Product Guides

Loctite Application Guide: Which Grade & When to Use It

Loctite Grade Selector — Match Product to Job This guide is a working Loctite selector. Use the cards below to land on the right grade fast — every grade mentioned in the article body also links to its specific AIMS product page. How to use: 1. Match the job profile (threadlock, sealant, retaining, adhesive) 2. Click the grade to view AIMS stock 3. Use the application section below for technique Low-Strength Threadlock Loctite 222 — small fasteners, removable 222 View → Medium-Strength Threadlock Loctite 243 — workshop default 243 View → High-Strength Threadlock Loctite 263 / 271 — permanent / vibration 263/271 View → Pipe Thread Sealing Loctite 567 / 569 / 577 — anaerobic 567/577 View → Bearing Retaining Loctite 638 / 641 — slip-fit retaining 638 View → Gasket Eliminator Loctite 518 / 510 / 587 / 596 518/596 View → Instant Adhesive (CA) Loctite 401 / 406 / 480 401/406 View → Anti-Seize / Surface Prep Loctite Copper Anti-Seize + 7649 Primer Anti-Seize View → Quick rule of thumb: Loctite anaerobics cure where there's metal + absence of oxygen. Low-strength (222) = removable. Medium-strength (243) = workshop default. High-strength (263/271) = permanent / heat-required to remove. AIMS stocks the full Loctite anaerobic + instant adhesive + sealant + activator range. Need help? Call (02) 9773 0122. Jump to: Which Loctite? Loctite Guides Quick Chart Threadlockers Thread Sealants Retaining Anti-Seize Surface Prep Removing Instant Adhesives Related Loctite Guides Each Loctite product family also has its own dedicated category guide — grade-by-grade breakdowns, decision frameworks and FAQs beyond what's covered here. Threadlockers Purple, blue, red and green grades compared — including the 248 and 268 sticks. Full guide → Retaining Compounds Bearing installation, diametral clearance selection and troubleshooting. Full guide → Thread Sealants Hydraulic and pipe sealing — media compatibility and pressure ratings. Full guide → Which Loctite do I use? Loctite threadlockers are colour-coded by strength: blue (Loctite 242 / 243) for medium-strength fasteners you'll need to remove later, red (Loctite 262 / 271 / 277) for permanent high-strength fasteners that stay put, and green (Loctite 290) for wicking into pre-assembled threads. Loctite also makes thread sealants (567 / 577 for tapered pipe threads), retaining compounds (603 / 638 for bearing fits), and instant adhesives (401 / 406 cyanoacrylates). What is Loctite 243 used for? Loctite 243 is a medium-strength blue threadlocker for fasteners between M6 and M20 that you may need to remove later with hand tools. It tolerates light oil contamination on the threads, cures in around 10 minutes to handling strength, and reaches full strength in 24 hours. Typical uses: vehicle suspension bolts, pump and motor fixings, machinery hold-downs, gearbox fasteners. Need another reference chart? Browse the full AIMS Engineering Reference Charts library — drill bit sizes, tap drill, torque, viscosity, GD&T, AS/NZS standards and more. Loctite Quick Selection Chart For threadlocking on small fasteners use Loctite 222 (purple); medium-duty fasteners Loctite 243 (blue); high-strength permanent Loctite 263 or 271 (red). For pipe sealing use Loctite 567 or 577. For retaining compounds use Loctite 638, 641 or 648. Full grade-by-grade detail below. Grade Type / Colour Use For 222 Threadlocker — Purple, low strength Small screws M1.4–M6, grub screws, instruments 243 Threadlocker — Blue, medium strength General fasteners M6–M20, hand-tool removable 263 / 271 Threadlocker — Red, high strength Permanent fasteners — heat required to remove 567 Thread sealant — White Fine hydraulic and pneumatic threads 577 Thread sealant — Yellow BSP and NPT pipe threads, gas, water, oil 638 Retaining compound — High strength Close-tolerance bearing retention 641 Retaining compound — Medium strength Standard bearing / bushing retention 648 Retaining compound — Maximum strength Permanent high-temp cylindrical assemblies 401 Instant adhesive — Cyanoacrylate General-purpose bonding of metal, rubber, plastic 480 Instant adhesive — Toughened CA Impact-resistant rubber and metal bonds What Are Loctite Anaerobic Products? Loctite's industrial range is built on anaerobic chemistry — adhesives and sealants that remain liquid in air but cure rapidly when trapped between two close-fitting metal surfaces in the absence of oxygen. The metal ions in the substrate initiate polymerisation, converting the liquid into a hard thermoset plastic that resists vibration, leakage and corrosion. When stripping a stubborn old anaerobic threadlocker bond, mechanical heat is the standard release method — but for plastic-bodied components where heat is risky, the contrast-cooling trick from our freeze spray guide can shock-fracture cured threadlocker without damaging the surrounding plastic. Quick answer — Loctite grades by job Threadlockers (anaerobic, prevent vibration loosening): 222 low strength (small screws, removable) · 242/243 medium strength (general purpose, blue) · 263/271/277 high strength (permanent, red) · 248 stick form Instant adhesives (cyanoacrylate / super glue): 401 general purpose · 406 rubber/plastic specialty · 414 metals · 480 toughened impact-resistant · 435 low-blooming clear Thread sealants (anaerobic, pipe thread leaks): 567 stainless/coarse (white) · 577 general pipe (yellow, faster cure) · 542 hydraulic fine threads · 545 general purpose Retaining compounds: 603 oil-tolerant · 638 high strength, high temp · 648 high temp, fast cure · 680 slip-fit highest strength This guide covers every industrial Loctite product family relevant to maintenance, engineering and trade work in Australia: threadlockers (preventing fastener loosening under vibration), thread sealants (sealing pipe and hydraulic fittings), and retaining compounds (locking bearings, bushings and cylindrical assemblies). It includes full selection charts, application guides, cure time data, surface preparation requirements and removal instructions — plus a FAQ section that answers the most common grade comparison questions. Browse the full AIMS Industrial Loctite range — threadlockers, thread sealants, retaining compounds and primers stocked for fast Australia-wide dispatch. Loctite Threadlockers: Grades, Colours and Selection Threadlockers prevent fasteners from loosening under vibration, thermal cycling and dynamic load. They fill the microscopic gaps between mating threads, locking out corrosion and sealing against fluid ingress at the same time. Selecting the wrong grade — typically using red where blue is correct, or blue where purple is required — is the most common installation mistake, and can make fasteners impossible to remove without heat or damage the threads on small screws. The Loctite Colour and Strength System Every Loctite threadlocker is colour-coded by strength. The colour tells you immediately whether the fastener can be released with standard hand tools or whether heat will be required for removal. Colour Strength Level Removability Common Grades Purple Low Hand tools — easily removable 222 Blue Medium Hand tools — standard spanners and sockets 242, 243 Red High / Permanent Heat required — 250°C before applying torque 262, 263, 271, 272, 277 Green Low to High (wicking grades) Depends on grade — see table below 270, 290 Loctite Threadlocker Grade Comparison Chart Grade Colour Strength Bolt Size Max Temp Removable? Primary Application 222 Purple Low M1.4–M6 150°C Yes — hand tools Small screws, grub screws, instrument hardware, adjustment fasteners 242 Blue Medium M6–M20 150°C Yes — hand tools General purpose — older formulation; performs identically to 243 on clean threads 243 Blue Medium M6–M20 150°C Yes — hand tools General purpose standard — improved oil tolerance over 242; preferred current-generation grade 262 Red High M6–M20 150°C Heat required (250°C) Studs, press-fit bolts, high-vibration assemblies — smaller fasteners than 263 263 Red High M6–M36 150°C Heat required (250°C) Large permanent fasteners — higher breakaway torque than 262; structural joints 270 Green High M6–M36 150°C Heat required Wicking grade — penetrates pre-assembled joints; post-assembly application 271 Red High M6–M36 150°C Heat required (250°C) High-strength general purpose — wheel bolts, studs, structural and safety-critical fasteners 272 Red High M6–M36 230°C Heat required High-temperature applications — exhaust manifold studs, engine components, hot environments 277 Red Very High M20–M36+ 150°C Heat required Very large fasteners — maximum breakaway torque for flanges, heavy plant, large structural bolts 290 Green Medium M6–M20 150°C Yes — hand tools Wicking grade — post-assembly on pre-assembled or production-line fasteners; medium strength Loctite 242 vs 243 — What Changed? Loctite 243 is the current-generation replacement for 242. Both are medium-strength blue threadlockers for M6–M20 fasteners, and both develop the same cured strength on clean, degreased steel. The key improvement in 243 is better tolerance to light oil contamination on threads. In a workshop environment where threads are occasionally oily, 243 cures reliably where 242 may underperform. If you have 242 on the shelf, use it — it is equivalent to 243 on clean surfaces. For new stock, specify 243. Loctite 243 vs 263 — The Most Important Distinction This is the most common and consequential selection decision. The choice is simple: will this fastener ever need to be removed? Use 243 (blue) when the fastener may need to be removed for service, adjustment or replacement. Under vibration, 243 provides equivalent security to red — it will not self-loosen. But a standard spanner or socket applied with normal force will break the bond. This is the correct grade for brake caliper bolts, suspension components, machinery access panels, and any fastener in the service path. Use 263 or 271 (red) when the assembly is permanent — a structural joint, a stud that will never be pulled, or a high-vibration application where even low probability of movement is unacceptable. These grades require heating to 250°C before the fastener can be turned. Using red on a service fastener, or on a small bolt where that heat cannot be applied safely, is the most common Loctite misapplication on the workshop floor. Threadlocker Application Selection Guide Application Recommended Grade Reason Small adjustment screws, grub screws, M1.4–M6 222 (Purple) Low strength only — blue or red on small threads risks stripping or irreversible locking General fasteners requiring future service access, M6–M20 243 (Blue) Medium strength, hand-tool removable, the standard industrial choice Brake caliper bolts 243 (Blue) Service access required; OEM specification for most passenger and light commercial vehicles Wheel spacer bolts 243 (Blue) Vibration resistance with removability for tyre changes and wheel service Bicycle and bike component bolts 222 (Purple) Critical — titanium and aluminium threads cannot handle medium or high strength; purple only Flywheel bolts, ring gear bolts 263 or 271 (Red) Permanent structural joint; high vibration; rarely or never removed in service life Exhaust manifold studs, turbo bolts 272 (Red) High-strength with 230°C continuous service temperature — the only threadlocker rated for exhaust temperatures Pre-assembled joints — wicking application 290 (Green, medium) or 270 (Green, high) Low viscosity penetrates assembled threads via capillary action — apply externally after assembly Large structural fasteners M20 and above 277 (Red) Maximum breakaway torque for large thread engagement in heavy plant and structural applications Stainless steel fasteners into stainless 243 + Loctite 7649 Activator N Passive metal — requires activator for reliable cure; see surface preparation section below Stainless Steel, Aluminium and Other Passive Metals Loctite anaerobic products cure by reacting with the metal ions present in the substrate. Passive metals — stainless steel, aluminium, titanium, zinc plating, cadmium plating — have an oxide layer that slows or prevents this reaction. On stainless-to-stainless assemblies without treatment, cure may be incomplete, slow (days rather than hours), or fail entirely in cold conditions. The solution is Loctite 7649 Activator N: apply a thin coat to one mating surface, allow 30–60 seconds to dry, then apply the Loctite threadlocker to the other surface and assemble normally. The activator overcomes the passive layer and initiates rapid, complete cure. This step is not optional on stainless — it is the difference between a joint that works and one that fails at the worst moment. → Full guide: Loctite Threadlocker Guide — the complete grade-by-grade breakdown, decision framework and FAQs. Loctite Thread Sealants: Pipe, Hydraulic and Gas Applications Thread sealants seal tapered and parallel pipe threads against leakage of fluids and gases under pressure. They are a distinct product family from threadlockers — they are formulated for sealing pipe thread profiles (BSP, NPT, metric parallel), not for retaining standard bolts and fasteners. Product Type Max Pressure Max Temp Potable Water Best For Loctite 55 Sealing cord (PTFE alternative) 80 bar (gas) / 100 bar (liquid) −50°C to +130°C Yes — NSF 61 certified Gas, water, hydraulic; plastic and metal threads; instant pressure resistance on assembly Loctite 542 Anaerobic liquid 350 bar −65°C to +150°C No Fine metal hydraulic threads — instrumentation fittings, precision pneumatic connections Loctite 567 Anaerobic liquid 690 bar −65°C to +150°C No Metal pipe threads — hydraulic, pneumatic, fuel and oil systems; fine thread forms Loctite 577 Anaerobic liquid 400 bar −55°C to +150°C No Coarser BSP and NPT metal pipe threads — compressed air, water, oil and gas plumbing Loctite 55 — The PTFE Thread Seal Alternative Loctite 55 is not an anaerobic liquid — it is a continuous-filament sealing cord wound around threads by hand, replacing PTFE tape. Wound clockwise around the male thread (three to five turns for most fittings), it creates an immediate, compliant seal that develops full holding strength as the fitting is tightened. Its key advantages over PTFE tape: it can be hand-tightened to immediate pressure resistance with no cure wait; it works reliably on both metal and plastic fittings; it does not shred or delaminate into pipework; and it can be repositioned slightly after assembly if alignment is needed. Most importantly for Australian trade and construction applications, Loctite 55 is NSF 61 certified for potable water — it is the correct Loctite product for drinking water connections. It is also approved for gas service and is used on residential and commercial gas fittings where threaded connections are required. Loctite 567 vs 577 — Which Anaerobic Thread Sealant? Both 567 and 577 are anaerobic liquids that seal metal pipe threads. The difference is viscosity and thread form. Loctite 567 is lower viscosity — it wicks easily into fine hydraulic and pneumatic thread forms (SAE, metric fine), making it the correct choice for instrument fittings, hydraulic block connections and precision pneumatic assemblies where thread tolerances are tight. Loctite 577 is higher viscosity — it stays in place on coarser BSP and NPT threads during assembly, making it the standard choice for compressed air systems, water fittings and general industrial plumbing. If in doubt on a BSP fitting, use 577. If connecting hydraulic instrument tubing or fine metric threads, use 567. For cure times, fluid compatibility, passive metal guidance and a full application guide, see our Loctite 577 Thread Sealant Guide. → Full guide: Loctite Thread Sealant Guide — media compatibility, pressure ratings and application steps across the full range. Loctite Retaining Compounds: Bearing and Cylindrical Assembly Retaining compounds bond cylindrical assemblies — shaft-to-bearing, shaft-to-hub, pin-to-bore — by filling the microscopic clearance between components and polymerising into a rigid, load-bearing joint. They are used to augment or replace interference fits, to prevent fretting corrosion in light-clearance assemblies, and to salvage worn bores where a bearing has become loose in its housing. The two critical selection variables are the radial clearance between the mating components and the strength required. Using a product with a maximum clearance smaller than the actual gap will result in incomplete fill and significantly reduced bond strength. Grade Strength Max Clearance Max Temp Re-assemble? Best For 609 Low 0.10 mm 150°C Yes — press or hand Light-duty retention, small close-tolerance assemblies requiring re-use 638 High 0.15 mm 150°C With press or puller Close-tolerance bearing retention — maximum strength where fit is tight 641 Medium 0.25 mm 150°C Yes — press or puller Standard bearing and bushing retention — strength with serviceability 648 Maximum 0.15 mm 175°C Effectively no Permanent high-temperature assemblies where disassembly is never required 660 High 0.50 mm 150°C With press or puller Worn bore salvage — fills large clearances in worn housings and shafts 680 High 0.35 mm 150°C With press or puller General-purpose medium-to-large clearance bearing retention Choosing Between 638, 641 and 648 For new bearings in a correctly toleranced housing, 641 is the default choice. Medium strength, 0.25 mm maximum clearance, and removable with a standard bearing puller or hydraulic press — this covers the vast majority of bearing retention applications in industrial and agricultural equipment. Use 638 when the fit is very close and maximum strength is required. In a tight housing where interference fit alone is nearly sufficient, 638 augments the fit to create an exceptionally strong, permanent joint. Note that 638 in a tight bore with a light press fit is very difficult to disassemble — treat it as semi-permanent. Use 648 only when the assembly will never be disassembled and operating temperatures exceed 150°C. Loctite 648 is the most thermally resistant retaining compound and produces the highest bond strength in the range — but the joint is effectively destroyed on any attempt at disassembly. Reserve it for permanent high-temperature applications such as motor shaft assemblies in hot environments. For worn bores where the bearing is loose in the housing (clearance beyond 0.25 mm), use 660. It fills gaps up to 0.5 mm, locks the bearing in the oversized bore, and restores the housing to service without machining. This is the most commonly used retaining compound in field service and overhaul environments where worn machinery is being returned to service. Browse AIMS Industrial's full Loctite retaining compound range including 638, 641, 648 and 660. → Full guide: Loctite Retaining Compound Guide — diametral clearance selection, installation and bearing removal. Loctite Anti-Seize Anti-seize does the opposite of a threadlocker. Where threadlockers lock fasteners in place by filling the thread void, anti-seize prevents fasteners from seizing, galling and corroding in ways that make them impossible to remove. Never apply both to the same fastener. Loctite C5-A Copper Anti-Seize is the industrial standard — a copper-based paste rated to 980°C. Correct applications include stainless-on-stainless assemblies where galling is a risk (anti-seize is far more effective than threadlocker at preventing galling), exhaust bolts and manifold studs subject to repeated heat cycling, fasteners in corrosive environments such as marine, chemical plant and agricultural equipment, and any assembly where long-term disassembly is essential. Important torque note: Anti-seize reduces the friction coefficient of threads. If torquing to a manufacturer specification designed for dry or lightly oiled threads, the torque value must be reduced when anti-seize is applied — typically by 20 to 25%. Applying full dry-thread torque with anti-seize present will over-stress the fastener. Surface Preparation: The Critical Step Loctite anaerobics cure by reacting with metal ions in the substrate. Surface contamination — oil, grease, coolant, cutting fluid, rust preventative — inhibits this reaction and reduces cured strength. Inadequate surface preparation is the primary cause of Loctite application failures. Standard preparation for all Loctite anaerobic products: Degrease both mating surfaces with Loctite 7063 cleaning solvent or isopropyl alcohol. Apply solvent, agitate if necessary to remove oil film, and allow to evaporate fully — do not assemble onto wet surfaces. On threaded fasteners, apply solvent to the bore threads and the bolt shank and allow to dry before applying Loctite. For passive metals (stainless steel, aluminium, titanium, zinc, cadmium plating): Apply Loctite 7649 Activator N to one surface and allow 30–60 seconds to dry before applying the Loctite product to the other surface. This step is not optional — without activator on stainless steel, cure is unreliable, particularly at temperatures below 15°C. The activator is low-cost and eliminates a significant failure mode. Cure Time Reference Product Type Grade Handling Strength (steel, 22°C) Full Cure Low-strength threadlocker 222 10 minutes 24 hours Medium-strength threadlocker 242, 243 10 minutes 24 hours High-strength threadlocker 262, 263, 271 20 minutes 24 hours High-temp threadlocker 272 20 minutes 24 hours (full high-temp rating requires post-cure at 120°C for 30 min) Wicking threadlocker 270, 290 15 minutes 24 hours Standard retaining compound 638, 641 10–15 minutes (fixture) 24 hours High-temp retaining compound 648 15 minutes (fixture) 24 hours (post-cure at 120°C recommended for full performance) Thread sealant 567, 577 Immediate pressure resistance 24 hours full cure Cold temperature note: Below 10°C, all cure times extend significantly — allow 48 to 72 hours for full cure in cold conditions. Cure can be accelerated to near-full strength by warming the assembled joint to 80°C for 30 minutes. On passive metals without activator, add 50% to all cure time estimates. Removing Loctite Threadlocker The correct removal method for any Loctite threadlocker — blue or red — is heat. Apply a heat gun or torch to bring the joint to approximately 250°C, then apply torque to the fastener immediately while the joint is still hot. The cured Loctite softens above this temperature and releases. Do not heat the joint and then allow it to cool before attempting removal — the Loctite will re-harden and lock the fastener again. Blue (medium strength) threadlocker: Heat to 250°C is effective but not always required. Strong, steady hand-tool force will release most blue-locked joints without heat. If a blue-locked fastener resists standard hand tool force, apply heat before increasing effort — forcing a locked fastener with an extension bar risks breaking the bolt or stripping the thread rather than releasing the Loctite. Red (high strength) threadlocker: Heat is not optional. Do not attempt to remove a red-locked fastener with hand tools alone — the breakaway torque exceeds what hand tools can safely apply on most bolt sizes. Apply direct heat to the joint, apply torque immediately while hot, and repeat the heat-and-torque cycle if the fastener does not break free on the first attempt. Aluminium and composite components: Use a heat gun rather than a torch to avoid warping or heat-damaging the surrounding material. Apply heat gradually and test the fastener for movement frequently rather than applying maximum heat in one go. If heat risks damaging adjacent components, soak the joint overnight with a penetrating oil to assist, then apply minimum heat to break free. After removal: Clean old Loctite from threads with a wire brush and solvent before re-applying fresh product. Do not re-apply new Loctite over hardened residue — the cured material does not dissolve or re-activate. Loctite Instant Adhesives: 401, 406 and the Cyanoacrylate Range Loctite's cyanoacrylate (CA) range — commonly called instant adhesives or superglue — are chemically distinct from the anaerobic products above. They cure by reacting with surface moisture rather than requiring the absence of oxygen or metal ions, and they are not suitable for thread locking, pipe sealing or cylindrical retention. Loctite 401 is the standard-viscosity general-purpose CA adhesive. It bonds metal, rubber, rigid plastics and most hard materials in seconds. For most instant adhesive applications in a trade or industrial workshop, 401 is the correct starting choice. See our Loctite 401 complete guide for full substrate compatibility, cure times and storage information. Loctite 406 is formulated for difficult substrates — polyolefin plastics (polyethylene, polypropylene), rubbers and elastomers that standard CA adhesives cannot reliably bond. It contains a surface-insensitive primer agent that promotes adhesion on low-energy surfaces. For bonding rubber seals to metal housings, or joining PP and PE components, 406 is significantly more reliable than 401. Loctite 454 is a gel-form CA that stays in position on vertical surfaces and fills small gaps — the correct choice where a liquid adhesive would run before the joint is closed, or where mating surfaces are slightly rough or porous. Loctite 480 is a rubber-toughened CA for applications requiring a flexible, impact-resistant bond — rubber-to-rubber and rubber-to-metal joints where a rigid brittle bond would crack under flexing. Loctite Product Equivalents The most frequently searched Loctite equivalent products come from the Permatex range. The approximate equivalents for the main industrial grades are: Loctite Grade Permatex Equivalent Notes 222 — Purple, low strength Permatex 24010 Functionally equivalent; verify application torque values independently 243 — Blue, medium strength Permatex 24200 Direct equivalent for general-purpose medium-strength applications 271 / 263 — Red, high strength Permatex 27200 High-strength equivalent; verify temperature ratings for your specific application When substituting between brands, always confirm that the equivalent grade meets your specific temperature, gap clearance and torque requirements — equivalent strength does not guarantee identical performance in all conditions. Lock it. Seal it. Trust it. Related AIMS Selectors This selector pairs with AIMS's other fastener & adhesive guides: Loctite 222 Guide — purple low-strength threadlocker deep-dive. Loctite 243 Guide — medium-strength workshop default. Loctite 401 Guide — instant adhesive (cyanoacrylate). Loctite 577 Guide — medium-strength thread sealant. Loctite Threadlocker Guide — full threadlocker category guide. Loctite Retaining Compound Guide — bearing installation and grade selection. Loctite Thread Sealant Guide — full thread sealant category guide. Thread Locking & Sealing Guide — anaerobic chemistry + application technique. Industrial Adhesive Types Guide — broader adhesives hub: epoxy, RTV, structural. How to Remove Stuck Bolts & Nuts — when Loctite has done its job too well. Metric Bolt Torque Chart — torque values per grade and size. Or browse the full Loctite range, threadlockers, retaining compounds, gasket sealants, thread sealants, activators, cleaners & primers. Next-day Australia-wide dispatch from our Milperra warehouse. Shop the full Loctite range — threadlockers, retaining compounds & sealants From Loctite 222 low-strength to 263 high-strength threadlocker, 641 retaining compound, and 55 pipe sealant — AIMS Industrial is an authorised Loctite stockist with the full range available for fast Australia-wide dispatch. Shop Loctite at AIMS Talk to a specialist Frequently Asked Questions What is the best Loctite threadlocker for small screws?Loctite 222 (purple) is the only correct choice for screws up to M6. Small threads — grub screws, electronics fasteners, instrument hardware, adjustment screws — do not have sufficient thread engagement to handle the breakaway torque of medium or high-strength threadlocker. Applying blue (243) to an M3 or M4 grub screw will very likely make it impossible to remove without damaging the threads or the housing. Use purple (222) for anything M6 and smaller, without exception. What is the difference between blue and red Loctite?Blue Loctite (243) is medium strength and removable with hand tools — the standard choice for fasteners that need to be serviced, adjusted or replaced in the future. It will not self-loosen under vibration, but a spanner or socket applied with normal force will release it. Red Loctite (263, 271) is high strength and permanently locks the fastener — it requires heating the joint to 250°C before any torque will release it. The correct rule: if the fastener may ever need to come off, use blue. If it is a truly permanent structural joint, use red. Which Loctite threadlocker is the strongest?In the standard threadlocker range, Loctite 277 (red) has the highest breakaway torque and is formulated for large-diameter fasteners (M20–M36+). For the M6–M36 range, Loctite 263 and 271 provide effectively equivalent maximum strength for most applications. Loctite 648 is the maximum-strength retaining compound for cylindrical assemblies, though it serves a different function. For most industrial work, 271 or 263 provide more than sufficient permanent locking strength. Can Loctite cure on oily or contaminated threads?Standard threadlocker grades (242, 263) require clean, degreased surfaces for full strength development. Loctite 243 is formulated with improved oil tolerance and will cure acceptably on lightly oiled threads. On heavily contaminated or wet surfaces, no anaerobic product will achieve full strength — clean first. For post-assembly applications where disassembly is not practical, a wicking grade (290 for medium strength, 270 for high strength) applied to the external thread after cleaning the exposed surface will penetrate and lock the joint, but ultimate strength depends on the cleanliness of the thread interface. Can Loctite threadlocker be used on plastic threads?Anaerobic threadlockers require metal ions to cure and are formulated for metal-to-metal contact. On plastic threads, cure is unreliable, strength is substantially reduced, and certain Loctite formulations can stress-crack specific plastics — notably polystyrene and polycarbonate. For sealing plastic pipe fittings, use Loctite 55 sealing cord — it works on plastic threads without chemical incompatibility risk. For retention on plastic fasteners, mechanical solutions (nylon insert nuts, serrated flange fasteners) are more reliable than chemical threadlockers. Are Loctite thread sealants suitable for potable water pipes?Loctite 55 sealing cord is NSF 61 certified for potable water and is the correct Loctite product for any fitting in contact with drinking water. The anaerobic liquid sealants — 567 and 577 — are not NSF 61 certified and must not be used on potable water connections. For gas pipe connections (residential and commercial), Loctite 55 is also approved and is used on threaded gas fittings in Australia. It replaces PTFE tape in these applications with no need for cure time before pressurisation. How long does Loctite threadlocker take to fully cure?On clean steel at 22°C, most grades reach handling strength in 10–20 minutes — sufficient to torque the fastener and move the assembly without disturbing the joint. Full cure takes 24 hours. Below 10°C, cure times extend significantly — allow 48 to 72 hours at low temperatures. Cure can be accelerated by heating the assembled joint to 80°C for 30 minutes. On passive metals (stainless steel, aluminium) without activator, add at least 50% to all cure times and treat handling strength with caution. How do I remove a bolt locked with red Loctite threadlocker?Heat the joint directly to approximately 250°C using a heat gun or butane torch, then apply torque to the fastener immediately while it is still hot. The cured Loctite softens at this temperature and allows the fastener to turn. Do not heat the joint and then allow it to cool before trying — the Loctite re-hardens on cooling. If the fastener does not release on the first attempt, re-apply heat and try again. Never use an impact wrench on a locked fastener without heating first — the risk of shearing the bolt is significantly higher than the effort of applying heat. What is the difference between Loctite 567 and 577 thread sealant?Both are anaerobic liquids for sealing metal pipe threads. Loctite 567 is lower viscosity — it wicks easily into fine thread forms (SAE hydraulic fittings, metric fine, instrument connections) and is the correct choice for hydraulic and pneumatic precision connections. Loctite 577 is higher viscosity and stays in position on coarser BSP and NPT pipe threads during assembly. For most compressed air, water and gas plumbing on BSP fittings, 577 is the standard choice. For hydraulic block connections and instrument fittings with fine thread forms, use 567. See our full Loctite 577 Thread Sealant Guide for the complete application reference. Which Loctite retaining compound should I use for bearing retention?For standard bearing retention with normal bore clearance, Loctite 641 is the default choice — medium strength, handles clearances up to 0.25 mm, and the bearing can be removed with a press or standard puller for service. Use Loctite 638 for close-tolerance fits requiring maximum bond strength. Use Loctite 660 for worn bores with clearance above 0.25 mm — it fills gaps up to 0.5 mm and locks a loose bearing in an oversized housing without machining. Reserve Loctite 648 for permanent high-temperature assemblies that will never be disassembled. What is the difference between Loctite 401 and 406?Loctite 401 is a standard-viscosity cyanoacrylate (instant adhesive) for general bonding of metal, rubber and most rigid plastics. Loctite 406 is formulated specifically for difficult low-energy substrates — polyolefin plastics (polyethylene, polypropylene) and elastomers that standard CA adhesives cannot reliably bond. If you're bonding rubber gaskets, polypropylene fittings or PE components, 406 is the correct grade. For metal-to-metal, glass-to-metal or general rigid bonding, 401 is sufficient. The 406 premium is only justified where the substrate is a known adhesive-resistant plastic or rubber. For metric bolt diameter, pitch and head dimensions from M3 to M24, see our Metric Bolt Size Guide. People Also Ask — Loctite Grade Selection Q: What is the difference between Loctite 243 and Loctite 263? Loctite 243 is a medium-strength threadlocker removable with hand tools after cure — suitable for most fasteners M6 to M20 where future disassembly is expected. Loctite 263 is high-strength and permanently bonds fasteners; removal requires heat above 250°C. Use 243 for routine maintenance, 263 where vibration risk is severe and disassembly is not planned. Q: How long does Loctite threadlocker take to cure? Loctite 243 achieves handling strength in approximately 10 minutes on steel at 22°C. Full chemical cure takes 24 hours. Cure is slower on passive metals (stainless steel, zinc) and in cold conditions — allow extra time before applying service loads. Activator SF 7649 speeds cure on passive metals. Q: Can you use Loctite on aluminium threads? Yes. Loctite anaerobic threadlockers including Loctite 222, 243, and 263 are compatible with aluminium. Aluminium is a passive metal, so cure is slower than on steel. Apply Loctite Activator SF 7649 to one thread surface first to achieve reliable cure speed and strength on aluminium fasteners. Q: What Loctite grade is best for stainless steel fasteners? Loctite 243 medium-strength or Loctite 263 high-strength both work on stainless steel, but stainless is a passive metal — always apply Activator SF 7649 first. For stainless fasteners in food or hygienic environments, Loctite 2400 is a water-washable, low-odour alternative approved for incidental food contact. Q: What is Loctite 577 used for? Loctite 577 is a medium-strength thread sealant for parallel (BSP) threads used in hydraulic and pneumatic systems. It seals metal-to-metal pipe threads and fitting connections against fluid and gas leakage up to 150 bar, while remaining removable with hand tools for maintenance. Not a threadlocker — designed specifically for fluid-system thread sealing. Looking for anti-vibration mounts? Our anti-vibration mounts range covers the common sizes and brands.