A seized bolt, a rounded head, and a stud snapped off flush are three different problems on one shelf. Here is the order working mechanics follow, and the short list worth owning.
Look at the fastener before the shelf. Three cases cover nearly everything.
A seizing problem: chemistry plus patience. The penetrating-oil guide pulls six independent tests into three picks: Seafoam Deep Creep, Liquid Wrench, and Free All, the can veteran mechanics bring up unprompted.
A grip or repair problem; no penetrant fixes either. That guide separates the four failure modes and starts with the undersized six-point socket trick.
I have not used a bolt extractor. My own record here is a pool pump screw that beat WD-40 and a run of larger and larger screwdrivers, until I had to break it and strip it out. So the extractor advice on this page is the forums', not mine: straight-flute, centered hole, heat first.
Every rung hurts less when it fails than the one below it. A wasted soak costs you a night. A snapped extractor costs you the part, plus a conversation with a machine shop.
| Rung | What it does | Next rung when |
|---|---|---|
| 1. Penetrant + time | Creeps into the thread gap and lowers breakaway torque. Every product in Project Farm's finale worked better at 24 hours than at one. | An overnight soak has not moved it. |
| 2. Heat | Expands the casting and cracks the rust bond. A torch beat every oil in Project Farm's first test: 91.5 ft-lbs to break the nut loose against the winning can's 97.3, and lower is better. Never take it to red. A 2016 Garage Journal thread warns it hardens the bolt for any drilling that comes next. | Three cycles do nothing, or fuel, rubber, or aluminum is in range. |
| 3. Shock | A hand impact driver turns a hammer blow into a hard twist while forcing the bit into the recess; Lisle rates its 29200 at over 200 ft-lbs of shock torque. | The head or recess is rounding under it. |
| 4. Fresh grip | A six-point socket one size down, hammered on; bolt-extractor sockets or locking pliers on anything proud. The stripped-bolt guide owns this rung. | There is no head left. |
| 5. Left-hand drill bit | Drilling in reverse makes the cutting direction the loosening direction; a 2010 Garage Journal thread reports the stub often spins out before the hole is done. | The hole is drilled and the stub will not turn. |
| 6. Extractor | Straight-flute or spline only, in a centered hole, on a bolt that broke from over-torque rather than rust. Reasons below. | It slips or starts to wind up. Stop before it snaps. |
| 7. Drill it out | Step up bit sizes to just under the minor diameter, chase the threads with a tap, thread insert if they fail. That is the fallback in the 2020 Garage Journal thread. | The hole wandered; that is thread repair now. |
| 8. Weld a nut on | Heat exactly where the rust is, a new full-size head, and a stub that shrinks as it cools. Method per a 2023 thread: washer first on a flush stub, fill the nut's bore, work it back and forth, repeat if it fights. | No welder, or the stub sits in an aluminum head. |
The clearest statement is a July 2020 Garage Journal thread. The answers discuss type before brand: several posters warn that long round spiral easy-outs expand the bolt, and one calls buying them practice for removing broken extractors. The preference runs to straight-flute and spline tools: Lisle's spline set, Irwin's multi-spline, Proto's tapered squares, Snap-on's SR40K. All of them need the one thing no tool fixes: a square, centered hole.
A 2010 thread on the same forum says the same a decade earlier: spirals overgrip, straight flutes win, Snap-on's multi-spline first. The counterweight from the stripped-bolt guide: an extractor is built for a bolt that snapped from over-torque, not rust. I have not used a bolt extractor, so this page picks no set.
The penetrating-oil guide's best-overall pick: it won Project Farm's toughest single round and held up across his series. I have not bought a can; the pick is his numbers, not mine.
For: the first can on any seized bolt
Skip if: you already own a can that works
Check price on AmazonFive sizes, 5/64 to 19/64 inch, M-42 cobalt, 135-degree split point; Irwin's own page pairs them with extractors. I do not own this set; the pick comes from Irwin's spec sheet and the forum threads, not my bench.
For: any bolt snapped off flush
Skip if: you only fight rounded heads. That is a socket problem.
Check price on Amazon3/8-inch drive, 5–50 ft-lb, 72-tooth dual-direction head, stated ±3 percent accuracy, per etoolab's listing. I own it and use it. I have not put it on a tester, so those are the maker's numbers.
For: putting the bolt back to the number in the manual, not the number in your forearm
Skip if: your fasteners live above 50 ft-lb. That is a 1/2-inch-drive job.
Check price on AmazonLiquid Wrench and Free All are the penetrating-oil guide's other two picks. The Lisle 29200 hand impact set is the shock rung. Owners in a 2014 Garage Journal thread say the US-made driver freed rotor and motorcycle case screws for years. The included Phillips bits are the weak point.
No button for bolt-extractor sockets, locking pliers, induction heaters, or any extractor set. No product I can vouch for, no button.
Chase the hole with a tap and wire-brush the bolt. The Permatex anti-seize data sheet makes clean, dry surfaces the first step. A torque reading on a dirty thread is a reading of the dirt. I use the etoolab 3/8-inch click wrench above, wound back to its lowest setting between jobs.
Anti-seize is for fasteners that have to come apart later, after heat and corrosion have had their turn. Permatex's aluminum-copper-graphite Anti-Seize Lubricant is rated from -60°F to 1,600°F, listed for spark plugs in aluminum heads, exhaust bolts, and U-bolts, and carries one warning in capitals: not for wheel lug nuts or studs. One line, all caps. I take the hint.
Threadlocker is for fasteners that must not vibrate loose. Loctite 242, the blue one on my shelf, is rated by Henkel's data sheet for 1/4- to 3/4-inch fasteners, sets in about ten minutes, cures in 24 hours, and releases with hand tools. Both live on the workshop consumables page.
Now the conflict. Permatex says reassemble at normal torque values. Fastenal's chart computes torque as T = KDF, with K = 0.20 for dry threads and 0.15 for lubricated. Same torque on a lubricated thread, roughly a third more clamp load. That can be enough to pass yield. Two data sheets, one bolt. They disagree and I will not pretend otherwise. My rule: follow the service manual and its stated condition; if it assumes dry and you added anti-seize, back the number down or skip the anti-seize.
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