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Deep Hole Drilling and Coatings
Deep Hole Drilling and Coatings
Achieving tight diameter control, straightness and surface quality in machining workpieces that require high tolerances requires specialized deep hole drilling equipment.deep hole drilling oil hole drilling Deep hole drilling combines gun and BTA drills with other procedures designed specifically to meet strict tolerance limits in a variety of materials ranging from aluminum to super-alloys. Typically, deep hole drilling is carried out on BTA-style deep hole drilling equipment, which offers higher speeds and higher accuracy than other types of metalworking machines.
In general, a deep hole is defined as a hole with a length-to-diameter ratio of more than 5.deep hole drilling oil hole drilling The process of drilling these holes requires special tools, pressurized coolant and lubrication to ensure the correct chip control, prevent tool seizing and achieve optimal results.
While gun drills are capable of drilling holes to this ratio, the requirement for precision and accuracy in these types of jobs really pushes the limits of standard machine capabilities.deep hole drilling oil hole drilling This is why many manufacturers choose to utilize a dedicated deep hole machine such as the ones offered by Unisig. These are highly engineered turnkey systems that can perform five processes — deep hole drilling, gundrilling, milling, tapping and boring — in one machine.
Unisig’s UNE line of deep hole drilling machines includes some of the most advanced gun and BTA drills available today. These are outfitted with high pressure, through-spindle coolant to handle deep hole drilling applications up to a specified depth-to-diameter ratio. They can also be used with a wide range of different coolants, from emulsion to heavy-duty cutting oil.
In a recent study, Unisig’s team of engineers compared the wear behaviour of carbide grade P20 and three differently coated guide pads. They found that the tetra amorphous carbon (ta-C) coating was best at compensating the increased force and wear stress caused by the deep-hole drilling process. The ta-C coating also has an improved friction behaviour and increased layer hardness that reduces the occurrence of adhesive wear.
In addition to improving machining accuracy, the use of a ta-C coating on deep hole drilling tools can also increase tool life and reduce the need for frequent regrinds. It also improves the lubrication effect at the axial inlet area of the guide pad, where there is a tendency for adhesive wear to occur. This is because the ta-C coating reduces the frictional heat generated and increases the cooling capacity, resulting in lower adhesion and wear on the front support of the guide pad. This was especially significant in the case of the austenitic steels that were tested in this study. The ta-C coating also exhibited significantly lower wear on the rear support of the guide pad, as compared to the other two coatings.
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