During the drilling operation, it would seem that there is no complex machining problem to improve the productivity, but the following three important factors will directly affect the drilling speed, tolerance, and tool life, i.e.:

    Coolant; spindle speed and feed rate; tool clamping rigidity.

    Coolant

    Coolant keeps the drill bit at a relatively low working temperature and helps extend the life of the cutting tool. The accumulation of heat in one hole causes the drill bit to curl, dulling its cutting edge, causing it to "plow" through the workpiece. This can cause the drill bit to break in the hole. Some people think the function of coolant is cooling, but ChipBlaster president Gregory S. Antoun said that coolant has other functions.

    Coolant helps to maintain the drill bit at an optimum working temperature and also lubricates the workpiece. Lubrication helps to maintain the sharp cutting edge of the drill bit and extends its life.

    Antounsaid:“In a cutting fluid, the concentration of the lubricant depends on the work-piece and tool. A single-edged lathe with a small contact surface requires a concentration of5% of lubricant in the coolant. When you increase the contact surface of the drill, the concentration must be at least increased to8%.”He also said that a higher concentration of lubricant is needed in the coolant after drilling and before tapping, the concentration is12%. A decrease in concentration during drilling will reduce tool life by90%. At the same time, the coolant can also flush the chips out of the hole.Seco-Carboloydrilling product managerFrederik-Sundstromsaid:“If you don't flush the chips out of the hole, you will break the drill.”The same simple principle, the chips will tie up the tool tip, plug the tool tip, jam the tool tip, grip the tool tip, and cause the drill to break.

    Hermanpointed out that European machinists use a small amount of coolant, combined with compressed air from the machining center, to reduce the amount of coolant that is usually needed for drilling.ChipBlastercompany,Seco-Carboloycompany and AmericanKometcompany all recommend that the pressure of the coolant should be kept at a higher level,Hermansir andSundstromsir said, very high pressure can only improve the efficiency of the coolant. In addition, the three companies all recommend that machinists use coolant technology through the tool when performing hole machining, but it is often not done.

    There is a limit to the coolant technology through the tool when the hole size is0.1969inch(5mm)or smaller, and it is often not possible to supply coolant through the drill, and external coolant technology must be used. Although some square drills orGtype drills can also provide through-the-tool coolant technology when the specification is smaller than0.1969inch, it often requires the peck drilling technology to drill such small holes.

    Mike Herman,the sales director of theKometCompany in the United States,stated that“it is necessary to clean the hole when peck drilling, when the drill cuts to its diameter1or2times, by flushing with external coolant to remove the swarf. Although peck drilling is time-consuming, this is always better than the alternative.”,he said,

    Drilling spindle speed and feed rate

    Seco-Carboloycompany'sSundstromMr. said:“Finding the correct drilling spindle speed and feed rate is the second key factor in improving productivity in drilling.”

    Tooling suppliers provide a detailed list of cutting tool data in their product samples, which must be strictly adhered to. The specifications of the tooling manufacturers also help the mechanical workers to decide which tool is appropriate for machining the workpiece. These tools include: indexable insert twist drill, tungsten carbide or high-speed steel twist drill, welded twist drill, small spiral angle (12° spiral angle) twist drill or standard 35° spiral angle twist drill. For example, small spiral angle twist drills are generally suitable for particularly hard materials, as well as those that are sticky during machining, such as titanium, etc.

    Rigidity of tool clamping

    Finally, the rigidity of tooling clamping is also a particularly important factor in improving drilling efficiency. If the workpiece is not properly clamped, it can lead to poor surface quality of the hole, vibration, and many other problems, and even cause the scrapping of parts, reducing the working life of the drill bit.