M20-1.5 x 200mm Hex Head Cap Screws Strength Guide
By Mutual Screw & Supply | Published: 2026-10-29
Category: Buying Guides
Learn how to choose and use M20-1.5 x 200mm hex head cap screws with Class 10.9 steel plain finish. Get concrete decision rules for large-scale fastening.
Quick answer
For heavy machinery and equipment assembly needing high clamping force, the M20-1.5 x 200mm hex head cap screw in Class 10.9 steel plain finish offers a strong, corrosion-resistant option. Its partially threaded design suits applications where only the engaged threads need contact.
Why partially threaded matters for M20 x 200mm
The partially threaded shank leaves a smooth section near the head. This lets the screw pass through a flange or thick bracket without galling threads, making it ideal for blind-hole or through-hole assemblies where only the final grip needs threads.
Class 10.9 steel plain finish trade-offs
Class 10.9 steel provides high tensile strength (about 1,000 MPa) but the plain finish offers limited corrosion resistance. For indoor or dry environments, plain works well; for outdoor or wet conditions, consider a plated or stainless alternative.
Decision rules for M20-1.5 x 200mm hex head cap screws
- Thread engagement: Ensure the threaded portion (not the smooth shank) fully engages the mating component. For a 200mm screw, measure the threaded length and match it to your material stack-up. Use at least 1.5x the screw diameter (30mm) of thread engagement for full strength.
- Plain finish limitations: Class 10.9 plain finish offers no corrosion protection. Avoid in humid, outdoor, or chemical-exposure environments unless you add a protective coating or use stainless steel. Indoor dry applications only without additional plating.
- Drive tool selection: Use a socket or wrench matching the hex head size (typically 30mm for M20). Torque to manufacturer specifications for Class 10.9 (usually 200-250 N·m). Always use a calibrated torque wrench to avoid over-tightening.
Product facts
- M20-1.5 X 200mm Hex Head Cap Screws | Class 10.9 Steel Plain | Partially Threaded (30 / Pkg.): M20-1.5 x 200mm hex head cap screw in Class 10.9 steel plain finish, partially threaded, sold in packs of 30. The 200mm length with partial threading suits large-scale assemblies where only the engaged threads need contact, reducing installation friction on the smooth shank.
M20-1.5 X 200mm Hex Head Cap Screws | Class 10.9 Steel Plain | Partially Threaded (30 / Pkg.)
Who should use this screw
Best for
- Heavy machinery assembly where high clamping force is needed
- Through-hole applications with thick flanges or brackets
- Indoor equipment where plain finish is acceptable
Not for
- Outdoor or corrosive environments without additional protection
- Applications requiring full-thread engagement along the entire shank
- Light-duty or low-torque fastening where smaller screws suffice
