I’ve helped out a neighbor who has a LG stove. The oven knobs are notorious for wearing out and breaking the poorly engineered plastic that surrounds a D post. Unfortunately LG and others want to charge anywhere from $35 to $40 per knob to replace the defective knob with another that will fail in a similar fashion.
There is a gentleman on the internet (http://lgknob.com/) who has manufactured a very fine metal replacement but it also expensive.
Below are a series of photos demonstrating how to resolve the problem with a $6.50 oven knob kit.
From Home Depot purchase a $6.50 knob replacement kit. It includes a number of various sized D post inserts. Select the size that will fit your LG oven knob D post
Close up of the LG knob and its broken post
LG knob with top and metal insert removed
The work to be done is to trim the hard plastic D insert to fit into the LG knob plastic and metal pieces
Using a utility knife, carefully trim one end to fit the LG pieces. Trim it so it is angled so that the leading edge will fit thru the holes and remain snug after fitting
Test fit a number of times until the insert is thru the hole and remains snug
Now that the D insert is fitted, we need to trim down the old plastic post that failed
Here you can see how the new D post sits and how much we need to trim the old post so the metal insert meets the top of the knob
I’m using a oscillating tool to cut thru the plastic post
Progress on timing the post
Checking the fit. Trim many times and keep checking fit
Having trimmed down the post the metal insert now meets the top of the know and can be screwed back together
Bottom of the knob with the screws back in place and the new harder plastic insert ready to be installed onto the stove.