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How Much CFM Do I Need?

by Don McMullen

As we expand our shops, dust collectors tend to be almost an afterthought. Most of us have the experience of adding small stand alone units to table saws, planers and sanding equipment. One day it becomes obvious that we need more organized system. Where to start?

 

In this article we'll discuss a simple method for getting a rough idea of how much cubic feet per minute (CFM) of air flow your dust collector will need. Here are four easy steps:


  1. Take an inventory of all the dust producing machinery in your shop.

  2. Measure the diameter of each and every dust port on each machine (note: most manufacturers will state the cfm requirements in product manuals).

  3. Convert the diameter of the dust ports to cfm requirements.

  4. Add the cfm numbers and you'll have an estimate of the total cfm needed for your shop.

 

                         Dust Port Diameter      CFM

                                          1”                     24  

                                       1-1/2”                 53  

                                         2”                     98  

                                       2-1/2”               150  

                                        3”                     220  

                                        4”                     395  

                                         5”                    614  

                                         6”                    884  

                                         7”                   1203  

                                         8”                   1570  

                                         9”                   1990  

                                       10”                   2455  

 

Here's a simple example:

 

Table Saw with a 5” dust port              614

Planer with a 5” dust port                    614

Band Saw with a 6” dust port              884

Edgebander with a 4” dust port           395

                 Total System CFM             2507

 

You'll need at least a 2500 cfm dust collector in this example.

 

This simple rule of thumb will get you started. Bear in mind that larger shops with complicated systems and long runs of duct will need more computations. Also options like blast gates can enable you to cut off certain machines when not in use thereby reducing the total cfm requirements. Still, this is a good first step.

  



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