Dust safety question

(Samuel) #1

I’ve been reading all of the postings here about dust-heads and safety.

I use my Nomad to carve wood in a relatively small enclosed area, and it doesn’t have very good ventilation, so I am concerned.

I’m sort of new to all of this, so I was wondering if I really need to create a dust head, or whether I could connect, say, a Festtool dust extractor just to a port that I cut into the back of the Nomad enclosure.

Would that be sufficient to make it safe for indoor use when cutting hardwoods? Or is it really important that the vacuum vent be that close to the cutting tool? Do I need something like a Dust Deputy inline before the extractor?

I appreciate any advice from knowledgeable people!

Safe Dust Separation and Collection
(Mark Bellon) #2

The particles created when one machines friable (“easily crumbled”) materials (e.g. wood, carbon composite, FR4, Garolite, Fiberglass, MDF) are very dangerous to ones health. What’s more, the damage is cumulative - repeated exposure increases one’s risk.

The easiest way to deal with this problem is totally avoid it.

At a high level there are two solutions (EPA acceptable):

  1. Dump the air outside such that it cannot easily return inside.

    This solution requires that the air go through a dust separator (“cyclone”) to remove most of the
    particles. There may be an issue with neighbors having to deal with sound using this technique.

  2. Dump the air inside (where you are) by using a HEPA filter rated at 0.3 microns.

    HEPA filters are expensive - US$80-100 is not unknown - so one wants to avoid clogging up the
    filters rapidly and having to replace them. This is where the cyclone comes in. The cyclone
    removes 98% or more of the particles. The cost is about that of a filter so the cyclone is a really
    good idea.

A dust head provides lofting close the work and ensures the best possible collection. It also helps contain the mess. While we’re generally concerned with the small stuff, some hard woods (e.g. Cherry, tropicals) have dangerous chemicals and/or viruses in them. We really want to limit our exposure to the visible stuff as much as possible.

Just evacuating the enclosure is definitely a good thing… the negative pressure will prevent particles from escaping the enclosure… but it is far from best because a lot of particles are left.

The Festool is a dust collector, the cyclone a dust separator. Self disclosure - I have a Festool CT26 with an Oneida cyclone on top. Festool is some of the best to be found… and has a price to go with it. The price is due to being safety certified by the EPA, UL, EU and the German safety agency. Serious stuff.

Festool is the no questions asked “go to” solution. We can help with trade offs and alternatives.

If one can dump the air outside, that solution can be minimally expensive.

Of course, one could do the work entirely outside, then don a 0.3 micron HEPA filter mask (~US$50) and vacuum up outside…



This is my Festool:

I use 50 mm tubing to decrease friction issues with the air flow.

(Patrick Andersen) #3

An old thread I know but I have a question of mbellon (Mark Bellon). I have been scared by some of the things you have written about dust and I am seriously considering a CT26 E system similar to what you have in your pix above. Checking the Festool page I see that the hose diameter on the CT26 is 27mm.

In the pix above you seem to have hoses that are closer to 50mm dia. In other threads you have stated that one shouldn’t use a larger hose closer to the cutter than that close to the vacuum. Obviously you have used the larger hose for a reason, is that because of the cyclone or better airflow or what? Many thanks for your wise guidance.

(Mark Bellon) #4

I have been scared by some of the things you have written about dust

Everyone working in friable (“easily crumbled”) materials (e.g. wood, MDF, FR4, Garolite, carbon composite, fiberglass) should be very concerned. MDF and carbon composite are some of the most dangerous materials to CNC.

Machining friable materials generate particles that are similar to Asbestos and can easily be even more dangerous because they are hot and chemically active. Toxic, carcinogenic, and teratogenic properties are quite common. Exotic hardwoods (from equatorial areas) can also contain viruses and microbes that are dangerous.

Air safety is the naughty secret of the CNC machine industry. They are more than happy to sell machines and not tell people of the dangers of machining friable materials. Air safety - and sound safety as well - should be things clearly stated “up front” IMHO.

I am seriously considering a CT26 E system similar to what you have in your pix above. Checking the Festool page I see that the hose diameter on the CT26 is 27mm.

The Festool is one of the best; it’s not the cheapest but it’s not insanely expensive either - once one consider what it does and how it is rated. The Festool CT series is rated safe by the EPA and EU for cleaning up Asbestos, lead, and other nasties.

Keep in mind that it uses a HEPA filter rated at 0.5 (or better) microns to ensure very little (not quite nothing) dangerous gets past the exhaust. That said, HEPA filters are EXPENSIVE. The best way to avoid going through them like crazy is the use a dust separator (i.e. cyclone) ahead of the HEPA filter protected dust collector. The dust separator can remove 95-99% of the particles before they get to the filter.

The picture of my Festool has an Oneida cyclone on top.

It is much cheaper (to achieve the same air safety) to use a much less expensive dust collector and cyclone and dump the air outside the work area (e.g. outside your house). The downside of this method is NOISE. You and your neighbors will not be happy unless some care is used. An enclosure around the vacuum equipment handles the you part; a muffler the rest. This isn’t hard but it is a bit advanced. Since this is such a cheap method, it should always be thought about.

By-the-by, it’s very common for the vacuum equipment to make more noise than the CNC machine! This is especially true when the CNC machine is in an enclosure.

If one can go the dump the air outside route, I can discuss the best way to do this. One can trivially use 4 inch tubing and high strength dust collectors; they are cheap. Only at the last moment does one step down to the largest that can fit on your machine (2.5" recommended on small machines).

Particles moving in air generate static. This can cause the particles to clump, start a fire, or even cause an explosion. All of these things have happened at large shops; with small machines the risk is low but still present. The solution is simple - use static dissipative tubing or run a BARE ground wire through the tubing.

The Oneida is made entirely of static dissipative plastic; so is the tubing sold with it. All Festool tubing is static dissipative.

Any time static dissipative tubing is used, a solid ground is necessary. If you don’t have one, get a ground/neutral checker and check you outlets. If they aren’t correct, have a electrician come and fix them. By-the-by a swapped neutral and ground can be fatal.

Some of the rules for vacuum tubing can be found here:

Yes, the stock Festool machines come with a 27 mm, anti-static hose. That is too small to do a good job for CNC dust collection. Festool sells a 50 mm anti-static tube separately. This is what I use.

The reason is found in the vacuum tubing rules - stay as large as you can for as long as you can (from the dust collector to the dust head).

The Oneida is designed around 2.5" tubing but 50 mm tubing works fine. Another vacuum tubing rule comes into play - don’t reduce and then expand then reduce the tubing size.

I leave the 27 mm, anti-static tubing in the CT26 most of the time. I use it when I decouple the Oneida from the CT26 and use the CT26 as a shop vac (with a HEPA filter!).

Here is the part offered at Amazon:

A 4M version is also available.

Review the rule of vacuum tubing. If you can make the tubing shorter, do it! It is easily possible to remove the connector from Festool tubing, trim the tubing and reattach the tubing.

(Patrick Andersen) #5

Thanks Mark for your time and efforts. I have definitely decided I will go with a CT 26E and 50mm hose even though they are considerably more expensive here in Australia than they are in the US. I am also investigating the “Ultimate Dust Deputy” (as in your setup). Unfortunately it is not available here.

(Mark Bellon) #6

As I stated before, the Festool is an awesome solution… but it’s not cheap. You get what you pay for… but other solutions are possible.

There is no magic to a cyclone. The Oneida is nice since it sits directly on top of the Festool. It can also be placed alongside. Alongside, any quality cyclone can be used.

I can help you find a solution that will work on a budget. Message me and I can help you work out a solution. Remember, anything is better than nothing; perfection is the enemy of “good enough”; thinking before acting often finds an acceptable solution.

(Patrick Andersen) #7

Understood Mark. I will purchase a CT26E later this week. For a cyclone I currently have cheap Chinese ‘knock-off’ which seems to work pretty well with my shop-vac. My reason for looking at the 'Ultimate Dust Deputy" is because just recently I brushed by my dust hose when the CNC was cutting MDF, the hair on my arms and legs stood up as a result of the static buildup. I know that static and dust is not a good combination.

I also have seen a youtube video by the New Brit Workshop basically reviewing the ‘Ultimate Dust Deputy’ [https://www.youtube.com/watch?v=ZXFcnJ_LUvk] (https://www.youtube.com/watch?v=ZXFcnJ_LUvk) and the CT26. I was impressed by the combination and performance. I also have a high regard for this man’s recommendations. I currently have email enquiries out for prices for a UDD landed in this country.

Meanwhile perhaps you can advise, if I were to run a bare copper wire inside my current dust hoses and the mini cyclone and earth it, will that help ameliorate static build-up in my current system? I have seen references by others that this really works and by others that suggest it is a waste of time.

(F B) #8

I’ll preface this by saying I run a Thien Baffle separator with a 1 micron filter bag on my dust collector. The research Matthias Wandel did had some interesting results. Check out the link below.


(Mark Bellon) #9

Wood (“saw”) dust, in the general case of wood working, is not that small and not that dangerous. CNC and modern, high speed wood working tools generated particles that are an entirely different matter.

Machining Medium Density FibreBoard (MDF) is dangerous. Yes, it is saw dust and glue. The dust can be an issue… but the glue certainly is. When machined at high speed, it splinters into tiny particles and generates nasty gases - toxic, carcinogenic, and teratogenic.

CNC particles are considerable smaller and hotter than most wood working and, as such, raise the danger to particle exposure. Things like FR4, carbon composite, and Garolite splinter in extremely dangerous particles, akin to Asbestos.

This isn’t simple about allergies; this is about respiratory health. The large stuff isn’t a problem; it’s expelled or you will cough it up (not fun). The small stuff is involved in cumulative exposure, not unlike smoking.

CNC machining hardwoods release some nasty stuff besides particles… they release nasty chemicals and may release viruses and microbes that one is not prepared to handle.

Constant exposure causes headaches, immune system depression, nasal issues… the list goes on.
You do not want to be exposed to these things.

A Thein Baffle is an excellent dust separator. The best studies I’ve seen show that it is not quite a effects as a good commercial cyclone but it is very close. Since the purpose of the dust separator is to reduce the volume of particles getting to your expensive (or pain in the neck to clean) filters, it’s perfectly good to use one.

There are other types of dust separators including suspended water droplet. No practical for most of us, hence the use of cyclones - the most easily accessible for most - or Thien Baffles.

I’m not aware of a commercial Thien Baffle (despite many years of looking; someone point me to one if you find it). This is because most cyclones are a bit more efficient.


No, I am not a Pentz “ite”. I find him extreme. That said, he isn’t totally off the mark either. His Physics (I trained in Physics) is correct about air velocity and particle pick up. Most people cannot afford to go to his extremes. I’m happy to get people to do the best they can and they can afford. Anything is better than nothing and it’s not hard nor expensive to get “close” to Pentz levels, especially with a little creativity.

He doesn’t address things like FR4 (make your own PC boards?) and carbon composite. This are things that are CNCed at home now-a-days and the particle exposure from these are NASTY.

(Mark Bellon) #10

. For a cyclone I currently have cheap Chinese ‘knock-off’ which seems to work pretty well with my shop-vac.

Virtually all shop vac are crap when it comes to filtering. They get the big stuff and let the nasty stuff through. That you have a cyclone is a real plus.

Cyclone dust separators vary in efficiency. Any reasonably designed on is going to remove 90+% of the particles and virtually all of the larger particles. The small ones are harder to catch and so some get past. Better cyclone, better particle catch. Regardless, no cyclone can come close to 100% for all particles sizes.

The Thien Baffle is an alternative to the cyclone. It is remarkably efficient… but as good as a good cyclone. It’s main advantage is that it is nearly trivial and inexpensive to build.

The cyclone is removing a HUGE amount of the problematic stuff, reducing your exposure. Since the risks are cumulative, you’re doing a great job reducing your risks.

The output of the cyclone could be dumped outside (where humans aren’t) and you would be done. No exposure! All that is necessary is a 5 micron filter (essentially an easy to clean cloth bad) to prevent “snow” below the exhaust port.

The output of the cyclone inside (where humans are) is where things get dicey. The cyclone can only do so much and the nastier stuff is the stuff most likely to be released. We need a better filter. This is where the 0.5 micron rated HEPA filter comes in. This ensures that the nasty stuff is caught, that the exposure risk is lowered to extremely low levels.

My reason for looking at the 'Ultimate Dust Deputy" is because just recently I brushed by my dust hose when the CNC was cutting MDF, the hair on my arms and legs stood up as a result of the static buildup. I know that static and dust is not a good combination.

Anytime particles move in air, especially when they are hot or chemically active, they generate electrical charge (static). This can build up until a discharge and fire and explosion are possible. The explosion risk is pretty small for the machines where talking about. Fire is an issue.

There is another danger… discharge into your dust collector. Today, many dust collectors use microprocessors and they don’t like static. The original Ultimate Dust Deputy for the Festool (long since replaced with the current model) was made of a plastic that generated static and they regularly destroyed Festool CT series dust collectors.

Needless to say, Oneida and Festool quickly figured this out. They offered retrofit kits for the existing machines and redesigned to use static dissipative plastic.

I admit bias, I have one, and I too say that these are excellent devices.

To solve machining static, one must start with a solid ground. The dust collector must be grounded. The dust separator must be connected to the dust collector AND ON THE SAME GROUND. With small tubing, static dissipative tubing does the job. Static dissipative tubing can be expensive; it’s a bit of a luxury item in that it takes care of things (“one stop shop”).

There is an alternative way to solve this… bare copper wire through the tubing. Make sure it’s not “magnet wire” or covered in varnish. Bare. Run the wire through the tubing to the same ground as the dust collector. If you dust separator is metal, ground that too!

Do not run the ground all the way to the CNC machine… this can create a “ground loop”. Start at the enclosure (or dust head) and run the wire all through the tubing to the same ground as the dust collector.

(Jude Marleau) #11

I’ve built a couple bill pentz small cyclone and they work great with the saw dust from my table saw and stationary wood tools. I built an air cleaner box that feeds my a/c unit (clean cool air) that runs all the time I’m in there. But that actually stirs up the settled dust and increases my risks. So with all that I wear a dust mask when I work with mdf or exotic woods. I also run it an hour or so after I leave. I am bias towards bill pentz because all the information is there, but he is very extreme and I can in no way afford the cost or space required to do it his way but I am able to understand the mfg’rs hype and the deficiencies of doing the best I can (hence the dust mask) and I have learn tons studying dust collection on his site (YMMV). It seems to me that people depend on a cyclone where as a cyclone is an accessory and the filter is what you need to depend on. I totally agree with Mark and a dust mask for the cnc is mandatory to me (my cnc setup returns the vacuumed air into the closed enclosure which will blast in my face when I open the door), that said here’s the merv rating chart for filters: Merv_Rating_Chart.pdf (79.1 KB)
If the filter doesn’t state a merv rating on it than I don’t buy it.
Question Mark, I’ve grouded the vacuum hose and vacuum like you said to a separate dedicated ground circuit (the shapeoko is grounded thru the circuit board ground and outlet on another independent circuit) is it good to connect bare ground wires from the router and just the base frame of the shapeoko to this ground circuit?? I’ve added side angle iron to the bottom of the mdf base board for stiffness and the whole machine sits on a rubber mat so “draining” the possible static build up in the rubber mat is my concern. Thanks Mark terrific information as always.

(Mark Bellon) #12

Grounding the body of CNC machine doesn’t hurt. It’s sometimes done to ensure that electrical noise doesn’t affect computers. It can also bleed off a static build up.

Grounding the spindle/router scares the living daylights out of me. My concerns about grounding a router/spindle that doesn’t have an explicit ground already is that I’ve seen too many weirdly wired. I’m concerned about ground loops and weird signs affecting the RPM control circuit.

It’s also overkill if the CNC machine frame is grounded.


(Jude Marleau) #13

Wow, noted. I will remove that ground wire from the router, thanks. A lot of people think it can’t hurt, glad I mentioned it to you.