The hallway of our new house is quite dark so we looked at getting some windows installed. My wife found some stainless-steel portholes online which fitted the style of the door. The challenge is to cut a big round hole into a door which is 44mm thick. It needs to be reasonably accurate as there is only so much adjustment in the window.
I mentioned this on twitter and a circle cutting jig was recommended. I found this simple one from April Wilker which explained what I needed to create.
The process for making it is on her page quick and easy circle cutting jig for a router
I also found some adjustable ones so I decided to make something along those lines. After tracing the base of the router, I marked out the main slot. These are the only things you need to get accurate. I ensured this slot was parallel to the side so that I could use the adjustable fence to get a straight slot.
The slot was the first thing to cut, I clamped the MDF to the workmate and set the fence so that the router was 1mm off centre. I cut a slot using a 6mm bit then adjusted 1mm off centre the other side and cut again. This results in an 8mm slot.
Then a freehand pass around the cut-out and again around the outside. I used a surform to smooth off the rough bits.
Next up is to drill some mounting holes and to create a sliding pivot. Most people seem to use a tiny nail or point for the pivot. I’m planning to drill a hole through the door and then use a bolt to hold the jig in place. I have a selection of bolts that I could use for this but it will likely be the one on the right which has a nice smooth shank that should act well as the pivot. I may have to cut from both sides to get to the depth required which is another reason to have a drilled pilot hole.