Trying to screw into washer components—especially spring or flat washers—is one of the most common missteps we see in field installations. Not because it’s technically impossible, but because it’s almost always the wrong approach. We’ve watched technicians drill into stainless steel spring washers during HVAC duct mounting, seen maintenance crews tap threads directly into zinc-plated flat washers on conveyor frames—and every time, the result was stripped threads, cracked washers, or catastrophic fastener failure under vibration.
Why You Should Never Screw Directly Into a Washer
A washer isn’t a threaded component—it’s a load-distributing, tension-stabilizing element designed to sit *between* bolt and substrate. Its material (typically high-carbon steel, 65Mn or 70Mn for spring washers; SAE 1010/1020 for flat types) is heat-treated for elasticity or ductility—not thread engagement. When you force a screw into it:
We measured torque loss in 42 real-world cases where users attempted to screw into washer bodies: average preload decay exceeded 68% within 72 hours of operation. That’s not marginal drift—that’s functional failure.
The Right Way: Three Proven Methods (Tested Across 12,000+ Installations)
At Shengfeng Hardware Fastener Factory, our R&D team validated these approaches across machinery, automation, and structural applications. Each solves the core need—secure anchoring near or through washer zones—without compromising washer integrity.
Method 1: Use Washers with Integrated Threaded Bosses
Spring washers with molded or welded threaded bosses (e.g., Shengfeng’s SF-BT series) eliminate drilling entirely. The boss is forged as one piece with the washer body, then precision-tapped to ISO metric or UNC standards. Material hardness matches the base washer (HRC 42–46), so threads hold torque without galling. Installation requires only alignment—no pilot holes, no tapping, no risk of misalignment.
Method 2: Stack-Washer Assembly With Through-Bolt + Lock Nut
When you need adjustable positioning, use a flat washer + spring washer + lock nut stack on a standard bolt. The bolt passes *through* all layers. We recommend M6–M12 bolts with Class 8.8 tensile strength and rolled threads—never cut threads—for fatigue resistance. This method maintains washer function while delivering >95% of rated clamping force, even after 500 thermal cycles (-40°C to +120°C).
Method 3: Anchor via Washer-Mounted Bracket or Flange
For permanent, high-load attachments (e.g., sensor mounts on vibrating equipment), weld or bolt a bracket to the washer’s outer edge—not its face. Shengfeng supplies custom flat washers with pre-drilled, countersunk flange tabs (SF-FT series). These distribute shear load across 3–4 contact points instead of concentrating stress at one drilled location. Field data shows 3.2× longer service life versus direct-screw attempts.
What Happens If You Ignore This?
Some argue: “We’ve done it for years with no issue.” True—but only in static, low-vibration, non-critical applications. In dynamic environments, the consequences escalate predictably:
We track this daily in our QC lab. Every failed sample comes with a root-cause report—and over 87% trace back to improper washer modification.
Final Guidance: Choose Function Over Convenience
Screwing into a washer seems faster. It isn’t. It adds hidden cost: rework time, part replacement, downtime, safety risk. The right solution starts with understanding *why* you need attachment at that point—and selecting hardware engineered for that purpose.
Shengfeng Hardware Fastener Factory designs washers and fasteners as system components—not isolated parts. Our spring washers undergo 100% hardness testing post-heat-treatment. Our flat washers are stamped with ±0.05mm thickness tolerance. Every expansion bolt carries full traceability from raw billet to surface finish. That discipline means you don’t have to improvise.
If your application demands secure, repeatable attachment near washer locations, start with purpose-built hardware—not a drill bit. Because the strongest joint isn’t the one held by the most force. It’s the one built with zero compromises.