V-COIL wire thread inserts
A wire thread insert to DIN 8140 turns a damaged or weak thread into a strong one: the coil of stainless spring steel sits in a larger tapped hole and forms the nominal thread anew on the inside. VÖLKEL supplies more than 1,000 V-COIL inserts as free-running type S, screw-locking type SL and tangless type SN (V-COIL notch), in lengths 1.0 D to 3.0 D, for metric coarse and fine threads from M 2 to M 42 as well as UNC, UNF, UN-8, BSW, BSF and G (BSP), singly and as refill packs.
Repair and reinforce
Two jobs, one insert. In thread repair the stripped thread is drilled out, tapped anew with the STI tap and the insert is screwed in; the nominal thread is back, often stronger than before. In thread reinforcement the insert is fitted from the start in materials with low shear strength: aluminium and magnesium alloys, plastics, wood. Typical fields are mechanical engineering, automotive, electrical and medical technology and aerospace, for instance in the HyEnD rocket engine or in the cosmetics industry.
Type S, SL or notch?
- Type S, free-running: the standard for all joints that are loosened and retightened normally.
- Type SL, screw-locking: one or more polygonal coils clamp the screw and secure it against loosening under vibration.
- V-COIL notch, tangless: no drive tang, so tang breaking is eliminated and no loose part remains in the hole. Sensible wherever the broken tang cannot be removed, such as blind holes and hydraulics. Found under V-COIL notch.
Choosing the length: 1.0 D to 3.0 D
The length is given as a multiple of the nominal diameter. 1.5 D is the rule in steel and cast iron; in soft materials such as aluminium and magnesium 2.0 D to 3.0 D are usual so that the shear area in the workpiece is large enough. What the figure means and how deep the pilot hole has to be is explained in What 1.5 D means. Why stainless inserts are nevertheless magnetic is here.
Tools for the job
STI twist drills, STI taps, installation tools and tang breakers are under assembling tools and STI threading tools. If you need everything at once, take a thread repair kit, which already contains the matching inserts.
