Key Features
Built for Steel-to-Wood This Simpson Strong-Tie SDHR31400 Strong-Drive SDHR Combo-Head Screw is made for steel side plate to wood connections in mass timber and cross-laminated timber work. That means a fastener matched to the job instead of forcing a general-purpose structural screw into a connection it was not built for. Dual Drive Options The combo head can be driven with either a hex head or a T40 six-lobe driver bit. That gives installers more flexibility on site when tool setup, access, or preferred drive style changes from one connection to the next. Fast Starts, Less Prep A Type-17 point helps the screw start quickly, lowers installation torque, and eliminates predrilling in most applications. The partially threaded shank and knurl are there to pull members together while maintaining strong withdrawal performance.
Overview
The Simpson Strong-Tie SDHR31400 Strong-Drive SDHR Combo-Head Screw is a partially threaded structural screw for steel-to-wood connections in engineered wood, cross-laminated timber, and mass timber assemblies. This is a structural screw designed for steel side plate to wood fastening in interior mass timber construction. Model Number: SDHR31400. In this size, you are getting a 4 inch blue-zinc coated fastener with a 0.315 inch shank diameter, 0.669 inch head diameter, Type-17 point, and packaging quantity of 100.
What matters on the job is how this screw installs and how the connection behaves once it is in. The SDHR31400 uses a heavy-duty partially threaded shaft with knurl so it can pull structural members together instead of just spinning in place and hoping the joint closes up. That matters in steel-to-wood connections where fit-up, clamping action, and pull-out resistance are not small details. They are the whole point.
The Type-17 point is there for a reason. It helps the screw start fast, reduces installation torque, and removes the need for predrilling in most applications. In real terms, that means less setup time and less fight driving into engineered wood on repetitive installs. When you are setting a run of fasteners into CLT or other mass timber members, easier starts and lower drive resistance add up quickly.
The combo-head design gives you two practical drive choices: T40 six-lobe or hex-head. That is more than a convenience feature. On some connections, a bit-driven setup gives better engagement and control. On others, using a hex socket may be the better move depending on your access and tool setup. Simpson also calls out a deep T40 recess for a secure drive, which is exactly what you want in a structural fastener this size.
For interior applications, the blue-zinc coating matches the intended service environment. This is not pitched as an exterior corrosion solution. It is an interior-grade fastener for dry-service conditions where the focus is structural performance in engineered wood connections. Used where it is meant to be used, that coating and design package make sense.
The SDHR31400 is specifically tied to steel side plate applications and engineered wood construction, not generic deck work or everyday framing. Simpson lists it for steel-to-wood connections and describes the line as designed for metal-to-wood connections in mass timber construction and cross-laminated timber assemblies. If you are working on CLT panels, glulam, or other engineered wood members with steel hardware, this screw is in its lane.
Dimensionally, this model sits in the SDHR31 group with a 4 inch overall length and 2 1/8 inch thread length. That makes it the shorter of the SDHR31 options shown in the product table, which can be useful where connection design, member thickness, or required penetration call for the 4 inch version rather than the 6 1/4 inch model. The larger 0.315 inch shank diameter and 0.669 inch head diameter also separate it from the smaller SDHR27 versions.
Who should buy it? This screw makes sense for builders, timber crews, installers, and engineers sourcing approved structural fasteners for interior steel-to-wood connections in mass timber work. If you need a screw built around engineered wood, steel side plates, strong pull-together action, and flexible drive options, the Simpson Strong-Tie SDHR31400 Strong-Drive SDHR Combo-Head Screw is a purpose-built answer, not a workaround.
Made for Mass Timber Connections
This screw is built around the kind of steel-to-wood connection you see in CLT and other engineered wood assemblies. It is not trying to be everything. It is trying to do this job right.
- Designed for use with steel side plates
- Listed for steel-to-wood connections in engineered wood applications
Secure Drive When Torque Goes Up
The head design is one of the big reasons this fastener stands out. You get a deep T40 six-lobe recess for positive engagement, plus a hex-head option when that setup makes more sense for your tools or access.
- Drive type: T40 six-lobe or hex-head
- Combination head gives installers more flexibility on site
Starts Fast and Pulls Tight
The business end matters here. The partially threaded shaft, knurl, and Type-17 point work together to help the screw start cleaner, drive with less effort, and draw members together.
- Type-17 point reduces installation torque and avoids predrilling in most applications
- Partially threaded shank with knurl is designed to improve pull-together action and pull-out resistance
What’s in the Box
- (100) Simpson Strong-Tie SDHR31400 Strong-Drive SDHR Combo-Head Screws
Key Specifications
| Length | 4 in. |
|---|---|
| Shank Diameter | 0.315 in. |
| Head Diameter | 0.669 in. |
| Thread Length | 2 1/8 in. |
| Drive Type | T40 6-Lobe or Hex-Head |
| Head Type | Combination |
| Point Type | Type-17 Point |
| Coating / Material | Blue-Zinc Coated |
| Packaging Quantity | 100 |
Compatibility
Driver Interface Accepts either a T40 six-lobe driver or a hex-head driving setup. Replacement Bit Replacement six-lobe bit reference: BIT40T-134-R2. Connection Type Designed for steel side plate to wood connections in engineered wood and mass timber assemblies.
Built For
Mass Timber Construction Cross-Laminated Timber Engineered Wood Steel-to-Wood Connections Structural Fastening Construction General Contracting Interior Applications
Pro Tip
If your crew switches between drive setups, keep both a T40 bit and the right hex socket on hand. The combo head gives you that flexibility, and using the drive style that best matches access around the steel plate can make installation smoother and reduce cam-out.
Tool Nut’s Take
Tool Nut’s Take
Simpson Strong-Tie SDHR31400 Strong-Drive SDHR Combo-Head Screw for serious timber connections
This is the kind of fastener you buy when the connection actually matters and you want a screw designed around steel-to-wood structural work, not a general screw trying to play up a class.
- Who it’s for: Builders, timber installers, and spec-driven buyers working in CLT, glulam, and other engineered wood connections with steel side plates.
- Why it stands out: The combo head is smart, the Type-17 point speeds installation, and the partially threaded shank is built to pull members together instead of just occupying a hole.
- Worth knowing: This is an interior-grade blue-zinc coated fastener, so keep the application aligned with the service environment it was designed for.
Common Questions
- What is this screw designed for? It is designed for steel-to-wood connections in engineered wood, mass timber construction, and cross-laminated timber assemblies.
- Can it be driven with more than one tool setup? Yes. The SDHR31400 can be driven with either a T40 six-lobe driver bit or a hex-head driving setup.
- Does it usually require predrilling? Simpson states that the Type-17 point ensures fast starts, reduces installation torque, and eliminates the need for predrilling in most applications.
- Is this a fully threaded screw? No. It is a partially threaded structural fastener.
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