CoilSert Free-Running Inch UNC Coarse #1-1 × 2-1/2D — P/N 1185-20CN3125
CoilSert free-running wire thread insert, inch UNC coarse 1-1/4 (1.2500)-7, length 2-1/2D, precision-wound from 304 stainless steel diamond-section wire; the coil expands elastically to anchor itself after installation—no staking required. Suitable for thread reinforcement, worn-thread repair and light-alloy joints. Volume pricing is negotiable.
| Part No. | 1185-20CN3125 |
|---|---|
| Features | Thread reinforcement / repair |
| Thread Size | 1-1/4 (1.2500)-7 |
| Thread System | Inch UNC coarse |
| Length | 2-1/2D |
| Material | 304 stainless steel |
| Finish | Plain (cadmium / silver / dry-film lubricant optional) |
Overview
A CoilSert free-running insert is a diamond-section stainless wire coil wound into a tapped hole to form a wear-resistant internal thread. Because the coil is free-running, the mating screw turns without resistance until it seats: there is no locking torque and no interference on assembly. The installed thread is larger in effective diameter than the tapped hole but smaller than the coil's outer diameter, so the load spreads over the full coil length instead of the first few threads of the parent material. This listing: thread 1-1/4 (1.2500)-7, thread system Inch UNC coarse, length 2-1/2D, material 304 stainless steel, finish Plain (cadmium.
Advantages
Inch sizes follow unified thread form, so an imperial screw can be installed into a metric-designed housing, or a damaged inch thread can be restored to nominal without changing the mating part.
304 stainless coils resist corrosion inside the thread path even when the host material is carbon steel, which keeps the fastener removable after long service.
The diamond cross-section creates a line contact with the mating screw rather than a face contact. Friction drops, so a given clamp load needs less torque and the risk of galling in aluminium or magnesium hosts falls sharply.
Spring action holds the coil against the tapped hole wall, which compensates for thread wear and thermal cycling in soft alloys. Thread life in aluminium typically improves several-fold over a plain tapped thread.
Applications
Aluminium and magnesium housings that must accept repeated assembly, repair of stripped or oversized threads in castings, inch-thread hardware inside a metric chassis, and any joint where the parent metal is softer than the screw.
Length is quoted in multiples of thread diameter (1D, 1.5D, 2D). Going below 1D gives little improvement over a plain thread; going above 2D rarely adds strength but complicates installation and inspection. Specify whether the coil must be tangless for blind holes.
Product information is supplied by Toprecision. Custom parts can be produced to drawing — contact us for samples or a quotation.
Specifications across this series
220 parts in this series
Values are taken from each part’s own attribute set. Changing length, material or finish changes pull-out strength and installation torque, so compare the row that matches your drawing.
Selection and test data: engagement length, standards, salt-spray hours
FAQ
What are the key dimensions of this part?
Part No. 1185-20CN3125, Features Thread reinforcement / repair, Thread Size 1-1/4 (1.2500)-7, Thread System Inch UNC coarse.
What material and finish is it supplied in?
304 stainless steel; Plain (cadmium / silver / dry-film lubricant optional).
What should I verify before ordering or installing it?
Length is quoted in multiples of thread diameter (1D, 1.5D, 2D). Going below 1D gives little improvement over a plain thread; going above 2D rarely adds strength but complicates installation and inspection. Specify whether the coil must be tangless for blind holes.