I’m wanting to install three eyebolts on each bumper of my full size, metal bumper van. However, I’m daunted by my lack of mechanical skills and severe poverty of tools, as well as the following perplexing engineering questions. Perhaps I could get some experience and thoughts.
Even if I can find my drill, last seen in the 80’s, what kind of bit do I need to drill through a full metal bumper? Probably expensive.
The hardware store has three kinds of eyebolts: zinc-coated, galvanized and stainless steel. Obviously I want bolts that will resist weather, but the SS ones are very expensive. What’s my best choice?
I carry 1-3 boats. For best rope threading and tensioning, should I position the diameter of the eyebolts vertically (the hole going side-to-side) or horizontally (the hole pointing up and down)?
The bumper shape is sort of like a curved ellipse. I could position the eyebolts straight out in front (3 o’clock), or pointing slightly upwards (2 o’clock), or slightly downwards (4 o’clock). Do you think it makes a difference for rope chafing and, well, bumping things with the bumper.
I don’t want the bolts to rattle or fall off. On the inside of the bumper I assume I could put two nuts or a lock nut. Which is best and do I need a washer? What, if anything, do I put on the bolt outside the bumper to prevent it from wiggling – a nut, a nut and washer, or nothing needed at all?
This all seems so complex, and I left my physics in the West End Bar 45 years ago. Oh, how I envy those old ladies with the rec kayaks who just toss them in the beds of their pickup trucks or stuff them in the hatchbacks of their Subaru’s.
Get a bimetal drill bit for metal cutting -- should not be more than a few bucks depending on the size (a bit larger than the diameter of your eye-bolts.) You want a drill with good torque and high speed. Wear gloves, eye protection and long sleeved cotton shirt when drilling the thick steel because the curls of metal coming off thick steel will be white hot and can burn you (I have 25 year old scars to prove that.) They will melt synthetic fabrics right onto your skin.
On the bolts, galvanized would be fine (the zinc plated ones will rust). Personally I would choose the stainless but it's up to you. I would install them with the "eye" in the bolt perpendicular to the ground. I presume you are going to be either threading rope through the eyes or using hooks -- for either that would be the best position. The pressure on one side of the ring or another would tend to pull the eye vertical eventually anyway and could loosen the nuts.
Get rubber washers and place between the steel washers and the bumper -- this will allow you to tighten them so they do not rattle and will protect against possible galvanic chemical reaction and corrosion between the different metals of the bumper and hardware. I presume you are using machine threaded eye bolts and nuts and fender washers. Make sure all the parts are galvanized or stainless to match the bolt. If you've got Boeshield (aircraft lubricant that bike and marine shops sell), douse the hardware with that as you assemble it. Helps resist corrosion and siezing up.
I know I'm a girl, but trust me, I used to be a construction electrician, drilled tens of thousands of holes in steel and have built a lot of structures with metal hardware including several rigs for boat hauling.
great tips^^^ I would add. You may want to drill a pilot hole with a smaller bit to minimize wandering of the bit. Also when drilling thick metal heat is the enemy. Start the drill slow and use pressure, not just opening up the drill at top speed and watching it smoke.
1. Just a regular "high-speed" bit is all you need. That's just the normal bit, of which 99 percent of the ones you see in the store will be. The hardware-store guys will know too. Also, they are dirt-cheap if you get standard quality bits, and you can buy them individually too, rather than as a whole set. Buy yourself a centerpunch too. The hardware-store guy will know what you need. This lets you make a tiny dimple in the metal where you want to drill. That dimple prevents the bit from wandering as you start the hole.
2. What material to use is your choice, but I'd go with any option other than stainless. Plain steel or zinc-plated will get rusty, but it won't be enough to matter until decades after the car is dead. Galvanized won't rust but gets duller in color. To me, stainless steel is overkill unless you really care how it looks.
3 & 4. I'd go with vertical alignment, partly because it lines the bolts up with the direction of stress. The stress will be pretty light, but a right-angle pull isn't such a good thing when the bolts are attached to something as thin as "bumper metal". The main reason for vertical alignment is the thing you already mentioned. Align them horizontal and they'll get smooshed if you bump into anything.
5. The simplest way to lock the bolts in place is to have one nut on the outside and one on the inside (in other words, spin one nut all the way up the length of the eye-bolt BEFORE inserting it through the hole in the bumper). Cinch the two nuts tightly together (with the sheet metal of the bumper between them) and the eyebolt will be as rigid as you can make it without resorting to fancier techniques. Placing a washer up against the bumper metal on each side will engage a larger surface area of metal to resist "bending action" of the eyebolt making it even more rigid, and it may make the nuts bind less as you tighten them. I looked at Willoleaf's response to this one, and she's correct about corrosion and different metals, and though I've never seen a severe problem from this on short-lifespan objects like cars, you could still get the effect of metal-on-metal contact and the strongest clamping force you can get with a slight modification. Paper gasket material (from an auto parts store) and silicone sealant will separate and seal the contact surfaces without introducing the "springyness" and eventual deterioration of rubber gaskets. However, I doubt if it will matter much how you do it. Oh, and regarding the lubricant, I just use automotive chassis grease (because I've got lots of it on hand). When I take apart something on my car that I fixed or installed ten years prior, even with all the road salt they use here, there's no seizing, the grease is still in the threads and the threads still look brand new, so I know grease works fine. By the way, ANY grease will work so just get some small container of whatever you can find (you can buy many kinds in little containers that look like toothpaste tubes: silicon grease, bike-bearing grease, fishing-reel grease).
Thanks. A question. The rubber/steel washer combo – are you recommending that for inside the bumper, outside the bumper, or both?
Thanks for the Boeshield tip. Never heard of it, but will investigate. Maybe it would be good for the bolts that screw my Thule towers into the pre-drilled roof holes on my Saab.
Use a small diameter bit fer a pilot hole foyst, use low-speed on yer drill wit 3-1 light erl (or similar) as a loobracant/coolant fer de bit an' dun't push too hard, let de tool do de woyk. Then go ta yer proper size bit an' use same prooceedure as above.
Ah' always use SS - yup - a few bucks more but wats a few bucks ta millionaires like us ;>}. Never had a prooblem wit galvanic corrosion wit steel-on-steel.
FE
Maker of many holes in me horseless carriages fer many moons.
Galvanized rusts eventually My Yakima setup uses some galvanized oversized bolts and they have som corrosion on them. Nothing too bad but not like stainless steel…
You might be better off removing the bumper first to get easy access to the inside. You do want to use locking washers so things will remain where you put them. Or use the locking nuts with the plastic insert instead or?and some anti seize/locking compound (that not only prevents seizing but also locks to some extend - there are different torque grades, depending on how easy you want it to come off)
The topic is eyebolts, not not eyebolts I’m well aware of all the all the alternative ways to tie down on my vans and other vehicles for more than 30 years.
I was specifically limiting this topic to the question of how properly to install eyebolts on a metal bumper.
Welding Why not get some bolts and take them down to a local auto repair and ask them to weld them in place? You won’t have to worry about them loosening up, and no drilling required…
Glenn, Get BIG ones too … 5/16s minimum. 3/8s better. Locknuts and fender washers. Beware the washers may need to be pre bent or just cranked in so the take shape of bumper if its really curved.
Right! Rubber is not needed to resist rattling. And, as it ages, the bolt would loosen. I’d go nut, lock washer, bumper, lock washer, nut. I might add flat washers next to each side of the bumper. Once tightened up, it will stay tight, and will not rattle.