Technical article courtesy of Regal Cutting Tools 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 TapsRoll 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:
When Not to Use Roll TapsWhile an excellent choice for most applications, there are a few situations that do not lend themselves to roll tapping including:
Types of Roll TapsRoll 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.
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This is Part 2 of our series on Carbide taps. Be sure to check out Part 1 if you missed it: Carbide Taps: A Practical User’s Guide to When, What, How and Why Carbide taps have a lot of advantages, especially when you’re cutting very abrasive materials. The absolute best choice for tapping glass-filled polycarbonates, space age alloys, nonferrous materials, cast iron, and a range of other exotic materials, their anti-friction qualities lead to a longer tool life.
Standard Screw Thread Insert TapsS.T.I. (Screw Thread Insert) Taps are special taps for helical coil wire screw thread inserts, which provide positive means for protecting and strengthening tapped threads in any material. Typically used on softer abrasive materials, these taps create more accurate thread forms than other standard taps. When you need to be precise, these carbide taps are the best choice. STI taps are correctly sized to produce an internal thread that accommodates a helical coil wire screw thread insert. The insert, in turn, will accept a screw thread of the nominal size and pitch at final assembly. Screw thread inserts provide stronger tapped threads (stronger assemblies) due to a more balanced distribution of loads throughout the length of thread engagement. Thread Forming Tap Roll Taps (aka, Thread forming taps, Form taps0 offer improved thread quality and strength due to the fluteless design, and therefore allows for greater fastener strength in the threaded product. This tap does not cut, so it is “chipless,” and therefore will not cause a chip problem. This is why thread forming, over thread cutting, eliminates costly and time-consuming chip clean-up and disposal. Thread forming taps are fluteless and include lubrication grooves. Not intended for general applications, they work by displacing the metal without removing it. Because of this, they are ideal for chip removal in blind holes. Roll Thread Forming Taps Features
Carbide Insert TapsA cost-efficient solution, only the cutting portion of insert taps is made from carbide. Their HSS body is able to absorb vibration and account for their lack of rigidity. If you’re considering testing the waters with carbide taps, insert taps are a great option. It's a very economical way to utilize the benefits of carbide with solid carbide cutting face inserts meticulously brazed to a H.S.S. tap body. Carbide Insert Tap Features
Once Upon a Time There Was a Magical Form TapIf you follow any industry long enough, history will become a useful tool to apply to your understanding of modern developments and designs. One such piece of history, as related by someone who was there in the 1950’s, will create an illustration of the importance of learning from errors, and creating opportunities. Once upon a Time, not so far away, a tap manufacturer with a long history in the industry made an error processing a manufacturing order. We all do from time to time. Where it went from there is the story. A cutting tap left the manufacturer missing a feature. The customer complained that they had received a tap without any flutes. Being desperate, they used it anyway, and reported that it “kind of” worked. The manufacturer quickly got the customer the finished tap as originally intended, but decided to research the performance of the “unfinished” tap. They saw the obvious benefits of a “chip-less“ tap, but identified multiple downsides. As the material is not being cut, but pushed out of the way, friction would likely be an issue. On top of that, threading a blind hole would create hydraulic pressure in the hole (with 100% thread engagement, there would be no escape route for air or liquid beneath the tap). Both issues would be addressed with “lube-grooves” and a geometry utilizing “lobes” (high points on the circumference of the tap) to reduce the surface contact between the tap and the material being threaded. These features would facilitate lubrication, by allowing some clearance between the surface of the tap and the material being threaded. They would also allow an escape route for any building pressure at the bottom of the hole. They realized that the material being formed “flows” in multiple directions, both into and away from the thread-form of the tap. One very important detail was quickly recognized. The material being formed must be malleable. No flow, no go! Ferrous and glass-filled materials are not a candidate for forming. A different hole size would be recommended to reduce the percentage of thread produced to a more acceptable level, and allow the same clearance for the minor diameter of the mating part allowed by a “cutting” tap. Further tweaking followed. Method and form of “chamfer” was changed, to more efficiently begin the threading process. Lobe geometry tweaked for better performance in different materials.
Additional lube grooves were employed in applications that benefited. Recommended speeds were increased. Coatings were added to reduce friction and improve wear resistance. Coolant-holes became an option for those with the machine capability. Base materials were developed and improved. Like anything else, improvements continue as application demands evolve. According to the trusted source, this is the way it happened. The real point of the story remains the same whether or not it is completely true. The “error” and solutions that followed illustrate most of the differences between the two styles of producing thread, and the taps that do the job. |
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