Cross Cut Sled w/Dust Collection

[Greg Peterson]

Some of you may already have a cross cut sled in your shop. Some of you may even have an acrylic cover to deflect dust and chips and as a general safety device. I thought a cross cut sled could easily have some dust collection incorporated into it and have not seen anyone else offer a solution.

After some thought and experimentation I finally arrived at pretty simple prototype that you can build in no time at all. The concept is ridiculously simple, and once I found the right barrier material, execution was a breeze.

The barrier material was the most challenging. I originally wanted to use a natural fiber brush configuration, but to find an inexpensive source for the lengths I required was cost prohibitive.

I tried some 5 mil. vinyl I cut off the bottom of a new shower curtain. This material was too light and just got pulled up toward the DC port, making them useless.

Finally, at Rocklers one day I spied some of the synthetic finishing pads. Stiff, porous and cheap.

Here are some pictures that show the first, functional prototype. I am generally happy with this design but find the barrier is a little stiff. I think cutting longer, finer 'fingers' in the synthetic pad material will make it yield more easily.

One barrier. One dado to hold the barrier material, the second dado to attach to the acrylic shield.
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Here you can hopefully see the 'fingers' in the barrier. Allows it to conform to various dimensions of materials.

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Standard acrylic shield with a DC attachment incorporated. Not really a tricky task. I cut an acrylic tube at roughly forty five degrees, transferred the elongated opening to the flat acrylic sheet, cut out the opening and glued them together. I lined the inside of the DC connection with a few layers of cork to ensure a nice, positive seal for the vacuum hose.

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One thing became apparent with the barriers installed; the dust shield likes to move around. I drilled a shallow hole at each end and used a nail to keep the dust shield from sliding around when positioning material on the sled. I left the nail head a little proud so I can quickly and easily remove the dust shield if necessary.

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And here it is, with the barriers installed. The porous nature of the synthetic material allows air to flow through it and the stiffness prevents it from getting lifted up towards the dust port. I have some more refinements to make but for now I find this to be an improvement over previous versions I have used.

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[Rod Sheridan]

Pretty clever Greg, looks very good..............Rod.

[david brum]

Great idea. I have a nearly identical set up which has similar, near perfect dust collection. I didn't think of the abrasive pads, though. I used pvc shower pan liner material from Home Depot. http://www.homedepot.com/h_d1/N-5yc1v/R-100343454/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053 (They sold me some by the foot). It's really thick and heavy, so doesn't get sucked into the dust shroud. I think that bristles would be more ideal, but you're right; they're too expensive.

[Cyrus Brewster 7]

That is pretty cool and seems fairly simple to make. If you do not mind I would like to copy it.

[Greg Peterson]

Rod - Thanks

David - Shower liner is a great idea.

Cyrus - Please copy and improve on it.

[Kevin Presutti]

Well that's pretty trick! That I'm sure will be copied many times over and whether you hear it in person or not many will be thankful for your sharing it with us here at SMC. Many of you here have shown me some tricks that quite handy indeed. Nice job Greg!

[Alan Schaffter]

Here is pic from several years ago of my old over-blade dust shroud which uses rather stiff bristles I removed from a broom.

http://www.ncwoodworker.net/pp/data/1403/medium/PB050012.JPG

I don't have a recent photo, but I subsequently replaced those with much finer and more flexible, "Metal-Backed Strip Brushes" used on conveyors from McMaster-Carr (http://www.mcmaster.com/#metal-conveyor-brushes/=f3hj58) (see page 1245). They are available with bristles 3/4" up to 6" long and in a variety of thicknesses. The strips come mounted to a metal backing strip and can be purchased in lengths up to 8'. MMC also sells straight and angled aluminum strip brush holders.

The ones I used, 74715T9, have .014" thick X 6" long nylon bristles and a 3/16" backer.

http://www.mcmaster.com/catalog/117/gfx/large/74405tc1l.gif

I purchased a second pair that I plan to add to my SCMS someday. Another "round tuit" :rolleyes:

[Greg Peterson]

Kevin -There is a wealth of information 'round here and sharing ideas and designs is how we advance the state of the hobby/craft.

Alan - Thanks for the link. That is one site I did not find in my previous searches. Bookmarked!

I initially wanted to use horse hair, but that notion was quickly dismissed. I wanted to keep the cost to a minimum and flexibility to a maximum. If parts have to be special ordered or the setup cumbersome and inflexible, people are less likely to build and use it.

In short, I was trying find the most elegant solution to a common problem. Hopefully others can refine it further. I'm still not entirely happy with the DC, but that's for another time.

[Alan Schaffter]

I initially wanted to use horse hair, but that notion was quickly dismissed. I wanted to keep the cost to a minimum and flexibility to a maximum. If parts have to be special ordered or the setup cumbersome and inflexible, people are less likely to build and use it.

In short, I was trying find the most elegant solution to a common problem. Hopefully others can refine it further. I'm still not entirely happy with the DC, but that's for another time.

I know exactly what you mean. For my design I needed long bristles. My first thought was truck/RV spray guards. One closeup look revealed they were too coarse and totally unsuitable. Then I thought about just using the bristles from a cheap bench brush/foxtail- I could find any long enough. I took a step back to save money and just to verify my design before looking further. I bought a really cheap (<$5) broom and harvested the bristles from it. It took a little work to remount the bristles into a strip - I used silicone sealer to attach them to a strip of fabric. The design worked, but as I suspected the bristles were too stiff. The ones I ordered from McMaster-Carr were much better.

The theory of operation works- the bristles conform relatively well to the stock and stop the high velocity dust from kinetically spraying out from the blade while at the same time allow make-up air to enter- but not without two issues. The saw blade occasionally does minor damage to a few front and rear bristles which may need to be replaced in a year or two and the dust shroud can't be used with tenoning, panel beveling, and other large jigs. You should have these problems with a sled shroud.

[Greg Peterson]

One detail that is not particularly obvious in the last photo is the 1 1/2" gap in the shroud at the back end of the sled. I left this gap solely for air take up as it will be an extremely rare cut where the blade will come into contact with material at this end of the sled.

I'm trying to configure a DC port that will mount in the front of the guard so as to accentuate the kinetic energy of the chips and dust. Right now the shroud mainly contains the larger, visible particles. But I am hopeful that a more strategic placement of the DC port will evacuate most if not all of those as well. There is a slight but noticeable 'puff' of dust as the blade exists the back fence of the sled. It's a drawback of the sled design.

I've not setup a particle count with my Dylos unit yet. Hopefully this weekend I will have some figures to post.

[Ben Hatcher]

Would disposable paint brushes be a cheap enough source of bristles?

[Alan Schaffter]

They were something I considered but ultimately too short for my application. If you look, the cost of the shorter McMaster-Carr brush strips is not that bad, and they should be easy to mount in a dado so you wouldn't need brush holders.

[Greg Peterson]

Ben - Thouht about that too. Fairly inexpensive, but too short and more expensive than the polyester pads I ended up using. Plus more work to retro fit the brushes. Needed something quick and easy.

[Myk Rian]

ACE hardware (or other places) 36" door sweep. $10
http://ace.imageg.net/graphics/product_images/pACE3-3907197dt.jpg

[Alan Schaffter]

ACE hardware (or other places) 36" door sweep. $10
http://ace.imageg.net/graphics/product_images/pACE3-3907197dt.jpg

I looked at those also, but found they were too short;

"ACE" DOOR SWEEP
Nylon bristles for longer lifetime
Bristles conform to any surface
Aluminum with nylon brush
Seals gaps up to 3/4" high

[Ben Hatcher]

How tall did you find the brushes needed to be to work well? 4"?

[Alan Schaffter]

I don't know about Greg's sled bristles but I used ones slightly longer than 4"- I figured I wouldn't be cutting anything 4" thick, so that is how high I mounted the frame. I used 6" long bristles on the second version because I mounted them on an angle- splayed outward.

[Greg Peterson]

I only required about 3 1/2" of clearance. And in practice I think it will be a rare occurrence where that will not be adequate.

[Greg Peterson]

I've updated the sled. While the overhead DC works OK, I felt I could improve the DC.

On the portion of the sled that rides directly over the throat of the table, I drill a series of 1/2" holes. This really seems to work nicely. I cut up some dark hardboard and watched the dark dust immediately swirl into plastic bag on the DC. And no dark dust was left under the guard, whereas before with just the top DC port working there was some dust residue. The guard at least kept this residue confined, but now with the DC unit contributing there everything is getting collected.

[Brian Kincaid]

I've updated the sled. While the overhead DC works OK, I felt I could improve the DC.

On the portion of the sled that rides directly over the throat of the table, I drill a series of 1/2" holes. This really seems to work nicely. I cut up some dark hardboard and watched the dark dust immediately swirl into plastic bag on the DC. And no dark dust was left under the guard, whereas before with just the top DC port working there was some dust residue. The guard at least kept this residue confined, but now with the DC unit contributing there everything is getting collected.

Well, I HAD a suggestion for you, but you already thought of it... very nice!
-Brian

[Aaron Berk]

I would guess then that you do not use a zero clearance insert when using the sled?

With perforations like that to your sled base, I would think running with NO insert would net you the best results.

Really like what you got there Greg, nice work!

[Greg Peterson]

Thank you gentlemen.

Aaron - Correct. I do not use a throat insert when using the sled.

[Aaron Berk]

Cool deal.

I'm inspired :D

[Chris Parks]

What a great idea, a lattice type insert into the sled might be an improvement but if it already works that might be overkill.

[Greg Peterson]

I did not think about a lattice insert. My concern was maintaining a degree of rigidity and stability in the sled.

[Adrian Anguiano]

I like it, but all I can think in my head is danger when you crosscut little pieces, or thin strips. Im sure they will get sucked up and twisted and hit the blade and fly, or the bristles forcing the cutoff pieces to move when you push the sled through the blade.

When Im making a 2" thick cutting board; my final step is making a thin cut on all 4 sides to make sure its nice and straight on the sides. im often left with a 1/16th or less thin strip thats 2" tall, and 12" long. I just smell disaster.

Whats your experience?

[Clint Olver]

Pretty slick Greg!

C

[Chris Parks]

Looking back on this and Greg mentions that he was looking for a way to put a dust port into the sled where the chips were thrown by the blade. If the rear "fence" of the sled were made hollow it could incorporate a dust port ala some router tables and the extracter hose hooked up to the end of it.

[David Tzeutschler]

260479260480My solution to the "brush issue" as in the case of above poster, I purchased brushes through McMaster Carr. I used 3" brush, dovetailed slots to hold in. About $20 with shipping in brushes (48") with Not the most elegant but mostly un-cumbersome and traps a large % of dust.

[Aaron Berk]

Well done.

I just finished cutting 20 pcs of lexan (40 cuts) and I have white snow all over the place as a result.

I really need to kick into high gear and make one of these.
Looks good David :)

[Greg Peterson]

David - Nice! I like heavy duty nature of your setup. Are you servicing the cabinet as well, or just the cross cit slider?