dust/chip collection

[Ted Miller]

Bill, Thank you for the post, I know after I installed the Clear Vue and jointing 100s of bf in a row I can not even smell the dust in my shop, now I do vent outside and I wish I would have found your site earlier in my woodworking years, but I guess better late than never. I look at it like this, I only do things 110%, I buy the best tools I can buy, so why not have the best air I can breath while I am working, I know living in Southern California had its advantages not having to worry about losing hot and cold air from my shop when the cyclone comes on, so venting outside is not a problem, but I do feel better about how I treat my lungs now than I did years ago, thanks again for your knowledge...

[Bob Dodge]

It's overwhelming.

What are you using?

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John,

Dust collection can basically be divided into two components; 1. The amount of air you want to move at your machines, and 2. The filtration stage.

If you're comfortable moving your dc close to your machines, you won't have to worry about a duct-network, so there's really no point in going there. However, if you do want to place your dc in a fixed location, then you'll have to take a closer look at optimizing your duct-runs. Basically, all that entails, is adequate velocity (through proper sizing).

The filtration stage is pretty well self-explanatory. Ideally, you'd want properly sized filters (for low pressure-drop) and an easy to maintain, well-manufactured filter (tight-fitting/no leaks/triple-stitched seams), and, efficiency in small particle capture. With many consumer-model dc's, a filter-upgrade is almost mandatory, however, some manufacturers/re-sellers such as Delta, and some of the General International, provide reasonably high-quality filters as "standard issue". You'll see many claiming to be "1 micron filters", but don't let the ratings fool you. There simply are no "mandatory testing standards" for consumer-model dc's. I'd highly recommend that you consider 16 oz needle-felt filtration.

Quality electricals may be a concern to heavy-users, as well as waste-capacity. Small capacity dc's means you'll have to shut-down more frequently to empty the dc. While these features can be desirable, it's up to you to decide whether or not you want to spend the extra money.

Let's look at the air-requirements of each of your machines. Many hobbyist shops will have a 10" table-saw, a planer, a jointer, possibly a bandsaw and a router-table.The table-saw will have one of the highest air-requirements. Buy a dc that can handle that saw, and you should have enough power to handle the others.

Ideally, you'd want two-point collection at the saw; one duct to the base, and another hooked-up to an overarm blade-cover (OA-BC). The OA-BC will dramatically reduce airborne waste (fines), especially if you work with "dirty" materials like MDF, Melamine, and particle-board. At the saw's base, a 4" hook-up should be more than adequate if it's properly set-up. If your dc is placed close to that saw, a well-designed 1 1/2 HP dc like the Delta 50-760 (11.5" impeller) will easily address that requirement. It would also run on 110v or 220v. For general hobbyist use, you won't find a better "standard equipment" filter. No upgrade required. Approximately $300. This was Fine-WoodWorking Magazine's "top pick" in the 1 1/2 HP category.

http://www.deltamachinery.com/index.asp?e=136&p=5815

If you do decide to run a duct-network, that 1 1/2 HP Delta should be placed reasonably close to the saw, and then run a properly "sized" duct to your other machines. If the dc will be placed "at a distance", in a "convenient location", well, I'd recommend that you consider a slightly more powerful dc.(2 HP/ 12" impeller / 6"+ porting / twin filters) A dc like the 2 HP Delta 50-761 will give you all of those features, with double waste-capacity, and 7" porting; along with twin over-sized filters (41 sq.ft.) Roughly $500.

http://www.deltamachinery.com/index.asp?e=136&p=5816

Beyond that price-point, you're starting to look at small industrial 2 HP sinlge-stages with heavy-duty Baldor motor, and twin 16 oz. needle-felt filtration, like the Pyradia/Belfab "J.J.". This dc has an ultra-small foot-print (21" x 21"), and is just under 7 feet tall. All 12 gauge steel construction, and built like a tank. High quality bearings, and balanced 12.5" non-sparking aluminum impeller. I use one of these im my shop, and it's an excellent performer. Pulls roughly 1100 ACFM at just under 5" SP. Availability can be quite limited depending on your location.

http://www.belfab.net/jj.html

In this same price-range, you might also want to consider one of the better-designed 2 HP cyclones. You'll lose mobility, and waste capacity can be a little small unless you have the ceiling-height to mount them higher with a larger-capacity drum. If not, you could always add a secondary pre-separator near those machines that produce the most waste. (planer/jointer). That market is currently very competitive, with excellent value to be had.

Regardless of which price-point you jump in at, you want to focus due-attention to your duct-work. Even the most powerful dc's will be brought to their knees by improper ducting. This can be especially important with a marginal dc. Ideally, you want a free-flowing network, devoid of unneccessary twists and bends, and limited use of small-diameter flex-hose. A good dc system, is all about "proper balance".

Good luck,

Bob

[glenn bradley]

I'll second the air scrubber although some folks feel they stir up more dust than they catch. I'm happy with my shopmade version. 1100 CFM gable fan on sale at the BORG, $35, filters on clearance at the BORG $1 each, scrap wood from the neighbor tearing down an old shed $0.

[John Piwaron]

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Ideally, you'd want two-point collection at the saw; one duct to the base, and another hooked-up to an overarm blade-cover (OA-BC). The OA-BC will dramatically reduce airborne waste (fines), especially if you work with "dirty" materials like MDF, Melamine, and particle-board.
Good luck,

Bob

Who makes overarm blade covers? That sounds good. The information on dust collectors is good too.

Bill's posting in this thread is usefull too. I want to acknowledge his contribution.

For me, money is an issue at this time, but only in light of my very recent TS upgrade. Upgraded for the purpose of being able to collect dust. That and an air cleaner were bought at the same time. Now I have to digest that. And while I'm digesting, I'll use the information every has (or will) contributed in defining my own course of action for my next move in the area of collecting the mess. My shop, er, "studio" is in my basement. I live in Milwaukee, so venting outside isn't gonna happen. I can't blow heated air outside. And my A/C barely keeps up in summer, so not then either, thought I must say, when summers here, the tools are mostly silent.

So in the hopefully before too long, I can implement better dust collection than the shop vac can do.

BTW, when I looked, the clear vue stuff looked good and wasn't priced all that unreasonably.

[Matt Moore]

There a number solutions for a overarm dust collecting guard.

Many are please with the shark guard.
http://www.leestyron.com/sharkguard.php

Many have something like the Penn State guard. There are several brands that are similar to this. I only put this one here since it is the first one I thought of and knew where to get the link.
http://www.pennstateind.com/store/tsguard.html

[Bob Dodge]

John,

If you're going to add an overarm blade-cover. I'd seriously consider the Excalibur. Not only is it well built, put it also has the best dust-collection. "General" now owns Excalibur. Any General, or General International dealer will carry that item.

There are also plenty of fine shop-built overarm guards I've seen posted by the members here.

Here's a discussion about OA-BC's that appeared elsewhere.


Question
I'm thinking of getting an overarm blade cover to help with dust in the shop. I've looked at Excalibur, Exactor and one offered by Penn State. Does anyone have feedback on these? Are there other ones I should consider? Are there other ways to deal with dust off the table saw that would work better? Any suggestions would be appreciated
Forum Responses
(Dust Collection, Safety and Plant Operation Forum)
From contributor R:
I have two of the Excaliburs and one Exactor mounted on cabinet saws. They are in use daily, so I guess I can give you an honest opinion of these two particular brands.
Excalibur - Good to excellent dust collection, difficult to remove from saw in the event that you need clearance to mill large parts. Very nicely designed dust hood, which is easily manipulated to provide optimum safety and dust collection.
Exactor - poor dust collection. I bought this model because of price ($249 three years ago) and while I do not totally regret the purchase, I have not been very impressed. They advertise as having a 3" dust collection boom, but in reality it is much less because the boom reduces from 3" to 2 1/2" and then even further down to 2" at the dust collection hood. On the plus side, the boom does swing completely out of the way for milling large parts, but I have to say this is the only plus. The dust collection hood is very difficult to adjust and is somewhat flimsy, where the Excalibur's is solid. But here is the final proof of which is better... On any given day doing equal tasks on PM66 saws hooked up to identical 3HP dust collectors, the Excalibur will pick up one full dust collector bag and in that same amount of time, the Exactor will have only picked up about 1/8th of a bag.

[Bill Pentz]

...Bill's posting in this thread is usefull too. I want to acknowledge his contribution.

For me, money is an issue at this time, but only in light of my very recent TS upgrade. Upgraded for the purpose of being able to collect dust. That and an air cleaner were bought at the same time. Now I have to digest that. And while I'm digesting, I'll use the information every has (or will) contributed in defining my own course of action for my next move in the area of collecting the mess. My shop, er, "studio" is in my basement. I live in Milwaukee, so venting outside isn't gonna happen. I can't blow heated air outside. And my A/C barely keeps up in summer, so not then either, thought I must say, when summers here, the tools are mostly silent....

John,

Thank you for the kind words.

In terms of your shop, if you don’t want to or cannot exhaust the air outside, then you are going to need to decide on what level of dust collection safety you want then get or make a dust collector or cyclone that will move ample air, fix your tool hoods and ports, move a portable DC between machines or put in large enough ducting, and then use a separator filter combination that will ensure you have good dust collection.

My goal with my web pages is to help others avoid the mess I found when I decided to clean up my shop air quality. When I started in 1999 there was nothing but controversy on just about every dust collection topic. Figuring out if fine dust is bad for us and how much before it becomes a problem was a mess with some experts saying no problem and others saying death would soon follow a fine dust exposure. There is no industry standard for small shops and at least five standards for commercial shops depending upon size and location, yet little has changed since. Small shop vendors still have no standards to meet so build anything they can sell. The next level up for shops subject to regular fire marshal inspections sell good “chip collectors" that do a good job collecting the same sawdust and chips we would otherwise sweep up with a broom. Then we got into equipment and dust collection installations that consistently meet OSHA standards. With too many getting ill at OSHA exposure levels ACGIH came out with a five times tougher air quality standard, so some equipment is built to meet that recommendation. With the announcement that some wood dusts are cancer causing agents, we also have firms that build dust collection equipment that will comply with the fifty times tougher medical recommendations that are now the European Union standard. Each still provides very different advice based on what they sell. We still have serious problems with vendor advertised performance at maximums instead of working levels for airflow and filtering. Most vendors still recommend graduated sized ducting solutions that work poorly for small one machine at a time shops. Likewise, the filter situation remains deplorable where what you get may or may not provide any real protection. Add the fact that most small shop tools still come with undersized ports and hoods that are pretty much useless for good fine dust collection and I fully agree with you that picking out a good small shop dust collection system is a pain.

After finding the equipment situation deplorable, especially the cyclones, I rolled up my sleeves and used my over thirty years of engineering experience to build my own cyclone and blower. It worked and my doctor pushed me into sharing. I shared with some Internet articles, got buried in questions, and in self defense moved those articles and answers to frequently asked questions to my personal web pages. The more I shared the more people wanted. The result soon overwhelmed my small local server so I had to upgrade to a commercial server able to handle the 3 million plus hits a day along with a unique visitor count that went over 18,000. Now seven years later I still get about 16,000 unique visitors a day and in spite of asking people to limit their emails rarely get by with less than four to six hours of email a day.

(edited by John Bailey)

bill

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John,

Dust collection can basically be divided into two components; 1. The amount of air you want to move at your machines, and 2. The filtration stage. This is exactly true for “chip collection”, but for good fine dust collection there is far more involved. My personal testing found that if you do not start with fixing your tools with hoods that amply contain, control, and direct the fine dust for collection there is zero chance of building a viable fine dust collection system. Even the big 5 hp Oneida-Air and 5 hp Pentz designed cyclones I tested with “ideal” ducting, airflow, and filtering had airborne dust levels that failed badly with more than double the OSHA maximums after just five minutes (54 linear feet) up wood cutting.

If you're comfortable moving your dc close to your machines, you won't have to worry about a duct-network, so there's really no point in going there. However, if you do want to place your dc in a fixed location, then you'll have to take a closer look at optimizing your duct-runs. Basically, all that entails, is adequate velocity (through proper sizing). Again ample velocity will gather the chips, but you also need ample volume to cover the surface area needed to also capture the fine dust. Layout, ducting material, minimizing run length, and having smooth clean runs with long radius bends is very important to keep the airflow we need for our minimal sized blowers to provide good fine dust collection. One of my friends who uses a 5 hp cyclone of mine that we built together started off with a nice looking all 6” HVAC ducting system, but he chose to use some harsh T and 90 degree bends. That cut his total airflow by almost a third below what we got after changing out some of his duct fittings..

The filtration stage is pretty well self-explanatory. Ideally, you'd want properly sized filters (for low pressure-drop) and an easy to maintain, well-manufactured filter (tight-fitting/no leaks/triple-stitched seams), and, efficiency in small particle capture. With many consumer-model dc's, a filter-upgrade is almost mandatory, however, some manufacturers/re-sellers such as Delta, and some of the General International, provide reasonably high-quality filters as "standard issue". You'll see many claiming to be "1 micron filters", but don't let the ratings fool you. There simply are no "mandatory testing standards" for consumer-model dc's. I'd highly recommend that you consider 16 oz needle-felt filtration. The experts say we need 1 to 2-micron filtration for good OSHA level fine dust collection and only 30-micron filters for good “chip collection”. A standard sized top filter bag that is about 20 square feet in area is more than ample filter area for a typical “chip collection” 30-micron filter to take care of an 800 CFM dust collector. The heavy 16 ounce felt rated at 1-micron when fully seasoned needs to be setup with at least one square foot of filter area for every 16 cubic feet of airflow according to Donaldson-Torit, one of the premiere suppliers of commercial dust collection systems for customers subject to regular OSHA air quality inspections. For the 800 to 1000 CFM airflows needed to meet OSHA or higher medical air quality standards this calls for a filter bag that is 40 to 50 square feet in area. A big filter bag today is one that has a 20” diameter and stands 4’ tall. That gives a top and side area of under 25 square feet. A typical fine dust collector bag is half that size. If you dig deeper, you will find in the Donaldson Torit and other filter material application notes that they actually recommend using at least double that minimum area. Doing so quadruples filter life and quadruples time between cleanings. Most that use these bags eventually tire of their turning hard like plaster and always being a messy pain that leaves us covered in dust during cleaning. Moreover, as these bags age, they tend to build very high resistance. My aftermarket fine filter bag developed such a thick cake of dust that it added over 4.5” of resistance. That was enough to all but smother the airflow from my good quality 1.5 hp dust collector. I strongly recommend either putting the dust collectors outside with a standard 30-micron bag or instead doing your homework and get ample bag area.

Quality electricals may be a concern to heavy-users, as well as waste-capacity. Small capacity dc's means you'll have to shut-down more frequently to empty the dc. While these features can be desirable, it's up to you to decide whether or not you want to spend the extra money.

Let's look at the air-requirements of each of your machines. Many hobbyist shops will have a 10" table-saw, a planer, a jointer, possibly a bandsaw and a router-table.The table-saw will have one of the highest air-requirements. Buy a dc that can handle that saw, and you should have enough power to handle the others. The table saw “chip collection” requirement is 350 CFM with only collection below the blade. For OSHA level collection the recommendation is 440 CFM below the blade plus use of a good blade guard with another 350 CFM for a total of 790 CFM at a typical 10” table saw. Add about 25% more CFM to get the collection needed for the higher standard. This is the easy part. Unlike commercial industrial blower technology which is mature meaning you get near identical performance from identical sized blowers from almost every vendor, the small shop blowers are all over the map making picking a properly sized blower difficult. The small shop tool marketplace is intensely competitive with low cost import tool vendors who have a long history of exaggerating their tool performances, especially for dust collectors and cyclones. Based on Fine Woodworking Magazine testing you might get by with a 1.5 hp Delta or Jet, but by the time you add overhead for much ducting you will be hard pressed to have ample collection to meet OSHA air quality.

Ideally, you'd want two-point collection at the saw; one duct to the base, and another hooked-up to an overarm blade-cover (OA-BC). The OA-BC will dramatically reduce airborne waste (fines), especially if you work with "dirty" materials like MDF, Melamine, and particle-board. You only need lower collection for good “chip collection” and need the two point collection only if you are going after OSHA or better air quality. Although over arm blade covers with collection are nice, many get excellent dust collection with splitter mounted blade covers. The best of these arrangements I’ve seen uses a Biesemeyer anti kickback riving knife splitter with a Hammer/Felder blade guard hood connected to a larger shop vacuum. If you are not willing to pay the big bucks to get a vacuum with a real 90” or better draw, then you should consider using a 4” blade guard hoods. The new Shark Guard looks good, but I have not tried one. At the saw's base, a 4" hook-up should be more than adequate if it's properly set-up. A 4” connection attached to a typical small shop dust collector like the Delta 1.5 hp unit described will support about 350 CFM which is great for “chip collection”, but to get our needed 440 CFM for fine dust collection we really should use a 5” lower connection. This means also using a 6” down drop and at least 6” ducting main. The exception we already discussed and this is instead using a powerful vacuum on the blade guard instead of a dust collector connection. If your dc is placed close to that aw, a well-designed 1 1/2 HP dc like the Delta 50-760 (11.5" impeller) will easily address that requirement. It would also run on 110v or 220v. For general hobbyist use, you won't find a better "standard equipment" filter. No upgrade required. Approximately $300. This was Fine-WoodWorking Magazine's "top pick" in the 1 1/2 HP category. I worked out the impeller sizing that Delta followed to make this unit a top performer. I also consulted on the Fine Wood Working magazine testing done by Michael Standish, someone I regularly talk with. The reason he chose to use my recommended cartridge filter upgrade during his testing for that article is there is such a wide difference in filtering level and quality. He wanted a consistent good quality filter that did not severely impede airflow. Yes, the Delta and the Jet that rated so well on his tests are both excellent machines. I own the Jet myself. However, neither is ample to support more than minimal dust collection when wheeled between machines even when using a short length of 6” smooth walled flex hose. Use 4” hose and have a dirty filter and you suddenly have a machine that will give great “chip collection” but be short of the air needed for good collection. Almost all who buy these eventually upgrade to bigger units.

http://www.deltamachinery.com/index.asp?e=136&p=5815

If you do decide to run a duct-network, that 1 1/2 HP Delta should be placed reasonably close to the saw, and then run a properly "sized" duct to your other machines. If the dc will be placed "at a distance", in a "convenient location", well, I'd recommend that you consider a slightly more powerful dc.(2 HP/ 12" impeller / 6"+ porting / twin filters) A dc like the 2 HP Delta 50-761 will give you all of those features, with double waste-capacity, and 7" porting; along with twin over-sized filters (41 sq.ft.) Roughly $500. Many firms offer larger dust collectors ample to power the ducting in a small shop. If you go through the resistance calculation and add the overhead for dirty filters, you will find the 2 hp dust collectors exceed the airflow we need for good “chip collection” but fall short of the minimums needed for good fine dust collection. The many who buy then later upgrade from their 2 hp units shows this to be true. Additionally, emptying filter bags continues to be an ongoing concern.

http://www.deltamachinery.com/index.asp?e=136&p=5816

Beyond that price-point, you're starting to look at small industrial 2 HP sinlge-stages with heavy-duty Baldor motor, and twin 16 oz. needle-felt filtration, like the Pyradia/Belfab "J.J.". This dc has an ultra-small foot-print (21" x 21"), and is just under 7 feet tall. All 12 gauge steel construction, and built like a tank. High quality bearings, and balanced 12.5" non-sparking aluminum impeller. I use one of these im my shop, and it's an excellent performer. Pulls roughly 1100 ACFM at just under 5" SP. Availability can be quite limited depending on your location. Few small shop woodworkers use these dust collectors because of their $900 to $1200 price. Their airflows likewise have been shown on prior SMC posts to not stack up very well against comparable Delta and Jet units at half the cost.

http://www.belfab.net/jj.html

In this same price-range, you might also want to consider one of the better-designed 2 HP cyclones. You'll lose mobility, and waste capacity can be a little small unless you have the ceiling-height to mount them higher with a larger-capacity drum. If not, you could always add a secondary pre-separator near those machines that produce the most waste. (planer/jointer). That market is currently very competitive, with excellent value to be had. Take away the overhead to power the cyclonic action, remove the overhead to power the ducting, then add the overhead to power a dirty filter and most 2 hp cyclones again will do okay “chip collection” but end up challenged to provide the airflows needed for good fine dust collection. Unless you have really short ducting runs and a very efficient cyclone design 2 hp is just plain not big enough to move the airflow that over twenty years of air engineering shows we need for good fine dust collection at our larger tools.

Regardless of which price-point you jump in at, you want to focus due-attention to your duct-work. Even the most powerful dc's will be brought to their knees by improper ducting. This can be especially important with a marginal dc. Ideally, you want a free-flowing network, devoid of unneccessary twists and bends, and limited use of small-diameter flex-hose. A good dc system, is all about "proper balance".Although this sounds good and is good advice, I am confused about the specifics of how to accomplish this along with so much else being a mix of good fine dust collection and “chip collection”. That is why I took the time to build my web pages that succinctly define what it is I recommend collecting and all the steps needed to do that job. My web pages are not a one person effort but instead the culmination of many for many years sharing their advice and techniques, plus innumerable professionals helping to keep us on track. In short, I would recommend you take the trouble to study and follow the advice on those pages if you decided you want to have good fine dust collection in your shop.

Good luck,

Bob

[color=blue]

[Bob Dodge]

John,

Let's ask the question "How much is enough?"

Is it possible to have an overkill situation? Is it realistic to recommend to an occasional weekend warrior that he needs the same protection as a career woodworker who will have 20+ years of exposure on a daily basis? If I remember correctly, you have only a few machines, and do roughly "perhaps 3 serious projects per year". Let's examine if it makes sense to spend $2000. on a dust-collection system. (small cyclone with complete ducting system and high-end filtration)

Just what is "overkill"? Where do we draw the line? Let's start directly "at source".

A dust collector, is nothing more than a waste transport system, with a filtration stage. It doesn't matter what style of dc you have, it is solely the suction pressure that your dc generates, that will deal with your dust. This suction pressure, in conjunction with your ducting and hood resistance, will determine your airflow, both in volume (CFM), and velocity (static-pressure).

When you select the volume of air you want to move at a particular tool, you have to consider two aspects. One, is the ambient air-mass surrounding you, and the second is, the high-velocity at the entry of your hood. Naturally, if you hold your open hand 3 feet from the duct opening, you will feel no suction pressure. Air is moving far to slowly at that point. As you approach the duct-opening within a few inches, the air is moving much more rapidly at that point, and eventually, the suction will "slap" your hand against that duct opening. How does that apply to your dust-collection requirement? Well, let's look at that more closely.

If your hood is placed close to your cutter, and you have properly sized your dc and it's ducting, the rapidly moving air will ideally draw all of your waste into the pipe. Not "some of it", but "all of it". If you're not achieving that goal, then some of those waste particles may have enough "escape velocity" to saturate the ambient air-mass around your work position.

That fine waste is best dealt with by a certain amount of CFM. Naturally, the more CFM you have, the quicker that ambient air will be drawn back in to the dc's hood, reducing your direct exposure.

Now, is it possible to have increased your exposure even if you move more CFM? That answer is "YES". How so? Because you may have a large hood opening, that larger CFM amount, is entering the hood at a reduced velocity. If that entry-velocity is lower than the waste-particles' escape velocity, then you will still have exposure. In other words, if you flow 800 CFM through a 6" pipe or hood, that entry-velocity will be roughly 4076 FPM. (roughly 46 MPH). A 10" saw-blade, at 3450 rpm, has a tip-speed of roughly 103 MPH. Some of those rapidly moving particles may escape into your ambient air-mass. This is a very simplistic example, but, it illustrates the principle.

Now, if you flowed 800 CFM into a 7" hood, your velocity will drop even lower, to 34 MPH. If you flowed that same 800 CFM into a smaller pipe, then the entry velocity will be much higher. You'd still be moving the same volume of ambient air, but velocity into the hood itself would increase dramatically. For example, a 4" hood would have an entry velocity of 9172 FPM.(104.3 MPH). Naturally, you'd have to have a dc capable of pulling that required pressure in the first place. With a bell-mouth entry, that would require 5.46" SP at the hood.

Once that 800 CFM has entered the hood, you want to ensure that you have appropriate velocity in your pipe, to support the waste to it's final destinatiion. In a horizontal pipe, 3500 FPM is more than adequate to support any type of woodwaste. The ideal pipe to deal with that 800 CFM volume, is 6" pipe. At 800 CFM, your air-velocity will be 4076 FPM, which would be reasonable. If you chose a 7" pipe, your velocity would be too low for transporting all waste-types. You'd have a velocity of 2994 FPM, which would handle low-density waste, but be inadequate for heavier waste. You'd risk a gradual "settling out" and accumulation in your pipe.

If you tried to move that same 800 CFM through a smaller diameter 4" pipe, you'd have a velocity of 9172 FPM, which would give you an astronomical resistance. With 4" flex, a 30 foot hose will have 28.7" SP. The horsepower required to deal with that load would be 13.8 HP.You'd be operating at 5700 FPM over your requirement. By selecting a 6" diameter pipe, you'll have adequate velocity, and low demand from your dc's suction-pressure.

A 30 foot long smooth-walled pipe such as PVC, would have a resistance of only 1.1" SP. For that particular machine's scenario, you'd require a dc capable of pulling 800 CFM at 6.56" SP. (4" hood, and 30 ft. of 6" pipe) If this is your "worst-case scenario" machine, then anything beyond that is overkill. Wasted energy pure and simple. You could connect a 50 HP Torit-Donaldson cyclone to that machine, and you won't be any better off. Sure , the numbers would be amazing on their own merit, but, there is simply no benefit gained. In fact, it can be detrimental at the far end of the chain; your filtration stage.

With excess air flowing into the filter, your filter's efficiency will drop. A filter's efficiency is directly related to the interstitial velocity at that filter. That interstitial velocity is the speed at which air (and particles) flow through your filter. When you see a certified filter spec, it's not only about particle-size; it's also about particle velocity. For example, you may see a filter with certified 1 micron capture efficiency "AT" a certain velocity. Usually, that will be expressed as particle-size only, accompanied by a "letter", like "G" rating. Well, that "G" rating would be the velocity-spec. In otherwords, that filter will only effectively capture it's stated particle size, perhaps 99% of the time, at or below that given velocity. If the velocity spec is exceeded, that particle-size and capture percentage rating will not apply. Filters are not "brick-wall" for particle size. That's how you calculate the required filter.

This brings us back full-circle to your specific requirement. If your table-saw requires 800 CFM to deal with your ambient air, will a 1.5HP delta be adequate? Acccording to FWW Magazine's test earlier this year, that dc supposedly pulls 925 CFM at 3.5" SP as I recall, so yes, it will accomodate your requirement, as long as you choose the proper pipe-layout. If you try to "squeeze" that 925 CFM through too small a pipe, or too much length, then it simply won't do. With properly sized pipe, and an efficient layout, you'll do very well indeed. If you ask me if i believe those test results, well, no I don't. Mr. Standish who performed those tests, used a centerline velocity-pressure reading only, to calculate CFM. This is not uncommon among consumer-model dc's. Reduce that total CFM reading by roughly 10%, and that will be a more relistic airflow. Still, that same dc would have an airflow of roughly 835 ACFM at 3.5" SP. More than enough to deal with your saw.

Bob