Best cobalt drill bits for drilling harder metals like stainless steel - what is best drill bit for stainless steel
To increase the life of carbide inserts, they are sometimes coated. Four such coatings are TiN (titanium nitride), TiC (titanium carbide), Ti(C)N (titanium carbide-nitride), and TiAlN (titanium aluminum nitride). Most coatings generally increase a tool's hardness and/or lubricity. A coating allows the cutting edge of a tool to cleanly pass through the material without having the material gall or stick to it. The coating also helps to decrease the temperature associated with the cutting process and increase the life of the tool. The coating is usually deposited via thermal CVD and, for certain applications, with the mechanical PVD method at lower temperatures.
BTA drilling is a deep hole drilling process that uses a specialized drilling tool on a long drill tube to produce deep holes in metal, from holes with a diameter of 20 mm [0.80 in] and larger, up to depth-to-diameter ratios of 400:1. BTA drilling is the most effective method of drilling deep holes, as it is a cleaner, more reliable and capable process than conventional twist drills, and can achieve larger diameters and higher feed rates than the alternative gundrilling.
BTA deep hole drilling is the ideal process for a range of larger deep hole drilled depths and diameters. BTA drilling, and secondary processes, are capable of drilling extreme depth-to-diameter ratio holes while achieving strict tolerances.
BTA drilling can achieve drill feed rates of typically 5-7 times faster than gundrilling at the same diameter, due to the tool design, more efficient chip exhaust, and machine design and power. BTA drilling machines introduce coolant around the tool head, and evacuate chips through the drill and machine spindle, compared to gundrilling, where coolant is introduced internally and chips exit through an external groove. BTA drilling is effective in holes from 20 – 200 mm [0.80 – 8.00 in], a greater size range than gundrilling.
Cemented carbides are composed of a metal matrix composite where carbide particles act as the aggregate and a metallic binder serves as the matrix. The process of combining the carbide particles with the binder is referred to as sintering. During this process, the binder eventually will be entering the liquid stage and carbide grains (much higher melting point) remain in the solid stage. The binder is embedding/cementing the carbide grains and thereby creates the metal matrix composite with its distinct material properties. The naturally ductile metal binder serves to offset the characteristic brittle behavior of the carbide ceramic, thus raising its toughness and durability. Such parameters of carbide can be changed significantly within the carbide manufacturer's sphere of influence, primarily determined by grain size, cobalt content, dotation, and carbon content.
BTA drilling tool heads are threaded or mounted onto long drill tubes, and use multiple cutting surfaces on a single tool to remove chips efficiently, exhausting them using high-pressure coolant through holes in the tool head, then out the drill tube and through the machining spindle. BTA tooling is available in brazed or inserted carbide configurations.
BTA drilling tools are chosen and integrated into the deep hole drilling system to achieve the highest tolerance standards possible.
Carbide inserts are replaceable and usually indexable bits of cemented carbide used in machining steels, cast iron, high temperature alloys, and nonferrous materials. Carbide inserts allow faster machining and leave better finishes on metal parts. Carbide inserts can withstand higher temperatures than high speed steel tools.
BTA stands for Boring and Trepanning Association, and is also sometimes referred to as STS (single tube system) drilling, as it uses one single drill tube for the BTA tool, compared to other processes such as ejector drilling, which use two.
Deep hole drilling machines that are designed to perform BTA and related processes are complex systems of high-precision components, designed and built for extremely deep holes and strict tolerances. View a machine diagram to learn about BTA drilling machines.
Carbide is more expensive per unit than other typical tool materials, and it is more brittle, making it susceptible to chipping and breaking. To offset these problems, the carbide cutting tip itself is often in the form of a small insert for a larger tipped tool whose shank is made of another material, usually carbon tool steel. This gives the benefit of using carbide at the cutting interface without the high cost and brittleness of making the entire tool out of carbide. Most modern face mills use carbide inserts, as well as many lathe tools and endmills.