Thread: Dust Catching for a Riaial Arm Drop Saw.

BB

I am familiar with radial arm saws, drop saws and even compound mitre saws. Is yours one of these? May need a picture if it is a hybrid.

All three of these saws are difficult machines with which to capture dust as you have identified.

Let us see the machine.

Regards
Paul

there's maybe some good ideas here Miter Saw Dust Collection | Fine Woodworking Knots
and here Dust Collection-Radial Arm Saw | Fine Woodworking Knots

I built my new miter saw bench by the old KISS method, “Keep It Simple Stupid” for I found the more completed I tried to make the dust pick up on the old bench the problem got worse. In the new bench the Centre section of the bench pivots back to create a backing board and the hole in the bench is for the miter saw, air is pull from the top of the blade housing through a 50mm flex hose and the 100mm hose from the dust extractor pulls the dust from the bottom/ back of the cabinet, behind where the saw is stored when not being used, and because it’s at the bottom of the cabinet it creates a draft behind the saw, drawing the dust down (gravity)<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>

Originally Posted by ian

there's maybe some good ideas here Miter Saw Dust Collection | Fine Woodworking Knots
and here Dust Collection-Radial Arm Saw | Fine Woodworking Knots

There is good discussion on the knot 'Miter Saw Dust Collection' forum, and it shows the problems that I am facing, so nothing is new under the sun, as they say.

I have a Ozito, and for the money it does a good job. It is a Compound miter RAS and will cut 600mm with a turn over of the substrate, which only means it cuts 300mm on the radial arm. It has a 10 inch (Notice how deftly I change from metric to imperial) saw blade.

In the Knots forum the users have said exactly what I have found, the dust port on the saws are useless as most of the dust comes from the blade, through the saw gap in the fence and then onwards and upwards in any undefinable direction.

I have seen a builders rig out for these saws which consisted of a sort of a tent around the back of the saw...a bit ungainly for a small work shop.

Thank yous' blokes for your ideas.

I will post a photo of the saw and the problem with the saw in action so that the dust can be seen.

BB

Hi BB,
I have been thinking of making one for my RAS. I have a few ideas rattling in my head.

One is using aluminium flashing to direct the dust under the table into a bin. My saw is mounted on the original frame. It won't catch all of it but will make clean up quicker.


I will post when I get around to building it.

cheers
conwwod

Teh two photos show the mess of my invention. The box is not fixed and I just push it to the side when doing angle cuts.

I have a length of ducting on the outlet hole, and some dust goes through that, but because is t does, it blows the dust already collected back towards the saw.

I am wondering if I connect the 4 inch dust extractor to a fitting in the box if it will suck t he collected dust out?

There is dust on top of the box, on the floor and on the table that the saw is attached to, and even some in the box.

Naturally, when the saw is full forward the dust is greater and less inclined to enter the box at all.

Thanks
BB

BB,


Your saw is a SCMS (sliding compound mitre saw) rather than a Radial Arm Saw. However both exhibit the same problem of clearing dust.

For my money I would scrap the tube on the dust port and cap it. Then most of the dust will be thrown into the collector box and stay there. My other suggestion us to tweek the box if possible so it has a drop box at the back to collect the dust. If you wanted to run a hose to a dusty, you could bring that into the drop box via the side and draw the dust from the drop box as it reaches it.

Originally Posted by malb

BB,


Your saw is a SCMS (sliding compound mitre saw) rather than a Radial Arm Saw. However both exhibit the same problem of clearing dust.

For my money I would scrap the tube on the dust port and cap it. Then most of the dust will be thrown into the collector box and stay there. My other suggestion us to tweek the box if possible so it has a drop box at the back to collect the dust. If you wanted to run a hose to a dusty, you could bring that into the drop box via the side and draw the dust from the drop box as it reaches it.

Thanks mate, I have thought of that drop box thing. I have to keep in mind the side distance for the miter cuts, but That may be much the same as it is now.

I have never used this saw as a compound angle saw, but I doubt that the dust collection would be much different.

I also need to develop a cover for the back of the saw, below the dust port, as this is the major dust ejection area.

Thank you.

More heads are better than one, even if they are only sheep's heads, My old Daddy used to say.

BB
I can't see anything that would provide negative pressure inside your box

What I think is happening is that the wind from the saw blade is hitting the back of the box and bouncing right back out bringing the dust with it

Can I suggest you add an outlet for a shop vac or dusty to the rear of the box so there is some negative pressure inside the box.

Originally Posted by ian

BB
I can't see anything that would provide negative pressure inside your box

What I think is happening is that the wind from the saw blade is hitting the back of the box and bouncing right back out bringing the dust with it

Can I suggest you add an outlet for a shop vac or dusty to the rear of the box so there is some negative pressure inside the box.

I agree, Ian, and that is the next try out. I also think I need some more catching flaps for when the saw is fully out as the dust is alway deflected upwards it goes over the top of the box; there is dust on top of the box now.

One 4 inch hole coming up!!!!!

Originally Posted by Black Bear

I agree, Ian, and that is the next try out. I also think I need some more catching flaps for when the saw is fully out as the dust is alway deflected upwards it goes over the top of the box; there is dust on top of the box now.

One 4 inch hole coming up!!!!!

I agree with that. You might like to consider bringing the small connection from the saw itself via a flexible hose to the top of the collector box, preferably close to your 4" connection (or directly into it if you have an adaptor).

I have noticed that on my own sliding compound saw the sawdust goes directly upwards into the nozzle while ever the blade is fully in the timber. However as soon as the saw breaks though the timber towards the fence the dust is directed horizontally.

Regards
Paul

Originally Posted by Bushmiller

I agree with that. You might like to consider bringing the small connection from the saw itself via a flexible hose to the top of the collector box, preferably close to your 4" connection (or directly into it if you have an adaptor).

I have noticed that on my own sliding compound saw the sawdust goes directly upwards into the nozzle while ever the blade is fully in the timber. However as soon as the saw breaks though the timber towards the fence the dust is directed horizontally.

Regards
Paul

I think there would be some problem with he hose as the saw goes into the sliding mode. I know you said flexible, but there would be nothing, in that short a length, that would do the job..Plus, I would have to disconnect the hose to remove the box for emptying.

I think that the concept that I am trying to improve must be met with its limitations, otherwise I end up with some monstrous device that still only does half the job.

I will try the 4 inch connection to my dust first and see how that goes.

Thanks
BB

BB
the other thing to try (and I think there was a design at Fine woodworking) is change the box to a triangular one with the point of the triangle behind the blade and the wings covering the full throw of the saw

I'll have a go at this. Build a box with a plenum behind the main box, basically a small are at the back of the box and at the bottom. The inner rear wall does not go to the bottom of the box, the gap being equal to the square area of the dust extractor pipe. If using a 150mm pipe then the area of that pipe needs to be the same as the gap and the pipe is attached to the plenum. Fire up the extractor and all the air rushes through the gap so any dust that is fired into the box falls to the gap and is drawn through it and into the extractor. The problem is most extractors just don't pull enough air and that is the important bit. BTW the back wall slopes away from the top box to the bottom so the dust hits it at an angle. The first link shows the idea in action

[ame=http://www.youtube.com/watch?v=W9Ll10MZMmg]YouTube - Miter saw dust collection hood in action[/ame]

This one shows what a decent air flow does, notice how the dust actually changes direction due to the enormous air flow.

[ame=http://www.youtube.com/watch?v=8AIITfs51PE&NR=1]YouTube - Chop Saw Dust Collection with a Clearvue Cyclone[/ame]

In the end if you want to build a good collector for a mitre saw then it needs strong air flow. This is the main reason so many hoods just do not function as they should. It has to be the hardest tool in the shed to collect dust from.