Thread: TS Overhead Guard Extraction

http://www.sawmillcreek.org/showthre...n-from-the-top

Post 6 in this thread shows the original brush guard with the overhead arm that was used. It may give you some ideas.

Cheers. I have been looking around on the net and saw some of those spiral spring sash window mechanisms that allow one to open and close a sash window with a minimum of fuss. I think Whitco make one as short as 350mm which would work for me. The way I'm thinking, I could make a simple vertical timber post which adjusts up and down via a Kipp lever, and install the spiral spring in the middle of the post to support the weight. I like the use of T-track on the guard on the sawmill thread you posted. Very nice indeed!

Just need to find a source of spiral spring mechanisms -- all the places I've looked on the internet say "trade packs" in the quantity description!

Great thread. Some interesting stuff here.

Regarding making "trim cuts" where the blade wants to throw material out of the side of the guard opposite of the fence (especially when the cut is the thickness of the blade or smaller), I have temporarily solved the problem with a piece of 40X40X300 timber. It is positioned against the side of the guard. Dust bounces off it and is swept away. Not a final solution, but it will do until I steal Chris's idea.

On my existing guard I removed one piece from the back to ensure enough air was getting in. Works fine.

The only real problem I have now is that little puff of dust that is thrown forward as the blade exits the wood. If using a sled or my shop made mitre, this is not a problem as the blade does not exit. But when ripping I still get that small puff of dust. However, the saw's dust collection system works a treat in every other respect. A longer brush at the front may help. It would not obscure vision, and may do the job ... one more mod I might try after stealing Chris' idea and fiddling with it for a while.

Here is an update on my TS Guard. It has taken me much longer to make than I anticipated, but finally, here are some pictures.






As you can see (hopefully), I have tried to incorporate BobL's suggesting that the flex duct should be located at the front, as close to 30 degrees as possible, so the material is simply thrown into the flex and aids extraction. The flex is 140mm, and is now well balanced with a 160mm duct below table, which feeds into a 200mm duct line over head.



At first I thought I was going to use springs or some other mechanism (reverse gas strut?) to help hold up the guard. I know others have used a counter balance weight which is effective but my shop is too cramped and I cannot afford the space. You can see in the above photo that I have a horizontal harm extending forward over the top of the guard to which I was going to attached the springs. However, I've used nylon nuts on the bolts and these actually hold the guard up quite nicely. The nuts have to be nipped up quite tightly in order to avoid the guard settling from machine vibration, so it is not super convenient. However, it can be moved up and down with a little application of muscle power! I'll live with it for a while and see how I go...



The dovetails are entirely unnecessary, but I just got a bad axe tool works dovetail saw so I was keen to try it out. Very nice indeed!




The above photos show what was left on the table saw after approx 1 hour of solid ripping (a bunch of New Guinea Rosewood). These are all heavier chips and come almost exclusively when trimming the side of a board -- i.e. not the full-width of the saw blade. As this is not fine dust I'm not too worried about them. That said, I can see how brushes (BobL and Chris style) would certainly help. I'm also keen to try to use mag switches inserted into some timber which I can use to block the left hand side of the guard when ripping (fence on the right). I was thinking of incorporating some steps into the timber so I can use the guard for say 1/2" 3/4" and 1" stock (which would cover most of my needs).

I don't have airflow measuring equipment but the suction is considerably better than the horrible Felder guard I previously had. I assume this guard is not going to be desirable for many, as visibility is seriously impeded by the position of the flex. That said, I can still see to set up rip cuts, and this is what I use the TS for most of the time.

Thank you for your ongoing input over many months. I'm still open to improvements, including ditching this guard and starting from scratch again! I reckon dust extraction solutions are incremental -- this one is better than my last one -- and maybe in the future I'll make another one that suits my needs even better.

Cheers.

A nice looking job.

As you say, an improvement over the original, I could certainly live with the bits on the table after an hour of work.

Something to ponder....I think it might be on one of the Felder saws but the blade guard has a wheel on the front of it, thus when a piece of wood is pushed upto and under the wheel the wood lifts the hood and allows the wood to slide under thus keeping the hood close to the work, and then dropping down as the work leaves the cut.

You would need to allow the center hood attach point to pivot (loosen off the nut/s) and then allow the same thing (pivot) with the arms that hold the hood.

To take that a step further you could have a split hood, basically two halves of the same thing that lift up independant of each other, so for a trim cut (less than blade width) one half stays on the table while the other lifts up when the board is pushed thru.

I would have taken the front section a lot higher before putting the extraction point on purely for visibility reasons.





Pete

Another problem is if the full length of the hood is sitting on the timber being cut extraction will basically cease because the hood has no method of replacing the extracted air. All hoods I have seen suffer from the issue but there are many problems with the whole concept that have never been addressed and it is just one.

Originally Posted by Chris Parks

Another problem is if the full length of the hood is sitting on the timber being cut extraction will basically cease because the hood has no method of replacing the extracted air. All hoods I have seen suffer from the issue but there are many problems with the whole concept that have never been addressed and it is just one.

That's why I reckon that the back of the hood should always be left partially open.

Originally Posted by pjt

. . . . .I would have taken the front section a lot higher before putting the extraction point on purely for visibility reasons.

Yep that's where mine really works well, although I wish the dust collection was a bit better.

I do not agree with that, I think there should be a short inlet into the shroud. If it has a properly designed baffle across the air inlet there is no way dust can escape. A rear opening if used with an insufficient air flow will allow dust to escape and not everyone either realises that or has a DE that flows enough air to guarantee no dust escape through the rear opening.

Pete: interesting concept although it would necessitate a complete redesign and build on my part. Perhaps for 2016! I agree that the front section could have been made taller to aid better vision to the blade, but I was trying hard to capture BobL's notion of having a flex port directly in line with the majority of the material being thrown off the blade.

BobL and Chris: the whole back of my guard is open; I guess I didn't take good enough pictures of that part. That said, there is definitely not enough cross section to allow for adequate air flow. As long as the guard is off the table, lots of air gets in under the sides, but probably not enough. I do know that I made one cut on a very wide board (280mm) and the guard happened to centre over the surface of the board so there was no usual "gap" on the left side (opposite the fence) for air to come in. It actually sucked the entire board up a quarter of an inch, which proves that the open back is not enough for my 140mm flex port. The back opening is 150mm wide by 80mm high. Chris, how big are the inlets you're thinking of? And wouldn't the baffle seriously hinder airflow, something we are trying to increase? BobL, what do you think about drilling some large holes on both sides of my guard? I'm thinking that this might help with my airflow problem? I made the guard so wide to try to help it breath, but in the end I should have made it taller so that the back had a larger cross-section. I don't have the dust counter to see if your suggestion that dust is coming out that back area Chris. That would be an interesting experiment, although I would have thought the flow of the blade, and the position of my flex port, would negate much/any (?) dust escaping out the back...

I would make the whole top area less the extraction port open with a suitable baffle to stop dust being ejected. I made a baffled inlet on one design which was a failure for other reasons and it easily flowed enough air to supply a 100mm extraction port on my Clearvue. Properly designed there is no need for more than 100mm extraction as the dust is already trapped and airborne in a confined space. The problem from my perspective is no one has really sat down and thought about all the issues surrounding the overhead guard and there needs to be some innovative thinking to get the final answer. When my health improves and I have nothing else to do I will have to rebuild mine in good material that does not fall apart. It is still not the final answer as it has shortcomings I have already identified.

Hi ...

I am resurrecting this thread because I am about to embark on building an overhead guard for my TS. Now - I will say upfront - its only a Triton - but one day it will be replaced with the real McCoy - and in any respect - it still spews dust all over the bloody place.

In reading the earlier parts of this thread - I really like where LDs design ended up; and, with an eye to continual improvement would like to make the following suggestions and invite comments.

1. I think I would prefer a system where a spring or gas strut lifted the guard off the table by default - and it must be fastened down into position. That way - in the event of any locking failure - the guard gets up to safety rather than dropping down onto the saw. In many designs I have seen so far - the default position is to have the guard drop to the table rather than lift into the air. I think that worries me.

2. Someone mentioned the "last puff" of dust as the saw exits the cut. I wonder if this can be addressed by a hinged front similar to what Jason Beam has done in this video: https://www.youtube.com/watch?v=cxZOO_zcpNM That way, as the timber is pushed beyond the front of the guard, the front drops down against the table providing physical barrier to chips/dust being thrown forward.

3. Someone also mentioned taking half blade cuts and the dust exiting sideways. Again - potentially resolved in a similar fashion to Jason's video ?

4. Along those lines, I wonder if having the front as two hinged pieces - with one on the left of the blade, and another aligned to the right of the blade might be beneficial.

Thoughts welcome !!

Originally Posted by Glenn.Visca

1. I think I would prefer a system where a spring or gas strut lifted the guard off the table by default - and it must be fastened down into position. That way - in the event of any locking failure - the guard gets up to safety rather than dropping down onto the saw. In many designs I have seen so far - the default position is to have the guard drop to the table rather than lift into the air. I think that worries me. !

Mine uses a steel counterweight up against a wall. The CW is attached by SS wire up to a pulley near the roof, then across to another pulley directly above the guard. The guard is on the end of an elbowed Dust Picker arm attached to the ceiling. The guard position is ilocked in place by a plastic handled locking bolt near the Dust Picker elbow. The whole shebang is just under balance so if I loosen the locking bolt or it becomes loose by itself, the arm and guard lift up. I can move the guard into place and a light twist of the locking bolt handle will hold it at that position.

A front hinged panel is a good idea.
I reckon long bristle edges around the guard provide a better all round seal.

The dust collection port has to absolutely be at the front like LDs and the back has to be fully open to maximise fine dust collection.