Board logo

Fasteners + the SVA
FASTdan - 9/2/09 at 12:59 PM

Just a couple of questions regarding fasteners - stuff I've half picked up on whilst reading other posts etc:

1) 2 exposed threads - is this a requirement on all fasteners? ie 2 exposed threads extending past the nut?

2) secondary method of fixing - something someone mentioned about some of the suspension nuts etc, a second method of securing them? I didnt quite get what this was about? possibly a nyloc coupled with a tab washer?

3) acceptable heads - I presume hex heads are a no-no, but are button/dome heads ok? in either hex key or cross head form?

Cheers

nick205 - 9/2/09 at 01:06 PM

Exposed threads should be applied to all nut and bolt type fixings as a matter of course.

2ndary fixing method applies, for example, to the rear hub carrier to upright bolts where (typically) the bolt locates in a threaded hole in the rear upright. The examiner will be looking for the application of threadlock, lockwire, tab washers etc. Similar for brake caliper and mounting bracket bolts.

Dome head socket caps should be fine on interior and exterior projection/radius checks. Some have reported that examiners have failed these although this can be resolved with a blob of silicone for test purposes.

If in doubt, post pics of your concern areas for people to comment on.

FASTdan - 9/2/09 at 01:21 PM

quote:
Originally posted by nick205


2ndary fixing method applies, for example, to the rear hub carrier to upright bolts where (typically) the bolt locates in a threaded hole in the rear upright. The examiner will be looking for the application of threadlock, lockwire, tab washers etc. Similar for brake caliper and mounting bracket bolts.



If in doubt, post pics of your concern areas for people to comment on.


cheers mate.

So to clarify, the secondary method of fixing - does it apply only to tapped holes? and to 'safety critical' areas only, such as suspension, chassis, brakes etc? Do spring washers qualify?

I suppose what im asking is, is ONE locking method enough - ie if your going into a nut then nyloc is ok, if your going into a tapped hole then any of the ones you mentioned is ok? its the word 'secondary' that is throwing me! to me that says a combination of two locking methods.....

Also, with regards to threadlock - is there not a danger you could just turn up and declare you've used it on everything, but in reality you havent?

sorry for all the questions , i just want to make sure i've got this totally clear!

Canada EH! - 9/2/09 at 03:09 PM

Secondary, think of the lock tabs on the caliper bolts, they just stop the bolt from turning out on it's own, safety wire, hole drilled through the bolt head, then stainless wire put through the hole and twisted to another hole on the mounting to prevent the bolt from turning. In aircraft practice with nylocks, three threads must be showing when the nut is fully torqued, all critical bolts are safety wired, automotive think header bolts, oil pan, waterpump, rocker cover. Keeps the fluids in.