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Engine Building Fundamentals: Stretch Gauge

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Stretch Gauge

01.38

00:00 - While it's common practise to tighten fasteners in the engine using a torque wrench, as we've seen in the fasteners section of this course, remember, what we're really trying to do is stretch the fastener by a very specific amount.
00:13 If we can achieve the correct amount of stretch, this will result in the optimal amount of clamping force from the fastener.
00:20 Traditional techniques of using a torque setting or torque and angle are only effective to a point and the results can be influenced by the lubricant used as well as the condition of the threads.
00:32 A superior technique is to directly measure the amount of stretch in the fastener as it's tightened and to do this, we use a stretch gauge.
00:41 The stretch gauge uses a fixture that holds a dial gauge and the bolt is placed in the fixture before being installed and then the dial gauge is zeroed.
00:51 As the fastener is tightened, the stretch gauge is used to constantly check how much it is being stretched.
00:57 This allows for very specific and accurate amounts of clamping force to be achieved, while ensuring the fastener is not permanently deformed.
01:06 A stretch gauge can only be used where both sides of the fastener can be accessed and this limits where a stretch gauge is truly useful.
01:15 For example, it's impossible to use a stretch gauge where a bold is installed in a blind hole, where we can't access the back of the fastener.