Thread: Dust extractor for table saw

Let me just go and stop you from blowing any money unnecessarily...

Assuming that the Dewalt table saw extraction port is akin to my sawstop jobsite saw, and just about every other portable table saw on the market being about 2.5", hooking that up to a dust collector will do 2/3 stuff all. So many people think that a bigger extractor is the answer, where as it is usually bigger piping. Dust collectors are high volume/low pressure setups and vacuums are high pressure/low volume setups. Dust collectors work better on larger ports and ducting and vacuums work better on smaller ports and piping.

The portable table saws are designed to work with vacuums, not dust collectors as you'd never drag a dust collector out on site with you. Basically you'll get better extraction on a portable table saw with a $80 ryobi vac than you would a $2000 3hp powermatic dusty. Usually the cheat is to open up the port sizing, but that can't be done on portable table saws. Does your model dewalt have a dust port on the blade guard? I've just recently bought the dust port blade guard accessory for the sawstop portable saw and with both that and the main port hooked up to the vacuum in the shed I get stuff all dust escaping the saw, even using mdf.

Having said that... what model saw do you have? Can you post a pic through the throat plate (remove the plate) from above? Does it have any way to deflect the dust to the port?

Thanks for your answer. I use this saw:

https://www.gettoolsdirect.com.au/de...nS4aAhua8P8HAQ

It indeed has a small port underneath but I bought a plastic connector for 100mm hose. I am not sure if it has any other dust port , I have seen anything like this. I'll have a close look tomorrow but I am skeptical.
How your dust port blade guard looks like ? Do they have it at Carba ?

Ok so that saw doesn't have a dust port on the blade guard, that is one of the reasons I discounted that model from my search when I bought one. Perhaps it can be ordered through a dewalt dealer as an optional part if it exists?

The blade guard with dust port on mine looks like this: http://i126.photobucket.com/albums/p...psqsyfbvo5.jpg Yes, I bought it from Carbatec but it is specific to my saw and won't fit the dewalt. I use this to split the air from the shop vac http://www.festool.com.au/epages/too...roducts/488292 because I could be bothered rigging something up from scratch and by the time you buy all the connectors and hose it isn't much cheaper anyway!

The other issue I forgot to mention earlier is that with the high/low pressure/volume comments I made before is that if you take a dust collector from 4" down to 2ish" it will strangle it for airflow. Hence why you are getting such poor performance vs the bandsaw. If you've got a shop vac use that, if you don't have one, I'd go get one before buying another dust collector.

My comments assume you use the saw in the one place i.e. your shed, and are not using it as a mobile saw?

You will never control all the dust coming from that table saw using a 1HP DC, or a Stock 2HP DC, or any Vacuum cleaner.

A table saw (even a small one) needs as close as possible to 1000 CFM of air flow to control the dust coming from the underneath and on top of the table.
You will need about 2/3 of that 1000 CFM collecting from underneath the cabinet, and 1/3 from the blade guard.

My recommendation is to completely remove the plastic guard around the blade and encase the entire saw in a cabinet or box of ply/MDF or sheet metal.
It does not need to be air tight, in fact it can have quite large gaps (~cm) near the table top as this will help maintain the air flow

Then install a 6" port on the back of the saw and rebuild the blade guard to accept a 4" ducting or flexy - there are plenty of designs for this described on this forum.

For a DC the minimum that will get close to 1000 CFM will be a 2HP DC that has been modified according to the sticky at the top of this forum and uses a pleated paper air filter.
This will generate ~925 CFM, and while it's not 1000 CFM it is far better than a stock 2HP DC with a 4" duct which generates ~400 CFM
For comparison purposes a shop vac pulls about 100 CFM

Then use 6" ducting to connect the saw cabinet to the DC - this size of ducting is absolutely critical and the ducting should be as short as possible, preferably <3m

If you don't want to go through the hassle of modifying a DC then most 3HP DC will do this job and will allow you to use a greater length of ducting i.e. at least 6m long

BTW if you leave the DC inside the shed you will ALWAYS have a fine dust problem.
DCs constantly leak fine dust which is why they should be located outside a shed OR inside an air tight enclosure inside a shed that is vented outside the shed.

It sounds like you need to spend a few days reading the Dust forum to come to grips with the ins and outs of dust collection.

Bob that is all well and good for the 'typical' cabinet saw with a massive void under table. Most modern jobsite saws have venturis built in underneath as they are designed to operate with a shop vac. Is that the best solution? Probably not. Is it a better solution that trying to rig up a $900 saw to a $2000 DC setup? Probably yes.

"My recommendation is to completely remove the plastic guard around the blade and encase the entire saw in a cabinet or box of ply/MDF or sheet metal." What plastic guard are you referring to? If you're talking of taking the throat plate out to aid airflow then no. You'd be better off breathing in the dust than losing appendages as a result of that.

I tend to agree with most of your spill re dust collection, but most people buying a jobsite saw are either looking for portability across sites, or looking for a small footprint saw to be folded up on the stand when not in use, not to add a box around and make the unit more cumbersome. As I said, I get the theory, and agree with it for the most part, but spouting 1000+cfm 6" ports and 3hp every time a questions comes up about dust collection on jobsite saws isn't always the practical answer.

Originally Posted by socratous

Bob that is all well and good for the 'typical' cabinet saw with a massive void under table. Most modern jobsite saws have venturis built in underneath as they are designed to operate with a shop vac. Is that the best solution? Probably not. Is it a better solution that trying to rig up a $900 saw to a $2000 DC setup? Probably yes.

A shop vac will simply not be able to control the fine dust - remember that is the stuff to worry about - the stuff you can see is not going to hurt you.
I have measured sawdust particle size distribution from many different small machinery setups trying to control fine dust using a vacuum cleaner and they simply do not cope.

I don't recall mentioning a $2000 DC setup, A 2HP DC with a pleated filter can be had for about $600. The mods can be done using MDF for about $20 worth of materials.

I tend to agree with most of your spill re dust collection, but most people buying a jobsite saw are either looking for portability across sites, or looking for a small footprint saw to be folded up on the stand when not in use, not to add a box around and make the unit more cumbersome. As I said, I get the theory, and agree with it for the most part, but spouting 1000+cfm 6" ports and 3hp every time a questions comes up about dust collection on jobsite saws isn't always the practical answer.

If you look at my post I did say "I'm assuming he does not move his saw around", and the fact that the original OP doesn't mention portability, a lightweight cabinet is far from a silly idea. It does not have to be a full floor standing cabinet - even a lightweight plastic crate that sits on a bench, cut down so that the saw sits inside it and that has access holes cut into the sides would do the trick.

If portability is an issue I agree with you. Shop vac with an outlet port that can be connected to a 50 mm hose and hung out a window (provided one is available) is about as good as one can do. This is one reason construction carpenters are susceptible to very high levels of wood dust, more so in many cases than any other wood workers , closely followed by wood turners.

Thanks a lot for your recommendations. It is a very interested and useful discussion for may people. I indeed read most of the relevant posts before I asked this question. I'll try to take a few photos to explain better the conditions I have.

It is absolutely impossible to build any wooden cabinet around the table saw. I have to put up that I can't control 100% of all dust but I just want to decrease the main stream.

Also it is impossible to take any DC outside as the nearby house is behind the fence and I do not need any complains.
I am a bit confused with your CMF recommendations. You mentioned at least 1000 CMF. Please have a look at these specifications:

W394 | DC-3 Dust Collector | For Sale Sydney Brisbane Melbourne Perth | Buy Workshop Equipment & Machinery online at machineryhouse.com.au

R872 | RSDE2 Dust Collector | For Sale Sydney Brisbane Melbourne Perth | Buy Workshop Equipment & Machinery online at machineryhouse.com.au

It says that 2 HP DC generates 1200 CMF which is more then enough but PowerRecord shop vac has only 112 CMF. Is it a typo ? I like the PowerRecord machine I tomorrow I plan to treval to that shop and have a close look at it. It has a a bit more expensive model which comes with 2 motors.

Hi Caliqula

Contact Black and Decker the do have a blade guard with a dust port for the contractors saw. You may have to harass one of their reps or chase one up from overseas.

That will help but the other area you need to look at is the vents underneath. I removed the plate and clamped the saw to a table that I had mounted a dust port to.

The blade guard dust port is connected to a shop vac which is vented to the outside and the dust ports under the table and at the back are connected to a Y fitting then to a 2HP

DC60 with a pleated paper filter. There will always be dust, all we can do is to minimize it.

Ross

Originally Posted by Caligula

W394 | DC-3 Dust Collector | For Sale Sydney Brisbane Melbourne Perth | Buy Workshop Equipment & Machinery online at machineryhouse.com.au

R872 | RSDE2 Dust Collector | For Sale Sydney Brisbane Melbourne Perth | Buy Workshop Equipment & Machinery online at machineryhouse.com.au

It says that 2 HP DC generates 1200 CMF which is more then enough but PowerRecord shop vac has only 112 CMF. Is it a typo ? I like the PowerRecord machine I tomorrow I plan to treval to that shop and have a close look at it. It has a a bit more expensive model which comes with 2 motors.

The CFM specs on most dust collectors are absolute lies. The numbers they quote are basically the theoretical maximum airflow that the impeller can generate with no resistance and with no regard for how much HP the motor would need to generate to do so, plus probably adding 50% on top of that number for good measure. You can't trust these numbers at all. The 112CFM is not a miss print.

My Carbatec 2hp dust collector only generated about 250CFM with a short length of 4" hose connected and 350CFM with only 1m of hose attached. That is the reality.

My 5HP Clearvue can just get over a genuine 1000CFM.

Unfortunately there is no simple or easy answer / solution. The guys have provided some good suggestions. A good overhead dust collection guard is a good idea and if money and room is limited a 2HP dusty with the modifications suggested by BobL would also be a good start. Good luck.

Oh, do you have space outside your workspace that you could fit a dust collector in an weatherproof cabinet? This would perhaps allow for a larger 3HP dust collector and also eliminate the issue of poor filtration on most dust collectors effectively pumping a lot of the fine dust back into your workspace air.

Originally Posted by DomAU

The CFM specs on most dust collectors are absolute lies. The numbers they quote are basically the theoretical maximum airflow that the impeller can generate with no resistance and with no regard for how much HP the motor would need to generate to do so, plus probably adding 50% on top of that number for good measure. You can't trust these numbers at all. The 112CFM is not a miss print.

No resistance means no filters, cyclones, ducting or junctions, and especially no Dewalt table saw with a tiny dust extraction port on it.
The manufacturers testing on most cheap DCs is also done using an old industry standard test that is flawed.
Some of the problem is the DC manufacturers have no idea what their products are going to to be attached to so they publish a maximum figure - like fuel economy figures for cars and the times claimed for the standing 1/4 mile in MC magazines. The times being recorded had a team of factory mechanics on hand and 40kg rider.

I indeed read most of the relevant posts before I asked this question. I'll try to take a few photos to explain better the conditions I have.

Reading is one thing - perhaps the significance of what is posted is another.
There are many posts on this forum that refer to the criticality of opening up the ports in cabinets and around blades etc.
The other important point discussed is the size of a duct and post as critical in regards airflow.
A DC attached to 2" ducting can carry no more than about 100 CFM, 4" ducting carries ~400 CFM and it takes 6" ducting to get to 1000+ CFM

It is absolutely impossible to build any wooden cabinet around the table saw. I have to put up that I can't control 100% of all dust but I just want to decrease the main stream.

Just decreasing the amount of dust is not the best approach. Eventually the shed still fills up with fine dust but instead of taking seconds to send a shed over a safe dust limit, it takes minutes,
Dust control is a bit like a leaking boat, the pump has to be close to or faster than the ingress of water or eventually it will sink

If you do not remove that shroud with the small dust extraction port you will not have a hope of even getting close to managing fine dust from that machine.
The enclosure or cabinet does not have to be wood, it can be a lightweight plastic crate/box cut you pop the saw into, the box can be cut to size with holes cut in the sides to all access to the adjustments.

An alternative is to remove the shroud with the small port and see if you can make a new larger shroud or internal cabinet with a large dust port on it.
It can have lots of holes/caps and does not need to seal like the other shroud so that the shroud can slide in from the back or bottom past any mechanical bits.
With such a small machine I reckon if you just removed the shroud, blocked off just the back bottom and sides of the saw, put a 6" port on the back, a modified 2HP DC would easily clear that small saw of sawdust.
1000 CFM is equal to a air sphere with a radius of ~450 mm being removed every second while 800 CFM is equal to an air sphere of radius 440 mm/s, even 600 CFM has a sphere radius of 400 mm/s - the latter two of those are not possible without using 6" ducting.

RE; DC Noise outside
My DC is outside in the ~1m wide gap between the shed and back fence. I have a VERY picky neighbour whose pool and entertainment area is just on the other side of the fence. Using a suitable acoustical enclosure I have the noise level on the fence line from my DC down to less than that of the neighbours pool pump.

Originally Posted by DomAU

My 5HP Clearvue can just get over a genuine 1000CFM.

A 5HP Clearvue should pull about 1450 CFM through 6" ducting and about 2000 CFM through 8"

Originally Posted by BobL

A 5HP Clearvue should pull about 1450 CFM through 6" ducting and about 2000 CFM through 8"

Maybe with a low resistance ducting design but not in my current setup. At least not according to my measurements. May need to redo them at some point.

I have the same saw as the OP -- except it's the 15 amp at 120V Nth American spec. (BTW, the DW 745 retails for around CAD $400).

Neither DeWalt Canada nor DeWalt USA list a blade guard with integral dust collection as an option.
However, remaking the DeWalt guard to include a dust collection port could be feasible.

The die cast saw blade shroud is designed to be connected to a 2-1/2" shop vac hose (and the shroud itself "incorporates" a flow obstruction about 2" inside the port!).

My method for dealing with generated dust is to minimise the length of cutting made inside the garage. Wherever possible, I move the saw outside to use it, even when the outside temp is below zero. I also assiduously avoid cutting MDF.

Given the projects I'm currently working on, I also do most of my cross cutting by hand, reserving the power saw for rip cuts.


In terms of what the OP could do with his saw.
It would be relatively easy to box in the saw's support cage. The box would be pretty leaky, but with a 6" port and 2 hp Dc connected, the leaks would assist air flow to the port.
However, my observations are that most of the dust "thrown" around by the saw is released where the laminar flow associated with blade rotation is disrupted as the blade enters the cut. Capturing this dust requires overhead dust collection.