Thread: Compound Mitre Saw Dust Extraction

Originally Posted by johnredl

. . . . . Now I'll admit that 2800 CFM sucking through a 6" dust port may be deemed as extreme by some people, but luckily I'm not friends with any of those people!

Nicely done but I can guarantee you that it is physically impossible to move 2800 CFM through a 6" duct. The most a 6" duct can deliver at normal DC pressures is ~1250 CFM and since that hood is in effect a naked hood and by the time the filters clog up a little and there are a few bends in the pipe it will be down around about 1000 CFM. To removed the restriction imposed by a naked hood you might want to make that a bell mouth hood.

Details details Bob! I was just going by the rating in the dusty.

Speaking of which, I am about to permanently plumb it into my setup. Am I better using 8" for the main or is 6" sufficient?

Also, sorry I'm not sure what you mean by the bell mouth hood.

Originally Posted by johnredl

Details details Bob! I was just going by the rating in the dusty.

Yeah but some newbie will read this and wonder how does he get 2800 CFM

Speaking of which, I am about to permanently plumb it into my setup. Am I better using 8" for the main or is 6" sufficient?

By an 8" main do you mean 8" all the way to the SCMS hood? or as a main line running down the middle of the shed?
If the former then using 8" is not worth doing because the outlet on the hood is only 6".
If the later then its worth it but
a) you will need to keep an spare port open on the main line otherwise the air speed in the 8" will be too low and sawdust may fall out of suspension.
b) Unless you use sheet metal ($$$$), 8" is hard to find. If you use PVC you will have to go to 9" which means a) is even more critical.

Also, sorry I'm not sure what you mean by the bell mouth hood.

Have a look in this thread.
https://www.woodworkforums.com/showth...r+speeds+hoods

Very nice mate. I reckon the SCMS is one of the biggest sources of dust in my shop as I love using it often. Do you have some sort of rubber "curtain" on either side with the handle of your saw poking through? I can't quite see in the photos? Do the plywood "wings" work well? Looks like a nice set-up!

As it happens, I've been working on my own dust shroud. I hope you don't mind me posting my pictures on your thread, as your title is generic enough I think for a few different people to contribute? (I'm happy for the mods to move it to a different thread if that is more appropriate...)

Mine's a bit different as it is built into a bench, but the intention of capturing that dangerous dust is the same.

I've opted for two ports. It was recommended that I have a port coming up from the bottom, as this takes advantage of deflected chips/dust bouncing around and then falling. I have a second port up high on the side hoping to get as much of the invisible dust as possible.

The bottom port is on the left, at 140mm, while the larger port is 150mm, up higher on the right. They don't seem to fight for air. They are both fed from a 200mm vertical.

I have opted to keep the vacuum hose on the saw as the "chip" collection on the Kapex saw is very good, even with no hose attached. Consequently, I thought it might be prudent to take advantage of this built-in collection? However, I think this is probably only an interim step as I would really like to get rid of my portable vacuum exhaust (even from a Festool vac) as too many guys are reporting that these leak a lot of dust (which defeates the purpose doesn't it!)

Hopefully the pictures are reasonably straight forward. I have a second piece of ply on top, attached with butterfly nuts. This gives a more comprehensive cover over the top for 90 degree cuts (which constitutes the vast majority of my usage). Then, when cutting mitres or compound mitres, I can remove the top piece to reveal a secondary top which allows for different saw adjustments. The curvy cut-out bits at the sides is a result of the fact that I made the dust shroud a bit too narrow, and found out I couldn't quite get to a 45 degree cut!

I wonder whether I should try to build in the shroud further on either side of the machine -- primarily for those 90 degree cuts? I don't have any machinery to test dust emissions, but this has got to be better than what I had!

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nice done great idea makers for us who have not got a dust system fully set up
regards Michael

Originally Posted by coffenup

nice done great idea makers for us who have not got a dust system fully set up
regards Michael

Cheers mate. Whatever is right about my setup I owe to the dust gurus on this forum. Whatever is not the best remains my responsibility. I've been using the saw quite a bit over the past few days and am very pleased with the airflow volume from the two ducts.

Hi Johnredl:

Have you been using yours much? How is the extraction working?

Funny you should ask. Just a couple of days ago I made about 60 cuts through 140x50 Australian Oak.

I found that the side wings are not strong enough & bent with the timber weight. So I'm thinking of reinforcing them either with timber as an edge strip, or with angle steel bolted from underneath.

As for dust extraction, I need to make an adjustment to the front curtain, I think that I'm going to try overlapping the plastic by about a foot. It did work fine, but the front curtain was being sucked towards the rear, making it a little difficult to keep it out of the way of the saw. I did achieve about 95% or greater dust extraction. Really the only mess was left by moving the wood around.

To answer a previous question, I have glued sone cafe blind to the side cutouts, seems to be successful, I just need to reinforce the gluing. I was waiting to see how successful this project is before adding edge banding, wood over the glue lines and painting/oiling the enclosure.

Thanks for posting a pic of your setup, I did consider this type, but wasn't happy once I watched a YouTube movie.

Here's a link to the movie that gave me the idea:

http://youtu.be/ovfXlnGoT6U

Well done! I just watched the video link you gave and that fellow certainly has a nice set-up. I particularly liked the way he had the outfeed on his table saw so flexible. His dust extraction on/off system, integrated with his gates, is also a very nice feature.

I have an auto-start relay/contactor system which automatically runs for 10 seconds after I turn off any of my big machines. However, in various discussions with BobL, he thought 10 seconds was way too short a delay, and really we need to be running the dusty for 10-20 minutes after our last dust making activity.

Consequently, I now have three remote switches wired in around the shop, so that I can turn on my dusty and leave it running for longer periods. One of the switches is at the cross cut saw. So far it is working well, and the remote switches encourages me to leave the dusty running for much longer.

How do you turn on your dusty, and is it working for you?

At the moment I'm using my dusty with a 3m length of 6" flex hose. I haven't plumbed it in yet.

I'd love to tell you about my automatic on/off system, but I just walk over & turn it on/off!

I do need to plumb it in, I think I may start a thread asking for advice.

Good info. Something for me to do in this long weekend.

I can do a movie, but I'm not sure how to add it to this thread. Any ideas?

Originally Posted by johnredl

I can do a movie, but I'm not sure how to add it to this thread. Any ideas?

I post my movies to youtube and just provide a link here. That eliminates any restriction on file size.

Cheerio!

John