Vacuum Dogs - The Dogs that Suck.
looking at some vacuum clamp heads, I noticed they all had one thing in
common. They all have a grid layout that you apply a rubber seal to
hold your work. Where have we seen a grid before? The Festool MFT
workbench. So why do we need to buy an expensive new vacuum clamping
head when we already have something similar?
The Vacuum Dogs allow you to use a single MFT hole or multiple holes to
apply a vacuum to hold your workpiece. This could be for sawing,
sanding, routing, or virtually anything in woodworking. The rubber
strip creates the air gap that will hold the vacuum. The larger the
area under the rubber strip that can hold the vacuum, the more force
applied to your workpiece. MDF does not hold a vacuum well so it will
be necessary to cover the MDF top with shellac or a self leveling
Dogs will work in all the various holes sizes of the MFT. One end
accepts 3/8 inch O.D. vacuum hose and the other end has a threaded hole
for 1/4- 20 bolts. This is so the dog can act as a plug. When the bolt
is installed on the Vac Dog, I call it a Plug Dog since its new duty is
to act as a plug to a hole .
The rubber strips can be re-used many times. It's also possible
to carefully remove the rubber strip from the table and still re-use
them. The rubber strips and the plastic tubing are available
through local hardware stores so there is no need to re-order through
The Vacuum Dogs will be sold as a kit. The kit will consist of 3
Vac/Plug Dogs, 1 Vacuum Manifold that allows up to 3 Vac Dogs to
connect to one vacuum source, 4 pieces of 1/4" clear plastic tubing
approximately 4 feet long, and 15 feet of foam rubber strips. It is
possible to hook up another manifold to the first one and add extra
dogs if needed.
I will NOT be supplying the vacuum pump (and filter), vacuum gauge, and
foot switch. These are readily available and one source is Harbor
Freight. Vacuum Pump 66466 is $150 or 98076 for $105 will do the
job fine. You can also look for a RobinAir or MasterCool pump capable
of 3 cfm or more and they will work fine too. Don't forget to try eBay.
household vacuum or a shop vacuum will NOT work. These are designed to
have a free flow of air or the motor overheats. A vacuum has no free
flow of air so it will overheat these units. Likewise, the vacuum pumps
listed do not like the free flow of air, it will cause faster wear and
tear; they want a vacuum and will work for hours under those
A vacuum gauge is optional but it is well worth the money (Harbor
Freight 93547 $15). You wouldn't operate your air compressor without
the gauges, it should be the same for your vacuum pump. It is the
only way to know how strong your
vacuum is. It can be hooked into the pump with a barbed "T' connector
or it may be easier to hook it in place of one Vac Dog. Many setups
will be using one or maybe 2 dogs, so the vacuum gauge can be left
hooked up using the hose from the 3rd dog. The vacuum scale is usually
in "Inches Hg" and each inch equals 1/2 psi. We are wanting 20 inches
or 10 psi. A higher reading is even better.
There are many foot switches out there and many styles to select from.
A cheap effective one is at Harbor Freight (96618 for $15) that is all
plastic and has no covering to protect from accidentally hitting the
switch. A search on Google will find you all kinds of foot switches
with all kinds of prices.
I know most of you would prefer I sell a complete system with all
components. The problem is I would have to buy the pumps and switches,
un-box them, test them, and re-box. That takes time and I'm entitled to
be paid for that time. But if the pump goes bad during shipping, then
you have to ship it to me, I have to ship it back to manufacturer,
costing me more time and money. Next thing you know I'm too bust taking
care of "warranty work" that I can't get any dogs made.
The main problem you will have with Festool's MFT table is the top is
made from porous MDF. The MDF will stop you from getting a strong
vacuum. You are going to want to cover the MDF with shellac or
urethane. We have a found a "self leveling" urethane such as
Benjamin Moore's CM78 work excellent. You are wanting a thin
smooth layer on the top and in the holes. DO NOT let it run or you will
be sanding every run out before you will get any vacuum. We just trying
to cover small invisible pores so this all you need. If it is absorbed
in the top, this is perfect. Let it dry and you're done.
The area where the rubber strip is applied needs to be smooth, flat,
and kerf free. For smaller pieces (under 15 inches) one hole will
work fine. Select your hole and install the Vac Dog. Install the rubber
strip just shy of the other holes surrounding the selected hole. This
should give you a square of about 6 inches per side. It the
workpiece is long and narrow, let's say 18 x 12 inches, it may work
better to have the rubber surround 2 holes giving you a rectangle
of about 6 inches by 10 inches. All the air will leak through the
second hole so you need to install another Vac Dog or a Plug Dog (Vac
Dog with a bolt in it). You won't get any extra vacuum by using a Vac
Dog, it's just a way to stop the air from leaking. A longer workpiece
may require surrounding 3 holes with the rubber strip, giving your
about 6 inches by 14 inches.
Let's say you are routing a dado in a 4 foot long plywood. You can't
let either end wiggle or you will lose the tight fit of the dado. Here
you will want to surround one hole near one end of the board and
another single hole near the other end of the board. You will want a
Vac Dog in each hole so you can apply suction to both ends and stop any
If you were sawing a long board, you might consider covering one hole
the extreme left of the table, one hole under the guide rail, and one
hole to the right of the guide rail. This gives you positive control of
the workpiece and the cut off. If the long board hangs over the table,
the vacuum will hold it. If the long board is wide, you might want to
use multiple holes under each rubber strip to give extra support. You
will still be able to use the Qwas
Dogs and Rail Dogs with any of these setups.
With multiple holes in one rubber strip and multiple areas on the
table, the clamping options and possibilities are virtually unlimited.
The above examples are just a beginning of what you can do. It's
possible to use "L" or "T" shapes for 90 degree corners. Or have jigs
that use some holes for alignment and Vac Dogs to hold the jig. A
board with a couple of 20 mm holes cloud be attached to the MFT's side
extrusions for vertical clamping.
Here is a small video to give you an idea what it's all about: Vacuum
Dog Kit Domeonstration video