Ever wonder why threading a bolt seems kind of crunchy? Ever strip threads and not really understand why? Bolt won't start threading easily? This is mainly for newer riders, but it might also be informative to seasoned riders as well. I mainly will speak of bolts, but consider this can apply to any type of threaded fastener.
Sometimes bolts don't seem to thread cleanly
Beware the thread killer. This is a bolt which has either been damaged, deformed, or otherwise flawed. Sometimes a flake of aluminum will break off and stick to a steel bolt. Sometimes it might be thread lock which was not cleaned up adequately. In this case, removing the fastener may have already damaged the threads slightly. This really becomes and issue if you have 8 bolts and randomly insert them.
Sometimes the threads have become untrue due to rubbing against something, like during shipping or handling. Sometimes it's visually obvious, sometimes it's not. If you exert too much force to tighten a bolt and it's a thread killer, you're probably gonna have a bad day.
Here's some steps to help make sure you don't kill your threads
1) Inspect bolts visually, clear obstructions as needed.
2) Use a fingernail as a mock thread, running the bolts thread across your fingernail feeling for parts of the thread that aren't smooth. - Be aware that any scraping or resistance may indicate damaged thread(s)
- This can be useful for clearing small shavings and other obstructions
3) Inspect bolt hole visually, look for damaged threads, debris, metal flakes, etc.
- Clear obstructions (Google is a great resource)
- Blow out shavings and other loose debris with compressed air (always use safety glasses)
4) Proceed to follow the initial hand tightening, hand tool, torque wrench sequence
- follow service manual specifications for torque values, sequence, lubrication, thread lock, etc.
I see or feel an issue, how what do I do?
There's a variety of techniques I've used over the years. In the case of a chip of aluminum stuck to the threads, I've used a precision screwdriver to pick it out. I've used files, wire wheels, taps, etc. to polish out flaws or blemishes. Attempt to correct the issues. Always gingerly test your repair, in this case good enough isn't good enough. It's either correct or incorrect in this case. If you cannot effect repair of the bolt, replace it.
What brought this up
I recently bought a second set of rims for my bike. I want them to be ready to swap out as my tires need replaced, and track days (hopefully). At any rate, I bought brake rotors and all the stuff to outfit each set of rims. All this of course, 2nd hand, and much of it from different people and different bikes.
Last night I was installing the front rim's brake rotors. I ran into a thread killer and used the techniques here to identify the issue and effect repair. Had I went on and tightened it anyway, I know 100% this would've destroyed the bolt holes thread. It would've never torqued. Why you ask? In this case the location of the burr caused by the damaged thread is pivotal. Not only is the obstruction cutting and damaging the bolt hole's threads, the shavings created by this are now also adding obstructions to tightening and loosening. It's a perfect storm.
At the base of the bolt's thread was the worst burr. This one alone would've probably stripped out the threads itself. The bolt just did not want to start threading like the rest of them, and I didn't attempt to force it. They way the burr had formed, it was very difficult to see. Only using the fingernail thread check did I find the damaged thread areas that needed repair. I repaired the tips burr, took a few times with the wire wheel, checked, repeat until correct. Thread a bit further, I found what I thought may be another issue was. I basically ended up polishing the entire thread are of the bolt, just to ensure not only would it tighten correctly but loosen correctly later.
Hope people find this helpful. I read about people stripping bolts sometimes, and a lot of the times they don't know why. In some of these cases, it was probably a thread killer and they never knew it.
If you have tips to add, please do. For example, did you know acetone is helpful for breaking down dried thread locker?
* Last updated by: VicThing on 3/22/2015 @ 4:19 AM *
Thanks again Vicster.You da man!
