Residential & Commercial Security - Locks, Keys & Dead Bolts - Emhart & Corbin Russwin Locksets

I was at a physician's office yesterday putting up some bulletin boards and file holders. While I was there I was asked to take a look at some door knobs to their exam rooms that weren't working properly. I took a look and checked for a name. One had Emhart and another had Corbin Russwin. I was unable to remove the knobs to do any work on these doors. I was able to loosen (unscrew) the tube that connects from the door knob itself to the cover plate on the door. Once that was removed I saw what at first appeared to be a set screw, but it wasn't. On another door, underneath the tube was the head of a slotted screw. The tube interfered so that a screwdriver could not be turned. I was looking for a way to remove the knobs but was unsuccessful. What's the secret? Some sort of special tool?

Any help or advice would be appreciated.

Respectfully,

Handy Matt

These may be old Corbin 400 series locks. On these, you spin the collar back to loosen the lock up(sounds like you got this far). By pushing the lock towards the outside, you can expose the spring retainer behind the rose. Push this back with a small flat-blade screwdriver to release the knob.

Thank you for the quick response. I'm having difficulty translating your instructions into a picture in my mind. These door knobs had no locks on them. One of the doors could be locked from a button located on the side of the door at the bottom of the latch plate. Any illustrations I can be directed to for a clearer image?

Handy Matt

Nothing I could find on google. Last time I worked with these was over 10 years ago on an old building and I imagine these are not made anymore. If I have the right lock and the details correct, the retainer is like a fork that is perpendicular to the tube (and penetrates the tube through a slot) and up against the lock body. The knob, which need not have a lock cylinder, has a machined shaft with a groove in it that the retainer engages inside the tube.

Rose = the cover plate you mentioned

The retainer will be where tube intersects the lock body.

Your description of the locking button on the latch plate reminds me of a mortise lock, in which case we are on the wrong track. Mortise lock latch plate would be 8" high as opposed to a tubular knob lock which is what I thought it was.