Baldwin 0521004 4-1/2" Swivel Broached Spindle

The Baldwin 0521004 is a 4-1/2 inch swivel broached spindle, the square bar that runs through the door and ties a knob or lever on one side to the trim on the other so turning one side retracts the latch. The swivel construction lets one side turn independently of the other, and the broaching is the toothed engagement that grips the knob or lever hub. It is sold as a replacement part, not a complete lockset, so you are ordering it to repair or rebuild trim you already have.

Baldwin lists the 0521004 spindle as a residential part, and it belongs to the Estate Series of residential trim. For an apartment turn or a house door being rebuilt with Estate knobs or levers it is the right piece. For a commercial opening running a Grade 1 or Grade 2 cylindrical or mortise lock, this is the wrong part; those locks use the spindle supplied with the lock chassis and are not built around Baldwin residential trim.

Spindle length is set by how thick your door is plus the depth of the trim on both sides, so measure the old spindle you are pulling out rather than the door alone. The 0521004 is offered in the single 4-1/2 inch length. If the piece you removed measures shorter or longer than 4-1/2 inches, this is not the matching part and you want the Baldwin spindle in that length instead.

Alloy steel is the substrate, with an electro plated steel finish (Baldwin's 004). The spindle carries the full torque of every turn of the knob or lever, so steel rather than a cast pot metal is what matters here. The 004 plating is a functional coating, not a decorative finish; the spindle sits inside the door and is never seen once the trim is on, so it does not need to match the rosettes or levers on the outside.

Just the bar. Model 521 is the spindle on its own, a repair and service piece for Baldwin Estate trim. Knobs, levers, rosettes, screws, and the latch are all separate; if a door has failed because the knob spins without retracting the latch, the spindle is usually what broke, but confirm the hub in the knob is still intact before ordering only this piece.