# Miter saw dust collection question



## Bigun (Aug 24, 2014)

Today I decided to work on miter saw dust collection. The one I thought would best fit my needs is the box with a slit in the bottom back. I don't have the small hose so I taped it up on the saw and the 4×2" Y and just used the 4" to test. Little disappointed at the trial run though. A lot of chips was dropping closer to the saw but I didn't notice any dust clouds. I guess my question to you guys is, will attaching the 2-1/2" hose make a difference? It is better than nothing but I was hoping for more I guess. The gap is 1/2" would less be better?



























Thanks for any imput,


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## pjones46 (Mar 1, 2011)

Basically I did the same thing as far as the shape, however, I cut a hole and fitted a 4" flanged adapter onto the bottom of the box centered behind the chop saw as far to the back as possible and connected a 4" hose to it which in turn has one of Rockers fast connect fittings on the other ends connecting to my dust collector. I then connected a 1-1/2 hose to the chop saw exhaust port making it long enough to fit down the into the 4" flanged adapter. This allows for higher suction at odd angles off center.

It still doesn't pick up 100% but it is better than 90% and keeps the sawdust off the floor and wall behind the chop saw for a faster clean up at the end of the day.


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## PLK (Feb 11, 2014)

With the box that far behind the saw there will be little if no air movement to the 4" line. I gave up on my slider for DC and switched to a non slider for the shop and built a cabinet around it.

4" DC on the bottom and a shop vac attachment. It works well but it's again not a slider. I save my slider for work and on job sites.

Here's mine.












better view of it as it is actually used.

Paul


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## crank49 (Apr 7, 2010)

You want at least 400 FPM intake velocity in the slot.
1000 FPM would be ideal but that is industrial standard and may be more capacity than your DC can muster.

Just make sure the area of the slot is at least equal to the cross sectional area of the DC hose.
I'm guessing, but your hood looks to be about 24" wide so 24×1/2 = 12 sq.in. A 4" hose is pi x 2 squared = 12.56 in.sq. So a 1/2" slot is the absolute minimum. 1" would be much better.

Now if you are pulling ~400 CFM through that hose you have about .087 sq.ft. area divided by 400CFM = 4597 FPM. This pipe size is costing you effeciency loss. A 5" hose would be much better at about 3000 FPM..

Now the height of the hood looks to be about 1 1/2 ft. If so, the open face of the hood is 1.5 ft x 2 ft = 3 sq.ft.
Again if you have 400 CFM being extracted you have 400 / 3 = 133 FPM intake velocity in the hood opening. That is pretty weak. Will catch a floating dust cloud but not enough to grab particles with mass and velocity.

Sorry for being so windy. Bottom line, increase your duct or hose size to 5", increase the slot to 1" or 2", and add a shop vac hose to the blade shroud and you will have about the best you can get without more horsepower and bigger pipes.

Yes, the 2 1/2" hose would make a big difference if hooked up to a shop vac. Not so much so hooked up to a DC. DC is not enough static pressure to take advantage of the close capture of the blade shroud.


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## Bigun (Aug 24, 2014)

> Just make sure the area of the slot is at least equal to the cross sectional area of the DC hose.
> I m guessing, but your hood looks to be about 24" wide so 24×1/2 = 12 sq.in. A 4" hose is pi x 2 squared = 12.56 in.sq. So a 1/2" slot is the absolute minimum. 1" would be much better.
> 
> - crank49


it's 33 inches across and 21 inches tall, 4" collection hose.
I've got a 2-1/2" hose and fittings that I'll hook up tonight and see what that does. I'm used to bringing saw forward then down and push into the cut but maybe it'll do better if I leave it slide to the back and come straight down and slide only when i need to.


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