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Cutting metal dc ducting?

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Forum topic by Elizabeth posted 09-03-2011 02:40 AM 4907 views 0 times favorited 33 replies Add to Favorites Watch
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Elizabeth

814 posts in 2608 days


09-03-2011 02:40 AM

Topic tags/keywords: question ducting dust collection installation

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!


33 replies so far

View cabmaker's profile

cabmaker

1507 posts in 2274 days


#1 posted 09-03-2011 03:06 AM

Jigsaw with bi-metal blade.

View a1Jim's profile

a1Jim

115202 posts in 3042 days


#2 posted 09-03-2011 03:18 AM

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!

-- http://artisticwoodstudio.com Custom furniture

View Mickey Cassiba's profile

Mickey Cassiba

312 posts in 2496 days


#3 posted 09-03-2011 04:11 AM

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

-- One of these hammers oughta fix that...

View Elizabeth's profile

Elizabeth

814 posts in 2608 days


#4 posted 09-03-2011 04:14 AM

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.)

View Dark_Lightning's profile

Dark_Lightning

2635 posts in 2574 days


#5 posted 09-03-2011 04:30 AM

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.

-- Random Orbital Nailer

View Lee Barker's profile

Lee Barker

2170 posts in 2315 days


#6 posted 09-03-2011 05:20 AM

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

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

View Elizabeth's profile

Elizabeth

814 posts in 2608 days


#7 posted 09-03-2011 06:00 AM

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?

View Sawkerf's profile

Sawkerf

1730 posts in 2533 days


#8 posted 09-03-2011 06:08 AM

Sawzall with metal cutting blade

-- Adversity doesn't build character...................it reveals it.

View Elizabeth's profile

Elizabeth

814 posts in 2608 days


#9 posted 09-03-2011 07:21 PM

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..

View TopamaxSurvivor's profile

TopamaxSurvivor

17671 posts in 3140 days


#10 posted 09-03-2011 07:49 PM

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.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View Grandpa's profile

Grandpa

3256 posts in 2140 days


#11 posted 09-03-2011 08:06 PM

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.

View danr's profile

danr

154 posts in 2650 days


#12 posted 09-03-2011 08:19 PM

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.

View a1Jim's profile

a1Jim

115202 posts in 3042 days


#13 posted 09-03-2011 08:57 PM

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

-- http://artisticwoodstudio.com Custom furniture

View Jim Finn's profile

Jim Finn

2412 posts in 2387 days


#14 posted 09-04-2011 03:36 AM

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.

-- "You may have your PHD but I have my GED and my DD 214"

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Grandpa

3256 posts in 2140 days


#15 posted 09-04-2011 04:16 AM

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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