Roll Taps (Flute-less Taps)

[epicfail48]

Form taps are awesome, especially in smaller sized. Making butterfly knives a while back, i needed to put a 2-56 thread 7/16" through o1, trying to do that with a cut tap resulted in a broken tap about 60% of the time no matter what i did. Form tap with the proper drill went through like butter, under power no less, without any broken taps. The lack of flutes makes the taps way stronger

[johansen]

When i get around to it, im going to try and make a thread forming tap from a grade 8 bolt that has been squished between 3 complient surfaces such as mild steel, to press the bolt into a triangular profile, then harden the bolt.

the pitch diameter might be high but most bolts are on the low side of things to start with.

[mochinist]

not saying roll form taps can't be used in steel at all (though I think work hardening forms of stainless are a no no), just that I don't have the balls to try it yet

We use them down to 2-56 and m2x.04, in aluminum, steel, and stainless 303/304/316, almost daily in a job shop environment. For the smaller sizes we tend to drill and ream

[DR]

not saying roll form taps can't be used in steel at all (though I think work hardening forms of stainless are a no no), just that I don't have the balls to try it yet

A little secret...there are easy machining stainless alloys. 316 Carpenter Project 70 was one we used a lot. Amazingly easy to machine. Unfortunately Carpenter has gotten hard to buy small quantities from of late. Other stainless mills produce their own versions.

What they do is skew the elements that make machining difficult to the low side of the alloy spec. The elements that help machineability are skewed to the high side. And the material is fully annealed . Cost is two to three times regular material, but worth it in the savings on tooling.

[mattthemuppet]

that's good to know, thanks.

[tomato coupe]

We use them down to 2-56 and m2x.04, in aluminum, steel, and stainless 303/304/316, almost daily in a job shop environment. For the smaller sizes we tend to drill and ream

Yep, they work great in materials that work harden. We use them for blind M3x0.5 in invar.

[Fasturn]

Didnt read all the post, but they are used to repair a damage internal thread. Puts the folded over / damaged thread back in form without removing metal. Many companies ( air craft / space ) do not allow this kind of tapping. They are fine for the commercial boys? I have a love / hate for these taps.

[mochinist]

Didnt read all the post, but they are used to repair a damage internal thread. Puts the folded over / damaged thread back in form without removing metal. Many companies ( air craft / space ) do not allow this kind of tapping. They fine for the commercial boys? I have a love / hate for these taps.

yeah my shop doesn’t do aerospace work at all so can’t speak for that industry, the customers we do work for covers a wide range of other industries and I look at an average of twenty or so new prints a week for quoting purposes, for the past twenty years and have never seen no roll form tap callout on a print.

[DR]

Didnt read all the post, but they are used to repair a damage internal thread. Puts the folded over / damaged thread back in form without removing metal. Many companies ( air craft / space ) do not allow this kind of tapping. They fine for the commercial boys? I have a love / hate for these taps.

Hmmm, are you sure about that? Virtually all nuts are threaded formed.

[Fasturn]

Hmmm, are you sure about that? Virtually all nuts are threaded formed.

Well when you have worked for TRW, and Northrop Grumman for the past 25 years... Yeah you would be fired cuz the stress guys dont like rolled threads! Not that I have anything with roll tapping. Just have to get the minor right or..... Snap ! That's the love / hate.

[tom_d]

Well when you have worked for TRW, and Northrop Grumman for the past 25 years... Yeah you would be fired cuz the stress guys dont like rolled threads! Not that I have anything with roll tapping. Just have to get the minor right or..... Snap ! That's the love / hate.

I can understand not wanting a rolled thread when specifying a tapped hole as standard policy to prevent stress cracks in a thin walled part. When it comes to AN bolts though, aren't they all made by rolling the thread? I thought cut thread bolts were taboo in aerospace work.

[Dan Dubeau]

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?

[Fasturn]

I can understand not wanting a rolled thread when specifying a tapped hole as standard policy to prevent stress cracks in a thin walled part. When it comes to AN bolts though, aren't they all made by rolling the thread? I thought cut thread bolts were taboo in aerospace work.

That's the funny part, stress guys didnt like the cracks ( electron scopes and die ) but the bolts ,tapper head titanium and stainless were all thread rolled. What's not understood is when NASA builds a $ 10 billion satellite, it need to be slightly better than perfect ?? Was true for our division, no rolled tapping on flight hardware. That bird is the J Webb telescope on it way to be launched.

[mattthemuppet]

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

[DR]

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?

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.