A cut tap and a roll tap both create a thread but in a distinctive fashion. Like their names show, cut taps cut-removing the material as it sets up a thread, and roll taps (also known as a forming tap) form the material into a thread but without jettisoning any material. The thread quality produced with these two different tools is dimensionally identical but structurally different. Since the roll taps create a thread without removing any stock from a material, it is able to make a more structurally sound thread. With that being said, a roll tap is not always superior to a cut tap. Forming taps and cut taps are often material specific. Roll taps have numerous advantages over cut taps that will make you want to use them more often. For one, they don’t make any chips. The roll tap creates a thread into a hole with pressure as opposed to cutting a thread.
Roll taps are more solid and will last longer than cut taps. This will decrease the production lead time and reduce the general cost in the long run, as fewer taps are to break inside the parts. Not only will everything be stronger, but also you can run at faster speeds, substantially diminishing cycle times. Owing to the higher pressure on the tool and part hole, the roll tap requires some better coolant or oil with high lubricity. If your coolant isn’t good enough, the tap will have to work harder to form the threaded hole and eventually will disintegrate.
You need something with better lubricity that will cut down the load on the tool. In addition, if your countersink isn’t enormous enough, the first thread will be pushed up above the material’s surface and will give rise to interference if it’s a mating part. Besides that, there really isn’t much else to criticize about roll taps. Sometimes you just have to experiment until you discover what works the best. If your tap keeps malfunctioning, change it up with various speeds, coolant, or a different tap.
The two threading methods tap holes distinctively, but they also have a load of other differences, starting with the kind of thread each method makes.
Rolling taps are less versatile than cutting taps and can be utilized with more materials. When machinists use rolling taps, they can only use the process on aluminum, soft steel, and nonferrous metals. But machinists will have an unlimited selection of the materials when they decide to cut taps.
Many machinists agree that rolled threads are more formidable than cut threads, according to Balax. Rolling threads are stronger because the grain flow of materials is squashed at the crest and root of the thread form. In addition, rolling taps have a relatively longer tool life; they tend to last more than five times longer than regular cutting taps. Cutting taps and rolling taps both have advantages and downsides from stronger threads to greater compatibility. But it’s the machinist who decides which tapping style to use based on the job at hand.
● High efficiency and longer tool durability. The configuration of the lobes on the crests of the tap threads enables high-speed tapping possible and extends tool life in contrast with cutting taps. The additional tap surface treatment, such as OX, Ni, TiN, and TiCN allows the tools to expand the life more than five times over the cutting taps that are uncoated.
● Roll taps produce an excellent pitch diameter well within the class of fit of the pitch diameter tolerances. The material deformation process produces internal threads with a good surface finish and accurate pitch diameter.
● The control of the holes sizes before roll tapping must be held to a closer tolerance than that of cutting taps.
● The maximum deviation of the hole sizes for roll tapping should be less than 5 percent of the pitch.
● The flute-less design enables a larger core diameter cross-section on a tap. There is no problem with chip jamming with a cutting tap. This makes roll taps very strong against tapping breakage.
● Generally speaking, roll taps are more rigid and stiff than cutting taps because of the differences in their design.
● When using roll taps the tapping torque is two to three times larger than that of cutting taps.
Roll tapping needs a larger drill than a typical drill size for a cut tap. This larger hole is generated to enable room for the material to flow to create the minor diameter of the thread. Roll tapping is usually employed in stainless steel, steel, light metal alloys, and non-ferrous materials.
Tapping via roll tapping is suitable for materials with tensile strength less than 1,200 N/mm2 and fracture strain of 5 percent or less. If a continuous chip is created when drilling using unwritten rules, the material may be pliable enough as a candidate for roll tapping the threads. Nevertheless, suitable materials react to roll tapping in various ways.
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