Loctite Threadlocker Blue 242 Review (2026)
By Nate Sawyer, Editor · Updated July 2026
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- Locking bolts
- Serviceable fasteners
- Automotive
- Vibration
The default threadlocker for anything you'll service again: valve covers, brackets, bike and equipment bolts. It stops vibration loosening but still breaks free with a wrench, which is exactly why it's the most-reached-for bottle in the shop.
Pros
- Locks bolts against vibration yet comes apart later with ordinary hand tools
- Fills thread gaps and seals against corrosion and leaks between mating threads
- One drop is all it takes; a single small bottle handles dozens of fasteners
Cons
- Anaerobic cure needs metal-to-metal contact; it won't set on plastic threads
- Medium hold can be too weak for high-vibration or safety-critical bolts (use red 271)
- Full strength takes 24 hours, so don't stress the joint immediately
Specifications
| Type | Medium-strength anaerobic threadlocker |
|---|---|
| Set time | Fixture ~1 hr on steel |
| Full cure | 24 hr |
| Bonds | Metal threaded fasteners up to 3/4 in (M20) |
| Strength | Medium; ~115 in-lb breakaway on 3/8-16, removable with hand tools |
| Temp range | Up to 300F (149C) |
Frequently Asked Questions
- How long does Loctite 242 take to cure?
- It fixtures in about an hour on steel and reaches full cure at 24 hours. Do not stress the joint immediately - the bolt will feel locked well before the threadlocker is actually at full strength.
- How do you apply Loctite Threadlocker Blue 242?
- One drop on clean, dry threads is all it takes, then assemble and torque normally. A single 6 ml bottle handles dozens of fasteners. It works on metal threaded fasteners up to 3/4 in (M20) and also fills thread gaps, sealing against corrosion and leaks between the mating threads.
- Will 242 work on plastic threads?
- No. It is an anaerobic threadlocker, which means it cures in the absence of air and in contact with metal. On plastic threads it simply will not set.
- Is blue 242 strong enough for high-vibration bolts?
- Not always. It gives roughly 115 in-lb breakaway on a 3/8-16 fastener and comes apart with ordinary hand tools, which is exactly right for anything you will service again. For high-vibration or safety-critical bolts the medium hold can be too weak and red 271 is the correct choice. Temperature limit is 300F.