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Hardness for Sear Surfaces

Discussion in 'Gunsmithing and Repairs' started by Johnm1, Jul 12, 2020.

  1. SGW Gunsmith

    SGW Gunsmith Member

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    Especially on Ruger Mark pistols. Over the years I have found that to be the case and can vouch for the through hardness of Ruger Mark sears. During the hardening process, in many cases the pivot pin hole will become distorted, and sorta elliptical. I have a set of carbide reamers in 0.001 increments that I'll use to get that pivot pin hole back to being round again so they work more smoothly. That does go beyond what some owners really need, but it does make for a much smoother operating trigger pull.
     
    Last edited: Jul 28, 2020
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  2. Johnm1

    Johnm1 Member

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    I am concerned about the pivot pin hole as well as the actual sear surface changing during the heat treating process. That is one of the reasons I am going to practice on a piece or two to see how the steel reacts. In my case, I don't have the proper tools to make it right after the fact and I may end up with a hardened piece that I can't finally fit.
     
  3. Blue68f100

    Blue68f100 Member

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    You may need to have you pin hole a 1/1000 or 2 under size if you get some scaling. If your using the SS foil bag it pretty much eliminates the scaling. Then use a Carbide reamer to clean up the hole.
     
  4. BBBBill

    BBBBill Member

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    You got that right! Those things are harder than woodpecker lips!
     
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  5. SGW Gunsmith

    SGW Gunsmith Member

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    After heat treatment Ruger grit blasts the sears to remove scale, that's why they have the dull finish they do. Can you post a picture with a factory sear that has heat treat scale still on it? After working with many, many Ruger factory sears, I've not seen one with scale in the pivot pin hole, or anywhere else on it:

    W9VFjgfl.jpg

    Here's just one example of a Ruger factory sear that I pulled out of a Ruger Mark II pistol. The owner complained about having a trigger pull that had an extremely rough trigger feel:

    hofSNIil.jpg
     
    Last edited: Jul 29, 2020
  6. Johnm1

    Johnm1 Member

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    That is one ugly sear!
     
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  7. BBBBill

    BBBBill Member

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    I have two of the Series 1 and a Series 2 with quite a few adapters. Excellent jigs for hammer and sear work! Got several of the other Ron Power tools, too. Ron Power tools are some of the best things that have come along for gunsmiths and serious amateurs.
    By this point Ruger probably expects everyone to buy Volquartsen parts.
     
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  8. SGW Gunsmith

    SGW Gunsmith Member

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    VC does offer an outstanding sear for the Mark I, II, III & 22/45 pistols, but only a complete kit for the Ruger Mark IV. As time allows, I've been experimenting with a few of the Ruger Mark IV factory sears and am close to getting those to improve and lower trigger pull weight and provide smoother interaction with the hammer notch. After spending what folks do for a Ruger Mark IV Competition Target, it's sort of a kick in the groin to need to shell out the amount necessary for a complete accuracy kit. I'm lookin' for a more economical, and functional system that involves using the factory parts. Gettin' pretty close. :)
     
  9. SGW Gunsmith

    SGW Gunsmith Member

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    Thank heaven they ain't all this way, but can you imagine what the trigger pull was like for this poor owner? If you look closely at the picture you can see where the hammer notch engagement burrowed into the sear.
     
  10. Johnm1

    Johnm1 Member

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    Both of you appear to be professionals. Working on a sear still intimidates me. After this experiment I have no idea if I can make this year surface work. At least I know how to tell if I failed. At least The sear appears to be simple. A flat surface with 90 degree corners. But the engagement is dependent on the relationship between the pivot and the sear surface for both angle and length from pivot to engaging surfaces. I’m not sure what wiggle room there is but I’ll know if it isn’t right.
     
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  11. SGW Gunsmith

    SGW Gunsmith Member

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    Over the years, I'm sure Bill, as well as myself, have found that getting, and keeping, the outcome of sear work safe, the aid of a well make fixture helps control what's being done and prevent from going TOO FAR. A vise alone to hold the sear just doesn't cut it.
    Rather than assemble the sears and hammers into the grip frame while I work on them, to check progress, I made up a set of pins whereby I can mount those parts on the outside of the grip frame in the exact holes for the pins they pivot on:
    HOuiKNQl.jpg
    Fitting sears to hammer notches is not a "one size fits all" proposition, especially on the Ruger Mark pistols I deal with quite often. During the manufacturing and production of the grip frames, the pivot pin hole locations have "positional tolerances" allowed. So, we can't rely on those locations being the same with every grip frame, and that's why I made up the pins to check progress in an easy manner.
     
  12. Johnm1

    Johnm1 Member

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    That is a brilliant idea that I would not have thought of. And, it seems I can fabricate this myself.

    Thanks for that!
     
  13. BBBBill

    BBBBill Member

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    Appearances can be deceiving! Lol! I'm just a serious amateur. Real pros have nothing to worry about. I had an FFL and enjoyed building guns for a number of years for the local shooters, but it was mostly a way to enjoy my hobby legally. I never tried anything on a customer's gun that I was not qualified to do and ejoyed a good reputation. Alas, Uncle Sam decided that he needed me again after 9-11, so all of that went out the window. Post retirement health issues related to my military service have limited my ability to reingage, although that seems to be getting better... at least until the next orthopedic surgery takes me out of circulation again.

    Yep. Brownells sold some for the 1911 and a couple other guns. Problem with those is that not all frame holes are the same size, so I like to have about 3 sets per gun type to account for the variations to be more precise. I like to use long gauge pins in the frame to check for parallel on the pin holes, too. I've found a number of frames over the years that had pin hole not parallel by several thousandths, leading to wonky hammer/sear engagement.
     
  14. SGW Gunsmith

    SGW Gunsmith Member

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    I've had no issues with the pins I made for the Ruger Mark pistols. The pin holes only vary a few tenths of an inch in size on the grip frames, and consider, those I made go through the frame and out the hole on the other side, just like the actual pivot pin works. That keeps 'em from being wobbly, if any is actually present.
     
  15. Jim Watson

    Jim Watson Member

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    Anecdote Alert: A guy here had a Norinco copy of 1911A1 and waxed poetic over the metallurgy. He just kind of tossed off the information that his had skew pin holes. No problem, he said, I just stoned the hammer and sear at the same angle to get full contact.
     
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  16. SGW Gunsmith

    SGW Gunsmith Member

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    Can't help but wonder how far those pin holes were "skewed", and then, if both sets of holes were skewed in the same direction. :uhoh:
     
  17. BBBBill

    BBBBill Member

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    You should see an early Colt OACP that I have. It was made during "the troubles" when the union almost shut them down. The right side hammer pin hole looks like it was drilled twice at different angles. You can insert the hammer pin or a gauge pin through the right side and tilt it about 30 degrees.
     
  18. SGW Gunsmith

    SGW Gunsmith Member

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    What a shame!
     
  19. Jim Watson

    Jim Watson Member

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    I don't know where you could find a real gunsmith to fix that, but it could be done. Probably cheaper to buy a correct gun.
     
  20. Johnm1

    Johnm1 Member

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    I have been a bit remiss in replying to this thread and thanking Dave. I got distracted on a Marlin 1892 that I have been working on for the last 6 months that I just got to the point of cycling and firing reliably. It has been a fun project. The progress on that project can be found here. https://www.marlinowners.com/threads/1892-rifle.611795/page-7#post-8370174

    I did receive the steel from David and now have something to practice on. It will be the most difficult steel to work with compared to what I probably will end up with as the 3V steel reaches the limits of my furnace. The 01 and similar types of steels austenitize at lower temperatures and likely will be the choice for the actual part when it comes time. This will test my ability to maintain temperatures both going up and down. Remember I have to monitor and adjust my furnace manually
     
    Last edited: Aug 19, 2020
  21. David Hoback

    David Hoback Member

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    My pleasure John.
     
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