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Florian F Fortner

Belt Grinder Dust Issue

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I always wondered how to get a belt grinder "living room ready". The more power the machine has, the more metal dust it blows out into the room. Lucky are those who have a dedicated workshop where a thick layer of steel dust won't matter, but some like me who do all their work at their usual workplace (a bikeshop in my case). There it will stick to everything magnetic (like cellphone speakers) and the whole room is covered in a thin black layer of steel dust. So I thought about ways to catch and reduce dust pollution. 

Under the grinder I place a huge barrel that catches 90% of the rough particles that are shot downwards (as I only grind up to 60 grit the particles are not to fine)

My first modification was an aluminium box around the whole thing, with a side-door for belt-change access (see pictures, though not yet finished). This catches most of the dust that will fly off the belt to all sides. Now only the platen area is exposed, but there are still sparks flying off to the sides and the fine dust that floats in the air can't be seen anyway.

So I thought about placing strong electric magnets close to the belt to catch the dust. What do you think about this idea? Might it work or is it bullshit? How much of the dust is steel and how much particles from the belt itself? 

I also thought about a fan system, but it needs to be quite powerful (could be done cheaply with used gastro/restaurant-ventilation parts). Then everything has to be super airtight and the fan needs a fine particle filter, otherwise it will just help to blow the dust into every corner... That's why I also don't vacumm clean, just use a broom and wet mop :D

Any other ideas are greatly appreciated!

 

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Edited by Florian F Fortner

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Yes you can use magnets, I've done it myself, more for fun than anything lol. But there is a caveat, until the sparks cool down the won't be caught by the magnet. So one right next to the platen won't do much good. But further in your box you should catch a lot. A good vacuum creating a strong negative pressure in your box will catch a ton of dust. As for your filter, buy the time the dust gets to the collection chamber, it'll be cool enough to be magnetic, so you could use them to pull a lot of dust out of the air to prolong your filter life. In the end, you'll never catch 100% of the dust, just be ready for that. 

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And be sure you add a water drop bucket in the line between the housing and the filter, otherwise you risk a filter fire or even dust explosion.

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Thanks for your replies! Good hint that hot sparks are not magnetic, I did never think about that!!

After some online research, I think I will go the oversized cyclone-blower route. I have already calculated the parts according to Bill Pentz' designs. Parts are cheap and the thin sheet metal is easy to work with. Some adjustments are needed because the designs are for wood dust which is less hot.

I will hook this up with 6" tubing to the rear of the grinder housing and just suck all the air with out of it. Let's see how it turns out... After grinding this device can also be used as a general air cleaner (with proper filters after the blower of course)

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Now I have time to start building the dust collection system and this turns into a WIP...

Here is the Cyclone body, handbuilt (what a stupid time-consuming job). Next step is the inlet and a cart to mount the dustbin, cyclone and blower. I am really curious how this will work!!

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I'll be eager to see your progress.  I've recently decided that I need to do something about dust collection myself, and have been weighing the options.  I'm curios to see what you are going to achieve.

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The beast is alive (and taller than expected)! :D We are just waiting for the filter mats, then It will be ready for the belt grinder. It sucks up shovels of sawdust, filings, shavings and doesn't spit anything out the other end... :P

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Wow, it's a beast :)  I hope you can do a video of it running!

What are the specs on the blower unit you used?

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Just don't forget the bucket of water between the grinder and the filters!  I'd hate to see all that work catch fire from a stray spark.

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Alan is right all that dust is explosive. I worked in a shop called kotzian tool  and before all the cigarette bans in the workplace and someone let there lit cigarette go through the dust collector and before anyone could get to the dust collector room the whole thing was up in flames

Edited by Jeremy Blohm

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Alan, I'll heed your warning! Thanks! Do you think filling the bucket under the cyclone with water will do it? The cyclone filters out most of the dust down to 2 micron, so this will be caught in the bucket. Only floating dust of smaller size will go out to the filter. 

Brian, the specs are: 2500m^3/h, 2HP, 12" fan wheel. Got it new for around $300. As soon as it's finished I'll tell you if it is strong enough :D

 

 

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That would work, but will fill up fast.  I would use the bucket as a sort of pre-cyclone spark drop.  I will see if I can find a picture later.

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The last thing you want to do is collect a bunch of fuel in one place waiting for an ignition source. Stop anything hot as close to its creation point as possible. 

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Found it!  Last post in this thread: https://www.bladesmithsforum.com/index.php?/topic/31928-my-new-dust-collector/

This is an absolute must as fine dust is fairly explosive.  Not to mention the cleaning bill you'll miss when the filter bag doesn't blow up, not causing you to need a fresh pair of pants...

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Ok, so this is a bucket with two pipes entering the lid, filled with water... How does this thing look inside? Do the pipes need to protrude far into the bucket? One more than the other? And doesn't most of the coarse dust also get caught in there? Then this bucket would fill up fast too... Or does it really just catch the sparks??

 

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In another post about this Jul said the input pipe stops about 15cm from the bottom and the outlet pipe is just on the lid, about 10cm of water in the bottom. And yes, it will also catch swarf and fill up, but it is probably easier to empty than the container under your cyclone.  That will fill up with finer dust soon enough!

The main thing is to have this bucket as close to the grinder as possible so you're not getting a buildup of fine dust in the first piece of tubing.  In small enough pieces even steel will catch fire.

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Iv'e seen two trains of thought on the water bucket, but haven't seen much in the way of hard data to back either of them up.  I'd love to hear first hand experience on either.

The first method is as is described in the post Alan linked to.  The inlet pipe dumps out just above the surface of the water, and the suction line only goes just past the lid.  I assume the theory of operation is that the hot particles will have too much inertia to avoid hitting the water, but it seems that some sparks may still get through.

I have also seen systems where the inlet pipe actually extends below the surface of the water so that the dust actually has to come up through the water in bubbles.  (Kind of like a thump keg)  It seems to me that a system like this would cause you to pull a lot of moisture through your fan shortening it's life.  I did have a setup like this for drywall sanding at one time, and it worked OK, but I didn't run it for enough hours to really see if it would shorten the life of my vacuum system.

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The machine is (almost) finished now. It looks impressive but doesn't really suck up dust from a distance as I hoped. It moves a lot of air and has good suction if it is very close to the dust, but this is not easily doable with belt grinders :P 

So the further plan is to add more "dust trap features" to the grinder around the belt contact area and make the box around the grinder airtight so the dust collector can suck the dust through it without too much loss. Placing the hose under the grinder, where the coarse particles fall down doesn't keep the fine dust from rising up (here lots of sparks enter the dust collector) and placing the hose close to the belt contact area is impossible without big effort and impeding the vision onto the working area (here almost no sparks enter the dust collector, as the sparks fall down into the dustbin). So my best bet so far is to pull the dust through the grinder box (keeping the inlet and outlet cross sections equal). 

Any other ideas I should try?

I am also still thinking about the spark trap bucket and how to keep it as loss-free as possible... However, the machine needs to work properly first!

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Here is a sketch of the three variants:

 

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Edited by Florian F Fortner
Added sketch

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I decided to try version Nr.3. To reduce the open area around the grinding belt, I attached some parts made of aluminium sheet and a clear cover. Now there is only little room to escape for the dust before it's sucked into the cyclone. 

It does work well. The only thing I notice is that the airstream does not enter the grinder enclosure symmetrically, because the grinder itself is not symmetrical (tooling arm, tensioner, etc..)

Will keep you updated after some serious grinding (I am starting a new sword WIP anyway :P)

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Forgot to post the finished machine: Our "holy roman belt grinder". After extensive use, I can say the time and money spent on the cyclone paid off! The airstream pulls away all dust, I don't need to wear a mask or clean up afterwards. It even cools the blades while grinding!!

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