Torque to yield fasteners and why?

1. TORQUE TO YIELD
TYPE FASTENERS

2. Why are Torque-to-Yield bolts
a better choice for clamping?
 More consistent torque over wider range of
operating conditions.
 Matched to gasket and engine
 Head gasket failures are very rare now

3. Torque-to-Yield Angle Gauge

4. How to use gauge

5. So…what is happening?

6. Twist a little too far and…
BANG!!!

7. So…what is happening?
 As a bolt begins to
tighten, it enters the
area known as the
“Elastic
Deformation”
Region where the
bolt stretches, but
will return to original
length when
loosened.

8. Example: Connecting Rod Bolt
 This special tool will
actually measure
the amount that a
bolt will stretch
when tightened.

10. Let’s tighten the bolt some
more!
 As the bolt is
tightened further, it
reaches the “Plastic
Deformation” region.
At this point, the bolt
will not return to its
original length when
loosened. But it will
be a better “Bolt”!

11. But, we can over do it!
 It just got real easy
to turn all of a
sudden! At this
point, you can’t back
it off a quarter turn
and save it!

12. Hey! It got real easy to turn
 Ok, dumb-bunny.
You didn’t follow the
special “Torque-to-
Yield” directions in
the shop
manual…and now
you have a real
problem!

13. What this looks like-Real World!
1st Step: Base Torque, Mark
Bolts

14. What this looks like-Real World!
2nd Step: 90 deg. Turn

15. What this looks like-Real World!
3rd Step: 45 deg. Turn

16. What this looks like-Real World!
4th Step: 45 deg. Turn Center
Bolts

17. Remember!
 Always check the shop manual for instructions
for:
 Bolt length
 Lubrication requirements
 Special torque values and procedures
 Mark bolts when finished with final torque angle