What is a torque-to-yield bolt? It is a one-time-use fastener that is designed to stretch during the torquing process (installation). Because of this stretching, the integrity of the bolt is compromised. These bolts cannot and should not be reused due to the stress caused to the bolt during its first installation.
Can torque-to-yield bolts be reused?
Torque-to-yield (TTY) head bolts are designed to stretch when used. Once stretched, they are not as strong as before. Consequently, they cannot provide the same amount of clamping force and may break or shear off if reused.
Can you torque a bolt twice?
A bolt that has already been used in a given application may or may not be reused, depending on the grade, application, and recommendation of the “Engineer of Record”. … Touching up or re-tightening bolts that may have been loosened by the installation of adjacent bolts shall not be considered to be a reuse.”
Can you replace torque-to-yield bolts with regular bolts?
With a standard bolt, a technician could torque the bolt to its yield point, and it would return to its original form and length when removed. It has elasticity; it can stretch and then return to its original form. … At this point, the bolt cannot be reused and needs replacement.
Are torque yield bolts better?
Torque to Yield (TTY) fasteners are used in many modern engines. When torqued properly, they provide better clamping force than standard fasteners. … When swapping heads or rebuilding an engine, always replace any TTY bolts with new ones.
What happens if you over torque a torque to yield bolt?
If the bolt is over-torqued and stretched beyond its limit, this exceeds its yield strength which means it can no longer maintain the needed clamp load and must be replaced. … Finally, using a breaker bar, the bolt is tightened, which moves the dial to the specified angle – hence the term torque-angle.
How do torque to yield bolts work?
A torque to yield fastener (TTY) or stretch bolt is a fastener which is torqued beyond the state of elasticity and therefore undergoes plastic deformation, causing it to become permanently elongated.
How many times should you click a torque wrench?
Turn the torque wrench until you hear two clicks. This means the correct amount of torque has been reached.
How many times can a bolt be used?
The answer to this question is: “When a bolt has not been stressed past its yield point it can be reused.” This answer brings to mind two more logical ques- tions: Question: What does it mean that a “bolt has been stressed past its yield point”?
Can you Overtorque with a torque wrench?
So long as users operate with caution and do not exceed the maximum torque, most torque wrenches can be used for undoing. However, if the bolt will not free within the maximum torque of the wrench, another tool should be used instead.
Why do manufacturers use torque to yield bolts?
Many vehicle manufacturers use torque to yield bolts; especially on engines with aluminum heads and or in conjunction with (MLS) head gaskets. Because, they provide more consistent clamping loads, across the entire head-to-block mating surface. … Reusing the old bolts, can cause expensive engine failure.
How do you install torque to yield a bolt?
How to tighten torque to yield bolts
- Tighten all bolts in sequence, and in two stages to a snug torque value of say, 30 Nm.
- Apply a 90 degree rotation to all bolts in the proper tightening sequence.
- Apply a further 90 degree rotation to all bolts in the proper tightening sequence.
Why are some bolts torque to yield?
Traditional fasteners are torqued to a load that will slightly stretch the bolt but won’t over-stretch it past its yield point. Torque-to-yield (TTY) fasteners are stretched beyond the point of elongation to ensure a more consistent clamp load on the joint.
Can stretch bolts be reused?
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.
Can you reuse head bolts?
Can I reuse head bolts? … 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.