shark guard port size

[Steven Triggs]

I'm getting ready to order a shark guard, but am looking for input regarding what port size to order.

Delta Unisaw
Delta 50-760 Dust Collector

I don't have a duct system, and just hook my dust collector up to the tool I'm using with a 4" flexible hose using Rockler's quick connect fittings. My plan is to run a 4" hose from the saw cabinet and a ?" hose from the shark guard to a tee or wye with a quick connect fitting on its single side, and then hook the dust collector's 4" flexible hose to the tee or wye.

Anyway, I have no idea what the pros or cons of using a 2.5" vs 4" port for the guard would be.

Thanks.

[Paul Wunder]

Steven,

Hopefully, the airflow experts will chime in, but here's my take:

If you use the single 5" port off of the Delta 50-760 and run 5" flex to the saw, use a 5/4/4 wye (no T's) you may get enough airflow to use two 4" ports. Using the standard 4" fitting from the DC and 4" flex to a 4' Wye will not give you enough flow. I run my SG with 4" above and below but I am using a 5HP cyclone. I owned a Delta 50-760 and it was strong but I would not expect it to support 2 4" open ports at the same time

[Ryan Wood]

I dont have a shark gaurd but I have been thinking about getting one and what i would do is hook up my dust collector to the dust port in the saw and get a shark guard with a 2.5 dust port and hook my shop vac up to that. By doing it this way you would lose all that suction that you would by having 2 dust ports open at once. The othere reasond I would do this is because a shop vac has more more suction but less voluem than a dust collector.

[Prashun Patel]

I used to have a shark guard with a 4" port wyed from the rear port of the cabinet. Much better than my current saw stop with a 2" port off the guard going to a shopvac.

I vote 4 inch all the way.

[ian maybury]

As the guys say it basically comes down to how much airflow you have - which in turn depends on the capability of your fan, and what you are pulling through.

I don't know the unit Steven, but if it's a genuine 1.5HP running a typical say 12x3in impeller at 3,450rpm it should be capable of 7 - 800cfm if the fan is ported big enough to properly run a short (less than 10ft - the shorter the better) 6in dia flex hose. At that it should in theory be capable of running 2 x4in dia branches at the 350/400 cfm plus needed to give the 4,000ft/min minimum recommended for reliable chip collection and transportation.

To get this airflow (which is around or slightly below the OSHA recommendation - about half of the Bill Pentz/ASHRAE recommendation for effective fine dust entrapment) you would need to check that the fan is as described, or very close to it, and as well as keeping the hose short make sure the branch is a 45 deg Y.

It's hard to finger the effect of filter blinding, but my own experience was that the filters on small bag units blind quickly, and that the airflow (even without a big bore top guard) falls away quickly to become marginal/incapable of decent collection in this situation.

It should be possible to mock it up on your saw for little time and cost before committing to the guard.

Flow balancing could be an issue - if the airflow through the cabinet/lower connection on your saw is very restrictive you could end up finding that the relatively open branch to the Shark Guard would hog most of the flow, and leave the lower connection rather short of 'suck'.

Restricting the duct to the top guard would divert more flow to the cabinet, but could then leave the top guard short. This because fan HP is consumed in overcoming the pressure drop as well as in generating airflow - meaning that the cabinet would consume more than its fair share of the available fan output.

What this really means is that there should be a free flowing 6in dia line all the way from the branch to the filter, and a free flowing 4in dia in both branches to that from both inlets. If either is at any point more restrictive than that then the result will be reduced airflow/CFM at one or both connections.

The other variable is the Shark guard itself. It'd be worth checking with the maker as to how they feel about the set up you plan on running. The reason I mention this is because the guard has large inlet area, and probably needs decent airflow to pull stuff into it. Plus they will probably have a fair idea as to how it will run on you saw and dust collector combo.

I don't know how people get on with these large guards - they could get in the way of some operations.

Bottom line is that if it's as above it can probably be done, but it's sailing fairly close to the wind on fan output..

ian

[Bruce Darrow]

I vote for the 2.5 port.

It's what I got, and it works just fine. I have a 6" port I cut into the side of my PM 66, and the 2.5 overhead, sharing duty with my router table fence, which is on the end of my saw table. The 2.5 is reduced from a 6x6x4 wye on the same trunk feeding the cabinet. I just switch it back and forth as needed. Both lines are gated so I can play with respective volumes. I run a 3HP cyclone.

It is my (non-scientific) take that the dust coming off the top of the saw blade is A) quite fine (although not as fine as sanding dust) and therefore fairly easily captured from the small Shark Guard enclosure, and B) considerably less than that thrown down into the cabinet, so less air volume is needed.

Additionally, I have experienced small chunks of cedar or pine knots being sucked off the table and into the system and thin ripping strips cleaving onto the intake of the guard and flopping around above the spinning blade! This with only a 2.5 port. Very unnerving. But if it will do that, there is plenty enough suction for dust.

[Matt Meiser]

I have the 4 and love it. You can always close a blast gate partly to regulate flow. The only drawback to too much flow is the tendency to pick up small pieces.

[ed vitanovec]

My 4" hose to the Table saw has a wye and it branches off into a 2.5" hose to my Shark Guard, the dust collection works fine and it gets most of the dust.

[Jim Andrew]

I have the 4", and also 4" to my unisaw cabinet, think I would rather have a 5" to the cabinet and the 2 1/2 to the shark guard. The 4" in the cabinet is really not enough, as dust tends to build up down there, and I have to use a stick to push it into the opening to get rid of it. Sometimes a stick will get sucked up into the hose above the shark guard, and it goes right on up into the system, so don't think it is my dust system.

[ian maybury]

A 4in branch to the top guard from a 4in hose seems likely to struggle on a typical small bag filter collector...

ian

[mreza Salav]

Technically, if you have a 5" connected to your DC you'd have to have 4"+3" to get the closest surface area of ducts in ideal situation
(5" gives you 2.5*2.5*pi=6.25*pi and 4"+3" gives you 2*2*pi+1.5*1.5*pi=6.25*pi).
That's what I have on my tablesaw and it works fine.

[David Kumm]

I'd get the three inch port. The unisaw has pretty mediocre internal channeling so you want as much cfm in the bottom of the saw as you can get. The 3" port is small enough to use with a shop vac and big enough to hook into your dust collector when you get a bigger collector. Dave

[Chris Parks]

I'd get the three inch port. The unisaw has pretty mediocre internal channeling so you want as much cfm in the bottom of the saw as you can get. The 3" port is small enough to use with a shop vac and big enough to hook into your dust collector when you get a bigger collector. Dave

Any cabinet TS must have an inlet port equivalent to the exhaust or it will fill with saw dust. Air in equals air out.

[Rod Sheridan]

Hi Steven, 4" is too small to handle a cabinet port and an overhead guard port.

My saw has a 5" cabinet port with an internal hose and blade shroud, and a 2" port on the blade guard.

Dust collection is very good with short runs of flex and a 1.5 HP cyclone.

Regards, Rod.

[Ole Anderson]

Bigger is better? Not always. IMHO a 4" SharkGuard is just too big, visually and practically. I went with the 3" and it is more than enough for topside collection, as it is, I still pull offcuts up the hose. I went with a 5" bottom and 3" top and not just because Mr. Pentz said those were the optimal sizes. In your case where you are restricted to a 4" main hose, I would go with a 4" on the bottom and a 2.5" on top. You won't reach the optimal velocities for a perfect solution, but it will be the best you can do with what you have, and if in the future you upsize to a cyclone with larger pipe, you can keep the 2.5" SharkGuard and still have a good topside solution. Here is what a 3" looks like (now imagine it with a honkin 4" hose):
(The extra hose is needed as I slide my saw back if I need to rip an eight footer in my tight basement shop) 3" hose into a 4" blast gate into a 5" duct, and it works fine.

[David Hostetler]

Something to consider. The present model, the SG-K1 is offered with replaceable top pieces, so unlike earlier models, if you decide later on your port is too big, or too small, you can order a new port piece and just swap it out...

I have the 4" and a 4" belly pan on my BT3100. It works wonderfully. I used to have an OLD 2" model that worked great as a guard, not so hot as a dust hood. Not terrible, just not nearly as good as the 4"...

[Ryan Brucks]

I have a "2hp" HF DC, and a minimax CU300 combo machine. 5" port to the cabinet, and stock blade guard is around a 1.5" hole. Even with this very restrictive hole, I get better DC and noticeably more airflow using my HF DC to power both ports, than if I just use the HF DC for the cabinet, and shopvac for the blade guard.


I just finished making my own Lexan blade guard that is supported from the ceiling and is height adjustable (based on wood central plans). I made it for a 4" port, but I designed the sides at an angle so the opening at the bottom is only 1.5" wide to get higher velocity (mostly matters for when the blade is not surrounded by the workpiece). But I am also upgrading to a 5hp DC soon. If not, I would use a smaller port since my HarborFreight can't really feed a 5" and 4" well.

Someone mentioned something to the effect of "the fine dust doesn't need much velocity"... well the sawdust coming off the blade can be over 120mph, and even at the best case scenario 1000cfm, we are only talking 60mph wind in our DC pipes. So IMO nothing is overkill :)

Some people wrongly think you need to use a smaller fitting on the blade guard to get high velocity. This isn't really the case. It's about the air velocity as it passes the blade, so what really matters is the design and volume of the blade guard and volume of air moving through. A bigger port would always allow more airflow, but if the guard itself doesn't have the right taper, that velocity will be killed (the Shark guard has that internal separator you can tell is to keep volume down). I don't know how much the shark guard rises up and down with the cutting, but if it does, the area for airflow will be different at beginning and end of cut. That's another major reason I wanted mine suspended from above. I can control the height above the workpiece, and thus manage the air velocity a bit more.

[Michael W. Clark]

You could buy the 3" guard and put a reducer on top of it for 2.5" hose. This way if/when you upgrade to a cyclone, all you have to do is remove the reducer and install a 3" hose. ACGIH recommends 350 CFM on the blade (4" duct). I think this would get bulky, but maybe not, the user would need to make that decision. I would definitely recommend running a 5" or 6" duct over to the saw. The 4" is going to struggle to carry both branches adequately.

Mike

[Michael W. Clark]

Some people wrongly think you need to use a smaller fitting on the blade guard to get high velocity. This isn't really the case. It's about the air velocity as it passes the blade, so what really matters is the design and volume of the blade guard and volume of air moving through.

This is on point and also addresses the comment earlier about area and flow entering the cabinet. Its the velocity generated at the hood opening (or cabinet opening) that does the work of collecting and containing the dust. The velocity in the duct is just to keep the dust suspended and convey it to the collector. The starting point for any hood design is to know the minimum velocity required at the hood opening and the hood opening area. Multiplying these two together gives you the minimum CFM required at the hood. The duct is sized for the conveying velocity and CFM required. Sometimes the CFM is bumped up to get to a common duct size. The SP required to generate this flow depends on the hood arrangement, taper of the hood, and duct size/velocity.

The thing to take away is that the more open area (bigger gap around the hood), the more CFM required. The more CFM required, the larger the duct needs to be to maintain the conveying velocity without incurring extra SP losses due to duct friction.

Mike

[David Kumm]

What the OP should take away from this discussion is the difficulty in splitting air into multiple ports from a small collector. In Ryans case, the MM saw, although it has a 5" port, has a smaller flex hose internally to the blade shroud- if I'm not mistaken. My Knapp is the same way. That hose negates the full port size and allows for some additional flow into the overhead. Without that internal restriction you are likely to get inadequate flow at either port if not careful. The interchangeable port on the sharkguard is great and if you have a big enough collector, the 4" does not interfer and is slightly offset- good for slider- bad for ripping against a fence. A 10" guard with no scoring is fine with the 3" port now that the shark guard is narrower. The larger guard benefits from the larger port. Dave

[Ryan Brucks]

David you are right on the money. The reason I went 4" was mostly because my guard is insanely long, to cover the riving knife AND scoring blade. in fact the bottom opening on my guard is 19.5" long by 1.5" wide... or roughly the same area of a 6" port. But then account for the guard being only 1/4" above the workpiece, (instead, parimeter * space offset, so [19.5 + 19.5 + 1.5 + 1.5] * 0.25). With that, the area for airflow into my guard is actually around 10.5 square inches. The 4" port has 12.5" of area, so in practice, I am restricting airflow very slightly, and will have slightly faster airflow into the guard.

[Michael W. Clark]

David, yes the blade shroud inside the cabinet is a good example of a more "efficient" hood design that requires less flow (as compared to a connection to the cabinet). I thought this might be the case with Ryan's saw, but wasn't sure. Ryan, yes the offest area is what is doing the work (perimiter area under the guard) as you describe. However, I wouldn't think of it as being "restrictive" because some CFM is generated by the saw blade spinning. The exhaust from the guard would be the CFM induced by the saw blade + the CFM pulled through the slot below the guard. The slot velocity is equal to the CFM pulled from the guard divided by the slot area only when the blade is not spinning. When the blade is spinning, it is something less, hopefully the velocity is still inward if your guard volume exceeds the volume generated by the spinning blade.

Sorry for getting off-track/hijacking, it was not my intent, just thought Ryan made a good point when talking about port sizes and inlet area. One concern I would have about the large guard is how close you can get the fence to the blade. On my original guard, I can only get the fence within about 2-1/4" of the blade which becomes a problem on almost every project.

Mike

[Michael W. Clark]

Just re-read David's post, I would look at the 3" guard. If your collector is as Ian describes, you could go 6" hose, 5" for cabinet, and 3" for blade guard. It's a good idea to put a blast gate in both branches to adjust the flow as necessary. If you only want one gate, I would start with it in the cabinet branch.

Mike

[Cary Falk]

As a point of reference, My Excalibur over arm guard has a 3" port. The Arm is 4" at the base. I have a 4" hose connecting the base of the cabinet and the over arm guard. With the gate to the guard fully open, the guard sucks itself to the table pretty good. I am using a 3 hp dust colllector. In my opinion th3 3" guard is getting kind of bulky and gets in my way.

[Brad Gobble]

I have 4", works great.

[Van Huskey]

Get either a 3 or 4" port. Then use a true union ball valve or a blast gate on the run to the guard and you can adjust the flow to make it work best for your situation, you can't make a small port larger port easily but you can make a larger port effectively smaller easily. I like as much adjustability in the DC applications as possible, without a degree in fluid dynamics and a super computer to model the flow it really is a wild guess as to what will happen in the real world. Outside the scope of this thread the other side to that coin is to get as much flow as possible since dealing with too much flow is easy, dealing with not enough is hard.

[Steven Triggs]

Several have mentioned running 5" to the base cabinet of the saw. The port is 4" though. Does running a 5" hose with a reducer into a 4" port perform differently than running a 4" hose to the 4" port? I somewhat assumed that this was a weakest link situation, where the smallest opening between the DC and the tool was the effective size of the run. Perhaps I was mistaken?

Also, I actually have two identical dust collectors (picked them up for stupid cheap when Lowe's clearanced them). I keep one near the planer and the jointer, and the other near the table saw and the router table. I could connect both when using the table saw (one to the base, the other to the guard), but I'm hoping this isn't needed as it would be extremely less convenient.

Oh, and for whatever it may be worth to the conversation, this is the model DC that Fine Woodworking reviewed in 2006. Delta claimed I think 1200 CFM, but Fine Woodworking found it to have a true max flow of 925 CFM (quite high for this "class" of DC they said).

[David Kumm]

Steven, generally you will get more flow with the 5" flex entering into a 4" port than running all the way with 4" flex. Depends on a bunch of things but as pressure increases cfm decreases and the flex really adds resistance. You need enough velocity to keep the flow over 4000 fpm in the larger pipe but anything you can do to reduce resistance- fewer bends, greater diameter, more filter area, all help with the cfm. Dave

[Mike Goetzke]

My vote is for 2-1/2" - I have used the 4" also. I have a CV cyclone and need to move my TS into position when I use it. With the 4" port I found I had to use a gate or else there is soo much suction it can pick up sizable cut-offs. Also, a 2-1/2" hose is much more flexible and doesn't tend to make the Shark lean over like the 4" hose.

Mike

[Ole Anderson]

Several have mentioned running 5" to the base cabinet of the saw. The port is 4" though. Does running a 5" hose with a reducer into a 4" port perform differently than running a 4" hose to the 4" port? I somewhat assumed that this was a weakest link situation, where the smallest opening between the DC and the tool was the effective size of the run. Perhaps I was mistaken?

To answer your question, yes, that does become a weak link due to the friction losses of such an abrupt transition, but, no, the smallest opening doesn't make the effective size of the run the same as the smaller opening. So you are better off running a large hose to a small opening than running a long small hose to that same opening. Think 5/8" garden hose with a 1/4" nozzle. Same concept applies. You don't want a 1/4" hose feeding that nozzle. Of course, I wouldn't run a 6" hose to a 3" opening as your velocities in the hose are likely too small and will lead to a possible buildup of material in the larger corrugated hose. As I previously noted, I have no problems with my 3" top collector hose being picked up by a smooth 5" steel duct.

My Grizz 1023 had a 4" opening in the cleanout door for the DC. The door was easy to remove to enlarge the hole with a metal cutting blade in my jigsaw. I got a 5" bellmouth from PSI. The rounded transition from 5" to 7" reduces the friction losses due to an abrupt transition.

[Ryan Brucks]

According to bill pentz research, those bell mouth fittings can help out quite a bit.

Mike you have me concerned that I will be picking up workpieces with my 4" guard when it's done. If it becomes a problem I was going to try enlarging the diagonal slants at front and back of the guard to give the air somewhere else to go. Wonder how this will work.

[David Kumm]

Ryan, you definately want a gate near the saw to adjust flow and yes you will pick up small pieces if run full. Don't ever turn off collector before the blade stops spinning and dial down the flow when leaving small offcuts. a lot depends on the power of your blower. A small blower will max out on 4" pipe at 4-5000 fpm due to resistance- a large blower may get over 7000 fpm and needs to be partially closed. Dave

[Ryan Brucks]

well since I am using the CVMax, I think I will definitely need to dial back. I was actually going to run 5" pipe across the ceiling down to a clear vue 6" to two 4" transition box with integral blast gates. One of those 4" lines will be for the tablesaw guard. The other will be for the shaper. The shaper hood does have a 5" port (120mm) then another 5" port under the table. hopefully 2-3' of 4" flex won't kill the shaper airflow too much. if it does I'll have to bypass that transition box and have a full 5" line wye off the 5" main.

if it turns out I have to close the blade guard air flow too much for the 5" mains, I'll just open the 2nd transition gate a bit to bleed some extra air into the 5" line to maintain FPM.

when you mention waiting for the saw to stop.... is that incase some piece of wood is suspended in the ducting ready to fall?

[Ole Anderson]

I guess that I don't understand why you would put a monster 4" hose to something as small as a SharkGuard, and then choke it with a gate? Why not just go with a smaller hose. My 3" works just fine.

[David Kumm]

Ryan, use as large a pipe as you can to the shaper. I run two 5" ports on mine with 1000 cfm in each so you want all the flow you can get. If short of cfm, you want more on the top when the cutter is above the wood and below when under. Seems obvious but only after the chips hit your face after you've forgotten to adjust. Dave

[Michael W. Clark]

According to bill pentz research, those bell mouth fittings can help out quite a bit.

Mike you have me concerned that I will be picking up workpieces with my 4" guard when it's done. If it becomes a problem I was going to try enlarging the diagonal slants at front and back of the guard to give the air somewhere else to go. Wonder how this will work.

Yes, the bellmouths are a HUGE improvement from a hood loss standpoint. I would suspect you gain about 0.5"wg of SP by switching to the bellmouth, maybe more. I'm going to check those out, I have a 1023 as well and that looks like a good upgrade.

Its very possible that you could pick up boards, based on the velocities and the comments from others. You have a few options:

If you want to keep the same flow, you can increase the opening area which will lower the indraft velocity. Maybe it is advantageous to have a 1/2" gap around the guard instead of a 1/4" gap? Maybe there is an advantage to have some additional openings somewhere else on the guard. You can also drill holes in the guard to let more air in and reduce the suction to the boards.

You can also choke it back like you discussed, but then there is the point about maybe you could have used a 3" connection if you do this. If you find that you have too much flow, you could always neck down the 4" port much easier than you can deal with a 3" port on the guard if you needed more flow.

If it were me and I had the collector capacity, I would install the 4" port and 4" hose first and see how it works. If you have to choke it back so much that you get dust and chips falling out of the ductwork when you turn off the collector and you have maximized your openings as much as you want to, then you may consider changing to a 3" hose. I'm probably going to use a 3" on my 1023, but my guard will be shorter and have less open area as I don't have a scoring blade.

Its going to boil down to personal preference whether you want more opening area and pull more CFM, or you want a tighter opening and pull less CFM. As you know, the goal is to get all of the dust and leave the wood on the table:). You may have to do some "tweaking" once you get it installed so it operates like you want it to.

Mike

[Ryan Brucks]

I guess that I don't understand why you would put a monster 4" hose to something as small as a SharkGuard, and
then choke it with a gate? Why not just go with a smaller hose. My 3" works just fine.

Fair question, I thought the same thing at one point. I just wanted to see how much I could get away with. If I do have to dial it back slightly to keep from sucking up workpieces that surrround the blade, maybe I can open up the full power when making cuts that are not surrounding the blade, ie a very thin slice or a cut that's less than blade kerf thickness (I sometimes make such a cut as my first cut to minimize waste and guarentee square)Assuming the cutoff would be too long to be sucked up in the 1st example.

Thanks for the suggestion David. I can probably find another use for that transition box I have and just Wye off the 5" line to the shaper..

Michael thanks, yes I like the idea of drilling some extra holes or opening up part of the bottom to allow in more airflow. I even thought about cutting a little curved hole in the bottom side of the guard, next to where the scoring blade is. I was thinking that would cause more air to suck in there, getting more of the dust from it... but then I started to think maybe the gap would let me chips through... who knows :)