8.7 Tooling
Micky R. Jennings
Tooling is a term used to refer to the cutting and measuring equipment used to make parts in a machine shop. On a drill press, the primary tooling will be the cutting tools used for making holes as well as the tools used for alignment purposes. These same tools are used in other operations as well, and mastering the skills necessary to use them will allow the machinist to perform a variety of hole-making operations.
Center Finder (wiggler)
A center finder, also known as a wiggler, is a device used on a drill press or milling machine to aid in finding the position, or center, of features. The indicator attachment is used to sweep features in a rotational fashion, allowing the indicator to help with accuracy. The disk and ball attachments are used to help find the sides or edges of surfaces. The pointer attachment is used to show the absolute center of the spindle rotation, allowing the operator to visually adjust the work position. These attachments are helpful on a drill press because it can be difficult to line up the spindle in the correct position when the job requires the drill press vise to be clamped in one place.
Center Drill
A center drillis designed to create a “center” for support of lathe work. However, because of their short, rigid construction and split point, they are often used to spot hole positions before drilling. Standard center drills consist of a small pilot drill diameter and a 60-degree countersink. The 60-degree countersink is what creates the feature lathes need for centering purposes. Center drills are identified by number size. Smaller numbers indicate smaller tools, while a larger number indicates a larger tool. For general purposes, #2 – #4 are common. A machining reference book will have charts that give specifics on the dimensions of the different center drill numbers. Some center drills may have a radius instead of a countersink. These are primarily used when cutting tapers on a lathe by way of the tailstock offset method, and will be discussed further in the lathe chapter.
Spot Drill
A spot drillis a short, rigid twist drill that is used to spot holes before using a twist drill. These drills are intended to cut just on the tip of the tool and do not have the relief or flute length required for through drilling.
Author’s Tip
A basic spot drill can have a larger diameter than the pilot of a center drill, although center drills are often used in spotting holes. I use this to my advantage and add extra depth to my spotted holes, creating an edge break or chamfer at the top of the intended hole. This can be a huge time saver because it eliminates the need for a chamfer tool afterwards, as well as deburring the inside burrs the chamfer tool will leave. Using a 90-degree spot drill helps me calculate the spot depth necessary to create the correct diameter for the chamfer. A center drill can be used for this purpose instead, but often, the center drill needs to be large, and it can be difficu