In response to the increasing prevalence of mass timber construction and the hydrogen embrittlement requirements defined in CSA O86:24, Simpson Strong-Tie has developed the next-generation Strong-Drive® SDCF Timber-CF (countersink fully threaded screws) and SDCFC TIMBER-CFC (countersink fully threaded cylinder-head) screws with a black e–coat finish. 

The hardness profile of the SDCF and SDCFC screws with the black e-coat finish now has a maximum core hardness of 36 HRC to align with new requirements in CSA O86:24. This reduces the risk of hydrogen embrittlement and improves construction durability. The CSA O86:24 standard specifications mitigate the risks associated with hydrogen embrittlement in screws while maintaining performance in dry service conditions. The updated core hardness reduces the risk of environmental hydrogen embrittlement (EHE) and stress-corrosion cracking (SCC), which can occur during long-duration mass timber construction projects where high-strength steel fasteners are exposed to moisture and sustained tension. 

The black e-coat finish is approved in accordance with ICC-ES AC257 for Exposure Condition 3, permitting the screws to be exposed to wet service conditions during the construction phase. However, prolonged or continuous exposure to moisture beyond the construction period should be carefully evaluated. In addition, the black e-coat provides corrosion resistance suitable for use with preservative-treated and fire-retardant-treated (FRT) lumber, subject to compliance with applicable code requirements and treatment chemical compatibility. 

The new SawTooth® tip allows fast starts and easy driving, and the deep 6-lobe recess provides a secure drive. 

The black e-coat SDCF and SDCFC have been evaluated in accordance with ICC-ES Acceptance Criteria AC233 (Acceptance Criteria for Dowel-type Threaded Fasteners Used in Wood) to allow for use in mass timber construction and general interior applications. They are listed in ICC-ES ESR-3046. 

The black e–coat SDCF and SDCFC use metric nomenclature and are offered in a variety of sizes and lengths. For example, for a SDCF8X120 screw, 8 represents the major diameter of 8 mm (0.315“) and 120 represents the screw length of 120 mm (4.72“). With the expanded offering, we now offer 25 new models in the SDCF and SDCFC families. The screw models and sizes for the SDCF and SDCFC with black e-coat finish, along with a list of equivalent models using imperial nomenclature and featuring the legacy yellow zinc finish, are listed in the tables below.  

In addition to expanding the reference design values for screws in new sizes and lengths, there are some updates to design values that you may want to review before making design decisions.  

• As a result of their relatively lower core hardness, black e-coat SDCF and SDCFC screws exhibit lower allowable tension and shear strengths than the corresponding yellow zinc finish screws.  

• Lateral design values remain unchanged for both black e-coat and yellow zinc finish screws of equivalent sizes.  

• Reference withdrawal design values for black e-coat SDCF and SDCFC screws now exclude the tip length. Please note that the effective thread length used to calculate the total withdrawal value is now defined as the total thread length minus the tip length.  

• Reference pull-through values for the equivalent sizes of SDCF and SDCFC screws are consistent across both finishes. In addition to the original 1.5″-thick wood member, reference pull-through values for a 3″-thick option have been added.  

• Regarding connection geometry: 

• If you prefer to use lateral design value based on testing results, the connection geometry for each screw remains unchanged and can be found in Table 4D, Table 6D, Table A5, and Table A10.  

• If you opt to use the lateral design values based on the NDS calculations, all SDCF and SDCFC screws can be designed using the connection geometry provided in Table 7B. 

Additional load-rating tests have confirmed that the new black e-coat screws can be directly substituted for the legacy yellow zinc screws in the following connectors and construction hardware: the HSKP™ heavy seated knife plate hanger; the ACBH™ aluminum concealed beam hanger; the SCBH™ steel concealed beam hanger; the MTLD™ mass timber lifting device; and the MTHLD™ mass timber heavy lifting device. 

If you are interested in learning more about the Strong-Drive® black e-coat SDCF and SDCFC screws, feel free to ask a question in the comments or visit the product pages for the black e-coat SDCF  or the black e-coat SDCFC