# Cutting hole in metal duct collection duct



## Ray Newman (Mar 9, 2009)

Colleagues: I need another Dust Collection line for a Table Saw over-the-blade dust collection/blade guard. 

To run it off the existing 6" TS DC sheet metal duct, need a hole in the duct then install a saddle tap Y connector on the 6" duct. See:
www.oneida-air.com/inventoryD.asp?item_no=SCOLLECT33

Seems to be rather straight forwarded, but how-in-the-heck do I cut the hole in the existing 6" diameter duct?

Considered a 6" 45 degree Y -- See: https://www.oneida-air.com/inventory..._no=SCOLLECT41 -- but I would need to dismantle the existing duct and blast gate to install it.

Any ideas?


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## tomp913 (Mar 7, 2014)

For the saddle fitting referenced, just cut a hole in the existing duct facing in the direction that you want the "Y" to point. You should be able to reach inside the "Y" and mark around the inside with a Magic Marker, then just cut the outline. Put a bead of the silicone sealant shown on the page around the outside, and fasten the saddle in place. One way is with self-tapping screws - think the heating duct in your house - but I think I would consider some type of hose clamp so you have nothing sticking down inside for debris to catch on.


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## Ray Newman (Mar 9, 2009)

Tomp913: what I need to know how to cut the *[email protected]#$$ hole and what do I need to do it ?

Tin snips--which I have -- came to mind right-off-the-bat with a hole drilled to start the cutting. But are there specialized snips to cut a circular/oblong hole??

Some one suggested a grinder with a cut off wheel to cut out a rectangle hole in the duct. If that is feasible, I have a air powered grinder and cut off wheels.


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## Stick486 (Jan 4, 2013)

tin snips or a jigsaw...


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## DaninVan (Jan 1, 2012)

Ray; tin snips or Aviation snips? Aviation snips come in three styles Right hand curve cuts, Left hand curve cuts, and straight cuts
.https://www.amazon.com/Wiss-Aviatio...=2025&creative=165953&creativeASIN=B00KXF26AE
Basically you perforate the metal in the middlle of the circle and get the tip of the ships into the hole, then start cutting in a spira outwards to the outline of your hole.
Drawing the hole outline is a bit more interesting.
The easiest way, assuming you have a bit of scrap of the smaller size to, is to draw the arc of the 6" pipe onto the side end of the smaller pipe, cut tat arc on both sides so it saddles the 6"pipe then trace that profile onto the 6" face.
Now, this is important, you need to make longitudinal slices maybe every inch or so around the crved end of your smaller pipe. This will give you tabs...anbe about an inch long(?). Fold every second one outward. Insert the pipe with the straight tabs into the 6" pipe.
Fold those ones outward , tight against the inside of the 6" pipe; the smaller pipe is now locked in place.
I would have used a short pipe stub for this item. This would allow you to get your hand inside to do the detail work. Now you install wahtever you need onto the small pipe stub.


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## Stick486 (Jan 4, 2013)

to draw the circle for the cutout...
place the saddle...
use a felt tip to trace mark the hole through the saddle's tap...
cut the hole about a ¼'' large to avoid a lip that will be prone to catch debris..
use ordinary elcheapo rubber cement to make a gasket... paint it on the inside of the daddle's flange, let dry, and assemble...
hose clamps are your bestest friend here...


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## Stick486 (Jan 4, 2013)

DaninVan said:


> Now, this is important, you need to make longitudinal slices maybe every inch or so around the crved end of your smaller pipe. This will give you tabs...anbe about an inch long(?). Fold every second one outward. Insert the pipe with the straight tabs into the 6" pipe.


Dan,,,
Ray is installing a saddle and not a crown...
no tabs required...

note...
the rubber cement forms a most excellent seal and won't let the saddle creep...


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## Semipro (Mar 22, 2013)

Here watch this


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## tomp913 (Mar 7, 2014)

Ray Newman said:


> Tomp913: what I need to know how to cut the *[email protected]#$$ hole and what do I need to do it ?
> 
> Tin snips--which I have -- came to mind right-off-the-bat with a hole drilled to start the cutting. But are there specialized snips to cut a circular/oblong hole??
> 
> Some one suggested a grinder with a cut off wheel to cut out a rectangle hole in the duct. If that is feasible, I have a air powered grinder and cut off wheels.


 @Ray Newman

Sorry, misread your question. Tin snips are your best bet, and I would use offset snips so that your knuckles are away from the rough edges. As Stick said, cut outside your Magic Marker line so there's nothing to catch on. You don't need too big of a hole to get started, maybe use a 3/4" holesaw if you need more room - drill inside your cut line and arc from the starting hole to blend with the cut line. Probably easier to take short "nibbles" rather than a full length cut and just walk your way around the hole. I don't know your access to the duct that you're cutting, it may be that you need both right and left cutting snips in order to do the job.

https://www.amazon.com/ABN-Offset-R...8-1-spons&keywords=offset+aviation+snips&th=1

My father-in-law was a HVAC mechanic and could do amazing things with sheet metal, I've seen him make a starting hole in a duct with a flat blade screwdriver and a hammer, work the snips around the hole and have the edges look as if they were sawn rather than cut with snips - he tried to pass his knowledge along to me, but did a lot of head-shaking watching me work.


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## DaninVan (Jan 1, 2012)

I hear that! I can't get near sheet metal without nicking myself. 

"What's this rust coloured stuff all over the ducting?"
Me: "Type O"


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## Stick486 (Jan 4, 2013)

Semipro said:


> Here watch this
> https://youtu.be/Hgp2mm8CgSA


go w/ hose clamps... screws tend to catch stuff...
rubber cent is better and cheaper.. make a gasket w/ it...


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## Stick486 (Jan 4, 2013)

hints..
use a Unibit to make your starter hole...
there is nothing like nipples or electric shears...


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## DesertRatTom (Jul 3, 2012)

Long ago I used a nibbler tool for a similar chore. Cheap, slow, clean and exact cut. 

https://www.amazon.com/Nickel-Plate...1509328897&sr=8-3&keywords=metal+nibbler+tool About $14 on Amazon. Snips are very likely to distort the curved sheet metal.


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## Stick486 (Jan 4, 2013)

I'm lazy...

.


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## DesertRatTom (Jul 3, 2012)

@Stick486 I saw those mechanical nibblers, kind of pricey for a single use, but suitable for lazy.


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## Stick486 (Jan 4, 2013)

my other shop...

.


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## DaninVan (Jan 1, 2012)

Still got all your fingers, Stick? 
Best advice I ever got was "If you drop a piece of glass or sheet metal _just let it go_. DO NOT TRY AND GRAB IT!!!"
(Well OK; there was that advice about women...but I digress)


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## Stick486 (Jan 4, 2013)

DesertRatTom said:


> @Stick486 I saw those mechanical nibblers, kind of pricey for a single use, but suitable for lazy.


they got way ore than a single use...
these cost a lot less...

.


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## DaninVan (Jan 1, 2012)

Or...
https://www.kmstools.com/astro-pneumatic-17ga-air-nibbler-134965

Mind you the compressor won't be cheap.

(Do _I_ have one you ask? Not gonnahappen!)


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## DesertRatTom (Jul 3, 2012)

Thanks for the safety reminder. Should print this up and post it in the shops.


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## DaninVan (Jan 1, 2012)

DesertRatTom said:


> Thanks for the safety reminder. Should print this up and post it in the shops.


Just 'Google' _Blood pictures_...great selection available! :0


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## thomas1389 (Jan 4, 2012)

DaninVan said:


> Just 'Google' _Blood pictures_...great selection available! :0


No thanks, I'll be up all night! Yuk!


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## thomas1389 (Jan 4, 2012)

PUZZLEMENT!! In the video from John: The Duct Shop. The mechanic says the air flow in the 10" line is his left to his right. The secondary is angled AWAY from the main from his left to his right. That would be okay if clean air was being delivered to two locations but if this is a vacuum setup should the secondary not be angled INTO the main from the left to the right. In the setup as shown would the debris in the secondary not fight the airflow. As shown, if used to vacuum, the debris would have to fight the airflow and then almost turn back on itself to get into the 10" main. Just sayin'.


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## Stick486 (Jan 4, 2013)

thomas1389 said:


> PUZZLEMENT!! In the video from John: The Duct Shop. The mechanic says the air flow in the 10" line is his left to his right. The secondary is angled AWAY from the main from his left to his right. That would be okay if clean air was being delivered to two locations but if this is a vacuum setup should the secondary not be angled INTO the main from the left to the right. In the setup as shown would the debris in the secondary not fight the airflow. As shown, if used to vacuum, the debris would have to fight the airflow and then almost turn back on itself to get into the 10" main. Just sayin'.


he's doing vent in the video...
DC is where this thread is...
DC air flow sucks and vent blows...
joints matter which way they are put together...


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## thomas1389 (Jan 4, 2012)

Stick486 said:


> he's doing vent in the video...
> DC is where this thread is...
> DC air flow sucks and vent blows...
> joints matter which way they are put together...


Yes, I agree, so if this is Ray's application we're talking about (DC air flow sucking) then this isn't a good example for him as this video is for venting. If someone unknowingly used this example for DC air flow sucking, and flow is mechanics left to right as he says, then the secondary should be turned around, or not ? But the hole pattern to cut would be the same shape whether the secondary was in one direction or the other, no ?


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## Stick486 (Jan 4, 2013)

cutting hole saddle was a good example...
but, for DC, everything else is reversed...
the male ends of the pipe (crimped) always point toward the DC...
the take off on saddles are pointed away from the DC unit...
the female of a joint are pointed away also..
using sealant on a DC system is expensive and unnecessary... don't even bother w/ the stuff..

use foil tape on the joints and rubber cement on things like the saddle...
rubber cement makes for reusable gaskets if you ever need/want to move a saddle..
the exposed hole only needs a short *C shaped pipe,* rubber cement and a hose clamp... you may want to put the saddle back where you had it...
cut a pipe to length, rip it in two, paint the inside of the patch w/ rubber cement, let the cement dry... install the patch...
never use screws or rivets, use hose clamps... screws tend to loosen on their own in a DC system... rivets add difficulty to change.. screws catches what's being pulled throuch the pipe... 
as a benefit, hose clamps seem to make the pipe stiffer... take a piece of pipe, squeeze it, it goes out of round easily...
install a couple of hose clamps, now squeeze the tube, see the difference...
once installed, vent is rarely changed as where a DC piping always in evolve/flux/change/modification/remodel/adapt mode...
clamps are ideal in this respect.. so make things easy on yourself and avoid waste.. make *EVERYTHING* reusable..
think KISS/MISS...

*NOTES*
if you have difficulty assembling joints because the pipes/fittings are out of round (wonky) put a hose clamp a bit back from the the edge and snug it down...
this will make the pipe/fitting round like it should be and way easier to plug together...
align the assembly, clean/tape the joint... put a hose clamp on top of the tape, tighten and then remove the 1st two clamps...
3M 1430 tape is some of the best tape out there but there are many others...
chinese made tape doesn't stick well and deteriorates in short order...
clean the pipe w/ DNA or MS before you tape or cement to remove the lubricant oils from the manufacturing process..
you can leave the Pittsburgh on your patches if you want...
chines hose clamps are weak, corrode, the gear boxes break, the worm screws break and the slots in the bands tear...
I like USA made gates clamps... getting them from a distributor really lowers the price...


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## Ray Newman (Mar 9, 2009)

Gents: gents thanks for the info and apologize for not responding sooner, but I ordered the saddle tap from Oneida.

Semipro looked at the video, but there is no way my hand will fit in a 4" diameter pipe to mark the needed cut line. 


What I am 'gonna' do is take the saddle tap and section of the DC pipe to hold the tap to a two local sheet metal shops for ideas. Sometimes green paper with portraits of dead presidents works wonders when you need a helping hand. Thanks again!


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## Ray Newman (Mar 9, 2009)

Gents: gents thanks for the info and apologize for not responding sooner, but I ordered the saddle tap from Oneida.

Semipro looked at the video, but there is no way my hand will fit in a 4" diameter pipe to mark the needed cut line. 

What I am 'gonna' do is take the saddle tap and section of the DC pipe to hold the tap to two local sheet metal shops for ideas. Sometimes green paper with portraits of dead presidents works wonders when you need a helping hand. Thanks again!


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## Stick486 (Jan 4, 2013)

Ray Newman said:


> there is no way my hand will fit in a 4" diameter pipe to mark the needed cut line.


tape a felt tip to a short piece of a dowel...


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