tap type for extra deep threads
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  1. #1
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    Default tap type for extra deep threads

    I need to tap 3/8-24 about 1/4" longer then a conventional tap flute length. An extended or pulley tap does not solve the problem. I have seen a few taps that would pass through the threads they have cut or at least are reduced diameter for a short length after the cutting flutes end. Is there a special name for this type of tap. I do not have a boring bar small enough to single point this on the lathe.
    Bill D

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    If you were to under cut the tap on the lathe with ceramic , would that work?

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    Quote Originally Posted by redlee View Post
    If you were to under cut the tap on the lathe with ceramic , would that work?
    Or spin in it in a drill in front of the bench grinder.

    Your relief needn't be pretty, though uniformity can be important for stress mitigation.

    Sent from my SM-G930R4 using Tapatalk

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    With this style of tap: McMaster-Carr It's a DIN standard (I think), and McM has other styles than this one. As it's a cobalt steel, if you grind it try to vacuum the swarf away with a good HEPA filter to avoid breathing any of it.

    Sometimes you'll get the length you need from the relief, or can use the relief as a "safe zone" to ensure a grind or cut with carbide or CBN doesn't damage the actual thread geometry.

    I've cut taps with regular carbide inserts - they won't be usable for regular work afterwards, but they'll do the job.

    These "nut taps" are extra long with relief-diameter shanks, but are more expensive and four flute hand style (which I hate compared to spiral point) which will work as-is. https://www.mscdirect.com/browse/tn/...061+4288247598

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    Nut tap> never heard the term. i will look for some. Thanks.
    Bil lD

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    No doubt special order, but deep hole taps do exist. I have this 3-flute one by Threadwell with about .5 inch more thread than normal.. It is marked 3/8-16 NC HS G H 5 3896-2 772 STL P 5544.

    Larry

    dsc02340.jpg

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    Quote Originally Posted by L Vanice View Post
    No doubt special order, but deep hole taps do exist. I have this 3-flute one by Threadwell with about .5 inch more thread than normal.. It is marked 3/8-16 NC HS G H 5 3896-2 772 STL P 5544.

    Larry

    dsc02340.jpg
    I turn taps and hss endmills all the time in my hardinge chucker, 3000 rpm light cuts using worn inserts.

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    MSC calls them "extension" taps. And yes, they are more expensive, but they work well.

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    Quote Originally Posted by Milland View Post
    With this style of tap: McMaster-Carr It's a DIN standard (I think), and McM has other styles than this one.
    DIN 376 (din 371 would be the thick shank)
    For example DC Swiss | N420-4

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    din 374? i have never seen a 371 tap except 3 mm and smaller. interestingly unc/f taps seem to be primarily thick shank. why is that? it wont break at the shank anyway, right?

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    I have a bunch of reduced shank extension taps. They aren't very hard to find.

    3/8-24 | 45743 | Small Shank Spiral Point Extension Taps - Reiff & Nestor

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    OSG has a line of spiral flute taps that have reduced shanks. They work great.

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    Reduce the shank on a standard.
    Emuge is the brand I prefer.

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    Can carbide reduce the shank of a tap in the lathe? Someone here said PCD will cut it fine.
    Bill D

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    Quote Originally Posted by Bill D View Post
    Can carbide reduce the shank of a tap in the lathe? Someone here said PCD will cut it fine.
    Bill D
    I do it with used up inserts, spin it fast, feed it moderate, taks small cuts. I wouldn't want to make dozens that way but if you just need one and would like it now. Very pretty my wife says as the bright orange shavings come off and turn to rainbows, I cool it between cuts but not while cutting. Used cermet works too.

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    Easy to snap off...Phil

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    Quote Originally Posted by Bill D View Post
    Can carbide reduce the shank of a tap in the lathe? Someone here said PCD will cut it fine.
    Bill D
    CBN would be correct tool for turning, PCD probably less than ideal.
    Carbide ”works” also, depending on tap and luck you might need one or several inserts per tap shank.

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    Could you explain why a pulley tap won't work? I believe you but I just don't see the problem somehow. It seems many posts are explaining how to relieve a standard tap, which is exactly what a pulley tap is.

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    Quote Originally Posted by Bluechipx View Post
    Could you explain why a pulley tap won't work? I believe you but I just don't see the problem somehow. It seems many posts are explaining how to relieve a standard tap, which is exactly what a pulley tap is.
    Seem to be "pulley tap" means different things depending on who you ask:
    Union Butterfield 15195/8X11X8 $173.05 Pulley Tap, HSS, Bright, 5/8" x 11 | Zoro.com

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    Default pulley taps

    Mattij, you are right, that's not my idea of a pulley tap, even though it is. I somehow came across about 10 of the 5/16-18 "real" pulley taps all new, anybody want to do some trading?pulley.jpg


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