Tool Tip: Removing Cogs from Threaded Sturmey Archer Drivers

 Older Sturmey Archer hubs, such as AW hubs from 1951 and earlier, have threaded drivers rather than three-spline drivers. This makes removal of the cog more difficult because it is screwed onto the driver rather than snapped-in using the circlip spring.

As the rider rides the bike, it tightens down the driver to a point that it is very firmly in place on the driver. 

 

 

Here is how I remove these threaded cogs:

1. Remove the driver from the hub. Remove the dust cap and bearings. Clean the driver and check that the bearing surfaces are clean and not pitted.
2. Put a stout adjustable wrench into a strong bench vise. Don't use a clamp-on vise for this; use a bolt-down vise on a heavy work bench. 
   
3. Slide the driver onto the thick end of the wrench handle close to the jaws of the wrench. Make sure that the wrench is slid well into the vise. There should be just enough room between the head of the wrench and the side of the vise that the driver can fit. See the above photo and below photo for the positioning of the wrench in the vise (note how close the head is to the vise - it's not sticking way out).   
4. Mount your chain whip (again see the photo above and the one below). Connect to as many teeth on the cog as you can.
5. Trickle some Kroil or similar creeping oil into the threaded joint between the cog and the driver.
6. Heat the cog around the threads using a propane torch. Heat it evenly going around and around. Keep heating gradually until the Kroil in the threads begins to bubble. CAUTION: if you heat it too much, you will start a fire or smoke out the oil.
7. Apply a little more Kroil to the heated joint. Let it cool for a couple of minutes.
8. Begin ramping up torque on the chain whip. Gradually build up you pull.
9. Apply additional heat and Kroil if the cog won't move.
10. Repeat until the cog unscrews.  
11. Carefully remove the cog, spacer(s) and dust cap. CAUTION: they are hot.
    

Once you get the hang of this, you should be able to save many of these old, threaded drivers. Your threaded driver is now able to take a larger rear cog (track style cogs will thread-on), or even a thread-on multi cog, such as a Cyclo bloc for hybrid gearing.