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Tamper-Resistant Tri-Groove Rounded Head Screws
Difficult to remove without special tools, these screws have three grooves. For installation tools, see Tri-Groove bits and drivers. Screws are zinc plated for corrosion resistance in wet environments. Length is measured from under the head.
For technical drawings and 3-D models, click on a part number.
| Lg. | Threading | Min. Thread Lg. | Head Dia. | Head Ht. | Drive Size | Tensile Strength, psi  | Pkg. Qty. | Pkg. | |
Zinc-Plated Steel | |||||||||
|---|---|---|---|---|---|---|---|---|---|
6-32 | |||||||||
| 3/8" | Fully Threaded | __ | 0.26" | 0.12" | No. 6 | 80,000 | 50 | 000000000 | 000000 |
| 1/2" | Fully Threaded | __ | 0.26" | 0.12" | No. 6 | 80,000 | 50 | 000000000 | 00000 |
| 3/4" | Fully Threaded | __ | 0.26" | 0.12" | No. 6 | 80,000 | 50 | 000000000 | 00000 |
8-32 | |||||||||
| 3/8" | Fully Threaded | __ | 0.28" | 0.148" | No. 6 | 80,000 | 50 | 000000000 | 00000 |
| 1/2" | Fully Threaded | __ | 0.28" | 0.148" | No. 6 | 80,000 | 50 | 000000000 | 00000 |
| 3/4" | Fully Threaded | __ | 0.28" | 0.148" | No. 6 | 80,000 | 50 | 000000000 | 00000 |
| 1" | Fully Threaded | __ | 0.28" | 0.148" | No. 6 | 80,000 | 50 | 000000000 | 00000 |
| 1 1/4" | Fully Threaded | __ | 0.28" | 0.148" | No. 6 | 80,000 | 50 | 000000000 | 00000 |
| 1 1/2" | Fully Threaded | __ | 0.28" | 0.148" | No. 6 | 80,000 | 50 | 000000000 | 00000 |
10-24 | |||||||||
| 1/2" | Fully Threaded | __ | 0.375" | 0.15" | No. 10 | 80,000 | 50 | 000000000 | 00000 |
| 3/4" | Fully Threaded | __ | 0.375" | 0.15" | No. 10 | 80,000 | 50 | 000000000 | 00000 |
| 1" | Fully Threaded | __ | 0.375" | 0.15" | No. 10 | 80,000 | 25 | 000000000 | 0000 |
| 1 1/2" | Fully Threaded | __ | 0.375" | 0.15" | No. 10 | 80,000 | 25 | 000000000 | 0000 |
10-32 | |||||||||
| 1/2" | Fully Threaded | __ | 0.375" | 0.15" | No. 10 | 80,000 | 50 | 000000000 | 00000 |
| 3/4" | Fully Threaded | __ | 0.375" | 0.15" | No. 10 | 80,000 | 50 | 000000000 | 00000 |
| 1" | Fully Threaded | __ | 0.375" | 0.15" | No. 10 | 80,000 | 50 | 000000000 | 00000 |
| 1 1/2" | Fully Threaded | __ | 0.375" | 0.15" | No. 10 | 80,000 | 25 | 000000000 | 0000 |
1/4"-20 | |||||||||
| 1/2" | Fully Threaded | __ | 0.375" | 0.155" | No. 10 | 80,000 | 50 | 000000000 | 00000 |
| 3/4" | Fully Threaded | __ | 0.375" | 0.155" | No. 10 | 80,000 | 50 | 000000000 | 00000 |
| 1" | Fully Threaded | __ | 0.375" | 0.155" | No. 10 | 80,000 | 25 | 000000000 | 0000 |
| 1 1/2" | Fully Threaded | __ | 0.375" | 0.155" | No. 10 | 80,000 | 25 | 000000000 | 0000 |
| 2" | Fully Threaded | __ | 0.375" | 0.155" | No. 10 | 80,000 | 25 | 000000000 | 00000 |
| 2 1/2" | Partially Threaded | 1 1/2" | 0.375" | 0.155" | No. 10 | 80,000 | 10 | 000000000 | 0000 |
5/16"-18 | |||||||||
| 5/8" | Fully Threaded | __ | 0.57" | 0.275" | No. 20 | 80,000 | 25 | 000000000 | 00000 |
| 3/4" | Fully Threaded | __ | 0.57" | 0.275" | No. 20 | 80,000 | 25 | 000000000 | 00000 |
| 1" | Fully Threaded | __ | 0.57" | 0.275" | No. 20 | 80,000 | 25 | 000000000 | 00000 |
Tamper-Resistant Tri-Groove Nuts
Tri-groove nuts are narrower than sloped and drilled spanner nuts to fit in tight spaces. Install with a tri-groove socket bit and either a drive handle or an open-end wrench (all sold separately). Use them to reduce the risk of unwanted removal for objects in public spaces such as signs, lighting fixtures, and displays.
Zinc-plated steel nuts are coated to protect the steel from corrosion in wet environments.
Zinc alloy nuts are lightweight and corrosion resistant in wet environments.
316 stainless steel nuts won’t corrode from water, chemicals, or salt spray.
For technical drawings and 3-D models, click on a part number.
Inch
Nuts | Tri-Groove Socket Bits | Drive Handles | Open-End Wrenches | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Thread Size | Dia. | Ht. | Pkg. Qty. | Pkg. | Each | Each | Each | ||||
Zinc-Plated Steel | |||||||||||
| 10-24 | 0.64" | 0.265" | 25 | 000000000 | 000000 | 0000000 | 000000 | 0000000 | 000000 | 000000 | 00 |
| 10-32 | 0.64" | 0.265" | 25 | 000000000 | 00000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
| 1/4"-20 | 0.64" | 0.265" | 25 | 000000000 | 00000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
| 5/16"-18 | 0.83" | 0.345" | 25 | 000000000 | 00000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
| 3/8"-16 | 0.83" | 0.345" | 25 | 000000000 | 00000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
316 Stainless Steel | |||||||||||
| 10-24 | 0.65" | 0.265" | 10 | 000000000 | 00000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
| 10-32 | 0.65" | 0.265" | 10 | 000000000 | 00000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
| 1/4"-20 | 0.66" | 0.265" | 10 | 000000000 | 00000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
| 1/4"-28 | 0.65" | 0.265" | 10 | 000000000 | 00000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
| 5/16"-18 | 0.83" | 0.345" | 10 | 000000000 | 00000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
| 5/16"-24 | 0.83" | 0.35" | 5 | 000000000 | 00000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
| 3/8"-16 | 0.83" | 0.345" | 10 | 000000000 | 00000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
| 3/8"-24 | 0.83" | 0.35" | 5 | 000000000 | 00000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
| 7/16"-14 | 0.83" | 0.34" | 1 | 000000000 | 0000 | 0000000 | 00000 | 000000 | 00 | 0000000 | 000000 |
| 1/2"-13 | 0.93" | 0.345" | 1 | 000000000 | 0000 | 0000000 | 00000 | 000000 | 00 | 0000000 | 00000 |
| 1/2"-20 | 0.93" | 0.345" | 1 | 000000000 | 0000 | 0000000 | 00000 | 000000 | 00 | 0000000 | 00000 |
| 5/8"-11 | 1.51" | 0.505" | 1 | 000000000 | 00000 | 0000000 | 000000 | 000000 | 00 | 0000000 | 00000 |
| 5/8"-18 | 1.51" | 0.505" | 1 | 000000000 | 00000 | 0000000 | 000000 | 000000 | 00 | 0000000 | 00000 |
| 3/4"-10 | 1.51" | 0.505" | 1 | 000000000 | 00000 | 0000000 | 000000 | 000000 | 00 | 0000000 | 00000 |
| 3/4"-16 | 1.51" | 0.505" | 1 | 000000000 | 00000 | 0000000 | 000000 | 000000 | 00 | 0000000 | 00000 |
Metric
Nuts | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Thread | Tri-Groove Socket Bits | Drive Handles | Open-End Wrenches | |||||||||
| Size | Pitch, mm | Dia. | Ht. | Pkg. Qty. | Pkg. | Each | Each | Each | ||||
Zinc Alloy | ||||||||||||
| M6 | 1 | 0.66" | 0.265" | 10 | 000000000 | 00000 | 0000000 | 000000 | 0000000 | 000000 | 000000 | 00 |
| M8 | 1.25 | 0.83" | 0.345" | 10 | 000000000 | 0000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
316 Stainless Steel | ||||||||||||
| M5 | 0.8 | 0.66" | 0.265" | 5 | 000000000 | 00000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
| M6 | 1 | 0.66" | 0.265" | 5 | 000000000 | 00000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
| M8 | 1 | 0.82" | 0.35" | 1 | 000000000 | 0000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
| M8 | 1.25 | 0.82" | 0.35" | 5 | 000000000 | 00000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
| M10 | 1.25 | 0.82" | 0.35" | 1 | 000000000 | 0000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
| M10 | 1.5 | 0.82" | 0.35" | 1 | 000000000 | 0000 | 0000000 | 00000 | 0000000 | 00000 | 000000 | 00 |
| M12 | 1.5 | 0.94" | 0.35" | 1 | 000000000 | 0000 | 0000000 | 00000 | 000000 | 00 | 0000000 | 000000 |
| M12 | 1.75 | 0.94" | 0.35" | 1 | 000000000 | 0000 | 0000000 | 00000 | 000000 | 00 | 0000000 | 00000 |
| M16 | 2 | 1.51" | 0.505" | 1 | 000000000 | 00000 | 0000000 | 000000 | 000000 | 00 | 0000000 | 00000 |