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Drills and taps for hardened receiver

Discussion in 'Gunsmithing and Repairs' started by Sun Tzu warrior, Jan 10, 2013.

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  1. Sun Tzu warrior

    Sun Tzu warrior Member

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    I am wanting to mount a Pachmayer Lo-Swing scope mount on a SS hardened receiver. Does anyone know a good source for carbide drills and taps?
    Thanks in advance!
     
  2. rcmodel

    rcmodel Member in memoriam

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    Brownell's sells Carbide drills.

    I don't know of anyone selling carbide taps, because they would break way too easy.

    I seriously doubt your stainless receiver is as hard as you think it is either.

    Receivers are typically not hardened super hard because that would make them so brittle they would shatter when fired.

    Exactly what kind of rifle is it?

    rc
     
  3. 4v50 Gary

    4v50 Gary Moderator Staff Member

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    High speed steel. Break off a carbide tool and it's tough to remove.
     
  4. Sun Tzu warrior

    Sun Tzu warrior Member

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    It is an early Mini 14, Has the "R" with a circle around it. Have drilled one hole (had to use carbide), and a tap wouldn't touch it.
     
  5. Jim K

    Jim K Member

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    Spot anneal it.

    Jim
     
  6. rcmodel

    rcmodel Member in memoriam

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  7. Sun Tzu warrior

    Sun Tzu warrior Member

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    Thanks guys! I wouldn't want to change the integrety of the receiver by heating it.
    The "R" with the circle, indicates Rugers initial problem with the heat treating of receivers, was corrected on this perticular weapon, wouldn't want to revisit that problem.
    Guess I'll just quit while I'm behind. I will just fill that one small hole with a ductile iron plug.
     
  8. 1911Tuner

    1911Tuner Moderator Emeritus

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    How hard is it? Rule of thumb...If you can file it, you can drill it.
     
  9. Kp321

    Kp321 Member

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    I drilled and tapped one of those early SS Mini-14's several years ago. My advice is to use a no-drill mount. I finally got the job done with a carbide drill and new hi-speed tap for each hole.
     
  10. Sun Tzu warrior

    Sun Tzu warrior Member

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    I can drill it, with a carbide drill bit, the tap however wont touch it. The tap is high quality from a mill supply, the bit is correct size for the tap. Can't get the tap to even start. I admit.... I'm chicken! Glad I tried to tap before drilling the other 3 holes!
     
  11. Jim K

    Jim K Member

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    Spot annealing shouldn't affect the heat treatment of the receiver. It uses a tiny flame to heat a spot about 1/4". Some folks say an electric soldering iron will do the job, but IMHO those won't get hot enough.

    Jim
     
  12. 4v50 Gary

    4v50 Gary Moderator Staff Member

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    BTW, I don't recommend scoping a Mini-14. The shell ejector shoots the empty case straight up and into the scope base or if a two piece scope base, into the scope body. Eventually the scope will break.

    That's why Ruger developed the Ranch. It has side ejection and a buffer to dampen the recoil.
     
  13. ApacheCoTodd

    ApacheCoTodd Member

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    Are you trying "spiral point" taps for the initial cutting?

    Also for me:

    When not available
    AND
    When unaffected by the lessening of the first couple threads
    I've bevelled and/or over-drilled an appropriate depth to allow the engagement of an otherwise problematic tap. Of course a fella's got to have sufficient engagement on the available full meat threads further down the hole.
     
  14. jmorris

    jmorris Member

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    Carbide taps are common in the industry. Google "carbide tap"
     
  15. jmorris

    jmorris Member

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    This one was done with both a carbide "drill" it actually burnishes the hole then a forming tap makes the threads.
     

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  16. jmorris

    jmorris Member

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    It is for forming high pressure NPT threads in SS. The "drill" pushes extra material down inside the pipe to allow for good seal.

    Not really what your asking about but the only example I have at arms length.
     

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  17. jmorris

    jmorris Member

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    Saves a lot of time and money vs welding and x-ray tests.
     
  18. Miked7762

    Miked7762 Member

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    It won't cut because you are literally forge welding the tap to the receiver. The tap displaces the chromium oxide layer and as it reforms due to oxygen exposure it traps the tap. You need an appropriate cutting oil that is high in sulfur content. It will prevent the oxide layer from reforming until the tap is removed.
     
  19. ApacheCoTodd

    ApacheCoTodd Member

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    Boy now there's a tip I missed. In addition to what I posted above, another factor in my past successes has been the use of Rapid-Tap. I bought a distributor out of it when it got outlawed in California and am still using up my copious reserves to this day.

    The difference showed immediately in the tool's life extension when we were using it to work ATS-34 before and after heat-treat. Fast, cool happy cutting with over a three-fold extension in tool life. Sweet!
     
  20. Sun Tzu warrior

    Sun Tzu warrior Member

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    Thanks everyone for the advice! My "Spidy senses" are telling me to leave well enough alone.
     
  21. docsleepy

    docsleepy Member

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    I'm not an expert on receivers and hardness but surely the receiver will hold together without the ENTIRE THING being harder than a file!!!

    I don't think steel anneals unless you exceed the critical temperature. If you have already created the hole, it should be much eaiser to use a very small oxyacetylene tip and heat the surface metal on the inside of the hole to just red hot (in a dark room) and allow to cool slowly. This might reduce the hardness enough to allow tapping.

    Of course, my willingness to try this would vary depending on the cost of the receiver involved.
     
  22. Clark

    Clark Member

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    I have drilled holes in annealed 4140 and the tool got hot and then got hot or the tool got hot and then got dull. At any rate, it made a spot that I can't drill with high speed steel or Cobalt. So I have to order a carbide drill. I hate it when that happens. So I flood the drill with coolant when going through tool steel.

    I would not have guessed it, but it looks like the mini 14 stainless receivers ARE hardened.


     
  23. Sun Tzu warrior

    Sun Tzu warrior Member

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    This perticular rifle has a serial number above the re-call, and one proof mark. So apperantly, although not "Excessively hardened" still hardened never the less.
    I was aware of the re-call and also that this one was not included. Thanks Clark, I don't think some belived that this receiver was hardened. Again, thanks guys for the input, but I am still shelving the project, due to consideration of "the cost of the receiver involved".
    As Docsleepy stated.
     
  24. rodinal220

    rodinal220 Member

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