Process of both external (e.g., thread milling) and internal (e.g., tapping, thread milling) cutting, turning and rolling of threads into particular material. Standardized specifications are available to determine the desired results of the threading process. Numerous thread-series designations are written for specific applications. Threading often is performed on a lathe. Specifications such as thread height are critical in determining the strength of the threads. The material used is taken into consideration in determining the expected results of any particular application for that threaded piece. In external threading, a calculated depth is required as well as a particular angle to the cut. To perform internal threading, the exact diameter to bore the hole is critical before threading. The threads are distinguished from one another by the amount of tolerance and/or allowance that is specified. See turning.

We had initially arranged the program to cut on the leading edge only, which is the traditional way to set up a lathe for threading. Increasing tool pressure often reduces chatter. However, cutting on the leading edge lowers cutting pressures, thereby causing chatter. We changed the program so the tool would plunge straight in and cut with both sides of the insert. This adjustment increased the pressure enough to eliminate the chatter.

1. Permanently damaging a metal by heating to cause either incipient melting or intergranular oxidation. 2. In grinding, getting the workpiece hot enough to cause discoloration or to change the microstructure by tempering or hardening.

UN thread dimensions are given as proportional values based on the pitch or distance between threads. All thread dimensions can be found in a number of reference materials and are not usually provided on the part print. In our situation, we had a UN designation, but the drawing included specific dimensions. Investigation revealed we did not have a UN thread. This prevented us from using a standard thread-cutting tool, because stock tools are made to cut dimensions and geometries given by specifications like the UN standard. Therefore, we were forced to purchase a special carbide threading insert.

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At the heart of a gas turbine is a rotor with hundreds of individual airfoils called blades. Blades are arranged circumferentially around a disc, and several discs are stacked together to make a single rotor. Discs are held in place with special bolts and nuts.

The 4NHT 06 corner R range insert has been extended (04R-20R) to meet the wider range of corner radius requirements demanded by today’s industry. Adding to the existing 8mm and 16mm radius inserts, TaeguTec has expanded the line to include a 4, 12 and 20mm radius offering. The extended 4NHT 06 is available with TaeguTec’s ML and M geometry, and the TT8080 and TT9080 grades, which combine to improve cutting load, minimise built-up-edge and generate high surface finish, says the company.

The StarMill SED range of end mills from TaeguTec has been expanded to offer a greater choice of diameters, lengths, radii, coatings and geometry

The new grade has improved abrasion and chipping resistance because of the latest substrates and coatings ensuring excellent performance, stable and longer tool life in low speed and interrupted machining of cast iron. A further advantage of the new grade is it capitalises on recent trends due to its suitability for ductile cast iron machining. Very good surface roughness is achieved due to the GoldRush post-treatment technology. The TT7025 grade’s black and yellow appearance, black on the bottom and top faces and yellow on the sides, helps to easily determine the level of wear to the insert.

Suitable for ramp and slot milling applications, Chase2Mill is available in end mill, modular or face mill designations. Initially launched with a four-corner, double-sided 4NHT 06 insert range featuring a 90° entry angle that is suitable for high ramp-down applications, the 4NHT 06 has been expanded and a newly developed 4NHT insert series released.

Going forward with the nuts, we plan on thread milling them, which will provide significant advantages. Thread milling will let us accurately and easily deliver the desired start and stop locations for the threads. In the lathe, we first mark the jaws with a scribe line. We then align the machined features to the line to ensure that the start location for the thread is correct. The machining center allows us to program the start point of the threads, so aligning features will no longer be necessary.

CNC machine tool capable of drilling, reaming, tapping, milling and boring. Normally comes with an automatic toolchanger. See automatic toolchanger.

DL chip former features The DL chip former is suitable for mild steel and low carbon steel machining due to its improved chip segmenting capability and the application range has been expanded.

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Gas turbines propel planes and helicopters, tanks, ships and locomotives. The largest turbines can be found in natural-gas power plants that produce electricity for homes and businesses.

Next, we will eliminate the lathe setup. The initial machining process required three setups: twoon the vertical machining center and one on the lathe. Our new process will be done on a horizontal machining center, eliminating the cost of setup on the lathe and reducing the lead time for the part.

After resolving the chatter issue, we found out just how difficult the bolt material was to machine. Our first attempts to cut the threads were dismal; we were unable to complete the threading cycle before insert failure. After investigation, we determined that the cutting speed was too high and, thus, generated too much heat. We also discovered that the coolant was not mixed to the proper concentration. The lack of lubricity resulted in excessive chip welding on the cutting edge, or built-up edge. To overcome these problems, we reduced the cutting speed and increased the coolant concentration. This allowed us to complete the threading cycle.

Success was finally reached when we changed the machining strategy. A CNC lathe allows the programmer to enter the thread-cutting cycle in one of three ways: leading edge only, alternating between leading and trailing edges, or straight in so both leading and trailing edges cut simultaneously.

Expands StarMill SED end mill series The StarMill SED range of end mills from TaeguTec has been expanded to offer a greater choice of diameters, lengths, radii, coatings and geometries.

The TT7025 grade – has been introduced to widen the scope in order to focus on low speed and interrupted cast iron machining

Substances having metallic properties and being composed of two or more chemical elements of which at least one is a metal.

All ranges within the SED StarMill portfolio incorporate unequal flute spacing and a high helix that combine to reduce harmonic effects and vibration during high-speed machining. Furthermore, the polished high-helix flutes improve chip evacuation, while the TT5515 grade coating prolongs tool life, even under challenging machining parameters, says TaeguTec.

TaeguTec has been supplying both the TT7005 and TT7015 grades for cast iron machining with great success. Now, an additional grade – the TT7025 grade – has been introduced to widen the scope in order to focus on low speed and interrupted cast iron machining.

Topdrill – New DL chip former for mild steel machining The TopDrill line’s current DP chip former is a multi-purpose insert that works wonders on various types of materials. Now TaeguTec has expanded the line’s capabilities by introducing the DL chip former specifically dedicated for mild steel machining applications.

Chase2Mill line extended by TaeguTec First introduced two years ago the TaeguTec Chase2Mill series of end mill tools is being extended with the arrival of two additional insert designations.

Condition of vibration involving the machine, workpiece and cutting tool. Once this condition arises, it is often self-sustaining until the problem is corrected. Chatter can be identified when lines or grooves appear at regular intervals in the workpiece. These lines or grooves are caused by the teeth of the cutter as they vibrate in and out of the workpiece and their spacing depends on the frequency of vibration.

Making threads can frustrate the most-experienced machinists. But threading problems can be overcome with the right information, guidance and some research.

Tangential velocity on the surface of the tool or workpiece at the cutting interface. The formula for cutting speed (sfm) is tool diameter 5 0.26 5 spindle speed (rpm). The formula for feed per tooth (fpt) is table feed (ipm)/number of flutes/spindle speed (rpm). The formula for spindle speed (rpm) is cutting speed (sfm) 5 3.82/tool diameter. The formula for table feed (ipm) is feed per tooth (ftp) 5 number of tool flutes 5 spindle speed (rpm).

Korean cutting tool manufacturer TaeguTec has recently launched new products with promises that there will be new developments that will be launched at the upcoming EMO 2019 exhibition that takes place in Hannover, Germany in September 2019.

TaeguTec’s 4NHT 06 insert designation has also been launched with the 4NHT 06-ML, which is said to be characterised by its ability to generate low cutting loads and high surface finishes (credit to ground cutting edges that minimise built-up-edge).

Our first attempt to manufacture the nuts was done on a horizontal turning center, which is traditionally used to manufacture these parts. We made a complete set of nuts and installed them in the turbine. However, the start and stop locations of the threads made producing them a painful process.

Spindle bolts are made from difficult-to-machine, high-strength superalloys. They have very tight dimensional tolerances, which makes thread cutting a challenge. As a result of facing several thread-cutting problems during process development, we have learned important lessons at Mitsubishi.

In addition to the SED4 UL line, TaeguTec has also introduced a complete line of SED4 UR end mills with a corner radius for enhanced tool life and machining performance. The SED4 UL range is available in diameters from 2 to 16 mm with each diameter offering the customer a selection of corner radii. Although the 4 mm diameter tool offers users the choice of a 0.1, 0.2 or 0.5mm radius, the largest 16mm end mill is available with a 0.5, 1, 2 or 3mm corner radius.

After resolving the thread form issue and having the special made, we discovered that our spindle bolt workpiece material was difficult to machine. Initial test cuts produced chatter that could wake the dead. Spindle bolts are long, relative to their diameter. This length makes all machining operations difficult. Because the threads are always cut near a supported area, we decided the tool itself must be producing the chatter.

For any other turning operation, the machinist could adjust the feed rate to put more pressure on the tool to minimize chatter. Because threads require a fixed feed rate to generate the proper pitch, we could not adjust the feed rate. Instead, we lowered the cutting speed. However, when we reached the point where the chatter stopped, the cutting speed was very low and the cycle time was unacceptable. Therefore, changing the cutting speed was not the solution.

At Mitsubishi Hitachi Power Systems Americas Inc., we refer to the hardware as spindle bolts and spindle nuts. These nuts and bolts exert enormous forces on the discs and must last for hundreds of thousands of hours in extremely harsh environments. Therefore, thread quality is critical to the life of both the spindle hardware and the gas turbine rotors.

The product line already includes several types dedicated to various materials: The DP for general purposes; The DK for cast iron, as well as the DA for aluminium machining. With the introduction of the DL insert for mild steel machining, customers now have a wider range of chip former options across more material types.

Workpiece is held in a chuck, mounted on a face plate or secured between centers and rotated while a cutting tool, normally a single-point tool, is fed into it along its periphery or across its end or face. Takes the form of straight turning (cutting along the periphery of the workpiece); taper turning (creating a taper); step turning (turning different-size diameters on the same work); chamfering (beveling an edge or shoulder); facing (cutting on an end); turning threads (usually external but can be internal); roughing (high-volume metal removal); and finishing (final light cuts). Performed on lathes, turning centers, chucking machines, automatic screw machines and similar machines.

Nuts for the spindle bolts were the next challenge. Nuts are made from material that is much easier to machine, but the thread geometry is difficult to generate. We also had to produce precise start and stop locations for the threads.

Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.

Turning machine capable of sawing, milling, grinding, gear-cutting, drilling, reaming, boring, threading, facing, chamfering, grooving, knurling, spinning, parting, necking, taper-cutting, and cam- and eccentric-cutting, as well as step- and straight-turning. Comes in a variety of forms, ranging from manual to semiautomatic to fully automatic, with major types being engine lathes, turning and contouring lathes, turret lathes and numerical-control lathes. The engine lathe consists of a headstock and spindle, tailstock, bed, carriage (complete with apron) and cross slides. Features include gear- (speed) and feed-selector levers, toolpost, compound rest, lead screw and reversing lead screw, threading dial and rapid-traverse lever. Special lathe types include through-the-spindle, camshaft and crankshaft, brake drum and rotor, spinning and gun-barrel machines. Toolroom and bench lathes are used for precision work; the former for tool-and-die work and similar tasks, the latter for small workpieces (instruments, watches), normally without a power feed. Models are typically designated according to their “swing,” or the largest-diameter workpiece that can be rotated; bed length, or the distance between centers; and horsepower generated. See turning machine.

TaeguTec has also recently released Chase2Hepta, new carbide shim type cutters and inserts XNM(H)U 06 for reliable roughing and finishing of difficult-to-cut materials

The main issue with thread milling is the cost of the tools, which are specials. Fortunately, they should last a long time, and the reduction in setup and lead times should justify the extra cost.

This lathe is used to manufacture Mitsubishi Hitachi’s spindle bolts. Difficult-to-machine alloys and the large length-to-diameter ratio make machining a challenge. All surface finishes are critical, but having a good finish on the threads is particularly so.

Already available for use on difficult-to-cut materials such as stainless steel, titanium, Inconel and other high-temperature alloys, StarMill has been extended with the arrival of the SED4 UL range of 4-flute extra-reach end mills. The UL extension introduces end mills in 3, 4, 6, 8, 10 and 12mm diameters with an overall reach from 63mm to 92mm, depending upon the chosen diameter. With a flute length from 10mm to 40mm, this addition to the SED line-up enables manufacturers to access small cavities and difficult-to-reach surfaces.

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Fluid that reduces temperature buildup at the tool/workpiece interface during machining. Normally takes the form of a liquid such as soluble or chemical mixtures (semisynthetic, synthetic) but can be pressurized air or other gas. Because of water’s ability to absorb great quantities of heat, it is widely used as a coolant and vehicle for various cutting compounds, with the water-to-compound ratio varying with the machining task. See cutting fluid; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.

First introduced two years ago the TaeguTec Chase2Mill series of end mill tools is being extended with the arrival of two additional insert designations

Microprocessor-based controller dedicated to a machine tool that permits the creation or modification of parts. Programmed numerical control activates the machine’s servos and spindle drives and controls the various machining operations. See DNC, direct numerical control; NC, numerical control.

Threads are made in many configurations, typically to a recognized specification like the Unified National. UN and other standards dictate the size and shape of internal and external threads. Engineers usually reference a standard in their designs, but it is not unheard of to be asked to manufacture a nonstandard thread, which is the case with spindle bolts.