Wrenching Tips: Bolting and Unbolting

This week we’ll be getting back into more tips involving, you know, actual wrenching. Like, with wrenches. Specifically, these our our tips for making your life easier when it comes to cracking ’em loose and snugging ’em up. 

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Unbolting

Since no one here’s an assembly line worker (right?), we typically start with removal. When it comes to really stubborn fasteners, here’s my typical MO:

  • The day/night before, soak everything in penetrating oil. Hell, if you can hit it every night for a week you’re clearly not married gonna have an even easier time. WD40, carburetor cleaner and brake cleaner are not penetrating oils. My usual go-to is PB Blaster but Kroil is another top pick.
  • Get thee a torch. No need for an Oxy-acetylene beast, just a simple Bernzomatic
    is all you need (and all I have). Typically you want to heat the female fastener, which will cause it to expand and loosen its grip on your bolt’s threads. This expansion also gives your penetrating oil microscopic inroads to work its magic. Even if you can’t heat the female side exclusively, heat cycling and penetrant-dousing the whole assembly a few times can work wonders. This is where I warn you to be mindful of the flammability or meltability of materials in the vicinity. Also, after you heat something with a torch, it will be hot. You’d be surprised how easy that is to forget, right up to the point that you grab it.
  • With the fasteners properly prepped, get the right tool for the job: preferably a 6 point socket on the end of a breaker bar. If a good yank out on the end of the handle (you’d be amazed how many people give up 15% of their torque just by grabbing too far in) doesn’t do the trick, take a good look at the handle on your jack or any leftover plumbing supplies. Chances are there’s a tube that’ll fit right over that breaker and give you feet (a meter) more leverage. However, now’s a good time to pause and think: are you about to yank your car right off its jackstands? What happens if you break this bolt/nut right off? If it’s an exhaust hanger or suspension bolt…there are reasonable ways to deal with the consequences. Exhaust manifold? Maybe worth another round or three with the pentrant and torch.
  • Impact wrenches are tempting in such situations, what with their ridiculous torque ratings and one-finger operation. In practice, they rarely fit where you need them and provide no feedback as to what’s going on. I prefer to reserve mine for “known quantity” tight bolts, but not these ridiculous cases.
Hopefully the above will help with the stubbornest of fasteners, but those are generally rare to begin with. What follows are tips for quickly dealing with mildly recalcitrant fasteners: the ones that slow you down or make you look like a wuss while you struggle and whimper.
  • The wrench-on-wrench move is a quick way to get double the leverage without a second trip back to the tool box (assuming you’ve got more than one box-open end around). It takes a second to get the orientation right, but it’ll crack loose that bolt that’s just a little stickier than you’d like. If you find yourself really leaning on this assembly, stop and get the proper tool as this potentially a way to destroy a good wrench.
  • To quickly impart an impact load, I regularly employ a technique as follows: wrap one hand around the wrench, then ball the other one up in a tight fist. This will produce a bulge out the pinky side of your balled-up hand. Use this like a hammer to smack the back of your wrench-holding hand. I’ve found it’s a relatively painless way to transfer a good shock into a bolt in a situation where a longer tool won’t work or you just don’t want to go get it. Looks pretty badass if you can do it quickly, too.
  • Air ratchets (not impacts) are nice for spinning off grimy, tight-fitting fasteners on long bolts. You crack it loose, then spend another 3 minutes ratcheting (or, God help you, twiddling a standard box-open end) because it won’t spin off by hand. Not bad for one nut, but if some assembly has a half dozen of these, that time adds up.
  • For tough bolts that won’t allow a socket, use flare nut wrenches whenever possible. They’re almost a complete six-point, and have tighter tolerances than typical combination wrenches. As a result, they’re a lot less likely to round off a bolt head. They’re mandatory for brake line fittings, but definitely a good idea on any other small fasteners that are giving you trouble.
As a final note, put some thought in to the last bolt that’s holding something in place. If you’re sitting under something heavy enough to knock a tooth out, crack all the bolts loose, but leave the easiest-to-reach one for last. Doing so will allow you to support or control how the steering box (or whatever) drops before that ohshit moment when you’ve got one hand bent up around the frame to undo the nut and have to hold up 50lbs of cast iron with the other.

Bolting

Some assemblies like cylinder heads or differentials have very specific needs for tightening sequence, locking compound and torque specs. You absolutely need to follow these to a T. Second most sensitive are parts involving aluminum like spark plugs or exhaust manifold bolts (on a car with an aluminum head), as you will rue the day you stripped any of those threads. Over time you will develop a sense of about how much umph corresponds to a given amount of torque, but in the mean time get yourself a both ft-lbs and in-lbs torque wrenches. On the whole, you’ll find the proper specs feel lower than what most people consider “good and tight”.

Regardless of how great the torque spec, a torque wrench is the proper finishing tool, not an impact wrench. Yes even (especially) on lug nuts.

A torque spec (or your “about that tight” feel) assumes the threads in question are clean. If the crud on the threads is adding an extra 20% to the torque you need to give the bolt, you’re not actually tightening the parts together properly. The point is: clean your threads before you reassemble. A quick douse with WD-40 and a rag or wire brush is plenty. Of course, if you’ve had to give a bolt the previously described full monty to crack it loose, replacement is your best bet.

If you’re spinning a bolt in by hand and think it’s time to reach for a wrench because you’ve reached the end of the “easy part”, try lightly vibrating/wiggling the bolt as you try to spin it. Doing so helps relieve some of the friction as more an more rough spots rub together. You’ll be surprised how much farther you can go just by hand by doing it this way.

Let’s say we’re putting something big and heavy into place, a transmission or intake manifold, for instance. Keep the following in mind:

  • Make and use alignment pins. 80lb cast-iron transmission install? One man job with a few headless bolts. Put four in, line things up and put in the remaining bolt. Socket-head set screws work well too, as you can back them out with an allen wrench.
  • If you can’t get a bolt started, skip it and go to one that you can. The act of getting more bolts in place might help align things. If you’re down to the last of seven and it won’t start, then try backing a few others out and giving things a wiggle (or hearty kick). Sometimes shifting the part away from the thing you’re bolting it to will give you more wiggle room to get a bolt started.
  • Don’t just tighten down the first bolt you can get started. Get all the bolts started, then snug them up, then tighten them down. Do the last two in a criss-cross (will make you jump jump!) fashion to ensure things don’t go on cockeyed.

…and as we all know, installation is the reverse of disassembly. If I keep repeating it, one day it might turn out to be true.

 That’s it for me this week, but you guys never cease astounding me with great follow ups in the comments; what else do you have to add?

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