Drilling Flashcards
Drilling: definition
Machining operation that creates a round hole in the workpiece
types of holes
- through holes: open on both sides
- blind holes: open on one side
- countersink: conical entrance to help inserting a piece
- Counterbore: useful for fixing
twist drill: characteristics
- 2 helics
- helicoidal flutes allow the chip removal
- possible cutting fluid inside the drill
- diameter of the body smaller than the extremity to reduce friction
- web: no cutting speed near the center, so a web is used instead of a cutter to increase the robustness of the tool
reaming operation
finishing operation to improve the quality of the hole
it consists in enlarging an existing hole, obtaining a better surface finish
basic rules to obtain a good holeq
- generate a flat entrance for the drill, to avoid bending
2. possibly, drill the hole in many passes, increasing the diameter of the drill
tapping operation
a particular shape of the drill defined the internal shape of the hole
to maintain the internal surface, at the end of the hole the drill stops and restarts in the opposite direction to exit
work holding for drill presses
- vise: workholder with two jaws
- fixture: custom device designed for the particular workpiece
- drill jig: provides a guide for the tool during drilling
types of machines for drilling
- drill press
- base
- table
- vertical spindle
- column - radial drill press
- for large parts
- column
- axial movement
- vertical spindle
- table - CNC drilling machine
- table
- turret
- column
cutting forces in drilling
- forces due to chip formation, perpendicular to the cutting edge
- forces due to friction on flank faces
- force on the web due to the feed