RichardG
If at first you don’t succeed have a cup of tea.
I never seem able to keep the fence at 90 degrees in planer mode. There is a stop but I find that no matter how tight you do the clamp it seems to move. At some point I’ll probably made a fixed 90 bracket as I almost never use any other setting.
The following mod does improves things but still allows for other angles. There’s a flange where the 90 degree stop hits. I drilled this out and then replaced the bolt with a socket headed bolt and the existing half nut. This allows you to simply lock the fence at 90 degrees and allows fine tuning to get it spot on. Hopefully the pictures explain all. Make sure that the bolt length is sufficient to use nearly all the threads of the casting.
The following mod does improves things but still allows for other angles. There’s a flange where the 90 degree stop hits. I drilled this out and then replaced the bolt with a socket headed bolt and the existing half nut. This allows you to simply lock the fence at 90 degrees and allows fine tuning to get it spot on. Hopefully the pictures explain all. Make sure that the bolt length is sufficient to use nearly all the threads of the casting.