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Roll Taps (Flute-less Taps)

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  • JRouche
    replied
    Originally posted by JoeLee View Post
    How does that happen ? I would think it would be a clean V angle.

    JL..............
    Kinda weird right? What about the vally in the crest of the thread point?

    That was an extreame photo of what happens very quickly. The vally and peak are made at the same time. The metal has to move and it does. With the pressures much of it is moved downward where we want it.


    The evcess is pushed up and out the top, the peak. Sometimes it gets folded which that pic looks like is what is going on..

    In real time the machine is so fast that the "fold" never developes. So its a "seameless screw. Or not..

    You dont ever want to see how your chicken, beer or cheese is made. Just enjoy it. JR

    Leave a comment:


  • mochinist
    replied
    Originally posted by JoeLee View Post
    So do these taps work with a tapping head at those RPM's ? I can't imagine stopping on time especially threading a blind hole. On a CNC yes, but that's still a pretty abrupt stop on the down feed.

    JL.............
    generally in an albrecht drill chuck(gasp) they are fast, easy and cheap to rebuild, sometimes a collet. Tapping head has a bunch of dust on it and generally not worth messing with. We have mitutoyu quill dro’s on all the bridgeports, bring the tap down on top of the work, zero and run it in, turn it off when its close and engage the brake at depth, sometimes finish turning the drill chuck by hand and take the tap a little deeper if needed, then reverse out. If the tap hole is real shallow, I just hand tap it with a guide.

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  • J Tiers
    replied
    Originally posted by Rich Carlstedt View Post
    The void (?) is a function of the tap drill size

    unfortunately drill sizes are too broad to get it exactly right, but regardless of the criticism, Rolled threads are stronger
    I have done rolled threads down to 00-90 and in steel

    Rich
    Even if it were to exactly match the volume to be displaced and the volume available, there would seem a guarantee of a "cold shut" at the thread crest.

    Originally posted by lbender View Post

    Almost all the strength of a thread is in the root, with the tip contributing virtually nothing.
    Having a defect in the tip, or even the tip removed completely doesn't weaken the bolt.
    On the other hand, the cold work from forming can increase the strength by several percent.

    Of course, it is cross-section. And 75% threads, yada yada.

    But that goes for both. Equal strength threads ought to fail at the point on the flanks where both have the same cross-section through the thread. The void created by the forming should modify that point, one would think.

    What you are arguing, and quite possibly correctly, is that the work-hardening adds more strength than the voids remove.

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  • Fasturn
    replied
    Originally posted by Rich Carlstedt View Post
    The void (?) is a function of the tap drill size


    I have done rolled threads down to 00-90 and in steel

    Rich
    That's very impressive, did you do it in one pass CNC, or peck cycle? What kind of steel was it?

    Not to play the one up game, but the smallest tap I ever used was a .055mm x 205 microminiture thread.

    Hand tapping with a microscope. The young bucks can have it ! ! Your one of the few that can do that kind of work. Kudos~
    Last edited by Fasturn; 10-15-2021, 04:31 PM.

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  • Fasturn
    replied
    Originally posted by lbender View Post

    Almost all the strength of a thread is in the root, with the tip contributing virtually nothing.
    Having a defect in the tip, or even the tip removed completely doesn't weaken the bolt.
    On the other hand, the cold work from forming can increase the strength by several percent.

    You got it right...... the compression of the thread makes it stronger in most cases. A sharp thd is last thing you want, so we truncate to 75 - 80 %. No strength in that last 20% . Ya need the clearence too so they dont bind. We had a saying the molding business : CLEARENCE AND GREASE !

    Leave a comment:


  • JoeLee
    replied
    Originally posted by mochinist View Post

    This is a homeshop site, but at work we dont really use them for hand tapping much, there is definitely more torque needed to turn, no idea how much. We run the smaller sizes into the hole at 600 rpm for smaller taps and 1000rpm for 1/4” -1/2” on the cnc’s, on the bridgeport I put it in low gear and run them somewhere in the 100-200 range. About the only time I see broken roll forms is when the machinist didnt size the hole properly. We keep the correct drill and reamer for smaller sizes together in a box with the tap, people are people though and it happens occasionally. We used to see way more broken taps when we primarily used cut taps.

    someone else mentioned their tool guy said they were only for aluminum… There are specialty roll form taps for “soft metals”, not for cast iron or hardened steels, it is mostly coatings and oil grooves, things that make a difference in production environment. That said, if the material is ductile, not hardened, and you size the hole correctly for the material and the tap, it will roll form a great thread that shouldn't be on airplanes.
    So do these taps work with a tapping head at those RPM's ? I can't imagine stopping on time especially threading a blind hole. On a CNC yes, but that's still a pretty abrupt stop on the down feed.

    JL.............

    Leave a comment:


  • JoeLee
    replied
    Originally posted by Fasturn View Post
    Roll taps not used on space craft hardware seem to have hit a nerve ? Here is another reason that industry is against that thread. The entrapment at the Crest would be bad. Corrosion and forgien objects can cause an early demise of the satellite. For the rest..... Roll a way !
    Cross section of roll tap thread ~

    Click image for larger version

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    How does that happen ? I would think it would be a clean V angle.

    JL..............

    Leave a comment:


  • lbender
    replied
    Originally posted by J Tiers View Post
    That void, which also exists for rolled thread bolts, would seem to reduce strength.
    Almost all the strength of a thread is in the root, with the tip contributing virtually nothing.
    Having a defect in the tip, or even the tip removed completely doesn't weaken the bolt.
    On the other hand, the cold work from forming can increase the strength by several percent.


    Leave a comment:


  • Rich Carlstedt
    replied
    The void (?) is a function of the tap drill size

    unfortunately drill sizes are too broad to get it exactly right, but regardless of the criticism, Rolled threads are stronger
    I have done rolled threads down to 00-90 and in steel

    Rich

    Leave a comment:


  • Dan Dubeau
    replied
    Decided to live on the wild side today, and jam that 1/4-20 roll tap down a few holes in some O1 gauge pins I'm making. 4 holes, all I needed, just fine.

    So much of what I do is the same, but the parts, shapes etc all all different and 1 offs. I get to the finish line the same way, with the same process, same tools etc. It's nice to step outside the comfort zone and learn something new once in a while.

    Leave a comment:


  • J Tiers
    replied
    That void, which also exists for rolled thread bolts, would seem to reduce strength, it really extends rather deep into the thread form. And yet, rolled threads are always stated to be stronger than cut threads.

    Anyone care to discuss that?

    Leave a comment:


  • Fasturn
    replied
    Roll taps not used on space craft hardware seem to have hit a nerve ? Here is another reason that industry is against that thread. The entrapment at the Crest would be bad. Corrosion and forgien objects can cause an early demise of the satellite. For the rest..... Roll a way !
    Cross section of roll tap thread ~

    Click image for larger version

Name:	download.jpeg
Views:	78
Size:	3.1 KB
ID:	1966004
    Attached Files

    Leave a comment:


  • JRouche
    replied
    Originally posted by Dan Dubeau View Post
    Also known as thread forming taps. They actually "form" the thread instead of cutting it. Stronger threads, and stronger taps that last much longer in production machinery than traditional cut taps. I've been using the same 1/4"-20 form tap in our haas' at work for about 5-7 years now (can't remember when I changed it), and the number of holes it's tapped has got to be in the 5 figure range. They can be picky about starting hole diameter, so be careful of that. They need a bit bigger hole to start with than a cut tap. For the 1/4"-20 I use a #1. There is information out there, but it's not usually contained on the normal machinist thread charts in circulation.
    That was a great write-up. Thats exactly what they are and what they are like to use.


    Over size yer hole when using. When used accordingly they are the ever lasting gob stopper. No cutting edge. You have to have a tourqe monster to use them. And they love lube, flood even though no chips. JR

    Leave a comment:


  • The Metal Butcher
    replied
    Originally posted by JoeLee View Post
    I've seen these for years but have never used them. I can't believe that the shanks don't snap, especially the smaller sizes under 1/4".
    Approximately how much more force does it take as compared to a good sharp cutting tap. Comparing the force to use a 1/4" cutting tap vs the same size form tap, what would be the difference ?
    What is the hardest material that these will work on ?


    JL...........
    I was looking up a cutting guide for tungsten and it said to use form taps. Pure Tungsten is generally 55 HRC+.

    Leave a comment:


  • mochinist
    replied
    Originally posted by JoeLee View Post
    I've seen these for years but have never used them. I can't believe that the shanks don't snap, especially the smaller sizes under 1/4".
    Approximately how much more force does it take as compared to a good sharp cutting tap. Comparing the force to use a 1/4" cutting tap vs the same size form tap, what would be the difference ?
    What is the hardest material that these will work on ?


    JL...........
    This is a homeshop site, but at work we dont really use them for hand tapping much, there is definitely more torque needed to turn, no idea how much. We run the smaller sizes into the hole at 600 rpm for smaller taps and 1000rpm for 1/4” -1/2” on the cnc’s, on the bridgeport I put it in low gear and run them somewhere in the 100-200 range. About the only time I see broken roll forms is when the machinist didnt size the hole properly. We keep the correct drill and reamer for smaller sizes together in a box with the tap, people are people though and it happens occasionally. We used to see way more broken taps when we primarily used cut taps.

    someone else mentioned their tool guy said they were only for aluminum… There are specialty roll form taps for “soft metals”, not for cast iron or hardened steels, it is mostly coatings and oil grooves, things that make a difference in production environment. That said, if the material is ductile, not hardened, and you size the hole correctly for the material and the tap, it will roll form a great thread that shouldn't be on airplanes.

    Leave a comment:

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