Overhead Dust Collection on a Modified Ridgid 3650

djg said:

Initial thoughts

About a year ago, I modified my ridgid contractor saw to a workstation setup with lots of storage and some other features like a down draft table and integrated dust collection. I didn't want to spend a whole lot extra at the time to tackle the dust collection above the table so I modified the stock blade guard and hooked up a 2.5" hose to a vacuum which is plugged into a tool actuated power switch. Air is pulled through an overarm type setup that can fold down behind the saw when not needed. The vacuum provides some collection but there is not enough air volume to efficiently collect all particulate which gets beyond the shroud. The splitter has to be removed when doing dadoes and rabbets so collection is sub par during these types of cuts. Over the past few months I have been trying to size up a good solution to this problem.

I like the overarm solution but it limits the cross cutting abilities on my saw. The only way to improve this would be to make the overarm fold down behind as my current setup. I am not particularly fond of the factory splitter and it is a pain to take off everytime I need to do dadoes and rabbets. This screams out "over head dust collection" but there is an issue getting back to my DC main duct without the overarm. So I will do both. An overhead shroud and an overarm duct. More to follow….

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djg said:

Dust collection for my current setup

Now that my thoughts have been put on paper, I figured that it would be useful for others to see my current workstations setup and some details on the design.

The design was taken from an old shopnotes issue. I had to make some modifications to the dimension to accomodate the saw but for the most part the workstation is similar. However, rather than a router table in the right wing, I decided to put a downdraft table. The table saw has quite a bit of storage for storing blades, accessories and sanding supplies. A 6" blast gate is connected to the back of the workstation just behind the downdraft table.

In addition to the dust collection on the downdraft, a 6" duct connects to the botton of the table saw cabinet. getting behind the saw to move the blast gate proved to be a pain so I decide to use an old lawn mower switch cable and one of my wife's hair elastics to make a self closing blast gate. I pull the cable to open the blast gate. When I release the cable catch, the blast gate closes from the tension in the hair band.

I have access to the back of the saw through a cutout in the outfeed table which is removable. You can see I have the back of the saw closed off to help direct the airflow. Several opening in the front of the saw are left open in order to direct airflow from the front of the saw and down inside the cabinet to a chute which connects to the 6" port.

Thats it for now….Next up, I have started cutting parts for my overhead collection.

Click to expand...

djg said:

Dust collection for my current setup

Now that my thoughts have been put on paper, I figured that it would be useful for others to see my current workstations setup and some details on the design.

The design was taken from an old shopnotes issue. I had to make some modifications to the dimension to accomodate the saw but for the most part the workstation is similar. However, rather than a router table in the right wing, I decided to put a downdraft table. The table saw has quite a bit of storage for storing blades, accessories and sanding supplies. A 6" blast gate is connected to the back of the workstation just behind the downdraft table.

In addition to the dust collection on the downdraft, a 6" duct connects to the botton of the table saw cabinet. getting behind the saw to move the blast gate proved to be a pain so I decide to use an old lawn mower switch cable and one of my wife's hair elastics to make a self closing blast gate. I pull the cable to open the blast gate. When I release the cable catch, the blast gate closes from the tension in the hair band.

I have access to the back of the saw through a cutout in the outfeed table which is removable. You can see I have the back of the saw closed off to help direct the airflow. Several opening in the front of the saw are left open in order to direct airflow from the front of the saw and down inside the cabinet to a chute which connects to the 6" port.

Thats it for now….Next up, I have started cutting parts for my overhead collection.

Click to expand...

djg said:

The Blade Guard Part 1

There are so many ideas on the internet for table saw blade guards…Some are good, some are not so good. The main thing is to determine the need and purpose. Well, the need and purpose is easy: Something to cover the blade and provide some way to deter the user from feeding their hand through the blade or making mistakes like trying to pick up a 1/4" cutoff that is sitting next to a spinning flesh shredder! Dust collection is secondary. Here are some issues that I have found with dust collection with a overhead shroud:

1. They sit too far above the table to be effective or they have too many openings compared to the size of the duct used. The velocity of air decreases with the inverse of distance squared. Change the size of the crossectional area that the air is moving through and it compounds the issue. The biggest problem here is when the small harmful dust gets beyond the influence of the suction from the guard, there is little hope of catching it without moving a large volume of air. Most people use a shop vac. This setup can provide some collection with the right setup. A 3" hose is better. However, without the right guard, collection will be mediocre and you will be breathing in everything that escapes the shroud.

2. The mechanics aren't right. Often times, when a board passes under the blade guard, it pivots or raises and exposes a large area under the guard. If this area is substantially larger than the diameter of the duct, air velocity through the open area will suffer. You want both air volume and velocity.

3. It would be nice if you could use the guard in a variety of configurations: cutting dadoes, cross cutting, and ripping. Ripping with a rail in a vertical tenoning jig could be a challenge…But I think I have it figured out…the dust collection that is, and it's simple! Ripping small strips will be doable also.

I'm sure there are more points and I could keep going on but I want to get to the important stuff now: The blade guard. To address points 1 and 2 I had some ideas. However I still wanted to search the internet high and low for alternative solutions and I found this:

I'm not sure if he made up the shroud or copied it but it's a good idea and addresses several problems with 1 and 2 above. The guard has independent flaps on the front and back and each side moves parallel to the table top independently. If you pass a board under the guard to the left, only the left side moves upwards, etc. With this independent setup, it restricts the direction the air is coming from and also dynamically changes the cross sectional area through which the air can move. It looks to be a good solution. With the right overhead mount, offsetting the blade guard and opening one side can provide decent collection and enable operations with a tenoning jig, ripping small strips etc.

However, there are some minor issues with the design…I think. The front and back flaps may open the guard too much which will decrease the air speed in the opening. A bristle door sweep for an industrial garage door may work better on the front and back of the guard. With the length of the sides and possibility of opening too much area for air to flow beyond the already open areas in the guard, a 2.5" or 3" will be ineffective…So here is my plan: I will build the guard similar. It will have independent sides. I will experiment with the front/back flap and see if bristles work better. I will use 4" duct to connect this to my collector system. I will close off the blast gate on the table saw cabinet to an effective 5" opening. This will give me a total cross sectional area of about 32 sq inches which is less than my 7" duct but I may be able to play with numbers….So here is what I have completed so far:

Click to expand...

djg said:

The Blade Guard Part 1

There are so many ideas on the internet for table saw blade guards…Some are good, some are not so good. The main thing is to determine the need and purpose. Well, the need and purpose is easy: Something to cover the blade and provide some way to deter the user from feeding their hand through the blade or making mistakes like trying to pick up a 1/4" cutoff that is sitting next to a spinning flesh shredder! Dust collection is secondary. Here are some issues that I have found with dust collection with a overhead shroud:

1. They sit too far above the table to be effective or they have too many openings compared to the size of the duct used. The velocity of air decreases with the inverse of distance squared. Change the size of the crossectional area that the air is moving through and it compounds the issue. The biggest problem here is when the small harmful dust gets beyond the influence of the suction from the guard, there is little hope of catching it without moving a large volume of air. Most people use a shop vac. This setup can provide some collection with the right setup. A 3" hose is better. However, without the right guard, collection will be mediocre and you will be breathing in everything that escapes the shroud.

2. The mechanics aren't right. Often times, when a board passes under the blade guard, it pivots or raises and exposes a large area under the guard. If this area is substantially larger than the diameter of the duct, air velocity through the open area will suffer. You want both air volume and velocity.

3. It would be nice if you could use the guard in a variety of configurations: cutting dadoes, cross cutting, and ripping. Ripping with a rail in a vertical tenoning jig could be a challenge…But I think I have it figured out…the dust collection that is, and it's simple! Ripping small strips will be doable also.

I'm sure there are more points and I could keep going on but I want to get to the important stuff now: The blade guard. To address points 1 and 2 I had some ideas. However I still wanted to search the internet high and low for alternative solutions and I found this:

I'm not sure if he made up the shroud or copied it but it's a good idea and addresses several problems with 1 and 2 above. The guard has independent flaps on the front and back and each side moves parallel to the table top independently. If you pass a board under the guard to the left, only the left side moves upwards, etc. With this independent setup, it restricts the direction the air is coming from and also dynamically changes the cross sectional area through which the air can move. It looks to be a good solution. With the right overhead mount, offsetting the blade guard and opening one side can provide decent collection and enable operations with a tenoning jig, ripping small strips etc.

However, there are some minor issues with the design…I think. The front and back flaps may open the guard too much which will decrease the air speed in the opening. A bristle door sweep for an industrial garage door may work better on the front and back of the guard. With the length of the sides and possibility of opening too much area for air to flow beyond the already open areas in the guard, a 2.5" or 3" will be ineffective…So here is my plan: I will build the guard similar. It will have independent sides. I will experiment with the front/back flap and see if bristles work better. I will use 4" duct to connect this to my collector system. I will close off the blast gate on the table saw cabinet to an effective 5" opening. This will give me a total cross sectional area of about 32 sq inches which is less than my 7" duct but I may be able to play with numbers….So here is what I have completed so far:

Click to expand...

djg said:

Almost completed!

So my dust shroud is almost completed. I have now completed the overhead mount with guide wires for stalibization. The shroud has been mounted to the overhead mount and counter weighted although I may need a little more weight to make it easier to lift. I have added the adjustment knobs although i am currently short by one.

The overarm duct was constructed using 4" ABS pipe. This setup was a little tricky. I had to use the bill pentz static calculator worksheet to figure out static pressures and air flows. I used the calculator to determine the static pressure of my current setup converted to a 5" duct. According to my previous measurements, the table saw was drawing about 1000 CFM from the cabinet so I know that I wanted the sum of two airflows to be 1000 CFM. I set up two worksheets. One for my 5" duct to the cabinet and one for the 4" overarm with the lengths of duct and the right number of transitions. I varied the airflows in the worksheet until the static pressures from each of the overarm and cabinet were equal but the airflows added up to 1000 CFM. When these pressures are equal, you maximize the airflow through the smaller pipe. My current setup will be giving something like 700 CFM and 300 CFM through the overarm.

Connecting this to the dust collection duct was a little easier than I originally anticipated. I used a 4" saddle and modified the saddle section by bending so it would saddle around a 6" duct. All I had to do is scribe the shape of the 4" duct opening onto the 6" duct and cut it out. THe saddle was screwed and duct tape was applied to seal the gaps.

I connected the shroud to the overarm and the overarm to the main duct using 4" clear pvc flex hose. The overarm duct has a 4" aluminum blast gate that is easy to reach from the front of the table saw. The overarm is able to fold down out of the way to allow for crosscutting wide pieces while still connected to the dust collector. I still haven't tested the setup during cutting but turned it on long enough to determine that the amount of air flowing through the shroud is unbelievable compared to my vacuum setup…hopefully it all works.

Click to expand...