Closing air gap on tools? and adding hard bends to the DC design

[Kevinmk_37]

I am modifying my shop with an existing CV1800 and 6" pipes throughout. Ports are all 6" with 6" solid pipe all the way with maybe 12" of 6"flex hose at the very end of each run. My table saw is the first drop from the cyclone and everything has blast gates through out. All 90 bends are made with 2 45 deg and a small straight sections. Basically following all the guidance found here. FYI the dust collection system has been working great for years.

Question 1) I noticed under my tablesaw's cast iron top that I have about 1" air gap all the way around it between the top and the cabinet. I was going to close that gap off but figured that I need to keep air flow moving by keeping the total area of gap (plus the gap between the zero clearance blade and insert) to match the cross section area of the duct. Is this a correct assumption?

Question 2) I am adding an outfeed table (with drawers under it) to my table saw and the 6" duct is attached to the TS cabinet at the location where I want to put the outfeed table and no I don't want to add another port on the cabinet. I have two options: A) raise the bottom of the cabinets so that they are above the existing duct which will result in the loss of the lower 6" of drawers or B) add 2 hard 90 deg bends in the ducts and run the ducts around the back side of the outfeed table to the table saw cabinet. I am thinking there will be 8" or so of gap between the back of the drawers and the TS. I like option B but wonder how badly will it impact the performance of the DC? There is probably 30' of hard pipe plus 2 long wye(made with 2 45 deg as described above) between DC and the TS.

I appreciate any thoughts anyone has on this matter.

Kevin

 

[Curly1]

Question #1. You want about twice the area going into the cabinet as going out so leave the gap around the top open, maybe close a little in front of the blade if it is throwing dust through there. Total up all the openings and add more or crack open a door or panel, preferably opposite the intake port to improve the flow.

Question #2. Could you shorten the bottom drawer so it isn't full depth, allowing room for a radius elbow? Any door panels that could be removed and used for a dust port? If you had to use the sharper bends it will still be better than any 4" port saws usually come with.

Pete

 

[McRabbet]

I agree with Curly1 on #1. With regard to #2, your losses with a pair of 90 degree elbows will be very significant. You would be better leaving the existing duct in place and design the cabinet and drawers to avoid it. E.g., maybe the drawers can come in from the sides or a combination of one side and the back. Losing 6" of drawer space is not a big loss.

 

[Kevinmk_37]

Thanks for the quick reply Curly and McRabbet. Your comments on Q#1 are great as I had no idea. On number 2 I will take your advice and remove a row of drawers as the existing path of the duct runs at a 45 deg from corner of the future table to the port which is eliminate a row of drawers.