Fasten-ating (Post # 104)

Early on the morning of the Arizona Concours d'Ellegance I was talking to some of the other entrants when one asked a seemingly simple question: "What was the hardest part?" I started to say "The front suspension," but no, that was just the most frustrating part. Then I considered the process of stripping and cleaning the body and chassis, but no, that was just the dirtiest part. Finally, spontaneously, I blurted out "writing the damn blog!" That got a good laugh, but as I sat down to do this post that conversation came back to me, and I had time to give it some serious thought.  

So what was the hardest part?  Randy Davis.

The hardest part of the hands-on work was not one of the individual sub-assemblies like "the brakes," or "the wiring harness."  It was--and this time I'm serious--the fasteners.  Just to make sure you know what I mean, I'm talking about the nuts, bolts, washers, screws and other objects that hold the car together.  Every sub-assembly depends on some kind of fasteners, and when you start adding them up, they number in the thousands!  I haven't actually counted yet, but we probably have at least 100 different "types" of fasteners if you consider sheet metal screws and machine screws manufactured in both metric and British Imperial systems, with a multitude of head shapes, shaft diameters, shaft lengths, thread pitches, metalurgical properties, hardnesses, identification codes, and platings . . . and scores of different types of washers!   

By the time we got to final assembly we were sorting through hundreds of different fasteners.

Cleaned, photographed, and bagged Alfatross fastener
sets awaiting installation. 

So what makes fasteners the hardest part of the restoration? Well, consider the urban legend about the guy who took his car apart, carefully identifying each and every fastener as it came off so that he could put each one back in the hole it came out of.  Frankly, I find that hard to believe.  Not impossible, but highly unlikely.  Why? Well, if you just put each fastener into a bag and label it with a number that could be correlated to a map of the car with each fastener hole it would be a monumental undertaking that would greatly increase the amount of time needed for the disassembly phase . . . but that is just the tip of the iceberg.  

Vibratory tumblers for cleaning and polishing fasteners.

When it comes time to reassemble you can't just take them out of the bag and put them back where they came from.  Fasteners have an important job to do, so they need additional attention. Many of them will be rusted, bent, broken. Some cannot be restored and re-used; they must be replaced with an exact replica.  Many others will need "reconditioning" which means mechanical or chemical cleaning, sometimes even re-plating.  
For those readers who have never tried restoring an old car, don't even think about it unless you have a set of machine screw and bolt size gauges, the kind that can measure both fastener diameter and thread spacing. If you're dealing with a mid-1950s Italian car be sure to get both metric and British Imperial gauges.

Cleaning the threads is the worst part. First you have to use your thread gauges to determine if the part was created according to the metric system or the Imperial system. Then you determine the part's nominal diameter and thread pitch. Which can be coarse, fine, or "special." Don't forget that the pitch for Imperial fasteners is defined as the number of threads per inch, while the pitch of metric fasteners is the distance from one thread to the next. Armed with the diameter and thread pitch parameters you run the fastener through the proper die to recondition the threads to make sure it will fit.  Then, of course, you have to do the same thing with the threads in the nut or hole it came out of using the matching tap. Don't forget to use the proper anti-seize, thread-locker, or lubrication before you put the two together, and remember that although the majority of fasteners are right-handed, some are left-handed!

All this assumes that by the time you get to the reassembly stage you kept track of each fastener throughout the disassembly, bagging, cleaning, photography, storage, and tapping and die-ing processes.  

I think we need a 17 mm LOBO bolt with a castellated nut, a heavy beveled washer and a
3/32" stainless cotter pin . . . .

If I had it to do all over again I would certainly pay a lot more attention to fasteners.  It is easy to underestimate their importance at the beginning of a restoration project, but in doing so you make a lot of extra work for yourself in the end.  I have seen amateur "restoration" projects where the restorer just let the original fasteners fall to the ground to be swept up and discarded like so many cigarette butts.  How he expected to put the car back together again I don't know.  Conversely, I have heard of professional restoration companies going to great lengths to make their own replica fasteners to replace original ones too far gone to be reused. 

One area I am still largely ignorant of is "fastener engineering"--Why are there so many different types? Who determines where to use one type vs. another? What do those letters and numbers some screws and bolts have on their heads mean? Where is it appropriate to use castellated nuts instead of regular nuts with lock washers?  When did the Phillips screw head type appear for use in Italian automobiles? Is there any relationship between a bolt's head size or shaft size and the maximum torque it can take? When was the 14 mm hex head bolt and nut combination replaced by 13 mm parts?  

Yes, it's a fasten-ating subject!