The three keys to hole quality are diametral accuracy, form and position, and surface finish. Boring tools are the undisputed king in all of these areas, but they’re also one of the slowest methods of hole finishing, and in most cases are limited to 10:1 depth to diameter ratios or less.
Conventional carbide-tipped reamers produce good hole quality, are substantially faster than boring and able to reach much deeper, but they also have an Achilles heel. The steel shank to which the carbide flutes are brazed has a thermal coefficient three times that of carbide, and is subject to growth during machining operations. Carbide Rotary Burr Set
Worse, sharpening of these tools often leads to less than desirable results. The mixture of carbide and steel wreaks havoc on grinding wheels, providing a reground edge that is rarely as good as the original tool. Also, PVD and especially CVD coating of reground tools is problematic, because the temperature inside most coating vessels reaches upwards of 530 degrees C, leading to micro-movement of the brazed carbide flutes.
Widia’s Top Ream platform covers the majority of hole finishing needs, with diameters up to 42mm and a range of edge preps and geometries available
Widia Products Group has addressed these problems and more with its new Top Ream carbide reaming solution. Instead of four to eight (or more) individually brazed carbide tips, Top Ream uses a single carbide disc and brazed joint, providing a strong connection that is virtually immune to thermal effects during machining operations.
“Steel-bodied reamers tend to get banged up on the ends. The center can get nicked or distorted, preventing an accurate regrind. With carbide, you always have a good center to locate on.” The result is a minimum of four “like new” regrinds vs. an average of three questionable ones,” says Widia’s manufacturing engineer Tom Bobos.
“However, there’s more to Top Ream than its ability to hold an accurate edge. Overall it’s just a better design. A single piece of carbide is inherently more stable and resistant to vibration. The through-hole style has an 18-degree left hand spiral that does a great job of pushing the chip forward. It’s really best in class.”
Widia’s WU05PR advanced reaming grade was developed specifically for the demanding tool wear and surface finish requirements encountered in most hole reaming operations. For example, tests performed over a total cut distance 30m in length showed an ability to consistently maintain surface finishes of 0.8μm in 4 140 steel alloy and 1.6μm in grey cast iron, three times that of TiAlN-coated tools.
“The Top Ream covers hole diameters up to 42mm with the TRF shank-style starting at 14mm, and the TRM modular tool from 20mm and up. This size range covers the lion’s share of requests from our customers. We also offer a wide variety of custom geometries, diameters, and edge preps, all available in three weeks or less,” said Jerry Hanna, Widia Director of Sales Operations.
“If you’re worried about custom cutting tools, don’t be. With reaming, 98 per cent of the tools are custom. We encourage our customers to try standard sizes, but they should also ask us for advice. We have the ability to optimise solutions specifically for any application. If you’re machining titanium, there are specific geometries and coatings for that. Same with 316 stainless or Inconel. A slight tweak to the hone, or modifying the leading edge a little bit can make a huge difference in productivity and hole quality,” explained Bobos.
Give the locking screw a turn, pop in a new head, and you’re up and running, with no concerns over run out or rigidity
“One of the best features of the Top Ream is the TRM series’ mounting mechanism, which makes simultaneous contact on the cutting head’s face and taper. Twist the locking screw and the reamer head pops out, with no need for head to body orientation. This provides a strong, vibration-free, and, most importantly, extremely precise reamer interface. There’s virtually zero run out with the modular design. Once you have everything dialed in, you just put the head on and tighten it down. There’s never a need to re-indicate after a tool change,” said Bobos.
“The Top Ream’s unique design is geared towards anyone that needs fine hole finishes and high productivity rates, whether it’s a Tier 1 automotive company or the small job shop down the street. And as the use of additive manufacturing and other near net-shape processes continue to grow, so too will the need for accurate, cost-effective hole finishing. That makes Top Ream an ideal reaming solution for today’s manufacturers, as well as tomorrow’s. We’re very pleased with the design,” said Hanna.
Carbide Mining Bits For more information contact Widatech on TEL: 011 450 2108, email: info@widatech.co.za or visit www.widia.com