Description
KEEP-NUT™ Press-In Self-Anchoring Inserts (1/4-20 Thread)
KEEP-NUT™ by Specialinsert® is a revolutionary press-in anchor insert designed for permanent, high-strength fastening in exceptionally thin and hard surfaces. It is the industry standard for undermount sink installations, ventilated facades, architectural cladding, and modern furniture assembly.
Manufactured from durable stainless steel, the insert features a threaded bushing, elastic crowns, and a plastic retention ring. This compact design delivers extreme pull-out strength in materials like granite, marble, quartz, solid surface, HPL, glass, and fiber cement—all without the need for messy resins or adhesives.
1/4-20 Series Specifications
| Type/Thread/Height | Thread | Surface Min. Thickness | H1 Thread Depth | D2 Hole Dia (±0.2) | L2 Hole Depth (+1.0) | Crowns | Install Force kN (lbf) | Pull-Out Force kN (lbf) |
|---|---|---|---|---|---|---|---|---|
| IM1S/P1.4-20/H5 | 1/4-20 | 8.0 mm (.31″) | 4.5 mm (.18″) | 12 mm | 5.5 mm (.22″) | 1 | 0.2 (44.96) | 0.9 (202.33) |
| IM2S/P1.4-20/H6 | 1/4-20 | 8.5 mm (.34″) | 5.5 mm (.22″) | 12 mm | 6.5 mm (.26″) | 2 | 0.4 (89.92) | 2.5 (562.02) |
| IM4S/P1.4-20/H8.5 | 1/4-20 | 11.0 mm (.43″) | 7.5 mm (.30″) | 12 mm | 9.0 mm (.36″) | 4 | 1.0 (224.81) | 3.5 (786.83) |
| IM2X2S/P1.4-20/H11.5 | 1/4-20 | Contact Us | Contact Us | 12 mm | 12.0 mm (.47″) | 2×2 | – | Contact for Data |
| IM4S/P1.4-20/H15 | 1/4-20 | 17.5 mm (.69″) | 14.0 mm (.55″) | 12 mm | 15.5 mm (.61″) | 4 | 1.0 (224.81) | 4.2 (944.20) |
Applications & Sizing Guide
| Application | Recommended Size | Engineering Notes |
|---|---|---|
| Undermount Sinks | IM2S | Use 4–8 anchors per sink depending on basin weight. |
| Interior Panels | IM2S or IM4S | Select based on total panel weight and material thickness. |
| Mid-Thick Panels (13-15mm) | IM2X2S | Bridge size offering deeper embedment when a 15.5mm is too deep. |
| Exterior Cladding | IM4S | Provides the highest pull-out resistance for wind loads. |
| Furniture Assembly | IM1S or IM2S | Ideal for concealed, flush-mount designs. |
| Thin Panels (<9mm) | IM1S | Shallow 5.5mm depth prevents surface cracking or blow-outs. |
Compatible Substrates
KEEP-NUT™ is engineered to safely mechanically anchor into extremely hard, brittle, and thin materials without cracking the parent substrate. Rated for use in Natural Stone, Sintered Stone, Solid Surface, Porcelain, and HPL.
Installation & Workflow Videos
Performance by Material (Design Guidance)
P/S = Pull (tensile) / Shear load per anchor. Values shown are general design guidance based on ASTM C1354 testing and internal performance data. Always apply safety factors and confirm through project-specific testing when required.
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| Material | Typical Density | IM1S 5.5 mm P / S (lbf) |
IM2S 6.5 mm P / S (lbf) |
IM4S 8.5 mm P / S (lbf) |
IM4S 15.5 mm P / S (lbf) |
|---|---|---|---|---|---|
| Granite / Marble | High | 265 / 900 | 585 / 1,950 | 821 / 2,231 | 1,261 / 2,853 |
| Engineered Quartz | Med–High | 250 / 1,000 | 500 / 1,900 | 800 / 2,300 | 1,400 / 2,750 |
| Sintered Stone | Very High | 185 / 850 | 410 / 1,738 | 742 / 2,459 | 1,531 / 2,626 |
| Porcelain | Very High | 210 / 900 | 466 / 1,021 | 750 / 2,450 | 1,200 / 2,800 |
| HPL | Low | 247 / 600 | 427 / 1,021 | 951 / 1,344 | 1,500 / 1,650 |
| Solid Surface | Low–Med | 225 / 675 | 468 / 1,550 | 839 / 1,650 | 1,300 / 2,050 |
| UHPC | High | 210 / 900 | 275 / 1,350 | 441 / 1,565 | 603 / 1,592 |
Actual performance can vary by surface brand, density, panel thickness, and installation quality. Treat values as generalized guidance only.
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