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Starrett PT99021 steel lock bolt assembly for 4 inch square heads

Starrett

Starrett PT99021 lock bolt assembly for 4 in square heads measurement tool

SKU CH-4SPH-S54WH

Steel lock bolt assembly replaces the original fastener on 4 in Starrett square heads

  • Steel construction resists wear during repeated adjustments
  • Secures 4-inch square heads for consistent alignment
  • Compatible with Starrett 11H, 33H, C11H and C33H series heads
  • Direct replacement for worn or missing original lock bolts
  • Impact-rated no, suited for standard measurement tasks

Starrett PT99021 Lock Bolt Assembly

The Starrett PT99021 is a steel lock bolt assembly designed as a replacement component for 4 in square heads. It secures the head firmly during layout and inspection tasks. Machinists and toolmakers use it to maintain accurate positioning on compatible Starrett combination sets.

Fits Starrett 11H, 33H and C-series heads

This assembly fits Starrett models including 11H-4-4R, 33H-4-4R and their C-prefixed variants. It is not impact rated, so it suits hand-tightened setups rather than powered driving. Buyers needing a fastener for other head sizes or impact-rated applications should look elsewhere.

Steel construction for 4 in square heads

The bolt is made from steel and manufactured to Starrett tolerances for 4 in square heads. It replaces worn or lost original hardware on the listed compatible models. No other dimensions or compatibility data are supplied.

Highlights

  • Steel construction resists wear during repeated adjustments
  • Secures 4-inch square heads for consistent alignment
  • Compatible with Starrett 11H, 33H, C11H and C33H series heads
  • Direct replacement for worn or missing original lock bolts
  • Impact-rated no, suited for standard measurement tasks

Specifications

BrandSTARRETT

Questions about this item

When will the steel lock bolt need replacement on the PT99021 assembly?

The steel lock bolt is a replacement part itself; replace it when wear prevents secure clamping on the 4 in square head.

What stops the PT99021 from holding under continuous clamping force?

The steel bolt holds until thread wear or deformation prevents full engagement with the square head.

Does the PT99021 lock bolt generate heat or noise during all-day use?

No — it is a passive steel fastener with no moving parts, motor or electrical draw.

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