Typically, an under torqued bolt will deform and be unable to provide as much clamping force as needed. An over torqued bolt will break.

A good tightening sequence ensures that an even preload distribution is achieved in the joint (See Dia. A). Since joints containing conventional gaskets have a comparatively low compressive stiffness, bolt preloads in such joints are particularly sensitive to the tightening sequence.

Insufficient torque When you apply exactly the right amount of fastening force, you can rest assured that the bolt will transfer the ‘hits’ as well as the load of the belt to the bulk of the engine, which will absorb them. This, in turn, will lead to incorrect belt tension and, eventually, to belt and/or engine damage.

If you plan to do any major work on your engine or on some major powertrain components, you absolutely need a torque wrench. Overtightening cylinder-head bolts, for instance, can easily cause expensive damage and catastrophic coolant loss. Too-tight exhaust manifold bolts can cause the manifold to crack.

When you overtorque above 15% of recommended which in this case would be about 95 ft/lbs you basically turn the fastener into a rubber band. Some of the fasteners will stretch and you will have uneven torque. Add heat and pressure and head gasket blows and the head can even warp.

Torque screwdrivers can exert torques from 6 inch ounces (0.04 N⋅m) to at least 27 N⋅m. Although no single tool covers the entire range, low-, mid-, and high-torque ranges are available. Torque screwdrivers and torque wrenches have similar purposes and mechanisms.

Similar to the Allen or Hex, the Torx can withstand greater torque. Because of its larger surface area, it is the least likely to slip.

The countersink hole should be made slightly deeper into the deck board than the head of the screw. This allows the head of the screw to be set slightly below the surface of the deck board. When shrinkage occurs, the head will be flush or just below the surface of the decking.

While it is not considered necessary to pre-drill wood screws, it is highly recommended by professionals that you do so. When you do not drill pilot holes in advance, you are essentially putting extra pressure on the wood surrounding the screw (weakening it) and increasing the chances of the wood splitting or cracking.

The general rule of thumb is that the screw should enter at least half the thickness of the bottom material, e.g. 3/4″ into a 2 x 4.

It is a very bad idea to use dry wall screws with treated lumber. What is likely to happen if you use drywall screws for building a deck is that the screws will begin to corrode and ultimately dissolve away.

This increased level of corrosion should make the woodworker think more about the fasteners that they use on treated lumber woodworking projects. Just any wood screw or nail will not do; instead, look for fasteners that are specifically designed for use with ACQ-treated materials.

The choice of fastener material is dictated by both the decking material and the environment. Galvanized screws work well with pressure-treated decking, while Redwood or Western Red Cedar decks are usually built with stainless steel screws to prevent staining around the screw heads.

Mechanically galvanized screws are generally suitable for decks and other outdoor projects made of pressure-treated lumber. Nevertheless, you should not use them with PT lumber in contact with the soil, in high-moisture areas, or in areas with salt content in the air.

The Consensus: For a deck build it’s best to use a combination of nails and screws. Screws are superior for laying down the decking. They hold things flush better and have a better fastener/tensile strength, which keeps boards from popping up over time.

Allow treated wood to dry thoroughly before staining or painting. Before driving in a nail or screw, drill a pilot hole to prevent splitting the wood. This is especially important when fastening near the end of a board.

The two most popular chemicals for wood pressure treatment are alkaline copper quaternary (ACQ) and copper azole (CA), which are both active corrosion materials. All of these parts should be either hot-dip galvanized or fabricated using stainless steel to withstand the corrosivity of the treated wood.

Does Treated Wood Corrode Aluminum? Yes. Most of the new chemical treatments contain copper and should never come in direct contact with aluminum. Many contractors isolate aluminum flashing and trim from pressure treated lumber with building tape or house wrap.