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Satin-chrome steel swivel spindle, 9/32" square shaft with two removable centers

Tuff Stuff

Tuff Stuff 4521 Steel Swivel Spindle 9/32" Square 20 TPI 3/8" door lock

SKU CH-BFZX-KAM23 MPN 4521

Steel swivel spindle with two removable centres replaces surface-mount mortise locksets

  • Lock keyingKeyed Different
  • Surface finishSatin Chrome
  • Sold asBox
  • Swivel action reduces binding on mortise locks
  • 9/32" square steel shaft fits standard mortise cutouts
  • 3/8"-20 thread matches original spindle threading
  • Two removable centres allow flexible knob installation
  • Direct replacement for surface-mount mortise locksets

Replacement Spindle for Mortise Locksets

The Tuff Stuff 4521 is a steel swivel spindle built to replace the original hardware on surface-mount mortise locksets. It measures 9/32 inch square by 4-3/4 inch long and features 20 TPI 3/8 inch threading with two removable centers. The satin chrome finish matches common period hardware.

For Restoration and Maintenance Work

This spindle suits owners repairing vintage or existing mortise locks where the original spindle is worn or missing. The removable centres allow adjustment for varying door thicknesses without modification. It is not suited for modern tubular latchsets, cylindrical locks, or any lock body requiring a solid spindle or different thread pitch.

Critical Thread and Square Specification

The 20 threads-per-inch 3/8 inch diameter combined with the 9/32 inch square drive determines fit. If the lock body uses a different thread count, diameter, or square size, this spindle will not engage. Verify both measurements against the original part before purchase.

How it compares

Measured against everything we stock in Door Lock Sets & Deadbolts, at today’s prices. Recalculated every night.

Price $2.99
Cheaper than about 98% of the 2,145 comparable items (median $55.99).

Specifications

Product
Brand nameTuff Stuff
Model name4521
Size & build
Surface finishSatin Chrome
More details
Lock keyingKeyed Different

Questions about this item

Will the 9/32" square steel spindle need periodic lubrication or replacement over time?

The steel swivel spindle is a solid mechanical part with no service interval; it only requires replacement if the square section wears or the 20 TPI threads strip.

What is the first limitation when the spindle operates continuously in a high-traffic mortise lockset?

The 9/32" square cross-section and 20 TPI thread engagement determine torque capacity; sustained heavy use will show wear on these surfaces first.

Does the 4521 spindle generate noticeable heat or noise during all-day operation?

As a passive steel component it produces no heat or noise of its own; any sound comes from the lock mechanism it drives.

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