# Dust collection for bench grinders and belt grinders?



## Cavediver (May 24, 2017)

Do you have a dust collection setup for your bench grinders or belt grinders?

I'm planning a 2x42 belt grinder build and thought I ought to incorporate some dust collection if possible.  While I'm at it, I want to add it to my existing bench grinders if possible.

I'm planning on using a mid-size shop-vac in conjunction with a small cyclone separator lid and a metal 5 gallon bucket, probably with water in the bottom.  Will this be enough, or will I be wasting time and money?


----------



## woodchucker (May 24, 2017)

For my metal sander no. For my wood sander yes.
I don't want to ignite anything, so no I wait for things to cool and then vac them up.
A DC for a grinder would have to have a metal can, no plastic in the motor housing, and some way to close it if it goes on fire.
Why would it go on fire.. well oils on the metal and the sparks, or just hot metal.
It would be fine in a shop, they could isolate and control, but in the house, a little more trouble.


----------



## mikey (May 24, 2017)

Grinding anything, especially HSS and cobalt, is not nice to lungs so I agree that some kind of effort should be made to clear the majority of the dust as quickly and efficiently as possible. I have a water-filled tray directly under my lower grinder wheel and it catches most of the dust but not all of it. I tried making a shroud that hooked up to my Dust Deputy but it was a clumsy affair that got in my way and didn't seem to catch all the dust so I dumped it. I hope your iteration is more effective. 

Regardless of what you come up with, use eye protection and a respirator/dust mask. You cannot catch all the dust ...


----------



## Holescreek (May 24, 2017)

I built a dust collector for my surface grinder 15 years ago roughly based on a Torrit unit at a place I used to work at.  I have dual ports on it so I can use it with other grinding equipment.  The air is sucked into a dead space behind the filter box and comes out from under a  panel 3" from the bottom of the pan before passing up through the filter bags and a HEPA filter before passing through the blower and out the top of the muffler.  The design allows all the heavy particles to drop into the pan and the lighter particles to get caught in the filters.  The blower unit I used is from a portable 650CFM HF wood dust collector.  The exhaust chute (chimney) is lined with foam from a mattress pad to muffle the noise making it quite pleasant to work around.







I placed rocks in the bottom of the filter bags so they wouldn't get sucked up towards the blower.










I've been running it for around 15 years without any problems. I pulled the front covers off a couple of years ago to knock off the dust and check the filter bags expecting to see evidence of damage from sparks and there was none, the stuff doesn't burn. There was very little contaminant coloration on the HEPA filter either. I just vacuumed the grit out and buttoned it back up.


----------



## ACHiPo (May 24, 2017)

Holescreek said:


> I built a dust collector for my surface grinder 15 years ago roughly based on a Torrit unit at a place I used to work at.  I have dual ports on it so I can use it with other grinding equipment.  The air is sucked into a dead space behind the filter box and comes out from under a  panel 3" from the bottom of the pan before passing up through the filter bags and a HEPA filter before passing through the blower and out the top of the muffler.  The design allows all the heavy particles to drop into the pan and the lighter particles to get caught in the filters.  The blower unit I used is from a portable 650CFM HF wood dust collector.  The exhaust chute (chimney) is lined with foam from a mattress pad to muffle the noise making it quite pleasant to work around.
> 
> 
> 
> ...


Clever!  Can you post a pic of it installed?  I'm having a hard time figuring out where the inlet is in relation to the grinder.


----------



## Holescreek (May 24, 2017)

I don't have any current photos available (I'm at work) but here's an old one showing the chute.  Follow the hose and you'll see it enters the box below the sliding shelf that holds the bags.   There is a vertical panel inside the box that creates a 3" wide dead space with the opening at the bottom as I said previously.  My hose connections are on each side of the box, I have the surface grinder on the right side and a Deckel carbide grinder on the left.  I was just considering attaching a hose to my pedestal grinder (which sits in front of the dust collector) the other day.


----------



## Holescreek (May 24, 2017)

See if  this helps. The red area indicates the dead space created by an inside panel and a covered top when the filter tray is pushed back in place.  The blue line shows the air entering the dead space, then down towards the pan then up through the filters.


----------



## ACHiPo (May 24, 2017)

Holescreek said:


> See if  this helps. The red area indicates the dead space created by an inside panel and a covered top when the filter tray is pushed back in place.  The blue line shows the air entering the dead space, then down towards the pan then up through the filters.
> 
> 
> 
> ...


Got it.  Thanks!


----------



## woodchucker (May 24, 2017)

ACHiPo said:


> Got it.  Thanks!


Really, that confused me more.
I just don't see that airflow from that, or from the diagram laid on top of the pic.
Those hanging filters should be receiving the already filtered air, and those should be doing the secondary filtration, catching the fines.
I see you are moving air toward the impeller, but I don't see where the air is entering. What I do see, is that you expect the air to go through the cloth filters toward the bottom then come back up through the filter on top? and out.. how? won't it go back through the cloth filters? 

i just don't see that happening the way it's drawn.  
I do see the ability to make it work, but not as it looks now.  Since those cloth filters are made to fill with air, the air should hit the paper filter first and get pulled through the cloth filters and exit.  So either the impeller housing needs to suck the air from the hose and send it to the filter, or the impeller needs to move toward the bottom and pull the air through and push it out.  If those cloth filters aren't expanded fully while working then they will not work efficiently. the best way is to have the impeller after the filtered air, so that it is not hitting metal fines and destroying the impeller.

So what am I mising?


----------



## EmilioG (May 24, 2017)

A spray booth or filtered exhaust walls is one of the best ways to get most particles out of the air in your shop. They're expensive, but they clear out the dust quickly.
Plus direct suction right on the grinder or sander, plus a good 3m respirator, plus good eye protection...


----------



## Holescreek (May 24, 2017)

You're missing the direction of the air flow.

The impeller sucks air in from the bottom of the box and out through the chimney.  The air comes into the box through the hoses, drops down below the filter bags and then through the bags (going from the outside of the bags to the inside), then through the flat HEPA  filter.  The filtered air then passes through the impeller and out the top of the chimney.  

People naturally assume that filter bags do their work from the inside out, filling up the bags with debris. (This is true for liquids for the most part.)  For  this application the long bags provide lots of surface area for air movement. The original Torrit unit I took the design from also had a foot activated "filter shaker" that was a pedal outside the box attached to a cross bar that went through the box attached to the bottoms of the bags.  When the unit started lagging in efficiency you'd stomp the pedal a couple times to shake the grinding fines off the outside of the bags.  The fines would then be caught in the pan at the bottom of the box.


----------



## Holescreek (May 24, 2017)

Before I forget, I did a bit of research before I built this thing and 650 CFM is considered minimum size for grinding operations .  When building your own put some thought into how loud it is.  Mine measures just under 80 dB and has a very low pitch.  I've stood next to it for hours grinding while it ran and could still hear the radio/TV in the shop.  The lowest dB vacuum cleaner I could find at the time was a Fein model that ran at 110dB.  

You might also consider mounting your sander on a downdraft table similar to a sanding table with measures taken to keep it from catching fire.  Fire was my biggest concern beyond breathing everything that spews off of a surface grinder.


----------



## woodchucker (May 24, 2017)

Holescreek said:


> You're missing the direction of the air flow.
> 
> The impeller sucks air in from the bottom of the box and out through the chimney.  The air comes into the box through the hoses, drops down below the filter bags and then through the bags (going from the outside of the bags to the inside), then through the flat HEPA  filter.  The filtered air then passes through the impeller and out the top of the chimney.



That's the part that is bothering me. Since the air is coming from outside the bags to the inside of them, what is holding the bags open. Normally the air holds them open, but you are compressing them. Do your bags have spring coils?  I don't see it, they look flat.  your bags would be collapsing and flattening out. you would be losing the efficiency. You want those bags opened wide so the dust spreads out. Why? so you get the maximum filter area without clogging it all up. How many micron are those cloth filters? if they are fine, then being the first filter would be a mis use. as they would fill quite fast. you would want to go from coarse (less expensive) to medium(less expensive) to high filtration (most expensive and largest volume to avoid filling). if you put a plexi front on that, would we see the bags open or closed?


----------



## Holescreek (May 24, 2017)

I don't remember what micron the bags are, too much time has passed. I'd hazard a guess somewhere between 10 and 20 microns.  I've been using the same ones for more than a decade now without any noticeable changes in performance.  I can't answer your question about the use of plexi since I'll never take the time to find out.  The rocks I put inside the bags  must be doing the trick of holding them straight since they were pretty evenly coated at the last cleanout.  The Torrit didn't have cages inside either, actually they were kind of flat but they were attached to the shaker bar at the bottom too.  I'd always intended to install a similar system but didn't see the need after I started using it.


----------



## Cavediver (May 25, 2017)

Holescreek said:


> Before I forget, I did a bit of research before I built this thing and 650 CFM is considered minimum size for grinding operations .  When building your own put some thought into how loud it is.  Mine measures just under 80 dB and has a very low pitch.  I've stood next to it for hours grinding while it ran and could still hear the radio/TV in the shop.  The lowest dB vacuum cleaner I could find at the time was a Fein model that ran at 110dB.
> 
> You might also consider mounting your sander on a downdraft table similar to a sanding table with measures taken to keep it from catching fire.  Fire was my biggest concern beyond breathing everything that spews off of a surface grinder.



Yeah, no way I'm going to hit that with a shop vac or even a larger setup like yours.  
I'm not expecting or even shooting for perfection.  My goal is simply a good reduction in the amount of airborne particulate for health reasons and to help keep things clean.  PPE will still be worn while I'm grinding (and after).

Noise is a good point.  I don't mind the shop vac, but a blower setup would be better.  As with most home shops, space is at a premium and I hate to give it up, but this might be the way to go.  Thanks for the input!


----------



## Cavediver (May 25, 2017)

woochucker said:


> For my metal sander no. For my wood sander yes.
> I don't want to ignite anything, so no I wait for things to cool and then vac them up.
> A DC for a grinder would have to have a metal can, no plastic in the motor housing, and some way to close it if it goes on fire.
> Why would it go on fire.. well oils on the metal and the sparks, or just hot metal.
> It would be fine in a shop, they could isolate and control, but in the house, a little more trouble.



Fire prevention is definitely something I've been looking at.  I'm hoping the cyclone action with a high level of water in the cyclone can (metal) will take care of things.
My wife and I own a Rainbow vacuum; it uses a water pan to grab the debris as the air is drawn through the system (the air is actually pulled in through the water column).  Hopefully my setup will have enough suction to perform the same way.



mikey said:


> Grinding anything, especially HSS and cobalt, is not nice to lungs so I agree that some kind of effort should be made to clear the majority of the dust as quickly and efficiently as possible. I have a water-filled tray directly under my lower grinder wheel and it catches most of the dust but not all of it. I tried making a shroud that hooked up to my Dust Deputy but it was a clumsy affair that got in my way and didn't seem to catch all the dust so I dumped it. I hope your iteration is more effective.
> 
> Regardless of what you come up with, use eye protection and a respirator/dust mask. You cannot catch all the dust ...



Since it's a scratch build, I hope I can do a good enough job incorporating this from the beginning.  That said, my understanding of airflow and the rest of it is all based on practical experience and common sense.  Maybe that will be good enough, though I doubt it'll be as good as I want...  Regardless, I suppose some collection is better than none at all...


----------



## woodchucker (May 25, 2017)

Holescreek said:


> I don't remember what micron the bags are, too much time has passed. I'd hazard a guess somewhere between 10 and 20 microns.  I've been using the same ones for more than a decade now without any noticeable changes in performance.  I can't answer your question about the use of plexi since I'll never take the time to find out.  The rocks I put inside the bags  must be doing the trick of holding them straight since they were pretty evenly coated at the last cleanout.  The Torrit didn't have cages inside either, actually they were kind of flat but they were attached to the shaker bar at the bottom too.  I'd always intended to install a similar system but didn't see the need after I started using it.


now I understand, the rock helps. I would think the shaker bar if attached to rings inside the bags and pulled down might keep more shape. Then the tubes become more capable and you can shake the dust off.

If I were modding your setup, I would free the metal pan, attach a piece of wood to stiffen the pan bottom, put rings in the socks, and screw clips to hold the rings to the pan. Also I would attach springs to the pan at the corners and pull the setup toward the floor. Now you have a fully expanded tube, you can add an arm to shake the spring loaded platform ..


----------

