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  1. #1
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    Default Thread taps breaking

    Just busted 2 spiral thread taps, 3x.5mm
    Going 8mm deep into a 9mm deep hole in 6061 T6. Tried straight in and out and also with 4mm pecking depth, 3mm retract.
    I was able to remove both taps thankfully, and both had flutes full of swarf.

    I have done 100s of these no peck with a straight 3 flute bottoming hand tap! with zero issues same setup and machine, Robodrill. Just finished the job with the same original tap.

    Spiral taps i know are fragile in the reverse direction, which is when they seemed to break, but thought this would be no problem.
    Are they not good in smaller sizes?

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    Check your drill size. Run the biggest drill your spec will allow.

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    Same drill 2.5mm Only thing i changed was the style of tap.

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    Quote Originally Posted by Kenre View Post
    Same drill 2.5mm Only thing i changed was the style of tap.
    Check to make sure your tap and your drill isnt running out/ thats a common problem on smaller taps.

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    Form tap! Just be sure to control the hole to the correct diameter...

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    Milland,

    Might have to locate one and give it a go. Parts have rather thin walls so not sure if the thread will show.It wont affect function but will look ugly.

    I have one in 4mm, has done thousands of holes! Never in a CNC tho, only in a manual mill or cordless drill and it still lives.

    I thought Spiral taps were meant to wind the swarf out! not these ones.

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    Quote Originally Posted by Kenre View Post

    I thought Spiral taps were meant to wind the swarf out! not these ones.
    Some push the chips forward, some out the entry hole. If you have the former in a blind hole with only 1mm bottom clearance there you go.

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    Spiral point, or thread? Spiral point will still push the chips into the hole, spiral thread run them out of the hole.

    https://www.mscdirect.com/product/details/64048333

    https://www.mscdirect.com/product/details/87145629

    Also, a bottoming tap is alot more likely to break if you are using it to directly thread (instead of chasing a thread to the bottom) without using a starting (taper, etc) tap. We use thread forming taps with a modified bottoming point from 0-80 to #8 all the time without issue in aluminum and brass.

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    Mike, most certainly a spiral thread.

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    Quote Originally Posted by Kenre View Post
    Milland,

    Might have to locate one and give it a go. Parts have rather thin walls so not sure if the thread will show.It wont affect function but will look ugly.

    I have one in 4mm, has done thousands of holes! Never in a CNC tho, only in a manual mill or cordless drill and it still lives.

    I thought Spiral taps were meant to wind the swarf out! not these ones.
    Form tapping close to a wall will bulge it out.

    I always tap before I finish the wall when doing this.

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    Quote Originally Posted by Kenre View Post
    Just busted 2 spiral thread taps, 3x.5mm
    Going 8mm deep into a 9mm deep hole in 6061 T6. Tried straight in and out and also with 4mm pecking depth, 3mm retract.
    I was able to remove both taps thankfully, and both had flutes full of swarf.

    I have done 100s of these no peck with a straight 3 flute bottoming hand tap! with zero issues same setup and machine, Robodrill. Just finished the job with the same original tap.

    Spiral taps i know are fragile in the reverse direction, which is when they seemed to break, but thought this would be no problem.
    Are they not good in smaller sizes?
    blow out the chips from the drill and try some oil or tap magic because maybe there is a problem with your material.

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    Check your coolant type and concentration.
    I had similar problems at one point and found that the coolant being used was not reccomended for aluminum.
    Majority of the parts I make are toolsteel. Aluminum was actually something I hadent worked with for 10 years or more at the time.
    I couldnt get through 3 holes without breaking taps. I was even questioning the accuracy of my machine. Changed to a coolant reccomended for aluminum (much higher lubricity) and the problems all went away.

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    Quote Originally Posted by Milland View Post
    Form tap! Just be sure to control the hole to the correct diameter...
    I agree. Always ue roll taps in aluminum when you can.

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    Lots of great advise so far! I always trouble shoot one step at a time to find the cause and break things into 3 categories- program, part and tool.

    PROGRAM:
    - Speed/feed
    - Proper codes/sequence, coolant
    - Do drill and tap locations match?
    - Are drill and tap depth correct? (Is tap hitting the bottom?)

    TOOL:
    - Sharp/ good tap?
    - Correct tap type for application? (blind hole vs. thru hole)
    - Correct drill size for tap type
    - Measure tap for max depth
    - Tool held securely and is there run out/ wobble?


    PART:
    - Check hole size and depth w/ pin
    - Check part if it moved
    - Watch tool while single blocking

    If all else fails try a different style tap like a roll tap, change brands or add a peck to the tapping cycle.


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