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drill size for taps

Kimbercolt
does anyone have the chart, drill size for tap?
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9 comments

Date Votes
  • hawkeye6020
    quote:Originally posted by Kimbercolt
    does anyone have the chart, drill size for tap?


    Yes, what size are you needing?
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  • hawkeye6020
    here you go

    http://www.engineersedge.com/tap_drill_chart.htm
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  • shoff14
    Remember, drill size charts are calculated on a 75% to 80% thread engagement. Threads only need 50-55% to work just as well as they would at the higher percentage of thread. So look at the drill chart, then go with the next size larger. No reason to strain yourself or break a tap when you don't have too.
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  • FrancF
    quote:Originally posted by shoff14
    Remember, drill size charts are calculated on a 75% to 80% thread engagement. Threads only need 50-55% to work just as well as they would at the higher percentage of thread. So look at the drill chart, then go with the next size larger. No reason to strain yourself or break a tap when you don't have too.


    Not to mention harder or softer material, Two flute, and three flute taps, type of cutting fluid etc.
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  • shoff14
    quote:Originally posted by FrancF
    quote:Originally posted by shoff14
    Remember, drill size charts are calculated on a 75% to 80% thread engagement. Threads only need 50-55% to work just as well as they would at the higher percentage of thread. So look at the drill chart, then go with the next size larger. No reason to strain yourself or break a tap when you don't have too.


    Not to mention harder or softer material, Two flute, and three flute taps, type of cutting fluid etc.


    4 flute, spiral flute, spiral point, bottom, plug, taper, i can go on [:D]

    You could always be fancy and find someone to mill it with a thread mill. [:D] Raises hand

    There are two reason why taps are broken, you start the tap at an angle or you have to use to much pressure because of improperly sized hole. There really is nothing like taking an fixture that you have been working on for 2 days to your boss while working on the very last thing that needed done, "i broke a tap" oops isn't quite the correct word. Lucky for me, there was someone with a sinker EDM in town.

    I made a tapping block after that of all the sizes from #4 all the way up to 1/2" so my taps started straight.
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  • dheffley
    quote:Originally posted by Kimbercolt
    does anyone have the chart, drill size for tap?


    Lots of variables there. Are you going to use a cutting tap or a forming tap. There is a big difference in drills sizes for the two.
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  • FrancF
    Exactly!!
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  • Alpine
    Use a tapping head. Then the clutch will stop the tap before the tap breaks.
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  • shoff14
    quote:Originally posted by Alpine
    Use a tapping head. Then the clutch will stop the tap before the tap breaks.


    You can still break a tap in a tapping head. Besides who has the equipment at their home to use a forming tap, or who has the money for a snow tapping head. Heck, their collets are $76.00 a piece![:0]
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