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Fitting using hand skills
Published in David Salmon, Penny Powdrill, Mechanical Engineering Level 2 NVQ, 2012
A hole-forming tool is a cutting tool used to change the shape of a predrilled hole. This is usually required to enable the hole to accommodate a fastener (screw or rivet). Most hole-forming tools are made from HSS and have a straight or a Morse-tapered shank. Three of the most common types of hole-forming tools are described below: Countersink – Usually have a 90° included angle; they are used for flaring out the edge of holes for countersunk head screws or rivets. Also used for making a small countersink when riveting.Counterbore – Used for making a recess so that cap head screws can fit flush when tightened. To use a counterbore, first drill a pilot hole to fit the counterbore's pilot, then follow by opening out the hole to the required depth with the counterbore.Spot-facing tool – Used to clean up uneven surfaces around holes.
Working Safely and Effectively in Engineering
Published in Mike Tooley, BTEC First Engineering, 2010
Figure 1.30(b) shows a piloted counterbore being used to counterbore a hole so that the head of a capscrew or a cheese-head screw can lie below the surface of the work. Unlike a countersink cutter, a counterbore is not self-centring. It has to have a pilot which runs in the previously drilled bolt or screw hole. This keeps the counterbore cutting concentrically with the original hole.
3D CAD modeling of deep drawing tools based on a new graphical language
Published in Computer-Aided Design and Applications, 2018
Sergej Koch, Bernd-Arno Behrens, Sven Hübner, Robert Scheffler, Gregor Wrobel, Matthias Pleßow, David Bauer
Firstly, the counterbore holes of the punch holder serve to position and fix punch, punch base and punch holder on the load cell. The punch holder is connected to the punch assembly holder by counterbore holes. The parameterization of these counterbore holes is similar to the counterbore hole of the punch and is performed by means of a table and a rule. Due to the lack of space, the dimensions of the counterbore holes are defined for three screw sizes M4, M6 and M10 depending on the punch diameter. The distance between the counterbore holes and the central axis is defined by a formula as ¾ of the punch diameter. Thus, the counterbore holes are exactly positioned between dowel hole and external edge of the punch holder independent of the punch diameter.