Preamble : I don't want to write another list of what each woodworker should know in order to work safely. Everybody may find what matters using a search engine with key words "woodworking safety". Albeit all these articles talk to the others and I would have liked to find someone writing : "for my own safety I try to..." which means many more people convey a standard point of view about safety without wondering anything. I avoid these kind of topic that lead to nothing most of time. On the other hand I get involved in every exchange that tend to explain why something would be unsafe et try to find out a better way. It's all about mental attitude and the last one requires the point of view to be argued. Nothing good nothing bad but keeping open minded.WhyDi

I used to shield my fingers with that over arm blade guard although I knew it was not an enough safe device. After much consideration I came to the only reasonable decision : I had to dismantle the guard and design an effective one. To comply with known regulations I had to devise one that should prevent for damages whatever the sawing angle which means I should have built a narrow guard to cut at a ninety degrees angle and a larger one aiming bevelled cuts. Of course I could have replaced both with a large hanged cover but this matched only the single operation machines. The combination ones raise some other very essential needs. The guard should be quickly replace and remove but also never get in the way when shaping or planing as well as thicknessing and mortising. The only way to solve that first need was to come back to the origin mechanism where the riving knife held the over blade guard. The issue was to find out a satisfactory solution that could allow quick lift and sit guard but also non through cut riving knife and efficient dust collection.

As I had previously modified the blade housing I knew it held a thick cast aluminium plate accommodating the riving knife holder. It was the right place to start and if I achieved a satisfactory modification I could go further.

The two-position riving knives can be quickly raised and lowered without tool and are designed to never contact the balde teeth, at least during common sawing operations.

Here is the over blade guard that just needs a three quarter revolution of the bristol lever to go from the riving knife to its base bolted onto the rip fence. Lastly the over arm hose fitting connects the blade guard dusthood within some seconds (first image above). Over guard dust collection really matters but not all the time. Relying on my own experiment I am always be using the blade housing extraction (second drawing above) but the balde guard one is not needed when cutting some stocks which represent 80% of my sawing time.