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Old 04-03-2014, 03:30 PM
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Mainspring Housing Tune-Up



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Most often, mainspring housings don't offer up too many problems that require complete disassembly. In the event you want to "tune" your mainspring housing assembly up, to make it a much smoother operating feature on your Ruger Mark I, II or III pistol, here's a process that works for me.

The mainspring housing assembly in use here is from a Ruger Mark III Hunter Model. I realize that most folks here don't have some of the items I use in this demo to show how I smooth up these mainspring housings, but it's just to show you that it can be done, and these are the some of the steps involved.



Above shows the latch pivot pin, which must be drifted out of place to gain access to the mainspring housing internal parts that are intended to be polished. I use a jig to compress the mainspring housing spring and then drift the pivot pin out of place while the parts are still contained in this jig.



Once the latch pivot pin has been drifted over far enough, the latch detent ball and main spring will pop up for easy removal. With the above mentioned jig, once the latch pivot pin has been moved over and away from containing the spring, the screw is backed off (up) until all the tension on the compressed main spring is relieved. The ball, spring and the hammer strut cup can now be removed from the mainspring housing.



Above are the components in the mainspring housing assembly that are better served when polished. Some folks have had issues with the mainspring housing latch feeling gritty and rough when that latch is pulled for disassembly. The latch itself is a "stamping" and if you inspect your pistols latch closely, you'll see metal smeared over the edges from the stamping process. The radiused part of the latch rides on that hard steel ball when the latch is pulled down. With that rough latch radius on the smooth steel ball, you will feel that grittiness first-hand. Here I filed that radius smooth and then dressed it with #400 emery paper and then buffed it to a mirror finish. The mainspring was also polished on the periphery of the spring and the "cup" plunger for the hammer strut was also polished. As long as we're doing this polishing and smoothing of parts, it will pay to do the bottom end of the hammer strut also, as that too can be found with rolled-over raggedy edges that detract from smooth operation.



After polishing the radius on the mainspring housing latch, it will move much more easily. So will the bottom end of the hammer strut.



With all the internal parts removed and polished, the spring tunnel in the mainspring housing was then "lapped", removing all tool marks from the drilling process. An aluminum lap was turned to a "slip" fit in the tunnel and then with the last pass of the cutting tool, the tool bit was left in place and the cross-slide was just cranked over to the left, leaving a spiral in the lap for the compound used.



Here is where this jig does its part better than any other method I've tried to get those internal parts installed back into the mainspring housing. The hammer strut plunger is installed first, then the mainspring, followed by the ball on top of the spring. The screw is then turned down while the plunger pushed the ball bearing on top of the spring down and below the top of the mainspring housing until the latch pin hole aligns with the hole for it in the mainspring housing. Now, for the life of me, I can't figure out how anybody would be able to contain that ball on top of the spring, then push it down and into the mainspring housing, holding it there and in place long enough to insert the latch and pivot pin. Believe me, before I made this fixture, I tried doing what I just described. It's impossible.



Here's the assembly back together with a polished latch face that will ride much more smoothly on the hard, steel ball located on that end of the mainspring.



The latch pivot pin has been staked back in place with a method that I prefer more that the way Ruger does it. Ruger smacks hat pin one time, on each end, in the middle, or close to the middle to upset the diameter on each end of that pin. Unfortunately, those pins have still been know to drift with that process. I now prefer to use a center punch to roll over the edge of these pins with a dimple placed on the edge of the pin, 120-degrees apart, on both sides. This process seems to keep the pin in place more readily. Now, it has been mentioned that Volquartsen includes a "slave" pin with the reduced power mainspring, or hammer, pin they sell. Not so, the pin that is provided with the spring is just like the flock of pins I have in the above picture. Those are blued and stainless replacement pivot pins. So then, why does Volquartsen provide a replacement pivot pin with their reduced power main spring? From what I was told by Volquartsen, they provide a fresh pin because some customers have had much trouble trying to get the original pin back in place. That makes sense because the ends of the original pins have been expanded by the dimple that Ruger puts in 'em during assembly at the factory, so a fresh, NEW pin is much easier to install. In other words...........it's NOT a SLAVE pin.
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