Loctite 221 Threadlocking Adhesive(bottle)

LOCTITE 221 is a low-strength, anaerobic threadlocking adhesive specifically engineered for fasteners that must be disassembled using ordinary hand tools. This purple, UV-fluorescing acrylic dimethacrylate ester threadlocker fills a critical niche: securing small or delicate fasteners against vibration-induced loosening without locking them so permanently that removal risks stripping threads or shearing screws.

Key Features

LOCTITE 221's standout characteristic is its low viscosity (100–150 mPa·s) and low bond strength, making it ideal for small-diameter fasteners, set screws, and long-engagement-length threads where standard medium- or high-strength threadlockers would make routine maintenance difficult or destructive. The one-component formula requires no mixing and cures anaerobically between close-fitting metal threads, with UV fluorescence enabling fast visual inspection during quality control. Despite its low strength classification, LOCTITE 221 still reliably prevents loosening from shock and vibration in the applications it's designed for.

Performance Data

After 24 hours of cure at 22°C on M10 steel nuts and bolts, LOCTITE 221 delivers a breakaway torque of 5–12 N·m and prevail torque of 2–8 N·m — figures intentionally lower than LOCTITE's medium- and high-strength threadlockers to preserve easy disassembly. Compressive shear strength on steel pins and collars ranges from 3–10 N/mm². The product maintains reasonable performance through heat aging testing at 120°C and 150°C and resists motor oil, unleaded gasoline, brake fluid, and acetone exposure. Cure speed responds well to activator use, particularly on less-reactive substrates like zinc dichromate or stainless steel.

Applications

LOCTITE 221 low-strength threadlocker is the go-to choice for adjustment screws, instrumentation hardware, electronics assembly, calibration equipment, and any small-fastener application where a technician needs to revisit the joint without specialized tools or heat. It's particularly valuable in industries like precision manufacturing, electronics, and equipment requiring periodic field adjustment, where high-strength or even medium-strength threadlockers would be counterproductive.

Directions for Use

Clean all mating surfaces with a LOCTITE cleaning solvent before application and allow to dry. On inactive metals or where faster cure is needed, apply LOCTITE SF 7649 or SF 7471 Activator and let dry first. Shake the product thoroughly before use, and avoid touching the nozzle tip to metal surfaces to prevent clogging. For thru-holes, apply several drops at the nut engagement area; for blind holes, apply to the lower third of the internal threads. Assemble and tighten as required — disassembly is achieved with standard hand tools, with localized heating to approximately 250°C reserved only for rare cases of excessive engagement length.

Why Buy From Tapemart

Tapemart supplies genuine LOCTITE 221 low-strength threadlocker as part of our full LOCTITE threadlocking product range, spanning low-, medium-, and high-strength formulas for every fastener application. As an authorized LOCTITE distributor, we help customers choose the correct threadlocking strength for fasteners that require future serviceability, backed by responsive support and reliable stock availability. Order LOCTITE 221 from Tapemart for dependable, removable thread locking on your most delicate hardware.