Re: 1990 International-14" Roof Lift.
We started back to work on our bus a couple of weeks ago, buttoning up the exterior sheet metal that I did not get finished before the snow came last year. I am very pleased with the way it is progressing. To attach the new exterior skin (20 ga. sheet metal) I reused the sheet metal screws I had removed from the inside of the bus. These being about 5/8" in length and 5/32" in diameter with a 'star' head. I purchased about 15- 5/32" drill bits and went to work drilling hundreds of holes. Where the screws went through the sheet metal into a body strut or rib, (either a factory rib or a piece of angle iron or tubing that I have added) they held just fine. Where the screws went through only a couple pieces of sheet metal, either the existing sheet metal or an overlap of two sheets that I installed there was a bit of a problem with the sheet metal screws not wanting to tighten up. Some would snug, others would just spin. This was unacceptable.
After trying various sheet metal fasteners (screws and rivets) I came back to using the same screws I had removed from the inside of the bus. However this time I had my wife on the inside of the bus with a box of locking nuts and a 10 millimeter open end wrench. Instead of hassling with a standard lock washer and nut I used nuts with a nylon insert. I had used these nuts for years while rebuilding and servicing railroad cars and I have found them to hold exceptionally well while standing up to the constant vibration from traveling. I purchased the locking nuts at Ace hardware. Purchasing a few hundred (I needed 300) of these nuts is cost prohibitive if you buy them separately. If you look in the back of the bolt bins at ACE (pull the drawer out farther) you will find them by the box (100 each). These are priced very reasonably, I paid $5.99 per box of 100 rather then the .13 cents each that they had them individually priced at.
Turning the original sheet metal screws into bolts with locking nuts on them has made an extremely large impact on the installation of the new skin! Not only have I added a locking nut to each new sheet metal screw, I went back and removed & replaced each sheet metal screw that was not run through the sheet metal and a body strut, tubing or piece of angle iron. Almost all of the screws are easily accessible and this procedure has only added a day's work to each side of the bus. The payoff in strength and quality has been tremendous!