# Important Specs With Shop Vac?



## ghostrider

How important is hose size? How important is sealed pressure?

I know there are other variables to consider. If I'm using a separator and bucket, does the static pressure matter much? 

How important is the size of the hose (1.25" compared to 2.5")?

Will a shop vac with an advertised CFM of 325 work better for dust removal than one with a CFM of 210?


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## Dave Paine

Shop vacs are higher static pressure and lower flowrates than dust collectors.

In general the smaller the hose, the greater the pressure drop. More pressure drop, less flow. Less flow means not picking up the dust.

I have a shop vac with 2 1/2in.

I am not sure what you mean by "sealed pressure".

Higher static pressure normally means more potential suction.
The maximum amount of suction which can be developed if the machine is "dead headed" e.g., putting your hand over the inlet at the vac. This can be a difficult specification to find.

Another big unknown with a shop vac is the "head curve" which is how the flowrate drops with increase in pressure drop either from the hose, or the device connected to the hose.

A CFM rating is likely at the shop vac with no hose connected which is not very meaningful, since we all need to use some length of hose to use the shop vac.

A machine with higher CFM's with no load could perform worse than a machine with lower CFM's in real world conditions, namely hose and device connected.


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## ghostrider

Dave Paine said:


> Shop vacs are higher static pressure and lower flowrates than dust collectors.
> 
> In general the smaller the hose, the greater the pressure drop. More pressure drop, less flow. Less flow means not picking up the dust.
> 
> I have a shop vac with 2 1/2in.
> 
> I am not sure what you mean by "sealed pressure".
> 
> Higher static pressure normally means more potential suction.
> The maximum amount of suction which can be developed if the machine is "dead headed" e.g., putting your hand over the inlet at the vac. This can be a difficult specification to find.
> 
> Another big unknown with a shop vac is the "head curve" which is how the flowrate drops with increase in pressure drop either from the hose, or the device connected to the hose.
> 
> A CFM rating is likely at the shop vac with no hose connected which is not very meaningful, since we all need to use some length of hose to use the shop vac.
> 
> A machine with higher CFM's with no load could perform worse than a machine with lower CFM's in real world conditions, namely hose and device connected.


Shop-Vacs website refers to static pressure as, "sealed pressure" in thier specs. 

Specifically, I'm wondering the difference between the following two, and which one will provide better dust collection for my midi-lathe. 

http://www.lowes.com/pd_314974-2009...+vac&pl=1&currentURL=?Ntt=shop+vac&facetInfo=

http://www.lowes.com/pd_334645-2009...+vac&pl=1&currentURL=?Ntt=shop+vac&facetInfo=

Many machines have the smaller size collection port, and Fein and Festool extractors are used for dust collection while employing the smaller size. 

I think I have a fair understanding of the terminology, but just don't know how that helps me decide which unit will work better for my purpose. I decide on a larger shop vac instead of a portable DC from Harbor Freight, but am now wondering if the DC may have been better. I already have a small shop vac (10 gal, 2.75 hp) as well as a Dust Deputy. I like the idea of some sort of HEPA filtration (I get this with my shop vac, and will eventually build an air filtration unit), so I thought maybe the 16 gal unit from Lowes would fit my need. I'm just trying to make the best decision with what is available to me within my needs and means.


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## Dave Paine

I much prefer a larger hose so I would chose that machine.

I have an older Fein Turbo III (9-77-25) in the shop which has a 2 1/2in hose and a new smaller Fein Turbo II (9-20-25) with 1 1/4in hose for the wife to use upstairs to use in the car, etc.

I am not sure of the specs of my 9-77-25 without digging out the manual.

The replacement of the 9-77-25 is 9-20-26 which is rated as the same CFM as the 9-20-25 but with 99in static pressure vs 90 in for the 9-20-25.

My Turbo III has a lot more suction in real life situations.

I recently blew out the bag on the 9-77-25 and so clogged up the internal filter. I used the 9-20-25 to clean up the mess so I got a side by side comparison once the 9-77-25 was clean.

Some of the better performance of the 9-77-25 may well be the larger dia 2 1/2in hose which is about 1/2 the length of the 1 1/4in hose on the 9-20-25.

The main benefit of shorter hose is ease of moving it around, but I think this comes with lower effective suction at the end of the hose.


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## ghostrider

Dave Paine said:


> I much prefer a larger hose so I would chose that machine.
> 
> I have an older Fein Turbo III (9-77-25) in the shop which has a 2 1/2in hose and a new smaller Fein Turbo II (9-20-25) with 1 1/4in hose for the wife to use upstairs to use in the car, etc.
> 
> I am not sure of the specs of my 9-77-25 without digging out the manual.
> 
> The replacement of the 9-77-25 is 9-20-26 which is rated as the same CFM as the 9-20-25 but with 99in static pressure vs 90 in for the 9-20-25.
> 
> My Turbo III has a lot more suction in real life situations.
> 
> I recently blew out the bag on the 9-77-25 and so clogged up the internal filter. I used the 9-20-25 to clean up the mess so I got a side by side comparison once the 9-77-25 was clean.
> 
> Some of the better performance of the 9-77-25 may well be the larger dia 2 1/2in hose which is about 1/2 the length of the 1 1/4in hose on the 9-20-25.
> 
> The main benefit of shorter hose is ease of moving it around, but I think this comes with lower effective suction at the end of the hose.


Thanks a lot. That helps clear things up a bit.

It also leads to another question.

What about taking a vac with a 2.5" hose, and stepping it up to a 4" hose leading from the lathe to the Dust Deputy? Will that affect performance? Will it help the vacuum at the lathe, and if so what about using 4" hose for the rest?

Or, is the vac built so that the hoses usually sized for maximum performance?

How would the abilities of the vac compare to what the portable DC would do?


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## Dave Paine

ghostrider said:


> Thanks a lot. That helps clear things up a bit.
> 
> It also leads to another question.
> 
> What about taking a vac with a 2.5" hose, and stepping it up to a 4" hose leading from the lathe to the Dust Deputy? Will that affect performance? Will it help the vacuum at the lathe, and if so what about using 4" hose for the rest?
> 
> Or, is the vac built so that the hoses usually sized for maximum performance?
> 
> How would the abilities of the vac compare to what the portable DC would do?


Using a larger 4in hose will aid to reduce pressure drop, but it will also reduce velocity, and this can mean some particles tend to fall out of the airstream. They will eventually get pushed along, but this may not help performance in some instances.

Shop vacs are high static pressure and lower flow.

Dust collectors are low static pressure and high flow.

Different tasks need different combinations of static pressure and flow.

For example, my drum sander wants a LOT of airflow, but the design of the shroud is very open, so by this design it will be low static pressure.

My Random Orbit Sander has small holes in the pad. These want a high static pressure, but the design means a low flow.

The use of shop vac vs dust collector really needs to be based on the desired task.

I am lucky to have both. I would find it difficult to only have one.


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## ghostrider

Dave Paine said:


> Using a larger 4in hose will aid to reduce pressure drop, but it will also reduce velocity, and this can mean some particles tend to fall out of the airstream. They will eventually get pushed along, but this may not help performance in some instances.
> 
> Shop vacs are high static pressure and lower flow.
> 
> Dust collectors are low static pressure and high flow.
> 
> Different tasks need different combinations of static pressure and flow.
> 
> For example, my drum sander wants a LOT of airflow, but the design of the shroud is very open, so by this design it will be low static pressure.
> 
> My Random Orbit Sander has small holes in the pad. These want a high static pressure, but the design means a low flow.
> 
> The use of shop vac vs dust collector really needs to be based on the desired task.
> 
> I am lucky to have both. I would find it difficult to only have one.


Thanks,

It sounds like the _real_ solution is to eventually have both as different machines will be better with either one or the other, and the ones that require the vac are ill suited for the DC and visa versa. Until I can save for a DC and find the space, I guess I'll just go with the shop vac (the main uses will be my midi-lathe, Drill press, and Band Saw (all of the bench top variety)).. 

My next goal is probably going to be to find a blower motor and make a filtration unit, and maybe even a DC depending on what I can find. 

That of course depends on how well the shop vac works for my lathe. My old shop vac does pretty well at gathering the chips and dust from my drill press (I hold the nozzle right up to the work peice while drilling, and can't even smell cedar when drilling, somewhat to my disappointment It does the same when I'm sanding with the lathe also), and it used to work well gathering dust from by band saw until I changed the blade out for a wider one with Less TPI. 

Does this sound "on the right track", or am I neglecting something. 

I don't have much choice but to turn my pens in my apartment (very small. Almost studio size). It's either that, or just stop any woodworking until springtime (pen blanks can blow out at minus 0* and freezing temps).


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## woodnthings

*a few tips*

An air filtration unit is always a good thing, since it's difficult to catch all the dust with any system. Actually a good system will have shop vacs, a central or portable DC and an air filtration above the work space. A dust collection downdraft table for sanding parts would be the 4th method and a big asset if you do much sanding of small parts.

The ROS (random orbit sanders) usually have a multi size attachment for a shop vac. Problem is that the standard 2 1/2 hose is too bulky and stiff to use. A smaller flexible hose, 1 1/4" is what I use for that sander and my hand held belt sanders which put out a BUNCH of dust without a collection method.

A bandsaw will put out a lot more dust then you might think. 
So if you can collect it right near the lower blade guide. Some saws have the port way down at the bottom which is not as effective. A shop vac is effective near the blade guide and a DC hose at the bottom is best.

A lathe makes a BUNCH of dust, more than you might think especially when sanding. Chips are plentiful when turning and require a 4" DC with a hood. A shop vac would not be as effective on a lathe. 

A shop vac is useful coming right off the router cutter at the top of the table. I don't see any point in letting the chips get down below and into the motor housing which may prevent effective cooling. Some folks totally enclose the motor/router in a lower box that allows removing the chips AND keeps the noise down. It's a trade off in my opinion, and as long as the router is cooled effectively I don't see an issue, since they are loud even when not making a cut.

I use a shop vac to remove the fine dust that comes off the top of my table saw blade. You need a hanging overarm collector or a table mounted type. My saws have a splitter, a wide plate, that I mounted mine on.

Here some ideas I use in my shop:
http://www.woodworkingtalk.com/f7/dust-collection-woodnthings-shop-part-1-a-20273/


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## ghostrider

woodnthings said:


> An air filtration unit is always a good thing, since it's difficult to catch all the dust with any system. Actually a good system will have shop vacs, a central or portable DC and an air filtration above the work space. A dust collection downdraft table for sanding parts would be the 4th method and a big asset if you do much sanding of small parts.
> 
> The ROS (random orbit sanders) usually have a multi size attachment for a shop vac. Problem is that the standard 2 1/2 hose is too bulky and stiff to use. A smaller flexible hose, 1 1/4" is what I use for that sander and my hand held belt sanders which put out a BUNCH of dust withour a collection method.
> 
> A bandsaw will put out a lot more dust then you might think.
> So if you can collect it right near the lower blade guide. Some saws have the port way down at the bottom which is not as effective. A shop vac is effective near the blade guide and a DC hose at the bottom is best.
> 
> A lathe make a BUNCH of dust, more than you might think especially when sanding. Chips are plentiful when turning and require a 4" DC with a hood. A shop vac would not be as effective on a lathe.
> 
> A shop vac is useful coming right off the router cutter at the top of the table. I see any point in letting the chips get down below and into the motor housing which may prevent effective cooling. Some folks totally enclose the motor/router in a lower box that allows removing the chips AND keeps the noise down. It's a trade off in my opinion, and as long as the router is cooled effective I don't see an issue, since they are loud even when not making a cut.
> 
> I use a shop vac to remove the fine dust that comes off the top of my table saw blade. You need a hanging overarm collector or a table mounted type. My saws have a splitter, a wide plate, that I mounted mine on.
> 
> Here some ideas I use in my shop:
> http://www.woodworkingtalk.com/f7/dust-collection-woodnthings-shop-part-1-a-20273/


Thanks a bunch. 

With the explanations from David, and the way you laid it out for me helped me confirm what I was thinking. Like I said, I'll probably end up building a air filtration unit, and save up for a DC. Problem with the DC is that I just don't have enough room for anything more than one of those portable units (maybe even have to mount a wall unit to the side of my bench. My plan is to use the shop vac with HEPA filter for now, and do either the DC or Air Filter depending on what pops up on Craigs list when I have the $$$. Mean time I'm going to have to pick up some extra hose and fittings so I can at least have the shop vac running.


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## ghostrider

woodnthings said:


> An air filtration unit is always a good thing, since it's difficult to catch all the dust with any system. Actually a good system will have shop vacs, a central or portable DC and an air filtration above the work space. A dust collection downdraft table for sanding parts would be the 4th method and a big asset if you do much sanding of small parts.
> 
> The ROS (random orbit sanders) usually have a multi size attachment for a shop vac. Problem is that the standard 2 1/2 hose is too bulky and stiff to use. A smaller flexible hose, 1 1/4" is what I use for that sander and my hand held belt sanders which put out a BUNCH of dust without a collection method.
> 
> A bandsaw will put out a lot more dust then you might think.
> So if you can collect it right near the lower blade guide. Some saws have the port way down at the bottom which is not as effective. A shop vac is effective near the blade guide and a DC hose at the bottom is best.
> 
> A lathe makes a BUNCH of dust, more than you might think especially when sanding. Chips are plentiful when turning and require a 4" DC with a hood. A shop vac would not be as effective on a lathe.
> 
> A shop vac is useful coming right off the router cutter at the top of the table. I don't see any point in letting the chips get down below and into the motor housing which may prevent effective cooling. Some folks totally enclose the motor/router in a lower box that allows removing the chips AND keeps the noise down. It's a trade off in my opinion, and as long as the router is cooled effectively I don't see an issue, since they are loud even when not making a cut.
> 
> I use a shop vac to remove the fine dust that comes off the top of my table saw blade. You need a hanging overarm collector or a table mounted type. My saws have a splitter, a wide plate, that I mounted mine on.
> 
> Here some ideas I use in my shop:
> http://www.woodworkingtalk.com/f7/dust-collection-woodnthings-shop-part-1-a-20273/


After thingking about it, I came up with another question from this. 

I really do not want one of the bigger DC"s (The 16gal shop vac looks big enough), but the portable DC has a listed CFM of 750. I'm just hoping that that will be enough. I suppose I can return it if it isn't, but that would only leave the 2HP Unit from HF for me, which I do not want. Also, I just watched a video and it sounds louder than a shop vac. I've found a very good design for a lathe hood that one of the penmakers came up with on IAP, but he's using 1800 CFM. 

I know it's hard to tell without factory specs, but Central Machinery didn't put those in thier literature. For just making pens, I'm wondering if the 13gal DC from HF will be good enough with a good lathe hood?


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## woodnthings

*You don't want a Universal type motor*

That motor is a screamer like a circular saw. You want an Induction type motor. As long as the small hang on the wall DC has an induction motor that will be fine. Penn State, 
Grizzly and Rockler have the smaller Dc's:
This one isn't bad: http://www.grizzly.com/products/1-HP-Wall-Hanging-Dust-Collector-Polar-Bear-Series/G0710P

http://www.grizzly.com/products/category/570000|570030|570010|570020

http://www.pennstateind.com/store/bag-style-dust-collectors.html

By the time you hang something on the wall it may take up almost as much floor and wall space as one of the larger 2HP units. In my shop wall space is just as valuable as floor space.


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## ghostrider

woodnthings said:


> That motor is a screamer like a circular saw. You want an Induction type motor. As long as the small hang on the wall DC has an induction motor that will be fine. Penn State,
> Grizzly and Rockler have the smaller Dc's:
> This one isn't bad: http://www.grizzly.com/products/1-HP-Wall-Hanging-Dust-Collector-Polar-Bear-Series/G0710P
> 
> http://www.grizzly.com/products/category/570000|570030|570010|570020
> 
> http://www.pennstateind.com/store/bag-style-dust-collectors.html
> 
> By the time you hang something on the wall it may take up almost as much floor and wall space as one of the larger 2HP units. In my shop wall space is just as valuable as floor space.


When looking at them, how to I discern if it's induction or not?


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