Aerospace Materials Furthermore, there is a significant difference in the shape
of the cutting chips between the conventional carbide drill and the WHO-Ni. Typical chips from heat-resistant alloy materials are inconsistent in shape and size, and can lead to unexpected tool breakage. More importantly, tool breakage may damage the part and reduce production, which can be costly and should be avoided. WHO-Ni’s sharp cutting edges are designed to sup- press heat generation during machining and promote the stable creation of chips to enable trouble-free chip evacuation.
The Tapping of Heat-Resistant Alloys Special cutting tools are required in order to effectively fa-
cilitate the tapping of heat-resistant alloys. OSG has enhanced its Ni tap series with the WHR-Ni-SFT (for blind hole) and WHR-Ni-POT (for through hole). Te WHR-Ni series excels in nickel-based alloys and is well suited for machining parts such as jet engine components.
achieve more than five times the amount, with 111 holes. As illustrated by this application example, the higher the pitch, the less life a tap will have.
The Milling of Heat-Resistant Alloys Chattering is a common condition in the milling of heat-
resistant alloys and other exotic aircraſt materials. To facili- tate consistent and chatter-free milling, OSG has launched a variable index and variable helix end mill series called the Exocarb-UVX since 2009. UVX’s positive edge geometry with variable helix enables consistent and chatter-free milling. Its special flute shape with ultra-smooth finish further improves chip evacuation, thereby improving stability in slotting ap- plications of stainless steel. OSG has continued rigorous research and development to
further improve performance aſter the initial introduction of the UVX. In this article, we will discuss some of the test results that OSG has conducted specifically for heat- resistant alloys. OSG used the standard UVX as benchmark with two different helix angles, 38° and 65°. Te purpose of the test was to de- termine whether or not a stronger helix angle could suppress heat generation and further prolong tool life. A six-flute UVX with a 10-mm diameter
Spiral flute tap for nickel-based alloys has highly rigid point flutes to resist chipping.
A notable characteristic of the WHR-Ni tap series is its
adoption of OSG’s new HR coating. Tis exhibits a high level of wear-resistance properties against nickel-based alloys and can help attain long tool life when machining abrasive materials. A feature unique to the WHR-Ni-SFT series is its highly
rigid point flutes, which can resist chipping and wear resistant, resulting in stable cutting performance. WHR-Ni-SFT is able to effectively tap unified fine threads,
which are commonly used in the aerospace industry. In terms of tool life, the WHR-Ni-SFT was able to achieve three times the tool life versus a conventional cut tap. When tapping a 3/8-16 UNJC thread with the WHR-Ni-SFT, it was able to achieve 20 holes; while tapping a ¼-28 UNJF, it was able to
148 Aerospace & Defense Manufacturing 2013
was used to machine Inconel 718, with a cutting speed of 262 sfm (8 smpm), feed rate of 25 ipm (635 mm/min), axial depth of cut of 0.200" (5 mm), and radial depth of cut of 0.008" (0.2 mm). At a milling length of 13' (4 m), the two helix angles displayed insignificant tool wear differences. However, greater differ- ences could be observed beginning at a milling length of 20' (6 m). By 46' (14 m) significant wear differences were visible. With the 65° helix angle, the end mill was able to achieve stable and consistent wear from milling length of 20–46'. Te 38° helix angle, on the other hand, suffered greater wear aſter a milling
length of 20'. From this test result, we can conclude that a higher helix angle can lead to less heat generation. In another instance a chip created from a 38° helix angle
had a greenish-blue color while one created from a 65° helix angle appeared to be mostly white, an indication that less heat was generated with the 65° helix angle. In addition, the chip created from the 65° helix angle was long but thin. Te chip created by the 38° helix angle was thicker, further indica- tion that the higher the helix angle the less heat is generated. Although results may vary based on cutting conditions and environment, the helix angle may be a key component to further improving tool life and wear resistanc e for machining materials like heat-resistant alloys. ✈
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