DIY Overhead crown guard with dust extraction.

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Tugalis

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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.

OverheadG - Whole unit.jpg
OverheadG Saw Guard.jpg
OverheadG - Boom Arm.jpg
OverheadG - Washers.jpg
 
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MARK.B.

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Any improvement verses no guard at all has to be a good thing (y)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 :)
 

Tugalis

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Thanks Mark, I think you are right. We always used the riving knife but I think this will make work a lot safer, it only takes a millisecond to lose a finger!
 

EddyCurrent

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Fully agree with you on the rather high price of those units.
I'm not keen on the metal screws, nylon may have been better.
 

DBT85

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I've been thinking about doing similar for mine so this is an interesting build to me. I have been wondering whether I might try and build something with no metal like screws near the blade just in case it deflected or dropped. Maybe over worrying.

Would be nice to have a proper volume of air being sucked off the top though. Ghe stock guard in the Sip 01446 has a 20mm air port!

I'll give the vids a watch later though! Very nice.
 

Tugalis

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Mark - For sure, dont want to lose them lol.

Eddy - Yeah I dont understand the price of them. I think it must be something to do with the insurance liability maybe? Good shout, it never even occurred to me to use nylon screws to be honest. Ill bare that in mind for the next build or see if I can find some.

DBT - I think thats a fair enough concern to be honest. It didnt even cross my mind so I might change them out moving forward. The amount of air being moved is ridiculous. It can lift up a 5kg weight out right and move a 10kg weight so its got some suck!
 

Jacob

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Whole thing looks a bit flimsy! It needs to be solidly engineered - remember Steve Maskery's "flying Suva" guard?
You can get your fingers under it but you couldn't get a push stick near it - should be the other way around if anything.
Not easy to adjust.
You don't need so much extraction off the top - nearly all the shavings go down, which is where your LPHV extraction should be - from under the table.
A crown guard on the riving knife is a much, much better option and most designs have an extraction port for high pressure low volume dust extraction, which yours does not have.
Back to the drawing board in my opinion!
Good try though.
PS is "acrylic" strong enough? Steve's "flying Suva" guard caught the blade after a little nudge and got yanked round and shattered/exploded, injuring his finger in the process. Could have been worse!
To be honest - I think your design is potentially dangerous.
 
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Inspector

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You stated you used acrylic in the construction. I hope you were using it in a generic way and that you are actually using polycarbonate (Lexan is a trade name) rather than Perspex / Plexiglass. Perspex shatters where Lexan does not. That is why Lexan is used in face shields and machine guarding. Much safer product for a saw guard.

Moving the dust hose to the front half of the guard will pick up more dust than from the present location nearer the back. Also if it is set tight to the wood or floating on it having the back end open allows makeup air into the guard. If you use it above the wood a little the air is coming in from all sides.

Those observations aside, a good overall guard.

Pete
 

DBT85

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@Jacob I don't think I've ever seen anyone with both hplv and hvlp on a table saw before though I can understand the reasoning. Do you run yours in such a fashion?
 

Jacob

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@Jacob I don't think I've ever seen anyone with both hplv and hvlp on a table saw before though I can understand the reasoning. Do you run yours in such a fashion?
No I don't but I suppose I might use the top port if I was cutting a lot of MDF or similarly dusty stuff. As it is all the extraction is LPHV from below. This is a version of my machine. You can see the top extractor port on the crown guard. It's towards the back because the fine dust tends to come back up with the blade, with the coarser stuff safely extracted below - duct out of sight on the back.
On Tugalis's machine nearly all the dust will go down just the same, with only a little emerging back above the table.


Screenshot 2021-03-21 at 19.06.22.png


Had a quick google - nearly all the crown guards have a small top extractor port the same table saw crown guards - Google Search
 
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Doug71

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@Jacob I don't think I've ever seen anyone with both hplv and hvlp on a table saw before though I can understand the reasoning. Do you run yours in such a fashion?

I do, well kind of.

I have a Record DX 4000 on the bottom of my saw (think it's actually classed as hplv but it takes a 4" hose). When I split it to go to crown guard the extraction really seemed to suffer, I had a spare shop vac kicking around so put that to the crown guard instead. They both turn on together with remote switches, works really well.
 

Doug71

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I need an overhead crown guard but my saw is in the middle of the workshop so it will have to be freestanding.

I'm kicking myself because there was an Axi one on ebay local to me for £75 a while ago but I didn't have a saw to warrant it at the time :rolleyes:

I quite like Mike Farringtons version, love his laid back presentation style.



TBH I will probably end up buying the £300 Axi one as it will cost me more in time and materials to make one.
 

Jacob

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I need an overhead crown guard but my saw is in the middle of the workshop so it will have to be freestanding.

I'm kicking myself because there was an Axi one on ebay local to me for £75 a while ago but I didn't have a saw to warrant it at the time :rolleyes:

I quite like Mike Farringtons version, love his laid back presentation style.



TBH I will probably end up buying the £300 Axi one as it will cost me more in time and materials to make one.

Dear oh dear another dodgy flimsy gadget! I didn't realise there was a fashion!
Same very basic mistake; LPHV extractor above where it won't shift anything - it's really needed below.
Not to mention the overall flimsiness.
Here's Steve's job The importance of practising what one preaches different design but the same problem - flimsy construction and wrong materials.
I don't know why there's a prejudice against riving knife crown guards - they are very safe and sensible, not least because they move with the saw adjustment and stay permanently in position.
 
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DBT85

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Dear oh dear another dodgy flimsy gadget! I didn't realise there was a fashion!
Same very basic mistake; LPHV extractor above where it won't shift anything - it's really needed below.
Not to mention the overall flimsiness
I thought the whole point of lphv was that it was able to bring in enough volume to catch all the finer dust that you said comes back above the top?

If I'm honest I'd not put much stock in the small crown guard ports being there because you're supposed to use hplv and more likely just because companies aren't thinking about it properly. The machines don't mention it in any literature and in fact just ask for a large volume.

I have a suspicion that all the saw stops that actually have the guard and extraction fitted (hahaha no but really some do!) have 50 or 60mm ports designed to be used with lphv.
 

DBT85

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I do, well kind of.

I have a Record DX 4000 on the bottom of my saw (think it's actually classed as hplv but it takes a 4" hose). When I split it to go to crown guard the extraction really seemed to suffer, I had a spare shop vac kicking around so put that to the crown guard instead. They both turn on together with remote switches, works really well.
Same hplv as me then there Doug. Where did you find the extraction suffered when only using the dx4000? Above ghe table or under the table?
 

Jacob

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......
If I'm honest I'd not put much stock in the small crown guard ports being there because you're supposed to use hplv ......
You are right the crown guard port is not a lot of use for the simple reason that nearly all the sawdust goes down under the table, which is where the extraction is needed. Only a little fine dust finds its way back above the table.
 

Doug71

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Same hplv as me then there Doug. Where did you find the extraction suffered when only using the dx4000? Above ghe table or under the table?

I was getting more dust than I expected above the table. On my old saw I had a LPHV to the bottom and shop vac to the top and was happy with it.

When I got a new saw and the Record extractor I hoped I would be able to split the hose and use it for both. I split the 4" hose with a Y then reduced the side going to the crown guard down to 60mm, I guess it might have been better if I took it all the way to crown guard at 100mm then reduced it.

Like I say I had a shop vac I wasn't using so I just ran that to the crown guard and left the Record just doing the bottom of the saw and get good results again.

Also my saw is designed to take a 5" hose at the bottom so I thought I had better have as much extraction at the bottom as possible.
 

ndbrown

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I am seeing good results on mine with a hvlp set up 100mm below and 50mm above connected to the same outlet. I roughed mine out in plastic pipe and plywood to try the concept and then manufactured it in stainless and aluminium. After a year of use, very happy with the performance
FEF59E75-5F29-4501-AB5C-3D7A0DCBEE4A.jpeg

7C197E5E-F63A-48B2-8B77-D31AFCF4BDF2.jpeg
5A50FB02-AA92-4283-9485-54111E90FEF8.jpeg
 
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Tugalis

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Thanks for all of the replies. I have bunched them all together below, let me know if I have forgotten anything.. Great job by the ndbrown, that pipework is something else!

Replies -

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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