Tapping Scope base Screws... what am I doing wrong?

Discussion in 'Gunsmithing' started by joshua99ta, May 22, 2015.

  1. joshua99ta

    joshua99ta Well-Known Member

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    BEFORE I HEAR IT AGAIN I KNOW I SHOULD HAVE LET A PROFESSION HANDLE IT.

    I picked up my new 6.5-06AI from my smith this week and instead of just getting them to do it(well I figured it would take another 3-4 months) I figured what the hell I'll do it I've done a few already. BUT the few I have done were on carbon steel actions NOT stainless.

    The stainless just isn't cutting much at all. I'm using an 8-40 tap and an 8-40 bottom tap, I'm using a bit that came with the setup from brownells. I believe its .139" and the OD of the tap is .155. So that's only .016" I'm having to cut but I can only get about 1/8 of a turn each time. I'll go in with the starting tap and come back with the bottom tap to try to clean it up.

    I've already broken 3 taps. IF I try to go much past an 1/8 of a turn it will just bind up and they just break. I've never had this much trouble tapping anything in my life!!!!!!!!!!
     
  2. MTBULLET

    MTBULLET Well-Known Member

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    use a #28 drill and LOTS of lube
     
  3. Trickymissfit

    Trickymissfit Well-Known Member

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    the issue may come from the type of tapping fluid your using. If it's something like Tapmatic, Tapfree, and a few other similar compounds; try something else. I like Anchor Lube for hand tapping stainless steel. There are better compounds yet, but most are home brew. Forget strait oil altogether.

    Breaking taps are often caused by chip build up in the flutes. I hope your not using a three or four flute tap! Use a two flute gun tap whenever possible.
    gary
     
  4. stenger

    stenger Well-Known Member

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    You have to break the chip. 1-2 turns and then reverse a 1/2 turn then repeat until done.
     
  5. EddieHarren

    EddieHarren Well-Known Member

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    How are you holding the tap wrench?
     
  6. J E Custom

    J E Custom Well-Known Member

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    +1

    Tapping fluid and the proper type of tap are very important.

    The reason that gun taps are normally two flutes is,= They are stronger and have larger groves between the flutes to help clear the chips. and the reason that this works better is= normally gun taps are very small 5x56 to 1/4x28 and most receivers are ether heat treated or surface case hardened,

    Carbide taps are great but if you break one off they are almost impossible to remove, so I recommend buying top of the line Taps (Not the cheep Chinese made ones).

    Also the use of a drilling/tapping fixture is recommended to hold the tap straight.

    J E CUSTOM
     
  7. EddieHarren

    EddieHarren Well-Known Member

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    "also the use of a drilling or tapping fixture is recommended to hold the tap straight."

    Exactly why I asked!
     
  8. shortgrass

    shortgrass Well-Known Member

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    And use a tap handle, not a Crescent wrench!
     
  9. Trickymissfit

    Trickymissfit Well-Known Member

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    just a side note to your post: a gun tap has the lead ground slightly different to make the chip string go back towards the handle. Hardly noticeable, but must work. I do recommend as you do, the use of a tap block to guide the tap strait. I've drilled and tapped #8-40 threads in just about everything from 1020CRS to 17ph4. For me anyway, CRS was the worst to deal with along with certain grades of aluminum. Not hard, but just very gummy materials.
    gary
     
  10. Trickymissfit

    Trickymissfit Well-Known Member

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    now don't knock the good old Crescent wrench! A lot of us would have been out of a job with out good old Crescent wrenches and pipe wrenches! (big hammers and Vise Grips too)
    gary
     
  11. bruce_ventura

    bruce_ventura Well-Known Member

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    A left-handed Crescent wrench is perfect for those pesky left-handed threads too!
     
  12. shortgrass

    shortgrass Well-Known Member

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    Use a metric Crescent wrench for metric threads! Really now, 8-40 threads should be no problem provided you're drilling the hole the right size, using a good high speed tap and a tap wrench, and using a good quality tapping/cutting fluid. I've been buying 6-48s and 8-40s from JGS Tool. Good high speed tools. Brownells is trying to become the "WalMart" for gunsmiths and some of the tools they offer, especially cutting tools with their name on them, are WalMart quality. MSC has special thread taps & dies, too. I do all my threading with the barrel removed Why deal with a 'blind hole' unless you have to. Sounds to me like you should have had a professional do it! 416R is no more difficult to drill and tap than 4140HT is.
     
  13. WapitiBob

    WapitiBob Well-Known Member

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    If you got the mtl hot when you drilled it, you're done. Stainless will get harder than the back of your head if it gets hot.
    Only getting 1/8 turn before the tap breaks tells me your hole is undersize or you got the mtl hot. I'm guessing it got hot. You could drop an end mill in there to open it up and roll tap it but you're not set up for that.
     
  14. shortgrass

    shortgrass Well-Known Member

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    Almost any hardenable steel, be it SS, medium to high carbon, or alloy can be 'work hardened' with the use of dull tools.