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Forum topic by cuttwice posted 01-18-2012 05:20 AM 1597 views 0 times favorited 10 replies Add to Favorites Watch
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cuttwice

60 posts in 1430 days


01-18-2012 05:20 AM

Greetings all -

I recently got a Saw Stop PCS, and am trying to work out what I need to do to accommodate a ClearVue DC system. The saw has a blade guard/hood that encloses the blade quite closely, but it has only (I think) a 1.5” port on it. The port at the back of the saw is only 4”, though it looks like it is connected by an interior duct to the bottom of the trunnion.

I’ve been reading my Bill Pentz, and am dismayed to discover that it looks as though this saw’s dust ports (like most) are way too small to deliver the airflow necessary to collect the fines that a proper DC system should collect. The folks at Saw Stop weren’t particularly helpful when asked about this problem – they said they’d done extensive testing and their system worked really well, but it’s pretty hard to square that with Mr. Pentz’s data, if I understand it correctly.

I’m reasonably handy, but relatively new to woodworking and have no experience with modifying power tools, so I’m one of those who is somewhat flummoxed by this problem (definitely NOT excited at the prospect of cutting a big hole in the back of my shiny new tool), and I’m hoping someone here can help me with a way forward. Has anyone adapted their SawStop for bigger ports? Is it indeed necessary? If so, how did you go about it? Did you need to change the size of the internal ducting as well as the port size? Was this possible, and if not, does it make any sense to change the external port to 6” if the 6” port will be served by a 4” internal duct? Also, do I need to discard the pricey new hood that “works really well” and get a Shark Guard with a 4” port?

<rant> I’m not an engineer, and I don’t know how critical all of this is, but I confess I’m a little grumpy that the saw I just laid out a premium price for doesn’t have larger ports already, since the evidence seems pretty convincing that it should. I can’t imagine a 6” port and duct would be much more expensive than a 4” system, especially when considered as a percentage of the price of the saw! </rant> (Thanks, I feel much better now…)

If this has been addressed before, I apologize, but I searched and didn’t find it. Thanks in advance for any thoughts, ideas you may have.

Best,
- John


10 replies so far

View cabmaker's profile

cabmaker

1311 posts in 1553 days


#1 posted 01-18-2012 05:32 AM

I would just go with the four inch that your saw is designed for, and yes 6 inch would be a little better. If you decide to cut out the saw cabinet just remember it is a tool and it wont feel a thing. Sadly, not many equipment bldrs. design their product to achieve the ultimate performance all the way around. Are you using above table collection also ?

View cuttwice's profile

cuttwice

60 posts in 1430 days


#2 posted 01-18-2012 05:41 AM

Thanks for the reply, cabmaker. If I decide to cut the hole, what should I use to do that? Also, does the 6” port still have value if it’s served by a 4” internal duct?

The blade guard/hood that came with the saw has only a 1.5” port on it, so I’ll have to do some serious stepping down to get hose to fit it (and the balance between main port and hood port seems way off, if they’re both being served by the same DC).

I will collect above the table, but I may just use a shop vac, or I may just get rid of the stock hood and get a Shark Guard, which has a 4” port as an option. (Seems a waste of money, and I’ve already spent plenty on this saw, though!)

View crank49's profile

crank49

3506 posts in 1715 days


#3 posted 01-18-2012 05:49 AM

As an engineer who has designed and built and installed hundreds of thousands of CFM of dust collectors, bag houses, cyclones, wet scrubbers, packed tower gas scrubbers, and cartridge filters I can tell you that probably 25% of what Pentz says is almost true.

It is completely absurd to make a blanket statement that you need a certain size of duct or a specific number of CFM to collect the dust from a given type machine. There are many many more factors that come into play. Particle velocity and direction of release, position of the source, cross drafts, temperature, type of blade or tool, speed of blade, how closely is the blade enclosed, duct velocity, etc, etc.

-- Michael :-{| “If you tell a big enough lie and tell it frequently enough, it will be believed.” ― A H

View pmayer's profile

pmayer

607 posts in 1810 days


#4 posted 01-18-2012 07:10 AM

I believe that the assumption that Bill Pentz makes is that table saws are not designed with dust collection as a consideration until late in the design process. Traditional cabinet saws have either no port or recently a 4” port that is positioned a long distance from the blade at the back of a large leaky cabinet. Through practical experience I agree with Pentz assessment that most dust collectors sold into hobbyist shops are capable of pulling enough CFM through a 4” duct in that configuration to extract enough of the fine dust to create a healthy environment. Having said that, the SawStop is not a traditional cabinet saw, and from what I understand they have made vast improvements over their competitors on this front.

I am not an engineer, but I have a fair amount of experience with dust collection and I would start by running a 6” port right up to the saw and transitioning down to 4” right at the port with a tapered transition. If you have a relatively short run from the cyclone to the saw you should be able to pull in the range of 800 – 900 CFM at the back of the saw using this approach so given their reputation for dust collection I think you should clear most of the dust from the cabinet.

The 1.5” port on the blade guard/hood is more troubling to me, but as crank said there are other factors to consider. If the tool does an adequate job of containing the dust and position the dust port closer to the source of dust then less CFM are required. Even though I am a bit leery of the small port, I bet you will find that it collects reasonably well given the other factors in the design. Hope so anyway.

Traditionally tools have been horrible at this which is what has fueled the passion of Mr. Pentz perhaps more than anything else. Well, actually I think the “dust pump” manufacturers piss him off pretty much too. :) In general I have a good level of respect for the information that he provides, but his generalizations probably don’t fit well here given the focus that SS has given to dust collection in their product design. I believe that the same holds true of Festtool, which uses modest hose sizes but yet clears the air quite well given their excellent containment of dust.

Bottom line for me is that I would not put a scratch on that tool until I was convinced that the stock gear wouldn’t deal with it. I have modified the dust ports on just about all of my tools, but only because I saw the poor performance of standard ports. If you end up needing to cut some material away to open it up, I have just used a jig saw with a metal cutting blade. You can search around and find plenty of pictures of guys doing this to their Unisaw, but I have never seen anyone do it to a sawstop.

-- PaulMayer, http://www.vernswoodgoods.com

View live4ever's profile

live4ever

983 posts in 1754 days


#5 posted 01-18-2012 10:58 AM

IMHO you’re going to be just fine with 4” and a Clearvue.

If you REALLY want to look into this further, determine first that the 4” hookup is inadequate. You’ll need a Dylos air quality monitor to do so, but I suppose that’s probably worth a few hundred bucks if you’re really planning on taking Pentz literally.

-- Optimists are usually disappointed. Pessimists are either right or pleasantly surprised. I tend to be a disappointed pessimist.

View Viktor's profile

Viktor

448 posts in 2163 days


#6 posted 01-18-2012 11:52 AM

I completely agree with crank49. Among the factors he listed design of the blade shroud is one of the most important. You’ll be fine with 4” port.

View Oldwest's profile

Oldwest

77 posts in 1548 days


#7 posted 01-18-2012 12:09 PM

I just got a Penn State 2.5 HP cyclone and am running 6” ducting to all my machines. I have a Delta Unisaw with a 4” dust port and was going to put a 6” port instead.

Penn State recommended that I put another 4” port above and to the right of the existing port and then run them into a 6” tee.

It seems like the Delta’s have a dead spot on one side of the saw and a second 4” would be much better than one 6” port. I have observed this dead spot as dust would accumulate there when running my HF dust collector.

-- Anyone who isn’t totally confused just doesn’t understand the situation.

View cuttwice's profile

cuttwice

60 posts in 1430 days


#8 posted 01-18-2012 01:27 PM

Many thanks, all. The advice to try what’s supplied before chopping holes in my cabinet saw is both sensible and comforting (a rare enough combination!), and I’ll follow it and see how it goes.

Crank49, many thanks – I appreciate your professional perspective in particular. Do you know of any reading which covers the principles you describe that is comprehensible by non-engineers like me?

Paul, I think that I’m looking at something on the order of a 35’ duct run to the saw, once I figure in the distance to the 13’ ceiling and back down to the DC intake. Does that sound like too much to provide the flow you describe?

live4ever, I’ve been thinking about getting a Dylos monitor – just working on overcoming my Scottish heritage (again!) and spending the $250

Now all I have to do is figure out a rig to get the dust from the blade shroud to the DC system – what do you all think – should I fit a boom, or try to work out an overhead drop for the small hose? If a boom, should I try to ease the radius of the first turn out of the shroud, or just go with a 90 degree bend there? Would you recommend a 1.5” hose all the way to the trunk line, or should I step up to something bigger right away?

View pmayer's profile

pmayer

607 posts in 1810 days


#9 posted 01-18-2012 03:39 PM

I have a run nearly identical to what you are describing where I ran 6” PVC all the way and reduced to 4” right at the tool and I am getting in the 850 CFM range with my Clear Vue. This hookup is for a 13” planer and it doesn’t leave any dust or shavings behind.

Oldwest, that is an interesting idea on running a second 4” port. I definitely used to see dust accumulation inside the cabinet on my unisaw with a 1.5 HP DC and a 6” port. But now with a 5 HP system I don’t have any dust accumulating any more, but the approach you describe might require less brute force CFM.

-- PaulMayer, http://www.vernswoodgoods.com

View Mark Shymanski's profile

Mark Shymanski

5119 posts in 2457 days


#10 posted 01-31-2012 05:48 AM

Are you getting a lot of sawdust in the air or above the table? I thought SS had very good dust collection, is there a chance you’d make things worse by modifying what’s there?

I think I’d want to see someone else’s retro it before I started sawing open new ports on my saw. I understand that with their over arm dust collection attachment they are capturing 90 ish % of the dust…that sees like a pretty high effeciency, one that may be hard to beat.

It will be interesting to see how you progress with this.

-- "Checking for square? What madness is this! The cabinet is square because I will it to be so!" Jeremy Greiner LJ Topic#20953 2011 Feb 2

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