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Drilling into C Pillar?

15K views 31 replies 17 participants last post by  USMC Vet 
#1 ·
Thanks to everyone who has documented their builds on this forum, it's been incredibly helpful to a newbie like me.
I am building a bed in the back of my 15 passenger wagon and am following a design from Deadwood. I am bolting a 1" flat peice of steel bar to the sides of the van using plusnuts and will support the bed using ikea bedrails. I have been using the predrilled holes that are roughly 21" above the vinyl floor, see attached photos. The only problem I have run into is the hole just below and behind the C Pillar on the drivers side. There appears to be another piece of metal about 1/4" behind the hole preventing me from installing a plusnut. It does not appear to be in the "no drill zone" but wondering if anyone knows if it is safe to drill into this in order to fit a plusnut? I know there is an airbag behind this pillar but not sure it runs the length or just in the ceiling? Any help would be much appreciated.
Steven
 

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#3 ·
Dave, thanks for the suggestion but not sure it would work in this instance as there is no more than 1/4" behind the hole before I hit that second peice of metal behind. The plusnuts have been great my only issue has been that I ordered them off amazon from the link that antoine posted and they may have sent me the size bigger than what I need (the bag says .280) I have had to put a small washer between the plus nut and the van sheet metal so it tightens down enough. The metal is pretty thin in the holes that I am using and they spin if I do not do this. Not a problem now that I figures this out but I did have to drill one of them out and start over.
Do you know if I could drill into the metal behind this hole?
Thanks
Steven
 
#4 ·
I mounted 3" aluminium angle in a similar location for a similar purpose. I also ran into a 2nd layer of metal in a similar location on the passenger side. In retrospect, with 3" to work with, if I had been more careful, I could have chosen an area without the 2nd layer of metal. But, I have a cargo van with no airbags to worry about, so I chose to drill, baby drill. I was really careful to avoid denting the outside of the van. I took more time to place the holes on the driver's side installation and was able to avoid that 2nd layer of metal.

I used rivnuts instead of plusnuts and have been very happy with them. It is possible that they don't need as much room behind the metal. I did, however, have one batch ordered from Amazon come in with metric thread instead of the 10-24 thread I had ordered. Amazon took them back, but it was annoying to have to wait.
 
#5 ·
pjtezza, thanks for info. I will try a rivnut and test what orton mentioned above. If that does not work, I'll see if I can snake a small bolt back there by undoing the panel below. I may just have to forgo that hole and drill a new one into the van but with all of the mods going on, I was hoping someone with a wagon figured out a workaround.
 
#6 ·
If you try the rivnuts, I'd be curious to know what you think about plusnuts vs. rivnuts. I've only used rivnuts.

For this location we are discussing, I used the largest rivnuts I had to support the bed. But, pretty much everywhere else, I used 10-24 rivnuts. They work great, but are a little too easy to cross-thread. If I ever build something like this again, I'll try a different thread pitch.
 
#7 ·
Only used the existing Ford holes that fit the 1/4-20NC plusnuts perfectly. Did enlarge the smaller holes in the sides of the roof rib to take the 1/4-20NC plusnut.

Did drill holes in the van wall for 1/8" aluminum pop rivits to mount the Panduit wireway that replaced the Ford wireway. That worked well until I got to the wall above the slider location. Must be boron steel there as I could not drill it. Used some existing holes for plusnuts for that section.

Did use the plusnuts in the square holes above the rear window indents. Did orient the plusnuts to line up with the square hole.

I do not know if you can drill into the second layer of metal.

The rivnuts are shorter so they can be used in a shallow hole where plusnut might not work.

I tried rivnuts but the tool I bought required three hands to put rivnuts overhead. Much prefer the plusnuts because the hole diameter is not critical because the four feet spread out much further than a rivnut.
 
#11 ·
Pressure/friction. The plusnut is sandwiching the van sheet metal with lots of pressure if installed correctly.
 
#9 · (Edited)
joefromga, plus nuts are very similar to rivnuts but instead of looking like a thimble with foreskin they are a bit longer and have slits in the back that allow them to collapse into the shape of a cross on the back. Not sure if they are any better but they fit perfectly in the predrilled holes in my wagon so that was my descision. I did find that I needed to add a small washer when installing in the sheetmetal of my transit to keep them from spinning but once I did that they were perfect with no problems.
Steven
 
#10 ·
Rivnuts are cylindrical and would only need to expand where they contact the interior (of the van) layer of steel. If you can drill through that second layer it won't affect a rivnut. Just put it in the hole(s) and cinch it up. Start by under drilling your hole. Once you penetrate the second layer, switch to the size bit you need. Otherwise, while your bit is working the second layer it is going to hog out the first hole.
 
#13 ·
Yes, I was able to drill through that no problem. Be careful as I almost drilled through the outer skin of my wagon when the drill bit caught. I ended up building a wooden stop from scrap I had laying around but folks on this forum have mentioned something called a step drill which may work. Good luck.
Steven
 
#19 ·
Unless you throw out some serious bucks, they won't last long opening up holes in Boron. The Irwin brand at HD will fail. They also leave a tapperd hole that can be troblesome with Rivnuts. A good set of Lenox hole saws are a better choice for anything you need to drill in the C Pillar that's over 1/2 inch.

The draw back to hole saws is Murphys Law. You can have a drawer full but will always be missing the size you need right now.
 
#25 ·
I have found more than just the pillars that were tough. Some of the horizontal panels over the slider are tough. Broke a few drill bits. Start with a very small bit and increase sizes of bits until you get the size you want, or purchase some expensive bits for the size you want. Boron steel is tough and the Transit has a bunch of it.
 
#27 ·
Good advice. I bought 1/8 and 3/8 carbide bits. Widening 1/8 to 3/8 was a pain, especially for the two layers on the D pillar. I should have use several more intermediate steps. The two size approach worked fine in other place, for instance the horizontal beams under the window areas.
 
#30 ·
Has it occurred to anyone else that drilling into highly stressed, engineered parts of the structure might not be a good idea? Yes, you can probably get away with it, but maybe you can design your mods in a way that avoids it and feel secure in that you didn't booger up the structure. That's what I did. I don't go drilling holes in the wing spar of my airplane either. Just sayin...

Best,

--Frank
 
#31 · (Edited)
Has it occurred to anyone else that drilling into highly stressed, engineered parts of the structure might not be a good idea? Yes, you can probably get away with it, but maybe you can design your mods in a way that avoids it and feel secure in that you didn't booger up the structure. That's what I did. I don't go drilling holes in the wing spar of my airplane either. Just sayin...
It did occur to me and I had some qualms about it. It's not quite like the wing spar on your airplane, either. I would never modify that. But in my case, I looked at the amount of structure in D-pillar and what it caries and decided to take the risk. I am a pilot also and an engineer in the aerospace biz, so I completely understand that from an engineering perspective this is not the right thing to do. I think (but have no proof) that the only thing that could cause structural failure in the D-pillar is a rollover or a rear-end crash. Because of the rollover risk, I would not drill the A or B pillars.

Could I stand up at a formal design review and defend this as an engineer? No. But I am comfortable with the risk. In the same vein, I am also installing a second row of seats and aftermarket seat swivels in the front. Will I analyze these and crash test them? No. Without the structural models I can't analyze them and without big $$$, I can't test them. So now I will be a "test pilot" for an "uncertified" van. Again, not quite the same as modifying your airplane.

I think that your advice is very good and we should all think long and hard about modifying structural parts. But in the end we need to use limited information to asses the likelihood and consequence of failure and decide whether the risk is acceptable to us.
 
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