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  • #31
    Originally posted by Dan Dubeau View Post
    What makes a roll tap suitable for use in steel or other material vs softer materials like aluminum? The ones that we have at work, I was specifically told by our tooling vendor that they were for aluminum and soft materials only, and don't use them on steel. I never really questioned that, because we do 95% aluminum anyway, but now I'm curious. I know there are different types, like the tri lobes, with grooves etc, but are they all material specific, or was I fed a line of bull?
    Coating on the tap maybe? IIRC, aluminium likes sticking more to some coatings, titanium nitride maybe? Then again, that would only explain why steel-specific ones shouldn't be used in aluminium, not the other way around...

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    • #32
      Originally posted by mattthemuppet View Post
      You worked on the James Webb telescope? That is beyond cool! My neighbour over the road shot the paint on the Cassini probe, which is also super cool. Shame it burnt up/ got crushed in Saturn's atmosphere.

      There are an awful lot of people that are really REALLY excited about the James Webb going up
      Yep was at a table top meeting for a Sun shade mockup. Was used in the parking lot with a meade 10 " 12 years ago. Then the cryocooler which is everything to make it happen. Last was RF feeds up and down links for data. Hope it works??? I have a lot of NGC stock sitting @ $ 391.00 a share? Nothing like working 40ft in the air on the mirrors.

      DR - I used roll taps to open up tight helicoil holes.
      Was not in the specs that we couldn't? In a clean room no metal chips are aloud so the roll tap was our best friend !! They have their purpose, but still not used for flight hardware at Northrop Grumman. BTW.. most everything is threadmilled.
      High quality carbide Hobbs.. 1 1/2 turns and you are done.
      Last edited by Fasturn; 10-14-2021, 04:41 PM.

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      • #33
        Originally posted by DR View Post

        I believe you were fed a line of crap. Back in the day I don't recall seeing any roll taps being listed as material specific (there might be now though). I bought both coated ones and uncoated, as a rule I would have used uncoated for aluminum only because I usually used everything uncoated for aluminum. In steel the coating or missing coating could give an indication of tap wear which we started to have after a couple thousand holes in steel.

        The grooved relief type were a problem in all materials with deep holes, even though it's a chip-less operation you still get a mush of swarf flakes to clog the groove.

        I have a theory roll taps work best in machines with fixed feed, as in rigid tapping on CNC's or lead screw tappers. Nothing to prove that theory, but then all taps perform better that way.

        We used to keep a running score of the number of holes we'd get for a certain tap, 5200 holes was the highest in 10-32, 7/8" deep in 12L14. We lost the tap in job setup, when the lathe changed tools the tap hit the end of the workpiece and broke.
        Thanks for the info. The ones we have are bright finish with grooves. This tool guy knew everything... so it's a possibility. I've lost count of the # of holes this one has tapped. The previous one was replaced because it was knocked off a bench and broke. Not sure of brands, no info left around. For our needs/purposes they are amazing, but as mentioned about stress, they are not an end all be all solution.

        Maybe I'll start trying them more in steel and see how they work. I know they've done it before, but not being production here it's generally not a big deal to grab a different drill/tap for steel parts.

        Epic, yeah he could have been talking specifically about the coating too. Don't know, it was a long time ago, and I took it at face value and didn't really investigate it much. I got them specifically for aluminum, and they've done that job very well over the years.

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        • #34
          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...........

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          • #35
            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.

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            • #36
              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+.
              21" Royersford Excelsior CamelBack Drillpress Restoration
              1943 Sidney 16x54 Lathe Restoration

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              • #37
                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

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                • #38
                  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 ~

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                  • #39
                    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?

                    2730

                    Keep eye on ball.
                    Hashim Khan

                    Everything not impossible is compulsory

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                    • #40
                      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.

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                      • #41
                        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
                        Green Bay, WI

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                        • #42
                          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.


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                          • #43
                            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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ID:	1966004
                            How does that happen ? I would think it would be a clean V angle.

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

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                            • #44
                              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.............

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                              • #45
                                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 !

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