Detailed Guide to Roll Taps

Technical article courtesy of  Regal Cutting Tools
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Most craftspeople will agree that whenever an internal thread can be made with a roll form tap, this is the tool that should be used for the job. Roll taps, also known as form taps, hold distinct advantages over cut taps. Roll tap advantages are inherent in the way they create the threads.

As the names suggest, these taps form the threads by rolling and deforming the material inside the hole. They push the metal out of the way to create the thread roots and base. Cut taps, also true to their name, carve metal away from inside the hole, ejecting chips as they go.

Reasons to Use Roll Form Taps

Roll taps are a great option when considering workmanship and price point. First, roll taps are chipless. Because they do not remove material from the hole, form taps generate no chips that must be removed. This carries several advantages:

• Tool Life – Cut taps have flutes cut into them through which chips migrate up and out of the hole during threading. Flutes take away the taps’ bulk and rigidity, weakening them and making them more susceptible to wear and breakage.

• Efficiency – Flushing chips from a blind hole and disposing of them takes time. Roll taps eliminate this wasted time so machinists can thread more holes in the same amount of time. Roll taps’ strength also permits their use at higher feeds and speeds, increasing their efficiency even more.

• Thread Quality – Forming threads rather than cutting them creates more precise pitch diameters and surface finishes. Just as important, rolled threads are stronger than cut threads because the metal grains are deformed along the thread contours.

• Speed – Roll form taps should be run at 1-1/2 to 2 times the speed of a cut thread tap for a given material. The forming action creates heat and can “work harden” the material being formed. It is a good practice to form the thread and reverse out of the hole as quickly as possible.

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When Not to Use Roll Taps

While an excellent choice for most applications, there are a few situations that do not lend themselves to roll tapping including:

• Threading a through-hole – Form taps may deform the exit hole, which will necessitate a second, time-consuming step to repair. Spiral-point cut taps are the best option for such a job. They push chips ahead of the cutting edges, keeping flutes clean. The chips fall harmlessly out the exit hole as the tap breaks through.

• You’re threading a big hole – Thread-cutting taps require less horsepower than thread-forming taps. Cutting large holes with a form tap requires twice or three times as much torque as with cut taps, which can take its toll when threading large internal surfaces.

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• The workpiece is hard –Form taps are suitable only for soft and malleable metals such as soft steel, some stainless steels, aluminum, copper, brass, and lead. Typically, the material to be formed should be less than 32Rc in hardness.

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Types of Roll Taps

Roll taps are engineered and manufactured in two main styles to match the type of hole and fastener to be used. Bottoming roll taps feature little to no taper on their end threads. This allows full thread production to the very bottom of the hole.

The bottom 3 to 5 threads on a plug tap are tapered to allow the tap to gradually begin deforming the hole material, creating less stress on the tool and giving the full threading edges a base from which to work.
 
Regal Cutting Tools has built a reputation for high quality taps and other metalworking tools and an uncompromising commitment to customer service. Regal manufactures a full line of roll taps to suit any application. Regal can even engineer custom taps quickly and affordably. To learn more about Regal’s taps and learn which products are best suited for your workflow, contact our team today.