Why you can't torque anything with a crush washer

[Bokerfork]

Bench racing with a buddy of mine (KoolAid drinker BTW) the subject of what to torque and what not to torque came up. During our discussion he mentioned that torqe values on anything involving a crush washer were meaningless.

Piqueing my curiosity, I requested that he elaborate.

The purpose of the crush washer he explained was to form itself into the nooks and crannies of the two parts it rides between. As it is being crushed, no real torque value can be applied since its malleability is in a constant state of flux. Once completely crushed, any further torqueing was simply destroying the washer itself and therefore negating any sealing effects it once had.

He went on to expain that the only proper way to get the proper seal on a crush washer was by feel. He said after the bolt makes contact with the washer, one should gently turn the bolt, feeling the crush of the washer itself until that magic point where resistance suddenly changes.

Listeniing intently, I couldn't help but think the boys on the FJR Forum would either have a field day with this or, magically, all as one, say "well duh". Either way, I thought I'd put it up for some discussion.

I should add FWIW, my buddy is a civil engineer by trade. I suppose that could work for or against him in this instance.

Just thought I'd throw it out there.

Mark

 

[odot]

Rules vary from state to state. Kalifornia is one very "special" state.

 

[BikerGeek99]

Wow.

And I thought that I had some geeky friends and geeky conversations.

 

[SacramentoMike]

Well, duh.

 

[wheatonFJR]

Well, duh.

I agree...but actually there were a few instances where people tried to torque the oil drain bolt to the excessively high number stated in the service manual.

So yes, you can torque...and overtorque with a crush washer.

 

[John d]

I guess not all civil engineers know what they're talking about.

Torque is simply resistance to turning measured by multiplying force and distance (e.g., foot-lbs). If a torque value is specified, then it may be torqued to that value unless the value specified is wrong. But yes, a crush washer can't deform as well into the nooks and crannies the second, third... time around, and most of us don't care, unless after twenty times it starts to leak.

 

[Spud]

It's the same thing that happens when you twist the cap off a bottle of beer. Only in reverse. That should clarify it.

 

[Old Michael]

Hell, I'm torquing one right NOW.

https://www.fjrforum.com/forum//public/style_emoticons/default/****.gif

 

[wnyfjr]

Hell, I'm torquing one right NOW.

Is that what they're calling it these days?

 

[huron52]

And where do you just put this crush washer again?

 

[PhilJet09]

With all due respect, your friend is wrong. I was a full time aviation mechanic for many many years. There were lots of applications where the manufacturer specified torque values for things with crush washers and I never had a leak or a stripped fastener when I torqued to those specs. The manufacturer calculated the amount of torque required to crush the washer the right amount, probably not that hard to figure out either. I will say though that aviation parts are tightly controlled, quality wise, and our torque wrenches were calibrated often.

 

[Chuck35]

For maximum sealing with minimum torque required (less stress on the threads) put a new washer on there ya cheap fucs

 

[RossKean]

Utter nonsense. It is possibly more important to torque a fastener with a crush washer. Too loose and a leak is almost certain - not to mention that the bolt could back out with vibration. Too tight and the washer is compromised. Harder to get the right value by "feel" since you never know the sweet spot.

And since its friday I thought I would mention that I am planning to replace the oil drain bolt crush washer on my '07 this summer. Sometime in July it should have 100,000 miles on the original one and decided I would buy the Feej a present to celebrate the milestone. I will torque the bolt to something a bit less than the factory spec!

 

[majicmaker]

With all due respect, your friend is wrong. I was a full time aviation mechanic for many many years. There were lots of applications where the manufacturer specified torque values for things with crush washers and I never had a leak or a stripped fastener when I torqued to those specs. The manufacturer calculated the amount of torque required to crush the washer the right amount, probably not that hard to figure out either. I will say though that aviation parts are tightly controlled, quality wise, and our torque wrenches were calibrated often.

DING, DING, DING!!!! This is the right answer my friends! Ignacio can close this thread now! )

(In the interest of full disclosure, I've never had a crush washer on the oil drain bolt and it has never leaked a drop). JS!

 

[McRide]

I guess not all civil engineers know what they're talking about.
Torque is simply resistance to turning measured by multiplying force and distance (e.g., foot-lbs). If a torque value is specified, then it may be torqued to that value unless the value specified is wrong. But yes, a crush washer can't deform as well into the nooks and crannies the second, third... time around, and most of us don't care, unless after twenty times it starts to leak.

yup

 

[TomInPA]

One of the important crush washers on the bike are on the spark plugs. I'm a strong believer in actually using the torque wrench there. I guess some can do it by feel, but the last thing I want to do is blow out a plug, or over-tighten.

 

[RedPorscheKilla]

Crush washer are there, like already alluded to, to create a seal, so kind of "air tight" basically prevent a fluid, liquid or even gas from leaking through. Material usually copper, so it can set properly upon the fastener tightened.....so the only way to warrant a proper fit is applying the torque the vendor does advise to use for.

So as sophisticated if not geekish your friends explanation sounds, it not accurate....but I enjoyed the topic a lot, especially the field day of our fellow forum members, thanks a lot for that

V

RPK

 

[majicmaker]

One of the important crush washers on the bike are on the spark plugs. I'm a strong believer in actually using the torque wrench there. I guess some can do it by feel, but the last thing I want to do is blow out a plug, or over-tighten.

Totally Agree Tom!

 

[RaYzerman19]

One of the important crush washers on the bike are on the spark plugs. I'm a strong believer in actually using the torque wrench there. I guess some can do it by feel, but the last thing I want to do is blow out a plug, or over-tighten.

Totally Agree Tom!

I'm assuming you're not torquing any more than it takes to seat the crush washer without over-crushing it, and that you trust the accuracy of the torque tool. My preferred method is install until gasket contacts base, then 1/2 turn more per instructions on the box.