Give me Your Opinion about this Idea

[Mike Henderson]

For those who have a DeWalt 735 planer, you know that it has a fan inside the planer that sucks up the swarf, and then spits it out the dust collector port. Seems to work well.

I bought a Festool Kapex and tried hooking it to my whole shop dust collection system but the swarf collection was not very good. So I got a small shop vac and hooked it to the Kapex and the swarf collection is much better. But the small shop vac fills up too quickly.

Suppose I was to remove the filter from the shop vac and then hook my big dust collection system to the exhaust of the shop vac. Seems that the system would work in a similar manner to the DeWalt 735 planer. The shop vac would provide the high volume of air through the 35mm hose and the swarf would be spit into the big dust collection system.

Can you see any downsides to this? Seems that the major issue is whether the swarf will go through the shop vac fan okay.

I know some people might suggest putting a small separator ahead of the vac but I don't have room for that extra container.

Mike

[Lee Schierer]

I don't think that the fan in your shop vac is going to like having all that swarf flowing through it. Most shop vacs suck the air out of the canister through a filter. Removing the filter would let dust and debris get into the fan which would not be good. About the only time you can safely remove the filter on a shop vac is when you are sucking up liquid.

Some people have success by putting small cyclone separators on trash cans ahead of their shop vacs to handle larger volumes of shavings.

[Frank Pratt]

I wouldn't want to try that on an expensive vac, but maybe on a Ridgid or something like that. The dust from a miter saw is pretty fine & I think it'd go through a vacuum OK.

My miter saw dust collection is great cause I've got it in a cabinet closed in on 5 sides with an 8" duct sucking ALL the dust out. But I've thought about doing that with the overhead collection on my SawStop. For the most part it's quite good, but it has a pretty small connection & the DC has a hard time drawing much flow through it. My fear though, is that tiny off cuts could get sucked up & through the vacuum.

[Jim German]

I don't think it would be an issue. Probably wouldn't do good things for the life of the shop vac, but they are pretty much disposable.

[Yonak Hawkins]

Mike, is it that the reduced suction of the shop vac does a better job with the swarf than the shop system ? If so, could you adjust the suction of your shop system ? Otherwise, in what way does the shop vac work better ?

[Keith Weber]

Mike, what if you were to gradually step down the pipe size of your shop DC near the Kapex so that it speeds up the speed of the airflow, and then hook that directly to the Kapex as you do with the Shop Vac? Not sure how many cfm a shop DC would pull through a small hose compared to a Shop Vac. Surely someone here has tried that already and would know if it would work or not.

[Dan Friedrichs]

You can't build some sort of "chute" behind the saw that catches everything well enough with just the DC? If not, sure, why not try it? I'd (personally) love to hear how it works out. What harm could it possibly do to the shop vac? I guess it depends on how the impeller is housed (relative to the motor). If there is a sealed bearing between them, seems like the risk is low. If the whole motor rotor and impeller are all one exposed piece, maybe it's worse (I have no idea how shop vacs are built, though).

I guess that assumes you only cut wood on the saw, and generally only produce fine dust. Maybe install a wire mesh in front of the inlet to avoid small offcuts from hitting the shop vac impeller. Likewise, I've often made long, stringy swarf on the miter saw, but only from cutting aluminum or plastic.

[Doug Garson]

Like the others I'd be concerned about the shop vac fan with no upstream filter and suggest some form of pre-collector. Also I think your comparison of the shop vac vs dust collector is backwards. Shop vac would be higher suction pressure and lower flow volume than a dust collector. So it's the higher suction not flow volume that helps swarf collection on the Kapex.

[Andrew Pitonyak]

I recommend against this (for not particular informed reason other than I expect the shop vac to not be setup for it.

I have seen the 735 used outside with no dust collection and it spits stuff everywhere.

I connected mine to my primary dust collection (A jet something or other) and when I turn on the planer, the bag inflates because the blower is so strong.

I vaguely remember hearing that a small hose cannot keep up with the volume generated by a smaller hose.

So, what if you just connect something like a garbage can with an input and an output so that the large can can take the majority of the shavings. You can then have the output connected to your shop vac. I expect that the fan in the 735 will do most of the work here.

[mreza Salav]

If the only issue is that the shopvac fills quickly (which I find it must be a very small, given that it takes a LOT of cut to generate substantial amount of saw dust from a miter saw) why not change the bucket to a larger one? You can still use the shopvac on that larger bucket; just make an adapter out of plywood or MDF to fit between the two.

[Dan Schmidt]

Get a dust deputy.
http://www.oneida-air.com/category.a...-B5C357DFE131}

[Prashun Patel]

how big's your shop vac? Can you just get a bigger one?

Or, can you use a drywall collection bag inside your shop vac to make frequent emptying less painful?

Do you have room ABOVE the shopvac for a preseparator? There are rube-goldbergish contraptions to minimize the space the preseps take. I know you said you don't want one, but besides making container emptying less painful, the filter performs better for longer than without it. (I'm sure you've considered that, tho).

[Peter Aeschliman]

I agree with those who are saying that the shop vac motor is not designed for unfiltered dust. It's not the same design as a dust collector, where there's a TEFC (totally enclosed, fan-cooled) motor and the dust never touches any part of the motor. It pulls ambient air through a fan to cool the motor. Shop vacs get their cooling air from the dirty air that it is sucking up. That's why the filter is upstream from the motor.

Have a look at this. Shop vacs typically use a "flow-through" motor. It's important to filter the air before it touches the fan and motor assembly.

http://www.westernwholesalevacuums.c...rs-guide2.html

The central vacuum system's equivalent of the dust collector design is the tangential bypass motor, which could be configured just like a scaled down version of a central dust collection system (dirty air goes through the fan/impeller, and is blown into a filter).

Also, I'm not sure whether your central dust collector would over-drive your shop vac, or whether it would have the opposite effect. I'm not sure I really follow the logic- it seems you're saying that you want the high static pressure of teh shop vac, but don't want the dust to accumulate in the shop vac bin. Honestly, I would just live with emptying your shop vac.

[Dan Friedrichs]

How about hooking your DC via a blast gate to the shop vac's existing bin? Makes emptying the bin much easier

[Myk Rian]

I have seen the 735 used outside with no dust collection and it spits stuff everywhere.

He isn't discussing the DW735. It's a Festool Kapex saw.