This is a project that I have needed to make but put off for around 18 months now. In our old workshop we had a huge gas furnace heater so never had an issue with opening the roller door when carrying out a lot of timber cutting. Now we rely on a wood stove the heat isn't as instant so we ended up keeping the door shut when working on big projects which wasn't the best idea. My chest was not pleased with this stupidity and so the need for an overhead guard was born...
To buy a 'turn key' option I was looking at between £500 and £1500 which is extortionate for what it is, the table saw only cost £900 new! I had a chat with some people on Facebook and a few other forums, to come up with some ideas and this is my design. Its been made from a mixture of 18mm Hardwood Faced plywood which has been laminated in places for strength and 3mm clear Acrylic for the guard. There were a few issues along the way but for the most part it was a fun build, one big one being an issue with the timber dropping due to the use of a single hinge on the outer arm but after a bit of a play I figured something out. The fix was a section from a centenary wire kit which was bolted to the ceiling joists.
The unit is hinged on both joins and so can move however I have a couple of stop blocks screwed in to keep it rigid. The saw is placed in front of the roller door so I want the option to swing the arm out of the way if I need to move the saw but its not something which will be done every day so thought this was the best option. I also might add a slider on it so I can move the guard left to right but haven't decided just yet.
The "paddle" arm moves up and down, it has a small 6mm slot cut into it and the bolts are secured using 50mm washers and butterfly nuts. Its not the most pretty of designs but it works well and its quick which is what we need.
I used a mixture of 4" spiral steel ductwork and 4" flexi pipe. It work pretty well, the flexi duct is old so its yellowed which I'm not super pleased with. Might end up replacing it at some point but as its so expensive it can just stay as it is at the moment. We don't have any issues with air leaking and that's the main thing.
The unit works as it should and has vastly improved the dust collection in the shop without limiting my options like a normal guard. We do alot of work on sleds so I need the ability to be able to use a guard that isn't connected to the riving knife.
FYI - I did use the shop laser cutter to cut the plywood and acrylic for the actual guard but everything else was built by hand. In all fairness, this could have easily been made with a jig saw or scroll saw and a drill if you really wanted to and lets be honest, who wouldn't use the tools they have at their disposal!
I would be genuinely interested in what you guys think and if there is anything I missed or could have done better. The hive mind is awesome for this sort of project so feel free to ask any questions!
I created a couple videos on Youtube detailing the process if anyone fancies having a look, just tap the link in my signature.
****EDIT****
Just adding this edit in here to deal with any issues, next time I will make sure to add all info in....trying to post things on a Sunday afternoon and I forgot to include some of the details.
Acrylic - Yes I have used 3mm acrylic as this is what I had on hand and able to run through the laser machine. I will be upgrading this to Polycarbonate but for the time being the main issue is dust extraction, not guarding the blade.
Rigidity - The whole boom arm does not move, at all. In terms of the guard, there is approximately 10-15mm flex either side and I think Im going to deal with this by changing the butterfly nuts to DIY wooden knobs which will allow me to add in plenty of clamping force. When the butterfly nuts are tight, there is no lateral movement
HVLP vs HPLV - I spent a long time researching CFM, reading Bill Pentzs ideas and speaking to HVAC companies when designing my original duct work system for the workshop. We run a Felder AF16 and 6"/150mm metal spiral ductwork on the other side of the shop so I would like to think I understand a fair bit. For this side we just have the Charnwood 2hp extractor which has 5" port reduced down to two 4" ports. There is a 4" hose which goes to the base of the saw and the other port is plumbed into the overhead guard.
Hose Placement - The issue we are having is when cutting long boards we get the tiniest of hits at the back of the cutting kerf which is throwing dust into the air and into my space. The placement of the hose is such so that as the dust flies up it should get sucked directly into the hose port on the top of the guard.
Riving Knife Guard - We do a huge amount of sheet timber cutting, alot of this is using custom built sleds and as such a riving knife guard wont work. We need to be able to keep the top of the riving knife free to allow this. I dont really know why they keep the ports so small on the top of the guards, I would think its easier to manufacture and ship a flat guard then it is a wide one with a 4" port. Felder uses an 80mm port on their overhead guard.
Guard Height/Location - Its worth noting that the guard is never meant to be within more than 25mm of the cutting surface which is why there are no brushes or a sloped lead in. This is by design as with a lot of the thinner boards we cut, there is a tendency to warp and this would cause us further issues when cutting if the timber hits the guard. As for the location and hitting the saw blade, unless there is a catastrophic failure with the boom arm, the guard shouldn't be able to come within 25mm of the blade. Again, I understand that we need to plan for the worst case which is why we will be upgrading the guard to polycarbonate and we always use glasses when cutting, regardless of a guard being in place or not.
To buy a 'turn key' option I was looking at between £500 and £1500 which is extortionate for what it is, the table saw only cost £900 new! I had a chat with some people on Facebook and a few other forums, to come up with some ideas and this is my design. Its been made from a mixture of 18mm Hardwood Faced plywood which has been laminated in places for strength and 3mm clear Acrylic for the guard. There were a few issues along the way but for the most part it was a fun build, one big one being an issue with the timber dropping due to the use of a single hinge on the outer arm but after a bit of a play I figured something out. The fix was a section from a centenary wire kit which was bolted to the ceiling joists.
The unit is hinged on both joins and so can move however I have a couple of stop blocks screwed in to keep it rigid. The saw is placed in front of the roller door so I want the option to swing the arm out of the way if I need to move the saw but its not something which will be done every day so thought this was the best option. I also might add a slider on it so I can move the guard left to right but haven't decided just yet.
The "paddle" arm moves up and down, it has a small 6mm slot cut into it and the bolts are secured using 50mm washers and butterfly nuts. Its not the most pretty of designs but it works well and its quick which is what we need.
I used a mixture of 4" spiral steel ductwork and 4" flexi pipe. It work pretty well, the flexi duct is old so its yellowed which I'm not super pleased with. Might end up replacing it at some point but as its so expensive it can just stay as it is at the moment. We don't have any issues with air leaking and that's the main thing.
The unit works as it should and has vastly improved the dust collection in the shop without limiting my options like a normal guard. We do alot of work on sleds so I need the ability to be able to use a guard that isn't connected to the riving knife.
FYI - I did use the shop laser cutter to cut the plywood and acrylic for the actual guard but everything else was built by hand. In all fairness, this could have easily been made with a jig saw or scroll saw and a drill if you really wanted to and lets be honest, who wouldn't use the tools they have at their disposal!
I would be genuinely interested in what you guys think and if there is anything I missed or could have done better. The hive mind is awesome for this sort of project so feel free to ask any questions!
I created a couple videos on Youtube detailing the process if anyone fancies having a look, just tap the link in my signature.
****EDIT****
Just adding this edit in here to deal with any issues, next time I will make sure to add all info in....trying to post things on a Sunday afternoon and I forgot to include some of the details.
Acrylic - Yes I have used 3mm acrylic as this is what I had on hand and able to run through the laser machine. I will be upgrading this to Polycarbonate but for the time being the main issue is dust extraction, not guarding the blade.
Rigidity - The whole boom arm does not move, at all. In terms of the guard, there is approximately 10-15mm flex either side and I think Im going to deal with this by changing the butterfly nuts to DIY wooden knobs which will allow me to add in plenty of clamping force. When the butterfly nuts are tight, there is no lateral movement
HVLP vs HPLV - I spent a long time researching CFM, reading Bill Pentzs ideas and speaking to HVAC companies when designing my original duct work system for the workshop. We run a Felder AF16 and 6"/150mm metal spiral ductwork on the other side of the shop so I would like to think I understand a fair bit. For this side we just have the Charnwood 2hp extractor which has 5" port reduced down to two 4" ports. There is a 4" hose which goes to the base of the saw and the other port is plumbed into the overhead guard.
Hose Placement - The issue we are having is when cutting long boards we get the tiniest of hits at the back of the cutting kerf which is throwing dust into the air and into my space. The placement of the hose is such so that as the dust flies up it should get sucked directly into the hose port on the top of the guard.
Riving Knife Guard - We do a huge amount of sheet timber cutting, alot of this is using custom built sleds and as such a riving knife guard wont work. We need to be able to keep the top of the riving knife free to allow this. I dont really know why they keep the ports so small on the top of the guards, I would think its easier to manufacture and ship a flat guard then it is a wide one with a 4" port. Felder uses an 80mm port on their overhead guard.
Guard Height/Location - Its worth noting that the guard is never meant to be within more than 25mm of the cutting surface which is why there are no brushes or a sloped lead in. This is by design as with a lot of the thinner boards we cut, there is a tendency to warp and this would cause us further issues when cutting if the timber hits the guard. As for the location and hitting the saw blade, unless there is a catastrophic failure with the boom arm, the guard shouldn't be able to come within 25mm of the blade. Again, I understand that we need to plan for the worst case which is why we will be upgrading the guard to polycarbonate and we always use glasses when cutting, regardless of a guard being in place or not.
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in time you might make a little tweak here and there but from what I can see you have made a great addition to your shop 
