How Do You Tell If A Bolt Is Stretched?

Should you oil head bolts?

Yes, you should lightly oil head bolts when you install them.

You don’t want to have the bores full of oil or anything, but lightly lubricate the threads and heads.

Torquing a bolt that size dry will give an inaccurate and insufficient torque because of the friction of the bolt head against the head surface..

How can you tell if a bolt is stretched?

You can identify a torque-to-yield or stretch-style fastener by the narrow shank just below the washer face and before the thread run. A bolt of this design is intended to be installed in the plastic range and cannot be reused after being tightened once.

Can you reuse a stretch bolt?

stretch to ensure proper securing when tightened down. (Bolts with Specification: Torque plus Angle). Some of these bolts can be reused, if you torque them to the same torque that you would use for a normal bolt of the same size, pitch, lubrication factor, and strength rating.

What is a bolt or nut tightening sequence?

Bolt tightening sequence, or torque sequence, is defined in the torque tightening procedure. Flange joints are torqued tight with the help of a torque wrench (manual or hydraulic). … Torque bolts and nuts in a “CRISS-CROSS” sequence using a minimum of three torquing passes and the maximum bolt stress as defined.

How tight should bolts be?

In general, you should make the bolt tight enough so that the items it is holding together stay together, but not so tight that you damage the bolt’s threads. You should tighten bolts properly so that the bolt performs properly.

When bolts are tightened They are also stretched?

In a bolted joint, tightening the nut actually stretches the bolt a small amount, like pulling on a stiff spring. This stretching, or tension, results in an opposing clamp force that holds the two sections of the joint together. If the bolt comes loose, this clamp force weakens.

Is it bad to over torque head bolts?

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.

How do you loosen a tight bolt?

How to Loosen Nuts and BoltsSpray the nut with penetrating oil and let the oil sit for 10 to 15 minutes to penetrate the threads of the bolt. … Hold a hammer against one side of the nut, and hit the other side with a second hammer. … If the nut is badly rusted, pour hydrogen peroxide on it to dissolve the rust.More items…

Will anti seize cause bolts to loosen?

Using anti-seize without reducing the required torque value can strip the threads or stretch the bolt in extreme situations.

Do I need to Retorque head bolts?

In most cases you don’t need to retorque head bolts or studs. … Always use lubrication on your head bolts and studs. Make sure your fasteners are clean and the holes are free from debris. Use a thread chaser, and not a tap, to clean out the holes in the block.

When should you Retorque head bolts?

The second torquing is usually done after the engine has been sitting all day or overnight. That allows time for the head gaskets to relax a bit and which in turn can cause some looseness of the head bolts. After 1000 miles and if possible, my preference is to go back and recheck them.

What happens if a bolt is over torqued?

Everyone who has ever worked with fasteners has accidentally messed one up at some point. One of the most damaging ways to do that is by over-tightening, or over torquing the fastener. This can result in stripping screws, snapping screw heads and damaging pre-tapped threading.

Can bolts stretch?

All bolts stretch when they are tightened, but usually they stay within their ‘elastic limit’. So, when they are loosened, they return elastically to their original length. The normal tightening method is by torque wrench.

How many times can a bolt be torqued?

Plain ASTM A325 bolts, however, possess sufficient ductility to undergo more than one pretensioned installation as suggested in the Guide (Kulak et al., 1987). As a simple rule of thumb, a plain ASTM A325 bolt is suitable for reuse if the nut can be run up the threads by hand.”

Should you always replace head bolts?

yes, you want to replace them. When head bolts are torqued they are supposed to stretch. They are only made to stretch once. if you reuse them you have a good possibility of one of them snapping which will cause big problems.

Can you reuse head bolts Chevy 350?

A head bolt should not be reused if the threads are galled or badly damaged. Chasing damaged head bolt threads with a die will clean up the threads but also remove material (metal) and undermine the head bolt’s ability to torque down and hold to specs.

What happens if head bolts are not tight enough?

But even the best head gasket won’t maintain a tight seal if the head bolts have not been properly torqued. … Uneven loading created by unevenly tightened head bolts can distort the head. Over a period of time, this may cause the head to take a permanent set.

Why do head bolts stretch?

As the head gets hot, thermal expansion is going to stretch the head bolts even more – especially in engines with aluminum heads. … A head bolt exerts its maximum clamping force when it is stretched to its “yield point.” This is the point where the bolt can stretch no further without being permanently deformed.

How much does a bolt stretch when torqued?

To appropriately answer this question, it helps to first consider that only approximately 10-15% of the input torque actually stretches the bolt; the remaining 85-90% of input torque is primarily used to overcome friction between the mating threads and friction under the bolt head or nut.

Should you tighten the nut or the bolt?

The answer depends on your application and the condition of the materials being fastened. In many situations you can apply torque to either the nut or the bolt head. Both will result in a tight connection and neither will avoid breakage more often (that occurrence can be avoided through other means).

What happens if you dont torque head bolts?

If the head isn’t torqued down properly, then the most likely failure is of the head gasket, which could lead to loss of compression, the mixing of oil and coolant, exhaust gases getting into the oil ways or cooling channels, erosion of the cylinder head, overheating and warping of the cylinder head.