Everything You Ever Wanted To Know About Spindles from Progressive Hardware

What models should the locksmith stock? A numbering system and the experts at Progressive can help you identify and purchase the right spindle for the job. And two Progressive spindle kits will cover a majority of mortise locks.


Some mortise lock makers used two different sized hubs for the knob spindle. This prevented the spindle from being pushed through; it made the spindle installation self-centering. Typically one hub was 9/32” square and one was 5/16” square. But not always! One side might be 9/32” or 5/16” square and the other was 3/8” square. But the threaded portion of the spindle may still maintain the 9/32” square even though the center of the spindle is 5/16” or 3/8” square.

Along the way someone decided it would be nice if you could have a doorknob only on one side of the door. Typically the other side might have a sectional handle set. To accomplish that, you would need a two-piece sectional spindle.

There are as many spindle variations, as there are ideas. In order to identify the correct spindle, consider the following.

1. There are three basic styles of spindles:

A. Straight spindles—primarily used for passage, non locking entries.

B. Swivel spindles—primarily used on mortise locks, provides a means of attaching two knobs or levers to the lock.

C. Sectional spindle—provides a means of attaching a knob or lever to one side of a door.

2. The size of the square rod, measured across the flats.

If you don’t have the original spindle to compare to, it will be necessary to measure the lock hub diameter. An easy way to do this is by using a drill. Find the largest drill that will go into the hub. That’s probably the spindle size.

Remember, some locks use two different size hubs. You will need to measure both sides of the lock.

At this point it may get a little tricky. The center of a swivel spindle, the part that ends up in the lock hubs, may be fatter then the spindle ends. You need to establish the spindle size that goes into the knob or lever and also if the center is bigger.

A. The majority of spindles are 9/32” square

B. A smaller portion are 5/16” square, mostly for levers

C. A very small segment are 3/8” square

D. All the rest

3. Is the spindle threaded and, if so, what thread is it? The vast majority of threaded spindles are 9/32” square. This means the thread is 3/8” -?? Unknown pitch. To calculate the pitch, you either need a set of pitch gauges or if your eyes are good enough: a ruler and count the threads in one inch.

By now you should have an idea of the basic spindle you need. We have assumed that the spindle is threaded or not threaded. But there are also many other variations on how the knob is attached.

Tapped holes—Older style doorknobs did not have any thread in the base of the knob for the setscrew. The setscrew passed through the knob shank into a threaded hole in the spindle. These spindles may or may not be threaded and they could be straight or swivel.

Pin holes—Some knobs are pushed over the unthreaded square spindle and then a roll pin is driven into the knob shank and thru the spindle. The location of the pin hole is now important in placing the knob correctly. Some of our spindles have pin holes pre-drilled but they may or may not be in the correct location. In this case, the installer may have to drill his own hole. We also sell knob washers that go around the spindle and under the knob to take up any play.

Knob pinned to swivel spindle—Only one knob or lever can be pinned in this manner to the spindle. You need to pass the opposite end of the spindle through the lock body and attach the other knob/lever in some other manner. The traditional manner is to thread on the other knob and secure with setscrews. Several manufacturers have come up with some ingenious variations. Usually it involves driving the setscrew into some sort of depression or groove in the spindle.

Spindle with a stop pin or notch—The pin or notch actually stops the spindle from being inserted further into the lock hub when both hubs are the same size.

Removable center versus solid center—The method used to increase the size of the spindle center can vary. Some spindles were actually cast with a larger diameter in the center. This method was expensive and we instead use a square sleeve that is a press fit over the 9/32” spindle. The diameter of the sleeve is somewhat less than 3/8” so that it can pass through a 3/8” lock hub. In an emergency this sleeve can be knocked off if you have a means of holding the spindles and hammering the sleeve off. Important: This works well if you need a smaller spindle (9/32”) and didn’t bring one.

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