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  1. #1
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    Drill & Tap Combination "DRAP"

    Anyone used these before? I am having a problem with run a M4-0.7 thru 3/8thk Aluminum. They keep snapping off. Also running 1/4-20 DRAP. Any help would be much appreciated.

  2. #2
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    I've seen them, but have stayed away from them for just that reason. I would think a tool like that would only work on very specific applications. Let us know how you resolve the issue.

    'Rekd
    Matt
    San Diego, Ca

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    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  3. #3
    Moderator HuFlungDung's Avatar
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    To tap that thickness without a chip clean move ( or three) would be equivalent to tapping 75 mm plate with a 24 mm tap without stopping to clear the chips. You can program two or three G84's in a subroutine to provide the chip break and clearing.

    You would be better off to use a seperate tap with a spiral point (for a through hole), or use a cold forming tap.

    For deep threaded holes, you are usually safe to increase the tap drill diameter just a whisker, in order to make it easier to cut threads. Unfortunately, the DRAP locks you in to a process with very little flexability.
    First you get good, then you get fast. Then grouchiness sets in.

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  4. #4
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    Yeah that is what I thought I have already changed to a drill and tap. Just not enough clearance.

  5. #5
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    I use them on 11 gauge CRS. Only to avoid a tool change. The part I use them on has 6 1/4-20 holes thru. So I use a DRAP and first drill all 6 holes at 110 SFM then go into tap mode at 60 SFM to tap the six holes. Not much of a time savings but every bit helps.

  6. #6
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    I've used an M4 drap on nominally 3/16" tk. Al and don't ever remember breaking one. I did it to save on tool holders--what's your excuse? I spot drilled with an engraving point but a center drill or real spot drill would work also. I wasn't concerned about location as much as a burr-free, countersunk top surface. I drilled through the part at high rpms, then called a G84 which was ridgid tapping mode. This was a very slow operation since the spindle was always changing speeds or direction. You have to use a drap in a hand fed drill press and a tapping head or in a CNC machine with ridgid tapping! A floating tap holder is not going to be ridgid enough for drilling in a CNC and you can't use a ridgid collet or tap holder in a CNC without ridgid tapping.

  7. #7
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    i personally use roll form taps with everything i do... sure it takes 3 holders to spot, drill and tap but youd be hard pressed to find a better tap for longevity i like the feature that mazak added into their m640 where you have a full retract style tapping so you can take depth cuts with a tap for chip clearing... i dont know if any other companies offer this because ive worked solely with mazatrol for the past 5 years with only a little fanuc turning and fadal milling experience prior

  8. #8
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    I never use one of those unless the material is less than the length of the drill flutes. I am not sure if those are capable of drilling and tapping at the same time. If they are, I will be surprised.

    Good luck.

  9. #9
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    Maybe I should proof read before I hit send. I mean "material thickness< drill flute length"

  10. #10
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    only way i would ever use a drap in thick material would be if it were a fine thread and i was spinning the tap at like 1300 rpm... like i said before roll form works for me... i can tap at 4000 rpm with a 6-32 tap 3/4" deep with no problem

  11. #11
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    Re: Drill & Tap Combination "DRAP"

    Is there such an animal as a thread forming drap ? (Combined drill & thread forming tap)

  12. #12
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    Re: Drill & Tap Combination "DRAP"

    i answered my own question; it's not possible to make a combined drap-thread forming tap since the final minor diameter of the threaded hole ends up smaller than the drill diameter. (Thread former displaces material towards inside of hole)

    Lol, would make a good trick question though.

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