I'm about to fit some sash balances to some of my sash windows. In case you haven't come across them, these are springs contained within 15mm plastic tubes, and are used instead of conventional cords and weights for counterbalancing the windows.
In order to fit these, I have to make some channels in the outer vertical edges of the sashes. These need to be 16mm wide and 16mm deep, but with rounded bottoms so that they will slide nicely on the tubes.
I have invested in a rounded bottom router bit from Axminster (like this
I have a few questions:
Should I use this bit for the whole job, or should I remove most of the material with a few passes of a circular saw first, and just use the router to finish off?
At what speed should I run this bit?
If using the router bit for the whole job, how many passes should I make
- presumably not just one full depth pass?
I'm familiar with the concept of moving the router in such a direction that the cutting edge is cutting into the material - but what happens when you're cutting a groove the same width as the bit diameter - so that you've got one leading edge and one trailing edge, so to speak?
Any constructive comments (preferably not "If I were going there, I wouldn't start from here"!) will be greatly appreciated.