Page 79 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

60 Making Things Move

You are probably familiar with the FIGURE 3-5 Drive styles of common screws
standard flat head and Phillips head
screwdrivers and matching screw drive
styles. Maybe you’ve even stripped the
screw head of a Phillips head screw. This
happens when you try to tighten or
loosen a screw that is stuck, and the
screwdriver slips out, squishing the
material on the head so much that it
becomes impossible to tighten or loosen
at all. If this happens, you’re screwed.
Avoid this problem by being particularly
careful with Phillips head screws, or
avoiding them altogether by using socket
cap or hex head screw drive styles.

TIP There is one way out of a stripped screw situation. Use a Dremel tool
with a cutting wheel to cut a slot in the screw head that will fit a flat head
screwdriver. Use your safety glasses and go slow, because these cutting
wheels are very brittle and break easily.

Socket head screws are slightly less convenient because you need to have a different
Allen wrench (also called an Allen key or a hex key) for each screw size, as shown in
Figure 3-6. However, these types of screws are much less likely to strip. This is
especially true when you’re trying to undo a screw you accidentally glued in place
because you thought you were done. Socket head cap screws are designed to resist
tension in the joint; button heads are not—they are designed to look nice. Hex head
screws are more popular for heavy-duty applications, or for when you can’t get at the
screw head with a conventional screwdriver but can get to it from the side with a
wrench.
The head style you use will vary depending on your application and convenience.
Wood screws commonly come in flat head styles that you can drive right into the
wood. Socket cap screws and machine screws come in a variety of styles. Some of the
most common head styles are shown in Figure 3-7.