TheMarvelousOne said:
please excuse my ignorance but I'm still trying to understand these Festool vacs before I pull the trigger and spend $550 on a MINI.
Is it all about the CFM? So a $120 shop vac that claims a 168CFM can perform better than a $550 CT Mini that has 137CFM?
I'm guessing the Festool motor is built better and has more features but just curious about the performance and ability to collect dust.
There are two key parameters: volume of air which the vacuum can pump through in a minute (measured in CFM or liters per minute) and water lift (measured in mm or cm or inches as height of the water column which a vacuum can lift). The first is a measure of volume without load, it is measured at the inlet of the vacuum without a vacuum hose. Any resistance to air flow would decrease this parameter. The second is a measure of vacuum without volume, it is a measure of how high water would be lifted in a hose if you dip end of the hose in a bucket of water.
The trick is that both of these parameters are lab-type characteristics. You never use a tool with a completely open or completely closed air passages. You are always in between. You always get lower CFM than written on the paper. By how much lower - depends on water lift, diameter of the hose, and size of air passages in the tool.
If you pump air through a large diameter hose and use it for dust collection from tools which generate lots of dust but do not have effective dust collection shrouds and do not have significant obstacles to air flow, you only need CFM. CFM would not drop much if you use a 4" vacuum hose and wide open air inlet on the tool. A $70 shop vac would beat Festool. A Jet vacuum can have 500 or even 1200 CFMs and will exceed Festool almost by a factor of 10 when it comes to collecting dust from a table saw where sheer air volume and air speed are needed.
If you pump air through very narrow passage ways, e.g., in a sander, and if you use a small diameter flexible hose, you need a lot of water lift to create enough vacuum to get air through them. You do not need much air flow. This is where dust extractors come into play. They have a different turbine design and they typically have twice the water lift of standard shop vacuums.
Hence, for a table saw, a shop vacuum (any brand) generally performs the same or better than any dust extractor (be it Festool, Bosch, or Fein). Typically, you get around 180 CFM from a $50 - $70 vacuum, and this is more than Festool. All dust extractors are rated around 140 - 160 CFMs. This is not hard to beat. In contrast, for a sander, a dust extractor will beat any shop vacuum by a wide margin. No shop vac can get even close in water lift. For tools in between, e.g., track saw, it is a wash, and there may be some small differences in performance of turbines in dust extractors from different manufacturers. Overall, this is the application where creature comfort features (noise level, auto on, hose rigidity and weight, etc.) come into play. No reason why you can't use a cheap vacuum for these applications.
As always, no tool is perfect for all conditions and all tasks.
For the track saw, you need a long and flexible vacuum hose. Dust extractors excel in this area. With Kapex, you can use anything, as long as you use 36 mm hose, preferably short. I used a Ridgid 12 gallons vac from the Home Depot which I got for $69 and found no visible difference in the efficiency of dust extraction. Hated it because of the noise and because one has to turn it on separately. You forget it, and your Kapex is all covered with dust, and you are covered with dust as well. Eventually, I replaced it with CT26 dedicated to the Kapex. I saw no measurable improvement in dust collection, but much nicer operation.
Not sure why you would want a Mini. It is almost the same weight as Midi, same specs, but it has a much smaller dust bag capacity. Storage space is the only advantage that comes to mind as is is a little shorter than the Midi.
