The appropriate size watchmaker screwdriver will not resemble a miniature pry bar. When the blade is sized correctly to the screw slot, you will not hear the watch movements; you will not feel out-of-control pressure on your hand; and you will not observe that the screw has been damaged on its corners. When a screwdriver is too small for the slot it is placed into, it will slip. When a screwdriver is too wide, it will rest above the slot, or it may scratch into the plate. Selecting a screwdriver size might sound a bit trivial, but it will dictate almost any outcome when working at a workbench.
Prior to turning any screws in a movement, set the movement in a holder, examine the screw under a loupe, and identify its dimensions and surroundings. Notice the screw’s slot’s width, its slot’s depth, and the space available in the area where the screw is located. There is typically less margin for error when a screw is positioned near the end of a bridge, or close to a jewel setting, than when a screw resides on an open plate. Your screwdriver blade should fill a vast portion of the screw slot in a left-to-right manner; simultaneously, your screwdriver should not rise so high that the blade will be difficult to turn. It will not rock back and forth when placed in a stationary position.
You may find a good practice test when inserting a screwdriver tip into a screw’s slot without engaging or turning the screw itself. Gently hold a tool handle with a finger on top and observe if the blade rocks. If the blade tends to rock in a left-right manner, it is most likely too narrow for the screw. If the tool handle’s tip cannot sit entirely within a screw slot in a smooth manner, it may be too wide or too thick a size. This inspection takes a couple of seconds and serves to avert a screw turning that could scratch a bridge, damage a screw slot, or result in a tool sliding away from a screw while applying pressure into an unintended portion of a movement.
How much pressure should be applied in turning a screw is just as crucial as what screwdriver size is used to execute a task. It is essential to apply downward pressure via a hand on the screw driver tool handle that rests on top and utilize your index and middle fingers of the hand beneath to engage in a turning motion of a small degree. A novice might often grip the screwdriver handle tightly because they fear damaging a small, delicate screw, but the tight grip could result in the tool jumping to a new position if pressure is met by resistance. You will want to engage in a contact manner that is consistent and stable rather than using force. A screw that requires tightening or loosening should never be pursued around a plate.
Additionally, practicing the selection of screwdriver sizes in an area away from a movement is recommended to a greater degree. Locate a few extraneous or spare screws for testing within a compartment of a parts tray or in the empty portions of a plate designed to be used for this purpose. Place two screwdriver tips side by side to compare their relative sizes; notice how the smaller tip slips out sooner. Observe how a better-fitted tip is easily turned with a lower degree of resistance. Finally, tighten a screw until it is snug enough. Tightening a screw past this point does not mean you are doing a good job; it could strip or damage the threads of a screw, it might cause bending to any components that come into contact while screwing, and it could render future screw-removal much more difficult.
Ensure that a screwdriver’s tip is clean and shaped appropriately. A tip that is damaged may ruin or damage a screw no matter how good the size is. Remove surface dirt on the tool tip by wiping it off using a piece of soft cloth prior to its use; also check the condition of the tip under a loupe. Never engage with a tip that is dull or rounded from overuse or damage, chipped in any way, or otherwise uneven. If you find it difficult to observe where the tool blade may engage in a screw slot due to debris, you will want to take a quick break from tightening to clear and clean an area of visible dirt via the use of peg wood or a dust blower.
A screwdriver that is the appropriate size will make the process of working in a watch repair area feel much more relaxed. The blade of a screwdriver will sit in the screw slot without difficulty; the screw may be turned without slipping; and movement parts surrounding the screw will not be at risk of damage. Before every screw engagement or disengagement, ask yourself the following question: does my screwdriver size fit this slot as it should, or am I just hoping it will work out? A mere few seconds may make the difference between a proper screw slot being cleanly turned and a screw head suffering from damage.