Tom has 17 years of experience as a commercial locksmith and over 20 years in door hardware distribution.
Ye Olde Mortise Lock
Above I have illustrated the basic guts of an early twentieth-century mortise lock. Most mortise locks today follow this same basic design. I have left out the springs and displaced the inside hub so you can get a good view of the outside hub.
NOTE: Mortise case contains springs that may fly out when you open it. They could go anyplace, including your eye. Be careful.
Notice that the inside hub and outside hub are different. Ah, now you begin to understand. They are different because the outside hub locks and the inside hub does not. Below I have drawn the hubs large so that you can really tell the difference.
Above you see the inside hub on top and the outside hub below. Both hubs have "wings" to retract the latch so that you can open the door, but notice that the outside hub has an extra feature.
The outside hub has two things sticking out. Let's call them legs, because we are going to put something between them. I have heard the thing that goes between the legs of the outside hub called different names, but let's call it the locking lever. The "legs" on the outside hub are designed to receive the locking lever. When the locking lever is inserted between these legs, the outside hub cannot turn. Therefore it is locked.
The inside hub has no legs, therefore it is always unlocked. That's how you want it to be so that you can get out in the event of an emergency.
Notice the illustration at the beginning of this article where I have shown the "stops," also known as "locking dogs" or "buttons." They are located in the "front" of the lock, that is, the part of the lock that you can only see when the door is open. The latch and the bolt stick out of the "front." When you push in one of the stops, the locking lever is inserted between the legs of the outside hub and the outside hub is locked. When you push the other one, the locking lever is retracted and outside hub is unlocked.
In the illustrations above, I show the locking stops in both the locked and unlocked positions. Here you can see how the hubs work together to accomplish the function of a doorknob that is locked on the outside of the house and unlocked on the inside of the house.
The square hole in the hubs (shown in black) are designed to receive a device called a "spindle." If you think of the doorknobs as wheels, then the spindle is the axle.
Note: in order for the lock to work properly, the spindle must be inserted correctly.
For the lock to work properly, the spindle must be inserted exactly halfway, so that both sides can swivel independently. If the spindle is inserted too far in either direction, you may find that if you turn your doorknob counterclockwise it will come off in your hand! Oh, no!
In the next section, I will discuss the design and use of the swivel spindle.
In the above illustrations I have tried to show all the variations you might find in spindles used in early twentieth century mortise locks, but I acknowledge that might be impossible. In the first illustration I show some of the variations you might find:
- Threaded spindle shafts
- Non-threaded spindle shafts
- Screw holes
- No screw holes
- Roll pin
- Spindle shim
Threaded spindle shafts are made to accommodate threaded doorknobs. Threaded doorknobs are usually secured to the spindle with a "set screw" that tightens against the spindle to make sure the doorknob does not loosen or tighten. Non-threaded spindle shafts often have threaded holes to accommodate a special doorknob screw. Some spindles have a roll pin to keep the spindle from being inserted too far. Some locks have a bigger hub hole on the outside than on the inside, and these require a spindle with a "shim" so that it rests snugly in the square hub hole rather than spinning uselessly inside it.
Notice in the illustration the small black shaft that holds the two halves of the spindle together. This is a threaded shaft that allows the halves to rotate independently. About 1/16" to 1/8" of this shaft should be visible. If the halves are turned so that they rest against each other and the shaft is not visible, the halves will not be able to turn independently and the lock will not work correctly.
In the second illustration above, I show the proper alignment of the spindle inside the lock hubs. Notice that you can see the spindle shaft between the hubs, indicating that both halves can turn independently.
Symptoms of Bad Spindle Alignment
- Spindle unscrews and you end up with the knob and half the spindle in your hand. Meanwhile, you are locked in!
- Knob will not turn from either side when locking stop is pressed.
- Knob turns clockwise freely for a full revolution or more.
- Excessive "play" in doorknobs, doorknobs flop back and forth.
A reader, Dave from Arizona, writes in this helpful process:
- Insert the spindle
- Mount the handle near the end of the spindle on the spindle opposite the one that contains the larger flat (ie. the one that screws into the larger Flat)
- Push the button that locks the outside and lets the inside operate
- Adjust spindle—move it in or out—until you can turn the inside handle
- Holding the spindle in that position, screw on the outside handle and tighten its set screw
- Reposition the inside handle to its normal position and tighten the set screw.
In the above illustration I show the probable location of the doorknob or set screw. Some of the symptoms of bad spindle alignment shown above also occur as the result of worn out doorknob threads, loose set screws, or missing doorknob screws.
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
Questions & Answers
Question: On which side is a spindle flat?
Answer: The spindle flat is one side of the non-threaded portion of the spindle. Measure one flat to find the diameter of your spindle.
© 2010 Tom rubenoff
June Summers Haas on July 07, 2020:
Thank you for assistance with repairing a 1940’s lock handle.
Tom rubenoff (author) from United States on October 11, 2018:
Thank you, Jay. For security reasons the roll pin should be on the outside to prevent pushing the spindle out of the lock from the outside.
Jay Hohmann on October 11, 2018:
With a split spindle should the roll pin be to the inside or outside of door? My thinking is that it ought to be on the inside, if the inner doorknob were to come off, the spindle couldn't slide out from the lock to the outside.
Rob Fleming on June 09, 2017:
Recently, somebody pushed the stop button on the edge of my front door, locking it. The house was built in 1905, had a hard life, and I don't have a key for that lock. I had to take off the trim plate and use a screwdriver to turn the hub to unlock the door. Then I took a small piece of flexible plastic and put it in the lock to block the notch that the stop button engages so that it won't happen again.
Tom rubenoff (author) from United States on February 10, 2016:
I have no data to make an educated comment on the durability of the product. Since it is marketed as a residential product it does not have to live up to an ANSI Grade 1 or Grade 2 standard. Personally I don't think it is likely to take the place of more traditionally functioning lever locksets anytime soon, but I could be wrong.
Tom rubenoff (author) from United States on February 03, 2016:
Sounds to me like the lock is fine, but you need either a doorknob that will fit your spindle, or a spindle to fit your knob. There are places out there that specialize in antique knobs and spindles, and although there is a tremendous variety of different variations, it is indeed possible to find one, the other or both.
I suggest a plan of action. 1) Find a place that sells antique doorknobs and spindles. 2) Remove both knobs and the spindle. Try to leave the outside knob attached, but if you can't that's okay. 3) Bring the spindle and knobs to the place and see if they have a knob that will fit your spindle properly and a screw to hold it in place.
With persistence I predict you will succeed. Good luck in your search.
Hey-mom on February 03, 2016:
I have an old front door on my old house and here's the problem...the doorknob inside the front door would occasionally come off in my hand. So, recently, as a surprise for me, my fiancee decided to replace the knob! Well, the problem is, the new one doesn't fit onto the split spindle well, and now it comes off everytime I try to exit my house! The split spindle is too large for the hole in the knob. I can't even get the knob onto the spindle, let alone try to tighten the little barrel screw on the side of the knob. I love my door and my lock set. I don't want to have to replace the entire mechanism, but I'm so frustrated with this darned "new" knob that I could scream. He didn't keep the old brass knob when he decided to "fix" my door knob problem. Should I just call a contractor and have an entirely new front door installed? Yes, I'm about that desperate! Help!
Tom rubenoff (author) from United States on December 14, 2015:
Thank you, Tisha!
Tisha on December 14, 2015:
This was super helpful rundown..possibly the most helpful that I have ran across.
Tom rubenoff (author) from United States on July 11, 2014:
That's great to hear, Michele. Thanks so much!
Michele on July 11, 2014:
Thank you so much for this post. Super helpful and saved me from having to spend money just to figure out how the lock worked. Seriously - A+ and many thanks. Figures out I needed a needed a new spindle on my own, but couldn't for the life of me figure out how to install it.
Tom rubenoff (author) from United States on May 20, 2013:
There are as many kinds of spindles as there are ways to disassemble them! I am glad you figured it out - that's fun, isn't it? But since I am a hardware geek I remain curious about which kind you had. Anyhow, good luck with all your mortise lock adventures!
David on May 18, 2013:
Figured it out, but thanks for the great site anyway. Love googling for help!
David on May 18, 2013:
So I'm a novice mortise adventurer, and am having a heck of a time. Attempting to remove the spindle so that I can pull the whole assembly out of the door and can't even manage that. I have both inside door knob and outside thumb removed, just can't get the spindle out. Don't see any screws left or any way to get to any more if there are. Is there a trick to removing the spindle?
Tom rubenoff (author) from United States on April 17, 2013:
Interesting, I've used hacksaw blades in the past ground down on a bench grinder in a pinch. But the HPC company of Schiller Park, IL, in the United States offers an assortment of round and spring steel stock, model FRS-4. I have never failed to find a piece therein I could not make work.
David A on April 16, 2013:
I'm having an issue trying to find replacement springs for a couple of old T&S style locks. The springs are the thin, flat ones about 3 or 4" long. I can't seem to find metal strips that could substitute and also have a similar flexibility/tension. It looked like someone had put an old jigsaw blade in one of the locks, maybe that is an adequate option? I'd still need to find blades that are the similar dimensions... Any thoughts?
Tom rubenoff (author) from United States on February 17, 2012:
This is a great story! You are certainly resourceful. Thanks for sharing this with us!
Dave Wachtel on February 17, 2012:
Restored my second mortise lock set, an ancient Corbin that was in really good shape internally. It's a solid spindle type - no drama - even found the key.
I found where the spring went in the old Russwin. It seems the original had broken so it actually was too short to fit where it belonged. See
It's not my model and is probably a lot newer but some of the internals are identical to mine. It's the spring on the bottom. I fabricated a new one from a spring taken from an old set of auto ignition points.
The lock set is a Russwin 2 1/2 0122. Any idea about the date of manufacture?
I looked carefully at the interior plate in the sun. They are steel with some kind of plating, Any idea what they were plated with originally?
I think I'm going to take a break from restoring lock sets. I've got twenty or so skeleton keys none of which fit the remaining lock sets. Sigh...
Dave Wachtel on February 16, 2012:
Thanks - the restoration was fun as was writing the story.
My lock set has no knob for the bolt, it's just keyed.
For the life of me I couldn't see where the spring could be fitted. Unfortunately I didn't write down the Russwin part number. Someone on the 'net had an old lock set with a cylinder rather than a skeleton key and Russwin claimed they didn't have drawings for something that old, since mine is much older there is no joy there.
I searched everywhere on the 'net with no joy either.
It looks like the Baldwin 6320.003.x but I'm sure the innards are much different.
BTW - I think the mechanical design is nothing short of brilliant! It's simple robust and generally amazing.
I have six doors that have antique lock sets which open and close but all of the locking mechanisms are inoperable. Since doing the front door was so much fun, maybe I'll tackle those too.
The front door also has a separate deadbolt that was apparently added when the main lock went paws high at least sixty years ago.
Sometime in the last few tens of years the key stopped working and a year or so ago I repaired it. Home Depot actually had an identical but expensive unit so I just replaced the cylinder without doing a full restoration. It works OK but not great. After the mortise restoration I think I'll do a full restoration on the deadbolt, particularly now that I can lock the front door with the mortise unit :)
Again, thanks for the diagrams and explanation. This was the most helpful article I found anywhere on the net!
Tom rubenoff (author) from United States on February 15, 2012:
Thanks for sharing your old mortise lock story, Dave! Many's the time I've done what you describe here - except for the hardware store part :) That leftover piece of flat spring steel could have done any of a number of jobs, but I'm thinking if you have a hub for a thumb turn to throw the bolt, it probably belongs nestled alongside there. But good for you the lock works fine and that's what counts! Thanks again.
Dave Wachtel on February 15, 2012:
Tom - Thanks for the info.
The spindle broke on my over 100 year old antique Russwin front door lock set. I just finished restoring it. For the first time in at least 60 years (I'm 65) the lock buttons and the dead bolt work properly. Luckily I found the original skeleton key in my "junk draw" - woo hoo!
A "new" replacement for this lock set is priced from around $250 to $500 so the 6 to 10 hours of work was well worth it. Most of the time was spent removing corrosion from the internal parts and several layers of paint from the trim plates.
Naval jelly works great for the iron and steel. Probably something like tarnex would work better on the brass though as the outer plate was quite pitted and didn't clean up as well as the indoor plate.
The inexpensive replacement lock sets from Home Depot didn't fit so I made the decision to jump into the unknown and do a complete restoration. Home Depot didn't carry split spindles but much to my surprise the local True Value Hardware store had a variety of them in stock, including ones that were both drilled and externally threaded.
Both the old knobs have untapped holes for screws but the holes in the new spindle didn't quite line up and adjustment looked like it would be a real chore.
To make life easier, I bought a solid spindle/doorknob set for the threaded knobs. I positioned the spindle, tested the lock buttons but I couldn't use both of the new knobs as they were not deep enough allow being tightened far enough to engage the flanges on the plates. So I affixed an old knob inside to the spindle hole that was nearest being lined up. (Note that I had to buy new screws for this to work as well as the "combination" spindle) Then I followed the above instructions and screwed a new knob to the spindle on the outside and tightened the setscrew. There was a minimum of fiddling about to get it working smoothly - about a half hour.
I have a part left over though. It's a piece of spring steel about 1.5 inches long that fell out of the rusty innards before I could examine it all in detail. Even so, the lock set seems to work as it's supposed to.
Tom rubenoff (author) from United States on December 20, 2011:
That's the best! Thank you!
Joe on December 19, 2011:
Was having trouble with the knob on our front door. Didn't understand the split spindle mechanics until I found your article. Then I was able to fix it. Thank you!
Tom rubenoff (author) from United States on December 01, 2011:
First, the two buttons are connected. When one is pushed in, the other should pop out, flush with the plate. Many times when a lock like this gets old, it's possible to push a button in so it doesn't line up with its hole anymore. Then it doesn't want to pop out again so you can unlock your door.
Take a screwdriver and a hammer and attempt to GENTLY tap the other button back in. Notice if the button that should be popping back out, unlocking your vintage lock, is lined up with its hole so it can indeed pop back out. If it isn't, then you need to take something sharp, like a utility knife, and jam it into the button that is pushed in so you can get a grip on it. Then, try to move it back into position with the utility knife while you push on the other button with a screwdriver. Maybe you will be able to get the button lined up so it will pop back out and unlock your lock.
Let me know how you make out. Good luck.
ajs8888 on December 01, 2011:
We have a vintage lock on our house. I pushed one of those little buttons that locks the outside latch and when I pushed the other to unlock it...nothing. The exterior latch (thing you depress with your thumb) is still locked. What should we do?
Tom rubenoff (author) from United States on October 09, 2011:
Most likely either the threaded rod between the inner and outer spindle is stripped or the hole the threaded rod screws into is stripped. Either way, time for a new spindle.
Definitely no glue!
MAtthew Purdon on October 09, 2011:
Hey Tom - this article is awesome! Thought I still can't figure out how to fix my door knob. I get it perfectly aligned and the door knob screws in place - everything works perfect - but the door knob with spindle attached still flies out on the inside sometimes - i think the screw thing in the middle is stripped. should I put some glue in before inserting?
Tom rubenoff (author) from United States on September 07, 2011:
signetfence from Online on September 07, 2011:
Great title and even better article.
Tom rubenoff (author) from United States on March 18, 2011:
I had fun writing and drawing. Thanks, Crystolite!
Emma from Houston TX on March 17, 2011:
Excellent article with cool pretty sketches that really represents.thanks for writing.
Tom rubenoff (author) from United States on July 13, 2010:
I'm glad to hear it worked out. It's nice being able to get through your door without too much trouble. :)
Patience Void on July 12, 2010:
Thank you Tom they do have them. I realized I could repair the one I had before I had checked back here.
Two wacks (one on either side) with a pointed punch and it was as good as new. Scott Jones
Tom rubenoff (author) from United States on July 04, 2010:
Thank you, Kenwrites!
PV, you might try these guys:
Patience Void on July 03, 2010:
I have a swivel spindle that separated off a PENN F.M.L. and am having a heck of a time finding the right thread size. It is threaded from both sides and has the shims on both sides as well. I checked the threads with my best reading glasses and I believe it is a 3/8 by 20.
We have a great old home supply here and even they didn't have the right size. Humph...
Ken Crawford from Yreka, California on June 02, 2010:
Great Hub Tom. I just recently came across a mortise lock to repair on my mother-in-laws house. Quite different than the standard locks, I must say. This would have been helpful. Clear and concise. Great diagrams.
Tom rubenoff (author) from United States on April 02, 2010:
It is so great you found this article helpful, Elisa :0)
Elisa V. on April 01, 2010:
well, i can't say that i put the spindles and doorknob back correctly, but at least the door can be opened. Thanks for the article which helped me out. with a little more thought i might be able to do it right.
Tom rubenoff (author) from United States on March 15, 2010:
I love drawing diagrams. Thank you, Deltachord. :0)
Deltachord from United States on March 14, 2010:
Good Hub Tom and the diagrams are appreciated.
Tom rubenoff (author) from United States on March 08, 2010:
Hey, Michael! It's fun to do the drawings. :0)
Syndrome, I think, is correct, Candie LOL Thank you
Candie V from Whereever there's wolves!! And Bikers!! Cummon Flash, We need an adventure! on March 07, 2010:
I myself have experienced "the knob came off in my hand" syndrome (or was it occurrence?) You rock the knob world!
Micky Dee on March 07, 2010:
This is an incredible endeavor! Thanks
Tom rubenoff (author) from United States on March 06, 2010:
Mortise locks are indeed a strange and beautiful universe, Teresa. :0)
Sheila from The Other Bangor on March 06, 2010:
Who knew? I'm a convert (and off to Home Depot to inspect their swivel spindles).