How to Choose a Deep Hole Drilling Tool
Deep hole drilling requires the use of a wide range of tools. This article discusses the different features of drilling tools, including the Pecking strategy, the Center drill versus the pilot drill, and the Guide bushing. Using the appropriate tool for the job is critical for the success of your drilling project. Read on for more information! We also explain what you need to know before choosing a deep hole drilling tool.
Pecking strategy
When choosing a deep hole drilling tool, the pecking strategy is very important for a variety of reasons. Pecking strategy is important for tool life and part performance. The recommended pecking strategy depends on the type of tool, material, and desired final product. Pecking cycles involve several passes to help chip evacuation and minimize walking. They also prevent chip packing and breakage. Compared to retraction, peck drilling gives better final part results.
Despite the numerous benefits of pecking, not all deep hole drills are the same. Pecking cycles vary depending on the type of material being drilled, the size of the hole, and the depth of the hole. Choosing the right pecking cycle is critical to increasing tool life and performance, and for producing a high-quality final product. Here are some tips to help you choose the right tool for the job.
Center drill vs. pilot drill
The selection of the drill is dependent on several factors, including diameter, point angle, and unused length. Unused length increases cost and decreases rigidity of the entire setup. Another important factor is the type of coolant, including internal or external. Coolant-cooled tools are better than those without coolant, but they also need more time to drill a hole. Drills that do not use coolant are generally more expensive, though.
To maximize performance and extend tool life, it is important to choose the right pilot drill. The pilot drill creates a clean working surface that will guide the succeeding drill. Pilot drills also have important dimensions, including point angle and diameter tolerance. These factors are often neglected, resulting in inconsistent results. Listed below are some considerations when choosing a deep hole drilling tool:
HSS or cobalt parabolic-flute drill
A high-speed steel (HSS) or cobalt parabolic-fuel drill is an ideal choice for drilling deep holes, but a different type of flute is best for tough materials. These drill bits feature wider flutes and higher helix, which reduce the need for peck cycles and chip evacuation. In addition, the design also provides superior surface finishes in the hole.
A cobalt and HSS parabolic-flute drill can be used for deep holes, and features a specialized ground point form for optimum centering. The point geometry of parabolic flutes is 130 degrees, which is optimum for deep holes. The resulting holes can be drilled to H10 tolerance. A high-speed cobalt parabolic drill can go as long as 600mm overall.
Guide bushing
While there are several important considerations when selecting a deep hole drilling tool, one of the most important is the type of guide bushing to use. For general-purpose drilling, the clearance between the tool and the workpiece should be about 1/2 to 1 inch. This clearance ensures that the tool can approach the workpiece without causing interference and to support the cutting tool. Guide bushings are generally measured by ID and OD, so the concentricity of the bushing should be 0.0000" to 0.0003" TIR for smaller parts.
A guide bushing pairs with a router bit that is the same diameter as the bit. These two components work together to align the centerline of the piece with the bit. The guide bushing is typically 3/4" in diameter, so selecting a tool with that size is the easiest way to achieve sliding dovetail sockets. Using a bushing with a half-inch O.D. will align the centerline of the desired slot. This is an important feature, as the widest portion of the bit never contacts the bushing, limiting adjustments in the depth of the hole. Choosing the correct thickness of material is also important.
Keeping control of runout
When choosing a tool for deep hole drilling, keep in mind the overall bore diameter and the id of the end part. These two factors are critical to producing an accurate final product, as well as repeatability, surface finish, and predictable tool life. Choosing the right drill for the job is essential, as is the right toolholder. In addition to selecting a drill that will achieve the best results, it is also important to choose a toolholder that will accommodate the increased runout of the longer drills. It is important to remember that the toolholder should compensate for increased runout from longer tools, and that accuracy is maintained even after drilling well over 2000 holes.
Generally, drills with a longer runout have longer cutting capabilities, but this length also means increased runout. The additional distance between the tool tip and spindle nose increases the risk of runout, which decreases productivity. Fortunately, there are ways to reduce or eliminate runout when choosing a deep hole drilling tool, regardless of size. In addition, drills with smaller diameters may result in misalignment of the tool in the turret, compromising the straightness of the hole and surface finish.