Reusing Schnorr washers?

[garment]

Can they be re-used? I kinda think I heard they are one-time use only. Application is for the motor and tranny mounts (the large bolts). Thanks Pelicans! And BTW - does anyone have 4 M12 Schnorr washers hanging about in the DC area?

[walt]

I have these on my driveshafts and have replaced the bolts and washers with new each time. Technically, I am not sure the correct answer but always err on the safe side.

[mepstein]

They are for one time use. All the big fastener companies carry them.

[OldSpool87]

Try Belmetric. They ship fast.

[Snitzler]

Just curious, what Schnorr washers? The M12 doesn't have a lock washer, just a torque value. I just swapped out my motor mounts and I am wondering about this. The parts list doesn't list any lock washers...

[juanbenae]

i've used standard stainless lock washers when schnorr were not at hand. never lost an axle even on my racecar...

[petercory]

Using Stage 8 Fasteners, they'll never loosen up - cheap insurance!!!

[manbridge 74]

I’ve reused in a pinch. Properly torqued axle bolts will not back out.

[Jeff Alton]

^^^ Exactly. Clean the threads on the bolts and out put flange. Torque properly and never worry about it.

[garment]

So, my application is for the motor and tranny mounts. Same logic still applies?

Originally Posted by manbridge 74

I’ve reused in a pinch. Properly torqued axle bolts will not back out.

[Harpo]

Originally Posted by petercory

Using Stage 8 Fasteners, they'll never loosen up - cheap insurance!!!

Ditto and they are reusable

David

[Walt Fricke]

There have been lots of discussions about this and related issues. Some favor doing exactly what Porsche did and nothing else. When it comes to these special washers, Porsche did not always use them for various applications, which suggests maybe it doesn't matter, really.

Jeff nailed what is the real key to keeping fasteners tight and in place - enough bolt stretch, which is approximated by torque. That's what race engineer Carroll Smith says in his book on fasteners. He says that even safety wiring won't do the trick if the stretch (and in the case of a bolted joint, the resulting clamping load on rotating reversing mating surfaces)is inadequate.

I use no washers and none of those plates with two holes on my 8mm bolt size CVs, and I have never had one which was properly torqued back out.

So it is a question of your comfort level, I guess - you can't go wrong if you have adequate torque.

Of course, not a big expense for those washers, and if sending off for new Schnorr's doesn't affect your schedule and you like the idea of following the actual factory manual for your model, why not. It makes sense that you try to keep the metal to metal joints on both sides of the CV pretty grease free.

And checking the torque of all of them after 100 or so miles of driving isn't a bad idea - if you missed something you can catch it. When torqueing mine I like to go one extra bolt around just to make sure I got all of them.

[T77911S]

you can get a bag of 50 from Fastenal pretty cheap, compared to what they are sold for EA.
you can also get the bolts in 5mm lengths. you want 2-3 threads sticking out past the flange.

[Mike Andrew]

A dab of paint on the bolt and mating surface after torqued will tell you visually if they have backed out at all. Easy to do and easily viewed.

[Pazuzu]

Originally Posted by garment

So, my application is for the motor and tranny mounts. Same logic still applies?

I have reused those big schnorr washers for years, basically because I don't want to bother shopping for them. Those are massive bolts, with lots of torque, which are loaded axially. Totally different scenario than the axles, which are undersized bolts, with very little torque, being loaded radially (and rotationally, to boot!)

You could 100% get away with simple lock washers as well. I don't see any real reason for Schorr washers on the engine and tranny mounts.

[Shaun @ Tru6]

I always supply new Schnorr, lock and wave washers in every customer's job.

[da Vinci Dan]

Do not reuse