The next project on the punch list was the dust shoe. I'm on the 6th or 7th iteration presently after trying a multitude of materials for the containment skirting. I have nothing but good to say about Kent CNC Split Shoe...
KentCNC. Dust Shoes & Accessories... however... his development of that particular design is geared toward the industrial 4" system... NOT a 2-1/4" shopvac system. So... I based my design loosely on Kent's removable brush and attempted to optimize the lower vacuum draw the smaller shopvac's develop.
The typical design of having a plate clamped to the router body with a vacuum inlet juxtaposed and the containment area of brush or skirt encompassing not only the vacuum inlet but also the router bit is just too optimistic for a shopvac. Having a directed vacuum draw focused at or centralized upon the router bit would be optimum. This would involve the necessity of a vacuum body to focus the draw at the bit or even better... surround the bit.
My attempt to create this directed vacuum was to make a 2 piece clamshell vacuum body having a tunnel that goes from the hose inlet to a surrounding ring chamber encompassing the router bit. I then created a reducer ring to neck the ring chambers diameter down to a 2-1/4" exit. Anecdotally this necking back down to the smaller dia exit created a greater drawing power or vacuum effort at the bit. I made the outside diameter of the reducer ring large enough so that the skirt material length when folded inward toward the router bit cannot contact the bit. I hope that makes sense...!
The material I ended up using for the skirt was cut from an old wetsuit I no longer could wear and had hanging in the closet at the forgotten end of the rack! It's 1/8" neoprene with a nylon outer shell. The skirt length is 1-1/2" and has the typical finger cuts. I created a 1/8" wide dado kerf about 1/2" deep on the bottom of the reducer ring. I then doubled up about 1/4" of the skirt top edge and jammed it into the kerf. It looks nicely finished and works great.
I test cut a MDF plaque and it works really well! There was no additional vacuuming of escapees required once the file was finished cutting!!!
There is one additional benefit of this shoe design. On the Hitachi M12VC router the cooling air exhausts from vents in the routers cast body straight down. This issue is overcome by the installation of a deflector plate. The deflector plate no matter how efficient interrupts the free air exhaust and causes the router to run slightly warmer than it would without the plate in place. With this new vacuum body dust shoe design the lower portion of the router body and thus the exhaust air is exiting into the vacuum ring chamber I created. I'm not certain but I believe the vacuum draw is greater in velocity than the router cooling air exhaust so that additional air is being pulled thru the router when in operation. I base this on the fact that after a 50 min run to test the system... the router body wasn't warm at all... it was ambient room temperature... hence the added benefit I mentioned.
Slowly I'm getting things checked off the list. The dust shoe is working great... so it is officially OFF the punch list!!!
Steve