of its nickel plating left. Most of the older guns have the nickel plated directly over base metal, so there isn’t the bond you can get if you first plate with copper or brass. The little gun was ugly and worth nothing as a shooter but having had guns like this in the past, I could understand how he might want it fixed if the cost wasn’t prohibitive. For all I knew, it might have been handed down in Mike’s family, so I obeyed my usual practice of not denigrating his gun or telling him it wasn’t worth any high repair bill until I looked into the gun’s overall condition. It was in about the same mechanical condition that it had been when it left the factory. Since the cost of a sear spring or lifter spring wouldn’t exceed $10, I just started looking for the part, knowing I could make one if necessary.

Tools & Techniques, Chapter 22 Replace Flat Sear Springs With Coils

Courtesy, American Gunsmith

As a mechanical engineer working in design every day, I have an acquired aversion to flat springs until everything else has proven impossible to use. They have a greater stress per space available than any other type of spring and their elasticity limit can be exceeded far earlier than that of a coil or torsional spring in the same situation or space. But this one was working and I don’t fix things that aren’t broken on someone else’s gun.


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After removing the grip panels, the assembly steps were pretty obvious; the cylinder was removed by pushing in the cylinder pin spring, (not a button or lever on this gun, but a bent wire spring that stuck through a slot in the frame to engage the cylinder pin groove). Pulling the pin and the cylinder, I was reminded that the loading gate usually had to be opened on most revolvers of this type and I swung it open and removed the cylinder.

The trigger guard was next, as it held pressure on the pins that went through the sear and trigger. This was obvious to me but I realized I had come to feel that way from experience. After doing such a job several times, the reassembly steps make disassembly the next time even easier. The trigger guard is held on by two screws, one in the front going up into the frame, and one at the rear going into the grip frame.

When the trigger guard came off, the flat leaf trigger return spring at the front of the frame and held in by the guard itself was easy to take out. It was in good shape, looking as if it had been replaced in the recent past. These religious-fish-shaped flat leaf springs are quite common in revolvers made from the 1900s through the 1930s but are about as poor a design as one can use for the job. As a mechanical engineer working in design every day, I have an acquired aversion to flat springs until everything else has proven impossible to use. They have a greater stress per space available than any other type of spring and their elasticity limit can be exceeded far earlier than that of a coil or torsional spring in the same situation or space. But this one was working and I don’t fix things that aren’t broken on someone else’s gun.

The trigger and sear pins were pushed out next and the trigger assembly, with its cylinder lifter, came downward and out. The lifter (hand) spring was still operating well and actually had quite a bit of strength, which ruled it out as the suspect part. The hammer was next on the disassembly list. The hammer is held in by a fillister head screw through the frame and the pivot hole in the hammer so it was taken out with the appropriate slot bit from my prized Brownells screwdriver set. Interestingly enough, there was less screw slot abuse on this gun than on most like it I had encountered. Maybe the people working on it in the past shared my belief in using the proper screwdriver bit for each screw.

Lifting the hammer out exposed the culprit—a freely flopping double-action sear. The little spring that should have been holding the sear out from the hammer was broken off where it was held into the hammer. This leaf, or flat, spring appeared to have had a 180 degree bend near one end that formed a loop to hold the spring into a slot/hole arrangement. I have seen this in other revolvers of that period. Early revolvers utilized flat springs quite a lot until someone arrived at the conclusion that coil springs last longer and go through less stress than do thin, flat springs.

I decided to try obtaining a replacement from one of my favorite parts suppliers rather than get the tail-end use out of a spring from a used parts dealer. Jack First Distributors of Lancaster, California checked and apparently had the replacement that I needed. As it turned out, I must not have made myself very clear because they sent an entirely flat piece of spring stock. I ended up making a replacement out of some stainless spring stock but I should have saved my effort. Replacing a proven bad design with another of the same ilk is an exercise in futility and I should have known it. The design was almost on the edge of spring steel’s elasticity limit and needed to be replaced with another spring design.

Tools & Techniques, Chapter 22 Replace Flat Sear Springs With Coils

Courtesy, American Gunsmith

Above: The tools needed for this conversion job include long-nosed pliers, a pin punch, a C-clamp, a screwdriver, two drill bits, a drill motor, lube, and a guitar string (although a new one wasn’t necessary).

Whenever I can, I incorporate coil compression springs into a design as they are far more reliable than other springs, suffering less from prolonged pressure and combine the internal action of a torsion spring and the bending action of a straight round wire spring. Since I knew Mike, at least through my son’s reports, I didn’t call to check about using another kind of spring in his gun. I would have talked to an owner I didn’t know before changing something in an old gun. Even when the gun has no real value, certain individuals want it “just like it was when Grandaddy had it.” That’s a valid reason to keep it that way because some people never plan on using the old guns. They’re keeping them for nostalgic reasons and customizing often changes their feelings toward the guns.

Tension springs are more apt to break and didn’t fit this situation. Normally, I could handle that in just a moment. But the spring collection I have acquired over the years was in my shop back in California and I didn’t know a place to get instrument springs in Austin. Faced with winding a spring without my homemade spring winder and not having any spring wire stock with me, I felt like I was going to a gun fight with a pocket knife in my hand.

In another life, I dabbled around with guitars and knew the strings were the same—basic music wire—as that wire used for winding coil springs. My electric drill motor would suffice for the rotational power I needed, a 5/64-inch drill bit inserted flutes first into the chuck would be the mandrel I needed, and an 0.012-inch guitar first string would serve as the wire. I taped one end of the string to the drill chuck to anchor it and gradually crept down on the trigger until it turned very slowly. Keeping the feed angle so there was an even separation of the coils being formed around the drill bit/mandrel, I sped the drill up and wound about a half inch of coil spring. Since I had only one 0.012 inch string and the next size I had was 0.015 inch, I conserved all I could to give me another chance if I needed another diameter spring.

Not having a vise or workbench in my apartment, the 12-inch kitchen bar served as a bench and an aluminum C-clamp filled in for the vise. With the double-action sear mounted to the hammer, I noted where there was enough metal to drill a hole for the spring and marked the location, giving the spring the best angle of attack that I could. Wanting the spring to be confined to the hole as much as it could, and not having much thickness with which to work, I compromised between the optimum amount of confinement, (near the pivot pin of the sear), and the optimum leverage, (nearer the end of the sear).

Noting the angle that the sear would push the spring, tangent to the radius from the pivot, I slightly angled the confining hole into the hammer to help the sear force the spring toward the pivot more than toward the end of the sear itself. I drilled the hole until the bit’s tip barely broke into the hammer’s pivot hole and cleaned the resulting burr from the hole.

Tools & Techniques, Chapter 22 Replace Flat Sear Springs With Coils

Courtesy, American Gunsmith

Above: A kitchen bar serves nicely as a bench and a C-clamp fills in for a vise when drilling out the coil-spring hole in the hammer. The drill also winds the spring for you.

In deciding how long to cut the spring coil, I opted for the long side since I haven’t yet figured out how to splice a spring. I needed the sear to have the minimum pressure to return reliably and quickly enough so the trigger spring wouldn’t have to be strengthened. I also needed to be sure that the spring was short enough not to bottom out, closing all the space between coils so that it became a solid tube. This called for cutting the spring several times, assembling the sear and hammer together with the spring, and twiddling it with my finger to check how it snapped back out. When the “snick” got to be just a “click,” I felt it was ready to oil and reassemble.

The sear is first to go back into the frame, with its heavy end to the rear. I pushed the sear pin through the rearward lower holes in the frame after the sear was aligned with these holes. The hand was not taken off of the trigger, so these parts were ready to stick up into the frame. Pushing the hand to the rear so that the hand plunger and spring were pushed into the trigger, the assembly was inserted into the frame with the land behind the breech wall. When the assembly got into the frame, the hand automatically jumped through the hand window in the breech. The trigger pivot pin was pushed through the frame and trigger.

Installing the trigger guard on this model of Hopkins & Allen is easier than it is on quite a few Colt, H & R and Iver Johnson revolvers. You just has stick the trigger spring into the recess in the frame with the upper (and longer) leg resting in the notch in the front of the trigger. The trigger guard is just pressed into place and the two screws are installed.

Using my long-nosed pliers, the mainspring was fitted up into the notch in the lower rear of the hammer and coerced into the front lower inside of the grip frame. The grips, cylinder and cylinder pin finished the job.

Now the reckoning. I dry-fired the little revolver to test the double-action function and to see how the trigger’s sear dragged over the hammer’s double- action sear. Did the trigger return spring have enough umph to depress the coil spring I installed, and would the guitar string I used play in tune? Yes and no, respectively.

Since I would not be communicating with my friend directly, I decided to write a note telling him what I had done and the conditions under which it was done. It’s not a big deal to change the type of spring when it benefits the firearm’s function. And, it didn’t take a lot of tools and machinery to do it, just some thoughtful planning.


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