A common question from procurement and engineering departments is: "Can we swap an SFI nut for an SFU nut?"
The short answer is no-not without verifying the flange dimensions and bolt patterns first.
While both are flanged single nuts that function similarly, their mounting geometry and standards differ significantly:
- SFU Series (DIN-Type / Trimmed Flange):
The SFU utilizes a standardized DIN 69051 Form B flange profile. It features flat-cut top and bottom edges, giving it a compact, square-like shape with rounded sides. This low-profile geometry is engineered specifically for tight clearance applications, allowing the nut to be mounted extremely close to a base plate or inside standard mounting brackets (such as the DSG series).
- SFI Series (JIS-Type / Round Flange):
The SFI features a traditional, fully circular round flange (typically conforming to JIS standards). Because the flange is perfectly round with no flat-cut edges, it occupies a larger radial footprint and requires more clearance around the nut body within your machine assembly.
Engineering Selection Advice:
Before ordering replacements, always verify the Flange Diameter (D1), Flange Thickness (H), and Bolt Circle Diameter (PCD) on the technical drawings. Matching the flange shape and standard is critical to ensuring the mounting holes align correctly with your existing carriage or gantry plate.