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Thread: Tapping Problem

  1. #1
    Join Date
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    Default Tapping Problem

    Hi All

    I'm trying to re tap an existing thread in a 12mm square lathe toolholder. The existing thread is imperial and because I cant locate the correct screw to hold the carbide insert I want tap it to 3.5 metric. So far I've had no success and have broken two 3.5M HSS taps. Is tool holder steel generally very hard? Would I be better of with a tungsten tap?

    TIA

    Scott

  2. #2
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    Default

    Hi Scott
    What size did you drill it out to and was it easy to drill

    Phil

  3. #3
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    Quote Originally Posted by Steamwhisperer View Post
    Hi Scott
    What size did you drill it out to and was it easy to drill

    Phil
    Phil

    From memory the tap drill size is 2.9mm and the existing hole is a little bigger. I ran a 3mm drill through which just knocked the tops of the existing threads.

  4. #4
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    Have you thought that the Tap you are using is catching in the existing threads and causing it to break.
    Is the Tap your using Fine or Coarse pitch?
    Last edited by pipeclay; 30th Jan 2012 at 05:10 PM. Reason: more

  5. #5
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    Default

    No. I was hoping the tap would recut the existing threads.

  6. #6
    Dave J Guest

    Default

    You will probably find it's at least case hardened, are you using some sort of lube with it?

    Dave

  7. #7
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    Quote Originally Posted by Dave J View Post
    You will probably find it's at least case hardened, are you using some sort of lube with it?

    Dave
    Yes, Tap Magic.

  8. #8
    Dave J Guest

    Default

    Unless you anneal it, you are probably going to keep on having problems.
    Not sure if you know how, but you heat it up and cool it slowly, the slower the better. You will then have to re harden it again when your finished, or could just leave it.

    Don't forget the tool holders are only cheap from CTC so don't go spending to much on taps.

    Dave

  9. #9
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    What's the imperial screw size? As the US economy is still largely imperial, I'm having problems with the idea of an imperial screw not being obtainable. (Large degree of difficulty yes, but we are machinists (or wanabees) - problems are made to be solved!)

    Michael

  10. #10
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    Tool holder shouldnt be that Hard will be Tough.
    Is it a fine or coarse thread.

  11. #11
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    Quote Originally Posted by Dave J View Post

    Don't forget the tool holders are only cheap from CTC so don't go spending to much on taps.
    Yep that's were I heading.

    What's the imperial screw size? As the US economy is still largely imperial, I'm having problems with the idea of an imperial screw not being obtainable. (Large degree of difficulty yes, but we are machinists (or wanabees) - problems are made to be solved!)
    OK - not easily obtainable in regional NSW and I dont feel like trawling the internet trying to find one in the US. Plus I'd rather all my tools using the same screws.

    Is it a fine or coarse thread
    Its coarse - 3.5 x 0.6.

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