The Mudcat Café TM
Thread #143314   Message #3308520
Posted By: JohnInKansas
14-Feb-12 - 03:20 PM
Thread Name: BS: Snap-On tool
Subject: RE: BS: Snap-On tool
One of the reasons that people have trouble with stripping the sockets on fasteners is that in the fairly distant past most of the utility fasteners were barely "stove bolt" quality, and weren't expected to to be tightened more than snug. Fasteners might have been tightened to 30,000 psi stress levels, but often were much lower. You just used bigger screws or more of them if you needed more strength.

Fairly generally, but especially in autos now, nearly all of the screws and bolts are at least SAE J429 Grade 4 or higher, and are expected to be "tightened to yield" for good retention. This puts the fastener tensile load up in the 90,000 psi range, and of course requires "more torque" to get there.

Structural fasteners are nearly always expected to be pulled down to something like 120,000 psi, and for "critical structures" the intended installed fastener stress may go close to 200,000 psi.

There are a lot more Fastener Choices easily available now than only a few years ago, and higher strengths are more frequently used. (The link shows a small sample of choices, there are lots more.)

You now run into lots more fasteners that are installed at higher torque than "back in the day" because they need to be tighter, and you need to install or reinstall replacements to the original higher torques. This obviously makes some of the older recess styles less suitable than they were in the uses for which they were designed.

There's nothing really wrong with the Phillips drive, if it's used for appropriate purposes. It does have a couple of weaknesses as commonly used. A main difficulty is that you must keep the driving tool lined up with the fastener. If you tilt the screwdriver it will cam out of the recess and is likely to ruin the screw. In addition, few people even know that the "screwdrivers" come in more than one size, and you must use the right size tool if you don't want to ruin a lot of screws. Unless you've had significant experience, or (gasp, choke) RTFM!!! it can be difficult to know which size screwdriver to use for a particular screw. An additional difficulty comes from the demand for a "bigger screwdriver" when using power tools to screw them in. A power screwdriver bigger than necessary will have too much "inertia" to stop when the necessary installation torque is reached, and will strip a lot of screws. The "automatic clutches" on popular sizes of "screwdrivers" don't really solve the problem.

Nearly all the more exotic drive configurations have been developed to facilitate automated power tool installation on assembly lines. You may have "preferences" for which others you like to see best, but if you're not on an assembly line "you're probably using them wrong." In this context, "wrong" can be perfectly satisfactory but the uncommon drive types are only there to make someone else's job easier, not yours. If the fastener is designed specifically for a high torque automated installation, you probably won't get it installed as intended (unless you RTFM again, and pay attention).

John