Dumb Question Re Dust Collectors
I know this is a dumb question because I already feel dumb asking it…but since I feel even dumber not knowing the answer, I will ask. I am going to purchase a dedicated dust collector (probably the JET Canister Model – 1.5 HP). I am told that this will make my basement shop much more lung friendly. With a newborn and a soon to be two year old in the house, I have been avoiding doing much of anything that will create a lot of dust for obvious reasons. I plan to move the DC from machine to machine until I figure out how I want to arrange the shop. Anyway, to my question. A dedicated dust collector generates 1.5 HP and has a 4″ hose. Meanwhile, my Craftsman Shop Vac is 6.5 HP with a 2.5″ hose. How in the world will a dust collector generate more suction and remove more dust? See, I told you it was a dumb question…I just don’t know the answer.
Replies
I had no idea myself, but this might be something related;)
"Movement of air through vacuum sources is measured two ways: cubic feet per minute and static pressure. Static pressure is a measure of how forcibly the vacuum source operates. Dust collectors typically move a great deal of air, generating the high-speed draft needed to grab large amounts of waste from relatively diffuse sources. They don't develop much static pressure, however. By contrast, shop vacs generate very high static pressure, but they usually don't move a lot of CFM."
A DC doesn't genetrate "more suction" (i.e. a greater differential pressure), but it does move much more air (i.e. higher cfm) due to the size and shape of the blower impeller.
Is that 1.5 hp Jet the 650 cfm model? If so, think about moving up to something in the 1100 - 1200 cfm range. I have the 650 cfm system and it does ok but I really wish I had gotten a larger system.
Thanks for the answers. Dave, the one I am looking at is the 1100 CFM. It is probably more than I need right now, but that will certainly change, and dust collection is probably one department where overkill is better than underkill.
About the HP difference. the rating on the shop vac is a crock. That's the HP rating of the motor at the instant before death, when it is pulling under mortality load. There's been a big beef for awhile about HP ratings just for the reason you put forth. What you want to compare is constant load ratings. These aren't marketing compliant for salespeople, so they fudge for bigger numbers like 6.5 HP shop vacs. Just remember, if it doesn't seem to make sense, it doesn't. Your good judgement should overcome the marketing departments anyday. And it just did. Glad you going with the higher cfm DC. Your family will appreciate it as much as you do.
We had the 1100 cfm in our shop and it is loud.
Yea, and I have the 1200 cfm Jet and am thinking about moving up - whatever it is, it's just never enough is it - LOL!
Vacuums move a little air really fast and dust collectors move a lot of air slowly, sort of like comparing a motorcycle to a 16 wheeler.
In addition, as a couple of others have pointed out, the HP rating of shop vacs is BS.
About those shop vac ratings....
1 HP = 746 Watts. Since a good motor is about 75% efficient, the rule of thumb is that it takes about 1,000 W of electrical power to produce 1 HP.
A true 6.5 HP motor would require 6,500 W, or 54 Amps at 120 V.
To put it succinctly, shop vac ratings are a crock.
Three Putt Joe,
With the little ones at home you are going to need dust collection at each machine and an air cleaning unit that will scrub the atmosphere of all the dust that escapes your collectors. I have a JDS unit that moves 1600 cfm, and seems to keep my 36' x 58' x 9' shop fairly clear. I have little ones at home too, and the air cleaner is the best money I ever spent, as far as the shop expenses.
"A true 6.5 HP motor would require 6,500 W, or 54 Amps at 120 V.
To put it succinctly, shop vac ratings are a crock."
Holy Moses, 54 amps for a ShopVac!!!!!!!!!!!
The next time my mother in law comes flying into the shop on her broom-stick, I will ask the witch to fly out on my ShopVac............
Willie
ThreePuttJoe,
I don't think your question is dumb at all! I've been looking for a dedicated dust collector also, and it can be a bit confusing what you need to look for when making your comparisons. I appeciate this discussion, as I have learned some things I didn't think of before.
On the HP ratings, I don't even pay attention to them any more. It's not just shop vacs, but practically every machine out there has fudged numbers on HP. I guess once this ball starts rolling, everyone has to inflate their numbers. If all your competitors are saying their 1.5HP machines are really 5HP, and you are the only honest one who says yours is 1.5HP, you lose, unless you can successfully explain your honesty (and the buying public doesn't have patience to deal with that). So I guess the companies give in and post misleading numbers. But I think in the end people start to ignore that stat. Of course, then the companies start inflating something else...
Should have said this in my last message, but anyway...I'm looking at the Jet DC-1100RCK dust collector. It has 1100 CFM, 2 4" ports, and a 2-micron canister filter. It is going for $549.99 at Woodcraft.Now here's my dumb question:
Has anybody used this dust collector on a power planer? I have the 13" DeWalt planer, and I would love to control those chips a little better.
I use my Jet 650 cfm system with my Delta 12-1/2" planer and it does just fine. I have Delta's dust collection attachment and I get around 90% of the shavings and dust. If I'm planing a lot of stock, I sometimes need to stop and clear the collecter attachment - usually a minor annoyance.
I just bought the DC-1100CK and I love it. It replaced a Ridgid 650 CFM. My shop is piped with 4" PVC and for a hobbyist it works great rarely is there more than one machine running at any given time. I also have an air filter running all of the time and I use a dust mask when sanding. I also wear hearing protection with routers, planers and other loud devices.
All of us would love to buy the best we can to protect ourselves and our families, but as always economics play a part. I got a bid from Onieda and they wanted $849 for the gorilla, and an estimated $1200 for piping. I do not have the room nor the budget for that. As with anything it life, we do the best we can.
With all of the discussion about dust collection and our lungs, how many woodworkers smoke? If one smokes and expose your family to second hand smoke you are putting you and them at a higher risk than your woodworking is doing.
have a 1600 hooked up to the planer clean as a whistle
Ditto to Segil's post about also having an air scrubber, and JDS in particular. The JDS are excellent units, and IMHO out-perform Jet, Delta and anything else.
Re: moving the machine from one machine to the other. I have the Jet cannister 1100CFM unit also. It's not all that easy to actually move it from one point to the other, but if you place it in a good spot relative to most of your machines and buy 2 or 3 10-foot hoses, you can swap it back and forth without moving it much. I use the quick-connect adapters rather than hose clamps to make it fast. Someday, I'll figure out the best layout and get permanent piping in. ;-)
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Another proud member of the "I Rocked With ToolDoc Club" .... :>)
A 1 1/2 HP dust collector is adequate for one machine at a time, when there isn't a lot of piping involved. A dust collector that small will be underpowered if hooked up to long runs of piping, so you shouldn't plan on using the unit with a duct system that serves the whole shop.
John W.
Ditto to what john says.
But in a small, one-person shop, only one machine is used at a time. A 1-1/2 hp unit can easily be positioned within just a few feet of several well-arranged machines, and with piping and blast gates, serve all the machines, one at a time.
Rich
Edited 9/27/2005 5:07 pm ET by Rich14
Thank everyone for the advice. Since I don't even have all the machines I need yet (bandsaw, etc.) my shop is not complete. But I can't really let the chips fly with just a shop vac. Most, if not all of you would get the dust collector before the air cleaner, right? I understand that both are needed, but Daddy can only harvest wood from trees, not money, so it's one at a time. It sounds like shop vacs are like Spinal Tap amplifiers, Can we all say, "But ours goes to eleven."
Joe,
Everything posted here is right on. The practical difference (in use) is that while a good shop vac will collect the shavings from a planer pretty well, the volume of chips when planing a wide board will likely clog the small hose. If you tried to put a bigger hose on a shop vac the velocity inside the hose whould quickly drop too low to keep the chips moving. Shop vacs really work amazingly well for smaller dust collection needs, although a good DC is much better. When I moved up to a 1.5 hp DC the biggest advantages I noticed was reduced noise, less frequent emtying of the cannister, and better collection at the router table, and radial arm saw. I still use the shop vac for my sanders. If you are concerned about air quality get a good pleated cannister style filter. Most bag filters dont remove the most harmfull dust.
Enjoy your now cleaner shop,
Mike
http://billpentz.com//woodworking/cyclone/index.cfm Hi As long as you are looking and thinking about dust systems take a look at this link. It is very informative and thourough. It will help you with all your d.c. questions. Good Luck Bob
The original subject of this thread as I read it, was about creating a safe breathing environment in a workshop for a man and his family. I am a little surprised by the resistance I've seen to the suggestion about using a JDS air scrubbing unit. My building is situated so that in June, strong sunbeams come directly through half of my shop. When I realized how much dust was floating in the air down there (because you can see it in the sunlight), I was really shocked! No wonder my wife was always complaining about having to dust everything upstairs so frequently. I have three dust collection clusters which do an excellent job keeping the machines clear, but they do not come close to collecting all the dust.! After I got my JDS unit properly oriented in the shop, this secondary dust has to be removed from it about every other week, and there is a lot of it in there! I would have breathed all that dust had this machine not collected it first from what appears to be normal, breathable air. How can anyone say that isn't worth $650? Find the money, guys. Otherwise the only secondary dust collectors is your house will be your lungs and those of your family!
Just a quick read of the "risks" section makes you want to give up the hobby entirely. "Nearly 100% of woodworkers develop serious fine dust related illness." Ouch.Maybe that CStan guy isn't so wrong using nothing but hand tools.
Air volume as others have said about the physics question.
You must and I mean must put in a scrubber or even two. The unit you are buying will not pick up everything.
I went and picked up the unit today, brought it home and fired it upht it ho. What a difference! I see what everybody means about the power. There is a huge difference in the airflow that goes through this thing. Now about the scrubber, I am looking at the JET unit and the JDS unit. Any comment on which way to go...or in another direction. Also, I am in a basement shop and don't do a huge volume of work...one small to medium project at a time. With the new JET Cannister DC Unit and a ceiling mounted air scrubber, can I be pretty confident that my family is safe?
One thing I would suggest with your installation: the two-headed plastic port that comes with the Jet collector that allows for two 4" connections. . . Remove it, and instead hook it up directly to 6" ducting, and run the 6" ducting to each of your machine locations. At that point, a short 4" run from the 6" duct to the machine will not retard air flow too much. This works great in my shop--but then again, my shop is quite small, and has very little run from the collector to any of my machines.
The visit to Bill Pentz's site is a must. Remember, it's not the dust you can see that you should be most concerned about.
Bob
Joe,
Here's another vote for Bill Pentz's website. It's probably the single best source of information I've seen on dust collection. Bill can get pretty technical at times, but he's giving you real understanding too. Well worth reading, and rereading. It'll give you a really good understanding of how it all actually works. One thing he talks about that I haven't seen anyone mention yet in this thread is the importance of good dust collection hoods. I've got one I made for my miter box that works pretty well for me and would be happy to take a picture and post it if you're interested. My miter box was one of my worst tools for throwing up a cloud of superfine dust.
Leo, I will study that site, thanks. I also would appreciate you posting a pic of your MS hood. That is also one of the worst offenders for the superfine dust.Thanks
Hey Joe, sorry it took me so long to post this for you. This dust hood is nothing to behold, for sure, but has done the trick so far for my miter saw. I made it out of junk, basically--duct tape and cardboard. It's actually a template of sorts for a more permanent one I plan to make out of sheet metal. I've seen hoods that connect to vertical pipes where everything gets pulled upward; I wanted to try something that pulled the dust down instead. So basically everything that gets thrown back toward the wall flies into the hood. The bigger stuff falls right down, most of it going into the pipe that runs right underneath the tabletop. The air flow entrains the small stuff and pulls it downward too. About the only thing that seems to escape it are a few chips that bounce to the side or forward, instead of backward. A couple of times I've started to use the saw and forgotten to open the blast gate; a plume of fine stuff started to waft up out of the hood right away; i walked over and opened the gate and you could see the downdraft pull that haze of stuff right back into the hood and down--and that was with another blast gate open elsewhere that I'd initially forgotten to close. I put the blast gate down the line beyond the end of the table so that I wouldn't have to reach under the table to open it every time I want to use the saw. You can sort of see it in one of the pics. The odd shape of the top edge of the hood is basically to allow clearance for the saw cutting various angles. It's asymmetrical because the saw is. The pipe under the bench is just 4" sewer and drain pipe. I made a deflector that I taped to the dust port on the saw to get the chips and dust that come out of it to go down instead of up, which is where it points when the saw is lowered into a cut. Good luck with everything. Congratulations on your new purchase. A clean workshop is so much nicer than a cloudy one. <!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----><!----> <!----><!---->
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My bad. Here's the photos.
those pics are 0k, in other words there are no pictures.
Well maybe there won't be any pics forthcoming. I've tried attaching them, and the attachments in my message in fact display the file names of the pictures; I don't know why they aren't there. I'm not the most computer savvy person, but this seemed pretty straightforward; anybody know why it didn't work?
Don't know why your pictures don't work. But in a related topic, I picked up one of those big tabletop dust "hoods" and mounted it to a piece of 3/4" plywood with enough clamping space on either side. It works like a charm clamped to my mobile miter saw cart. Plus, it can be used on any surface for work with hand power tools.
As others have explained, the shop vac hp figures are marketing hype, and don't mean anything. Domestic induction motors, on the other hand, like those on DCs, conform to the NEMA (National Electrical Manufacturers Association) MG-1 standard, which defines a whole slew of parameters, including performance. HP numbers for these motors are real, and if the nameplate says "continous" in the duty box, then they will output that power indefinitely.
In the case of air compressors, which until recently had those greatly overstated hp numbers on the label, the motor manufacturers get around the MG-1 standard, and the compressor builder's marketing desires, by putting "SP" or "Special" in the hp box on the motor nameplate. They can do this because the motor is being sold to the compressor manufacturer as an integral part of the machine, not as a general purpose unit on the open market, even though the exact same motor is likely sold on the open market, but with a number in the hp box. The same thing applies to table saws - if the motor nameplate doesn't have a number in the hp box, be suspicious. It's hard to compare one saw to another without it, since aside from construction quality and features, that's about all there is to compare.
Import motors are a bit suspect. Motors made in Europe and Japan conform to IEC (like NEMA), but some units coming out of China I'm not so sure about. The motor on my Harbor Freight DC doesn't even have a nameplate.
Be seeing you...
I installed the Jet Canister collector you're talking about last year in my small woodshop. I set up a system of 4 inch pvc ducting to my table saw, planer, jointer, band saw, edge sander and miter saw. I laid out a careful run of ducting with lots of blast gates to shut off unused trunks. I had read everything I could about installing dust systems in small shops, and I just hoped this would work. I have been extremely happy with this dust collector, and my dust system as a whole. The longest run of ductwork I have is about 20 feet, and it all works fine. I have my 15" planer hooked up to a duct that is just a few feet away from the dust collector, and it works great. You just have to be sure to empty the dust bag when it gets about one quarter full and periodically remove and blow the dust out of the top canister (outside of course).
Ralf
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