The axle size for the pushnuts used for weber ketle hub caps is 3/8".
It is well documented that you can order them direct from weber. If you are able to wait for shipping, this is a fine option. They are cheap and you get three. Order spares.
It is well documented they can sometimes be found locally. If you are able to find them locally, this is a fine option. Sometimes Home centers have them in stock. If you find them, buy spares.
But.
It is also well documented that typically your local Ace Hardware will carry the following:
- a black push cap that looks like the perfect match, but is actually 7/16" and is too big.
- a white push cap that is the exact right size ... except the plastic cap is white. If that is fine by you, knock yourself out. I like original.
Being impatient and desperate, I bought two of each and performed surgery.
I used aviation snips to cut the white plastic cap off of the properly sized but improperly colored white push caps, leaving me with just the metal starlock type fastener. The white plastic cap was sacrificed because it is not needed. Slightly more tricky is removing the starlock type fastener from the black cap. I used pliers to gently compress the black cup so the starlock fastener was slightly bent. Be careful not to scratch the cap surface if you want a pristine cap. I then used needle nose pliers, and a small screwdriver if needed, to carefully remove the starlock from the plastic cap without any marring. It is ok if you bend the starlock washer because it too is sacrificial. You are then left with plain black caps, and just the metal insert from the white caps. Carefully but firmly press the starlock in to the black cap, being sure that you are putting it in the right direction. You see, the white and black plastic caps themselves are the same size!
This worked perfectly for me. It took me just a couple minutes and no swear words.
That being said, it doubles the cost of your already expensive Ace Hardware push caps. It may not work for you. You may be able to save some cost buy buying the properly sized starlock and inserting it in the black cap, but I did not look in to that. You could just paint the white ones black couldn't you. And geeze, why not just wait for the right ones anyway?