Replies

1. 
   mysticvalleyfarm | Dec 03, 2007 09:45pm | #1

   Some time ago I found one in my local Plumbing/HVAC supply place.  I remember it being under $10.00.  I had to ask the clerk, but she produced just what I needed in less than 5 minutes. 

2. 
   frenchy | Dec 03, 2007 09:47pm | #2

   Bones,

      home depot had mine.. 5 inch furnace duct to 4 inch furnace duct

1. 
   bones | Dec 04, 2007 12:30am | #4

   Duh, I did not even think of HVAC supliers. I did not think 5" was a standard size. Thanks everyone.Government's view of the economy could be summed up in a few short phrases: If it moves, tax it. If it keeps moving, regulate it. And if it stops moving, subsidize it.

3. 
   brad805 | Dec 04, 2007 12:29am | #3

   I am pretty sure Grizzley does.  Check this one: 

   H1216 5" x 4" Reducer.

   I have built them too using stove pipe and pop rivets along with a little clear duct tape.

4. 
   KeithNewton | Dec 04, 2007 01:49am | #5

   Bones, If the reduction is from the 4" into the 5", the way the air flows, you can just make a wooden donut / bushing. That would be, if the dust hood was the 4" and you were bringing a 5" pipe to it. I am not sure about going back the other way though.

1. 
   t_mauery | Dec 05, 2007 08:32pm | #8

   This is true, but an abrupt change in diameter will cause a significant pressure loss.  Typical transitions range from about 2 to 1 to about 4 to 1 (length to diameter).  At about 8 to 1, the pressure loss is almost negligible.

   Non-intuitively, going from a smaller diameter to a larger diameter requires a smoother (i.e., longer) transition.

1. 
   bones | Dec 05, 2007 09:30pm | #9

   So to go from a 5" down to a 4", the 1" change should be over 8" for no pressure loss?Government's view of the economy could be summed up in a few short phrases: If it moves, tax it. If it keeps moving, regulate it. And if it stops moving, subsidize it.

1. 
   t_mauery | Dec 05, 2007 10:12pm | #10

   I'm not an HVAC guy, but yeah, that's about right. It's usually expressed as an angle (the half angle measured from the centerline), and you want that to be less than 8 degrees.

   There's still a loss associated, but it's a lot less significant when the transition is nice and smooth. If it's too abrupt, the flow "detaches" itself from the walls and causes excess turbulence.

   Of course, you're not designing a big HVAC system, so you don't need to go to extremes. But I always find it useful to know what the "ideal" solution is, and then modify it to fit my needs, if changing it is necessary.

5. 
   gboot | Dec 04, 2007 11:05pm | #6

   You might also want to check out a 4" (Clay pipe) to 4" PVC fitting at HD. It's a rubber boot with hose clamps that accomodates male fittings 5" on one side , 4" on the other.

1. 
   user-87215 | Dec 05, 2007 04:42am | #7

   Amazon has them in plastic for under $5.00 and so does Tools Plus http://www.tools-plus.com/woodstock-w1037.html   , which is where I got mine when I bought my dust collector -  they also had a great price on clear 5" hose.

6. 
   Al from Unionville | Dec 06, 2007 05:36am | #11

   I bought several reducers from Oneida. The 4 to 5 steel reducer is $10.86. It may a small matter but HVAC ductwork is backwards to DC ductwork (eg crimping on the wrong end on HVAC stuff) / Al

7. 
   PADDYDAHAT | Dec 06, 2007 05:47am | #12

   BONES , I bought one from delta for @$20 for my Unisaw, it may be on Amazon as a Delta part but you have to poke through all their screens to find it. Paddy