welcome advise on cutting large diameter PVC duct

[Bruce Seidner]

I normally use a hacksaw on 6" and 8" PVC pipe but I need to cut repetitive and accurate angles and was considering my 12" blade sliding miter saw for the job. I also hear that cutting a lot of PVC makes some nasty dust/powder.

I do have a proper band saw and a table saw but the ease of setting angles and repetitive cuts might go faster and more reliably on the miter saw, or not.

In any event I have looked around and more teeth seem to be better than less teeth and triple chip grind teeth TCG are non-ferrous metal/plastic specific. But I have been intrigued by the recommendation of using a metal cutting abrasive saw blade and have no experience using this kind of blade.

My instincts are to stick with what I know and already own and go with one of my plywood/veneer blades rather than purchasing a new TCG blade unless that is a mistake and I will lunch the high tooth count plywood blade cutting PVC and the tear out requires a TCG blade.

I also don't know what kind of cut the metal abrasive blade would make but was thinking if I needed a new blade I might expand my options by purchasing one of these and see what else it is good for cutting. I get to cut something ferrous now and again.

If there were some public outcry about the necessity of using a band saw for this operation I could be talked into this but such advise would have to come with the recommended saw blade and the jig most favored to cut precise angles on large pipe.

Thanking all in advance.

[Myk Rian]

You're right about more teeth on the blade.
I found my band saw did a good job cutting PVC. Not sure I would put a circular blade to it. Seems a bit dangerous to me.

[Prashun Patel]

Unless you use a sled, cutting 'tubes' on a bandsaw always scares me. I find the easiest way to cut pvc is to make a dedicated miterbox for a hacksaw.

A mitersaw can work, but you need a very reliable way to hold the piece still, so it does not roll. I wouldn't do it.

[glenn bradley]

+1 on a sled and the bandsaw if these require the precision for making your own joints. If they will slip into fittings the precision is pretty loose. Dad and I used a felt pen to mark and a jig saw to cut; much easier on those long sections. I ran the saw and dad rotated the pipe.

[Matt Meiser]

I've found cutting it with my miter saw is plenty safe--I just keep my hands well away in case it does grab. With 6" it won't cut all the way through so I make a partial cut and rotate 180 and make another cut. Let the blade stop before removing the blade from the partial cut.

On the other hand I tried cutting a small piece with the BS one time and had it grab and spin. Haven't tried again. When I need to cut a small piece, I either cut it off a long piece, or stick a board through it to hold it down that way.

[Paul Wunder]

http://www.amazon.com/s/?ie=UTF8&keywords=dewalt+pvc+saw&tag=googhydr-20&index=tools&hvadid=4431036055&ref=pd_sl_4yozyvs8y1_b

I cut all of my 6" PVC cyclone ductwork using a DeWalt PVC saw ($13) and a simple hand made miter box to fit the pipe. Worked well. Also, no dust because it was a hand saw operation

[Van Huskey]

http://www.amazon.com/s/?ie=UTF8&keywords=dewalt+pvc+saw&tag=googhydr-20&index=tools&hvadid=4431036055&ref=pd_sl_4yozyvs8y1_b

I cut all of my 6" PVC cyclone ductwork using a DeWalt PVC saw ($13) and a simple hand made miter box to fit the pipe. Worked well. Also, no dust because it was a hand saw operation

+1 if you don't need precise cuts, if you are just joining pipe with PVC fittings this is the way to go. They will have either this or something similar at the BORGs in the plumbing section.

[Jeff Duncan]

I've used my chop saw to cut PVC many times, though in general it was 2" +/- used for plumbing purposes. I just use the same general purpose crosscut blades that I use for crosscutting hardwoods. I can't imagine an abrasive blade would work...has anyone here tried this??? I would think it would grind and melt and just be pretty nasty....but who knows?

If your doing enough cuts you could always make up a jig to hold the pipe still in your chop saw. Or for quicker help simply use a little spray adhesive to secure some sandpaper to the saws fence and table to help grip the piece.

good luck,
JeffD

[Charles Robertson]

Chop saw. Have it well supported, keep it tight to the fence, rotate as needed. Have used also used circular saw with good results.

[Dan Hintz]

I just use the 4tpi negative rake blade already on my bandsaw... kept my hands far, far away in case of a catch.

[Erik Christensen]

I used a reciprocating saw with a long blade for my 6 & 8 inch pipe cuts. I build a plywood 3 sided box the diameter of the pipe and when clamped on either side of the cut there was enough give to the sides of the box that the pipe did not roll. For angle cuts I made the angle in the vertical plane vs horizontal (like a miter saw) so the face of the reciprocating saw was always flush and vertical to the sides of the box. I am not claiming the cuts were finish grade nor that the "guides" of the box lasted more than a few dozen cuts but it did all I needed to run DC pipe in my shop.

[Peter Quinn]

I've cut PVC on the bandsaw using what ever blade I have that has some life left. Its really the only accurate thing I own with a cutting height large enough to cut pipe that diameter. I've used a sawzall too, and I suppose you could jig that up easy enough by making a dedicated miter box from plywood scraps, I'll leave the details to your imagination. A similar miter sled fastened to a t square would help guide miters on the BS.

That said, I have cut a lot of PVC pipe and never once have I needed to cut a miter. Isn't that what the elbows are for? Just curious what you are making.

[John Coloccia]

For dust collection work, I use a PVC saw, eyeball the length, and cut it totally freehand. It takes be about 10 or 15 seconds to cut clean through 6", thin wall PVC. I'm curious about what you need a miter for too.

[Bruce Seidner]

That said, I have cut a lot of PVC pipe and never once have I needed to cut a miter. Isn't that what the elbows are for? Just curious what you are making.

Right you are mate. But when the cost of elbows vies with the cost of the original equipment you are ducting it gives one pause.

I am redoing the ducting for my dust system and have experienced sticker trauma looking at the cost of long radius elbows for 6" and 8" PVC duct. Steel is even more. I researched and experimented with dual heat guns and bending PVC of 6" and 8" diameter but it takes some practice and/or technique to heat it to the right temp of 200 F where it turns to rubber and wants to collapse or kink on you. Plus it stinks and is a carcinogen of the highest order. One can pack a pipe with sand or seal the tubes so the air pressure will keep it formed up but this is fine if you are making a cage of 1" pipe for your pet ferret, not if you are making a large diameter duct system. Long story short it is not something I want to spend more time with.

Making good clean cuts at 93.8 degrees, 86.3 degrees and 82.5 degrees will create a series of 8 segments that when glued up will yield a 2x radius 6" 90 degree elbow. The cost of material is about $7/foot or less than $21. By comparison, an 8" long-elbow in steel is $130 and it is 1.5 radius.

If this were a flat hardwood picture frame I would not be at such a loss. But the thought of trying to manage a 6" plastic pipe with precision and safety sort of escapes me. It is funny the more I look into the cost of a 12" miter blade or setting up a jig for the band saw, the more attractive those tube mounted hacksaw miter boxes look to me. They can be had for $50, seem safe enough, and there is the control that comes from a low power hand tool.

So that is the back story to your excellent question. I think I have talked myself into purchasing a miter box. They look like the old Stanley miter box saws but are not rusted and found in dank barns. So now the question has morphed into miter boxes that will do the job. The ones I have found all cost less than a 12" Freud TCB blade and call themselves precision.

Used any precision miter box saws lately?

[Peter Quinn]

Not sure I've seen a miter box that would handle 8" pipe? Maybe one of those Nobex units? On the BS I've basically made a U shaped frame from three pieces of 3/4" plywood the top is open except for a few stiffeners going across, you can use a destaco clamp, replace the rubber foot with a curved shaped piece of wood , radius to match the pipe, piece of sand paper to keep the pipe from spinning. You could clamp a mitered block to the fence for repetitive cuts?

So the plan is to make long radius elbows by welding segments of straight pipe edge to edge? I'm curious to see how that works under pressure?

Have you considered DWV sweep 90's? They are almost 1/3 cheaper than schedule 40 here, so say $65 per fitting rather than $95. I know a guy that has been using them for years without issue. I know the metal elbows get expensive quick. If you don't have a lot of 90's can you sub some flex pipe? I know that's not ideal, but its much cheaper than PVC.

[Bruce Seidner]

I can't get DWV long sweep 90's here in town. And for some reason 8" Schedule 40 cost's almost half of what 8" 3034D costs today. I am changing the main duct line to 8" instead of 6" because I was able to get 8" fittings with 6" wyes and my blower intake is 8". Pipe pricing was just the opposite when I purchased ASTM 2729 in 6" where it was half the price of 6" Schedule 40 last year. (And 8" fittings could only be found retail, ouch.) Anyhow I was pretty successful Craig's list dumpster diving this week and got a lifetimes inventory of connectors, wyes, reducers, etc., in Schedule 40 at $5 a piece.

In the pile was a longish sweep 6" 90degree elbow made up of 4 PVC segments welded together the way sheet metal elbows are welded together and the old light bulb went off above my Neanderthal thick brow ridge and I got onto the heroic project making these in a larger radius for myself. Jay Maiers (http://www.sawmillcreek.org/member.php?14112-Jay-Maiers) over in Workshops Forum drew up an elbow in autocad for me where it can be found in the thread Wye Templates.

At first I was going to build a dedicated 3 sided miter box and make different angles on each end and clamp the pipe into the open coffin box. But then the issue of which cutting machine to use and getting a plastic cutting blade came up and then the fact that the "shop" is the garage basement of my home and there is currently no dust system. If it were a detached barn no problemo. But there is also a bench where electronics is done and then there is the bike shop section of the enterprise. And lord help me when there is a film of dust all through the upstairs of the house. It was fix'n to became sort of like Dr. Seusse's Cat in the Hat and I just don't need Number One and Number Two around my Christmas vacation.

I may just forgo the miter box saws which as I research them may be limited in height of cut. But I have used that $15 Dewalt PVC saw and it is like butta. Likely make the little coffins lined with sandpaper. The segments are small so a handsaw makes the most sense for the small scale of making these elbows.

[Bruce Seidner]

Not sure I've seen a miter box that would handle 8" pipe? Maybe one of those Nobex units? .

The mac-daddy Nobex will do 185mm tall or just over 7" and my target is 6" pipe. All my 8" is a straight shot down the long side of one wall with 3 wye's at the beginning, middle and end of the run with a 6" coming off each 8"fitting. And as has been noted, cutting a pipe that will slip into a fitting is close enough for hobbyist work. From the wye's on down it is a 6" jungle to the machines I am to trying to tame.

As for the strength of the joints I picked up a Harbor Freight plastic welder a few years ago that uses a light touch of compressed air to help flow the material. PVC welding sticks are cheap and it is not much harder than soldering. Besides which, PVC is very forgiving and being able to adjust the heat means you can maybe mess up melting through things but nothing is burned and everything can be sanded. In addition I developed a deep respect for Bondo when I was a teen. It covered a multitude of sins in the rusted automobiles we were able to purchase. And truth be known it works just fine with wood projects covering pocket screw holes, bad miter cuts, and anything that is going to be painted or not seen. Haven't tried it on PVC, yet, but I bet it will work just fine if it doesn't melt the PVC too bad before it cures. I think there is an issue of Fine Wood Working that is going to be dedicated to the ubiquity of Bondo in high end custom furniture shops when your Lie-Neilson plane or Japanese hand chisels let you down.

[Dan Hintz]

That said, I have cut a lot of PVC pipe and never once have I needed to cut a miter. Isn't that what the elbows are for? Just curious what you are making.
Making a straight-Y is possible, which is what I did for my DC.

[Jim O'Dell]

I've used all the above to cut. Can't get a straight cut using the hand saw method. I had a piece of 6" pipe explode on me while cutting with my old Ryobi miter saw. Most likely was my poor choice of using the stock blade, but I was lucky and didn't end up with a piece of pipe sticking in me somewhere. BS worked fine, but gave limited length to cut because of the throat depth. So I perfected using my Jointech sled on the table saw. It has adjustable length on the arm with a flip down for cutting repeated lengths. I push into the blade, then rotate the pipe. Oh, and I got a plastics/laminate blade. Made all the difference in the world cutting the pipe!!! Jim.

[Jim Finn]

I have made a lot of wye fittings when I was a construction sheet metal worker. We made them of metal , fiberglass and Polypropylene, in sizes from 2" to 48". (those were fun) If I were doing this I would get a plastic welder and weld the pieces together with it. Plastic welding is easy to learn and is safe and fun to do. We put three beads of filler on each joint to give it the strength needed for those industrial exhaust systems. We cut the pieces with a sawsall because we were out on a job site with no stationary tools.

[ian maybury]

I've had good luck with one of those large general purpose, large and pretty cheap plastic handled pull saws sold by the big hardware chains. They have no back, and while I didn't do it it would be dead easy to build a mitre box to suit whatever size of pipe you have in mind.

Can't remember the name of the one I have, but it's quite similar to this: http://www.jamestowndistributors.com/userportal/show_product.do?pid=524&familyName=Carpenters+Pull+Saws

The choice of blade is pretty important if you want to use a power tool - especially lots of side clearance. It's otherwise easy to run into melting problems on PVC. Many jigsaw blades cause problems for example.

ian

[Bruce Seidner]

Well, I appreciate all the experiences shared and in eyeballing the options I have close to hand, I am going to tune up the Band Saw with a new blade. It has been sitting in the corner of the shop sighing and asking if I think it is too fat of late. I am going to have to do some surgery and put one of the extenders to make this mature Jet 14" BS taller, and I might even spring for some new tires. This can lead to some re-sawing I have wanted to try after I get the PVC cut up and welded together. But I already have a spanky but old Vega sliding miter with a clamp that fits the BS table so it is really just a blade and high heels that I am going to have to break down and buy. But it is clear that I am going to have to go all ShopNotes/Fine Wood Working Jig crazy and glue up some 3sided plywood throughs to ensure my life, limb and accuracy chopping up 6" and 8" PVC pipe. This will likely equal the cost of a good large capacity miter box but I think I will get more use out of it and the BS has not been fired up in over a year. I played with the compound miter saw and while nothing beats it for 2x4's and crown molding it is sort of like putting a muscle car on a grand prix track. Admirable power but insufficient control for my tastes.

[David Larsen]

I have cut a lot of PVC pipe with an abrasive cut off saw. It works great everytime. It has a 14 inch blade and a capacity of 5 inches or so. The largest PVC I have cut was 4 inch so the capacity has never been an issue. The base clamp can be adjusted for angles. Your PVC is larger and maybe this wouldn't work because of that, but it does work great for smaller diameters.

http://ecx.images-amazon.com/images/I/61tMZQsBbEL._AA1235_.jpg

[Bruce Seidner]

Ok, Cool. I had read about using this blade but wondered how well it worked. I have some questions and I would appreciate knowing your experience when you have a chance.

As you cut it is removing material. What is the material like? Big or little dust? Does it heat up the pipe and do you get any melting effect? How much filing or sanding is required to clean the inside diameter edges? I have used these on bolts but can't think through what PVC cuts like on one of these. How would you rate it for straightness of cuts?

These blades come in a number of sizes, from 1" Dremel to 24" commercial and if they did a better job than other blades it would be put back on the list of considerations. It might for instance be less scary than a tooth blade on a miter saw. A compound sliding miter saw is a jig in itself and would obviate the need of a jig on a band saw. And it is likely my technique but I have had BS blades deflect and I am not always getting as straight a cut as I can get with a miter saw which is much less demanding of skill but arguably more demanding of safe practice.

[Jim Matthews]

I use a plumber's wire saw (http://www.youtube.com/watch?v=za1G94aPIt4) on PVC.

The cuts are surprisingly clean, with no dust generated.
The heat does the work. Clamp the section tightly and go to town.

Cutting something that rolls on a bandsaw can work, but why deliberately risk injury when simpler methods suffice?

[David Larsen]

Ok, Cool. I had read about using this blade but wondered how well it worked. I have some questions and I would appreciate knowing your experience when you have a chance.

As you cut it is removing material. What is the material like? Cutting PVC with an abrasive saw is just like grinding through it. Big or little dust? Very little if any dust. Does it heat up the pipe and do you get any melting effect? There is some melting effect, but not like a hazardous smelly burn pvc problem. How much filing or sanding is required to clean the inside diameter edges? No filing or sanding needed. Just wipe it with your fingers to make sure there isn't any slag on the pipe. I have used these on bolts but can't think through what PVC cuts like on one of these. Cuts like a hot knife through butter. How would you rate it for straightness of cuts? Straight as long as you hold it tight to the rear guide. You can even clamp it down for the cut if you want.

These blades come in a number of sizes, from 1" Dremel to 24" commercial and if they did a better job than other blades it would be put back on the list of considerations. It might for instance be less scary than a tooth blade on a miter saw. A compound sliding miter saw is a jig in itself and would obviate the need of a jig on a band saw. And it is likely my technique but I have had BS blades deflect and I am not always getting as straight a cut as I can get with a miter saw which is much less demanding of skill but arguably more demanding of safe practice.

I have cut a lot of PVC with the abrasive chop saw for different plumbing projects in the past. I wouldn't use anything else.

[Robert Joseph]

Chop saw with an old blade turned backwards. Works excellent for gang cutting vinyl siding too. No exploding PVC, no shrapnel.

[Bruce Seidner]

This is worth an experiment. Its off to the Boarg when I get back to town. I will start looking into the options but I assume they come in various kerf and sundry materials. What do you recommend for PVC?

If they require cleaning how would you clean one? I am thinking of the trouble it can be getting melted mozzarella off a spatula. PVC off an abrasive blade has got to be a chore.

[Larry Edgerton]

I read this thread yesterday morning so at work I had an idea. I took a piece of plywood scrap and cut a elipse that would slip over a piece of 4" schedule 40 pvc that was on the job. I then cocked it so it was on an angle and followed around the plywood with a Fein Multimaster with a fishtail saw laid flat on the plywood. It worked amazingly well. When I flipped the two halves around they made a pretty nice fit. I wasn't going for any precise angle, so one would have to play with that. It also holds the pvc well. I suppose that you could use a hand saw just fine too.

Larry

[Craig Michael]

I have cut a lot of PVC pipe with an abrasive cut off saw. It works great everytime. It has a 14 inch blade and a capacity of 5 inches or so. The largest PVC I have cut was 4 inch so the capacity has never been an issue. The base clamp can be adjusted for angles. Your PVC is larger and maybe this wouldn't work because of that, but it does work great for smaller diameters.

http://ecx.images-amazon.com/images/I/61tMZQsBbEL._AA1235_.jpg

+1. This works great and it is very safe. There are no teeth to grab the material. There will be a very minor amount of melt, 1% or less. You can remove the frays from the burn/cut in a second with light sand paper or a utility knife. I would cut otside or in a ventilated area though. There will be some smoke, not a lot but some.

I would not use a miter band saw, especially for pipe greater than 2".

[David Larsen]

This is worth an experiment. Its off to the Boarg when I get back to town. I will start looking into the options but I assume they come in various kerf and sundry materials. What do you recommend for PVC?

If they require cleaning how would you clean one? I am thinking of the trouble it can be getting melted mozzarella off a spatula. PVC off an abrasive blade has got to be a chore.


I have never noticed any residue on the blade.