# Cutting metal dc ducting?



## Elizabeth (Oct 17, 2009)

I've picked up my ducting for my dust collection system. I've got 60 feet of spiral metal ducting in ten foot lengths: 30 feet of six inch, ten feet of five inch and 20 feet of four inch.

I asked the shop guys when I collected it (Woodcraft) what method I should use to cut it. They recommended using a metal cutting blade on my 10" miter saw. This sounded fine except for two things I thought of on the way home.

1) I was taught to never, EVER cut a cylindrical object on the miter saw, as it has the potential to start spinning when the blade encounters it.

2) Will a ten inch blade be able to cut six inch piping? Haven't I really only got the 5 inch radius of the blade to work with? I've never tried to cut something over four inches on it.

Thoughts on either of these points? How would YOU cut this ducting?

Thanks all!


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## cabmaker (Sep 16, 2010)

Jigsaw with bi-metal blade.


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## a1Jim (Aug 9, 2008)

They use metal chops saws all the time to cut round objects but it requires the correct blade and chop saw. I have cut 6" PVC pipe on my 12"chop saw with out a problem. You just have to hold the pipe firmly to the fence. Another way is measure down on 4 sides and put a mark at all 4 sides then use a piece of paper or thin card board and wrap it around the pipe hitting all the marks and mark it all the way around (I usually use a sharpie). After removing the card board I use a angle grinder with a metal cutting blade to carefully cut around the pipe.

Don't forget the safety glasses!


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## Mickit (Feb 6, 2010)

I've cut a lot of duct metal. I have used chop saws and other thing but the most efficient (and safest IMO) was a cradle with a strap clamp and a recip saw with a long bimetal blade


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## Elizabeth (Oct 17, 2009)

Hm, so far I haven't got any of the tools you guys have mentioned…jigsaw, angle grinder, reciprocating saw. I was kind of hoping there'd be a way to do it without buying something new, considering I won't have need to cut metal that often. (Though I may need to cut small copper/brass pipes in the future if I get into whistlemaking.)


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## Dark_Lightning (Nov 20, 2009)

Get yourself some tin snips. Left, right and straight. You can do all the cutting with those, no worry about injury. Any cutting of pipes you want to do later can be handled with a hacksaw.


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## LeeBarker (Aug 6, 2010)

Atomjack, I'm wondering if the snips would cut the spiral pipe.

E, I think this is a great time to buy a jigsaw. Mickey's idea sounds like a comfortable, safe way to do it. Remember you cut metal at a much lower speed than you cut wood.

If you don't want to pop for a jigsaw, then by golly a hack saw will do the job! Good blades, and a good frame, and a little elbow grease, careful marking, and you can practically hear those chips getting excited about taking a ride on the Cyclone!

Kindly,

Lee


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## Elizabeth (Oct 17, 2009)

Sounds like a jigsaw might be in my future. Can anyone recommend a good one, considering that it probably won't become a primary tool for me? But I still want to do a good job on this ducting. Blade recommendationed welcome too.

Micky, do you happen to have a photo of that cradle you mentioned?


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## Sawkerf (Dec 31, 2009)

Sawzall with metal cutting blade


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## Elizabeth (Oct 17, 2009)

Is the Sawzall better than a DeWalt reciprocating saw? I'm trying to find out the difference between a jigsaw and a reciprocating saw right now..


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## TopamaxSurvivor (May 2, 2008)

You will find cutting that light metal with a reciprocating blade to be a real PIA!! It will like make a mess of the edges. Like atomjack says, just get some tip snips, poke a hole in teh duct there you need to start the cut and do it.


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## Grandpa (Jan 28, 2011)

A/C folks use snips. They make it look easier than it is but they use snips. You can get the right/left/straight and you can get some that are bent 90 deg near the hinge area to keep you away from the sharp edges. Wear gloves when you use them. This leaves sharp edges and burrs.


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## danr (Sep 5, 2009)

Trust me, a metal cutting blade in a jigsaw is the way to go. The spiral pipe is most likely way to heavy of a gauge to cut with hand snips and you probably don't want to buy power snips. Mark your cut with masking tape, start the cut with a hand, hack saw (just to open up a slot to get the jigsaw blade to go through and then cut around the pipe with the jigsaw (piece of cake). I have done a lot of this and the results are great. I use a rat-tail file to clean up the small burs (not too bad) and then somtimes I will touch that up with a little sandpaper but niether are really necessary. This is a very very safe and effective way to do this.

Good luck to you.


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## a1Jim (Aug 9, 2008)

Elizabeth
I think your much better off with a jig saw for woodworking a Saw Zaw is more for construction work.
For the record a saw zaw is a much higher quality tool but Dewalt will do the job too . I have both.

Here's what a jig saw looks like .
http://www.google.com/products/catalog?rlz=1C1CHMD_enUS400US400&q=bosch+jigsaw&um=1&ie=UTF-8&tbm=shop&cid=17292027604781336240&sa=X&ei=5XdiTq-6Mc_C0AHCj4WFCg&ved=0CGkQ8gIwAA

Here's a saw zaw
http://www.amazon.com/Milwaukee-6509-22-Sawzall-Amp-Reciprocating/dp/B0000789HE


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## Finn (May 26, 2010)

Grandpa says: " A/C folks use snips. They make it look easier than it is but they use snips. You can get the right/left/straight and you can get some that are bent 90 deg near the hinge area to keep you away from the sharp edges. Wear gloves when you use them. This leaves sharp edges and burrs." 
//////////////////////////////////He is right. I am a retired sheet metal worker and that is how we did it. A Jig saw also works but is very loud and leaves an awful burr that needs to be cut with the tin snips to clean up. When you come to the spiral seam a hack saw helps to get through it. Electric double cuts will also do a nice job but they will not cut the spiral seam either.


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## Grandpa (Jan 28, 2011)

Thanks Jim. I watched a master in South Dakota once. He had a left hand snip in one hand and a right hand snip in the other and he was blazing around a big circle he had drawn in the plenum as I watched with my jaw down. One pair of snips going one way with the other pair going the other way at the same time. If that doesn't make it look easy then I don't know what would. The truth is I can't cut a decent circle with anything…LOL Another thing is he wouldn't loan you his snips. He had loaners but you didn't get his personal snips.


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## Elizabeth (Oct 17, 2009)

OK, I've unpacked the rest of the installation gear (and borrowed some tin snips from a neighbor) and discovered that I also have to cut some threaded rod. At least I assume I have to cut it - this project is seriously lacking in the instruction department. (Anyone in Western Oregon want an installation job?)

Tin snips obviously won't cut threaded rod. I don't have a metal cutting bandsaw blade. Can I cut metal on a Grizzly 14" bandsaw if I get a blade for it? Is that the best way to cut this stuff?

This is going to take forever. I also have to figure out how to attach the supports to a drywalled ceiling (there's a room above) and puzzle out a couple of bags of fasteners.


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## TopamaxSurvivor (May 2, 2008)

Cut threaded rod with a hacksaw and 24 tooth blade. If the threads get messed up, just take a pair of diagonal pliers, put one edge in the thread where it starts on the end of the rod and te eother edge on the end and break it off. The nut will screw right on then. It will save a lot of time screwing them on to straighten out the threads. Most of the time, the nuts just screw on anyway without any trouble. Too bad I too far away ;-))


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## Finn (May 26, 2010)

cut the threaded rod with a hack saw . Be sure to put a nut on the rod first and after the cut….. back the nut off the end and the threads will then be cleaned up enough to accept the nut back on. I used to cut duct and spiral pipe using two tin snips at one time but there are few professional sheetmetal workers that do that.


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## Elizabeth (Oct 17, 2009)

Just an update on this for anyone in a similar situation. The hacksaw with the metal cutting blade is working well. We got a stock bimetal blade with the handsaw which we are using for the threaded rod and I got a variable tooth metal blade for the ducting. The rod is cutting very cleanly, no problem with the threads, and the ducting does cut though it's pretty tiring on the hands to do more than one at a time.

The project is no longer going to take forever, but it'll still be at least a few more weeks of weekend work before it's all together. But I think I can see the end now! (And I can also see my workbench again, which until today was completely covered with ducting parts.) Here's a picture showing most of our progress!


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## Grandpa (Jan 28, 2011)

Looking good!! I would say I am impressed but thet sounds like I didn't expect good work from you so I will saw Great Job!! Keep it up!


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## TopamaxSurvivor (May 2, 2008)

My Oh My!! Looks like you are on a roll ;-))


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## Flyin636 (Jul 29, 2011)

Are those Hydro-formed elbows?Maybe a close-up pic of one…..thanks,BW


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## Elizabeth (Oct 17, 2009)

Sure, I'll get some closeups done this week. I believe the ducting components are from http://www.spiralmfg.com/ .


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## zzzzdoc (Mar 6, 2010)

I had pretty good success with a Roto-Zip with a metal blade. Cuts my ducting pretty quickly, and fairly smooth.


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## twiceisnice (Aug 29, 2010)

METABO 6" GRINDER WITH CUT WHEELS , YANO LIKE THEY USE ON ORANGE COUNTY CHOPPERS.


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## Elizabeth (Oct 17, 2009)

For anyone still interested in this project's progress, I've got two of my eight tool connections done! The first is the belt sander, which is the first tool off of the ducting:










...and the second is the bandsaw, which required additional engineering to avoid impacting the garage door above the saw's location. I call the resulting structure my Band Saw Suspension Bridge:










I still need to cut a small length of 4" pipe to connect the blast gate to the saw, but am waiting to do that last so I don't run out of the proper lengths of pipes for other things in the system.


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## twiceisnice (Aug 29, 2010)

Nice job. You should keep your pipe as high as you can to the ceiling that way when you rotate long boards you won't hit the pipe .


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## Elizabeth (Oct 17, 2009)

Yeah, we are. I had to run the bandsaw bit slightly lower than I'd wanted to in order to keep in line with the ceiling stud, but most of it is staying pretty high and I don't work with a large number of really long boards.


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## TopamaxSurvivor (May 2, 2008)

Looking nice. You should be a tinbender ;-)) You have a natural talent.


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## Elizabeth (Oct 17, 2009)

Nearly all the ceiling ducting is up now - just got to run a length to the table saw still. Then it'll all be finishing the drop-downs.

The photo is too long to show it all, but you should be able to right click on it and select "view image" or something like that and then it should show the rest of it.


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## Elizabeth (Oct 17, 2009)

Well, 86 days from my first post and I've finally got all 8 ports with blast gates on. Yesterday we connected up the final 5" drop down, (visible in picture above, at right) which connects to the planer, jointer and floor sweep. Still have to hook up the flex hose to those three tools but the heavy lifting is DONE and the connected tools are useable now that every opening can be closed. I've given my work crew (aka my husband) the rest of the winter off, and we will finish up the two small 4" drop downs (on left of pic) in the spring. One is just for future system expansion anyway, and the other goes to two lesser-used tools.

I also got to finally clear out the backlog of chips that had built up inside my jointer; my previous portable HF dust unit was simply not strong enough to suck it all out. It was like an explosion of confetti every time I tried to use the jointer…interesting, but messy.

More pics to follow later this week! I may try to make a blog post out of all of them, too.


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## Elizabeth (Oct 17, 2009)

One micron, according to various online sources. The DC is a Laguna 2HP cyclone.

Here's an updated pic showing the completed table saw and (except for flex hose) planer/jointer/floor sweep drop-downs.


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## Grandpa (Jan 28, 2011)

great job. Good update.


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