The BradyVac II – A Production Vacuum Fixture on a Shoestring Budget


 BV2_1 About 2 years ago, I set out to create a removable universal vacuum fixture for doing various jobs. (Please review my Nov. 2006 article) This universal fixture was coined the ‘BradyVac’ by Bill Young. The basic idea is to take a sheet of Trupan or other ‘bleeder’ material, machine a grid into it, flip it over and have an entire surface that would pull vacuum through the face of the sheet. This of course means that you must actually have a vacuum and a vacuum port – or hole – in your support board/spoilboard where the vacuum plugs in. All of the fixtures and solutions I have created are used in conjunction with a single Fein Turbo III vacuum, which is designed for industrial use. You can buy the Fein Turbo III directly from ShopBot for $399. I have run my Fein at times for 25+ hrs straight and it is a great unit for any shop. Keep in mind that the BradyVac and BradyVac II can be used with any vacuum source, from a single Fein vac to a full tilt roots blower and everything in between. It is important to note that you must have free-flowing vacuum air going to the underside of the BradyVac sheet in order to get the full advantage of this configuration. It is not meant to be used with a dedicated bleeder board since this restricts vacuum flow. Only you can decide what vacuum system will serve the needs of your shop, and in many cases a single Fein is not adequate for certain types of production. ShopBot sales and support staff can help you determine the most appropriate vacuum setup for your needs, if you need some additional guidance.

The subject of vacuum fixturing is a hot topic, and many are confused by how vacuum can be used as a production aide when cutting various types of parts. While vacuum is not the solution for all sizes and shapes of parts, it is often a viable alternative to screws, clamps and tape when you have a stack of sheets or boards to cut for a particular job. The original BradyVac is geared towards those who want a universal solution where they may be cutting one size part now and then a different sized part later. You can make the BradyVac any size you choose as long as you have a vacuum port in your table to feed vacuum to it. This works pretty well for many parts, but there is a trade-off when using a bleeder board. You get the advantage of reduced vacuum pressure loss when you cut all the way through your part. The cutting tool creates a kerf where vacuum will escape from the bleeder, but at a much lower rate than an open-air setup. This is why pegboard works great until your tool cuts all the way through the part and leaks out the vacuum. The bleeder functions to slow down the rate of vacuum loss, but it comes at the price of not being able to fully exploit all the vacuum power you have at your disposal.

Purpose-built vacuum fixtures that directly expose the bottom of your parts to vacuum have superior holding power. These types of fixtures are suitable for solid wood planks, small parts and rapid machining where your feed rates are fast and material cycle time needs to be kept in step with a production schedule. Some purpose-built fixtures require gasketing to make the best use of vacuum, and to provide traction when parts have a tendency to rotate into the bit at the last second of cutting. Many fixtures benefit from the gasket materials offered by All*Star Adhesive Products. Check out their website to learn more about these products, and see the example at the end of this article. While fixtures of this type are very effective, the amount of time and cost in constructing this type of solution is often prohibitive, depending on the scope of the job. If the customer will consistently re-order the exact same parts from you over the life of the fixture, then this cost can be amortized over several production runs. Since creating vacuum fixtures costs you in time and materials, you should charge the customer for them or build this expense into the cost of the job.

Better, Cheaper, Faster…

If you are anything like me, you invariably have some jobs that need to be quickly and effectively machined in the shop in order to satisfy the customer’s deadline. Taking the time to engineer a custom vacuum fixture is often viewed as a gamble. Will it work? How long is it going to take to make? What’s it going to really cost me? Whether or not it will work is a question that I cannot answer without knowing what vacuum you are using, the size of your parts and other factors. I always encourage users to do their own R&D to determine through experimentation the realistic limitations of their vacuum power plant and method of delivering vacuum to the part. The real key with vacuum is efficiency. By this I mean understanding the limitations of your vacuum’s suction (inches of mercury) and flow rate (CFM), and how get the most out of it. The majority of my experiments have used a single Fein Turbo III, which to date has successfully held down parts ranging from 5/8” square to full sheets with no skin or tabs left on the bottom of the parts. In some cases gasketing was used to reduce leakage and part movement. Only through your research will you really know what your system is capable of and how to best leverage its ability. The goal of all of the BradyVac configurations is to cut all the way through your parts with no bridges/tabs in the fastest most efficient manner possible, yielding parts with superior edge quality. When configured properly and sensibly, vacuum will prevent vibration and material movement that can influence cut quality. Better hold down means better looking parts. Aside from software preparation, holding your parts to the table is the entire job in CNC. Everything else is relatively easy to accomplish.

A typical 4×8 BradyVac II takes about 1.5 hrs to make. It takes about 30 minutes to create toolpaths needed for the grid on the bottom part of the sheet, plus part boundaries and vacuum channels on the top part of the sheet. It takes about 30 minutes per side to machine the grid and the in-board plenums that sit under each finished part. It may take you more or less time to make your fixture depending on your skills & feed rates. The BradyVac II goes one step further than the original BradyVac by using your part vector outlines as a basis for creating the fixture so that everything lines up with your master cutting file. You can think of this system as a collection of individual vacuum pods that are adhered by the BradyVac sheet itself.

In terms of cost, if you want to really get the most out of this system, you will need a sheet of Trupan Ultralight MDF. It consistently bleeds vacuum through its face compared to regular MDF, which has been known to have varying resin content. This resin content effectively seals off the porosity in the middle layers of the sheet and will not work with the original BradyVac. However, any material can be used with the BradyVac II since vacuum will flow through the grid and into individual plenum areas under each part. The only disadvantage of not using Trupan with the BradyVac II fixture is that your scrap material will not be held down by vacuum pulling through the face of the Trupan. If you use a non-porous material to construct a fixture, you will want to add some additional plenum areas to hold your scrap in place while cutting. Many overlook this important step since scrap can get stuck on your dust collector, tooling or other moving parts, potentially becoming a safety hazard.

Let’s take a look at the basic anatomy of the original BradyVac first and then the BradyVac II so that you can get a complete understanding of how it works.


The foundation for the BradyVac I or II is a sheet of Trupan with a grid machined into it and flipped over with the smooth un-machined face pointing up. The only other thing you will want to do is edge-band or seal the edges of the sheet since a substantial amount of vacuum can be lost through the edges of the sheet. The edges of a ¾” sheet of Trupan equal just over one square foot of area that will leak vacuum if left unsealed. You can use edgebanding, foil, painter’s or duct tape to seal the edges.

Bill Young created a BradyVac virtual tool in the ShopBot Labs area of the site for those that want an easy way to create vacuum grids. You can check it out HERE.



The examples above show how your vectors need to be setup for machining the BradyVac II. You will need to create four toolpaths to machine your fixture. First, use your part vectors and offset them to the inside of your part about .125” to .25” to create an Area Clear/Pocketing toolpath about .125” deep. This will serve as a mini plenum that will direct vacuum air only under the parts you want to cut. Note that if your material is thin or flexible, you’ll want to put some ‘islands’ in the middle of the Area Clear to keep the material from flexing downwards towards the plenum. Then create some .5″ to .75″ diameter circles where you know the tool will never cut. Use them to create an Area Clear .125” deep. These will become countersunk screw holes to fasten the fixture to your spoilboard so that it doesn’t move when you swap out sheets. Then create a Machine Along Vector toolpath about .3” to .4” deep, to puncture through to the grid below. You want this to be deep enough to intersect the grid channels below. Make the Machine Along Vector lines perforated to keep some strength in the grid. Finally, use the same vectors to run a 90° V-bit into the channel to clean up the channel and increase airflow. Place your material on the fixture and start cutting!


This setup certainly brings a lot of versatility to your machine with even the tightest of budgets. A typical BradyVac II can be built for under $30 using Trupan Ultralight. I have personally cut over 10,000 parts using this type of fixturing on parts of various sizes. The fixture works so well that I was able to increase my cutting speed from 2.5ips on one project using the original universal BradyVac to 7ips using the BradyVac II. Your results may vary, so be sure to conduct your own research using your tool and vacuum system.

A couple tips for production

Be sure to ‘crown’ your material before placing it on the vacuum fixture. If the material has any type of bow to it, you’ll want to have this pointing up towards the ceiling. In this configuration the vacuum can pull it down flat. If the material sits on the table like a potato chip, the vacuum will have a difficult time sealing, unless you flip it over. Severely bowed lumber may not be suitable for vacuum fixturing without the proper gasketing. You should plane or prepare solid wood before attempting to hold it down with vacuum if it is bowed, twisted, rough or otherwise disfigured.

When using the BradyVac II you will get some chips & swarf in the channels of the vacuum when you remove your parts and scrap. You want to take care not to disturb the raised vacuum seal between your cutting tool tracks and the center area clear/plenum. A vacuum wand can easily damage this and cause leakage. There are two ways I have found to clean off the fixture for the next sheet. 1) Blow off fixture with compressed air. 2) Program the CNC to drive around the sheet picking up the bulk of the debris with the dust collector and then blow off the small remainder. No dust collector is going to get all of the chips off due to static cling or chips getting embedded into the fixture because of vacuum suction.

Additional Examples

You can also use gasketing in many different configurations using the BradyVac system. It is  more efficient to drill holes through to the grid then attempt to cut the gasketing with a router bit, as it tends to tear the gasketing rather than cut it cleanly, even using a special bit recommended by All*Star with a climb mill strategy.


In a future article, I will be showing you how to create economical vacuum pods using off the shelf material. These are perfect for long moldings and other long, thin parts.

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