Well it’s kinda clunky and made outa junk ductwork, but the price was right, and it works!
I started with some old pipe from a friends vent hood off their old stove. It had an accumulation of gunk from years of cooking. It was serviceable after scraping and bending flat though.
Then I drew up the 4” high transition from a 13.5” x 2.75” rectangle to a 4” circle. I cut that half pattern out and transferred it to the sheet metal with a center punch and scribe marks.
After the most dangerous part of cutting it out, I used some c-clamps and angle iron as a brake and put the bends in. Then a quick trip to the hardware store re-supplied me with 1/8” pop rivets. A few dozen holes and popped rivets and there you have it.
Oh yeah. I had to cut off the last two inches of the original chute with a zizz wheel and die grinder. I knew I was past the point of no return then. But no biggie. Looks like heck but it sure beats cleaning up after it and sanding all the divots from chips being recycled through the head.
I learned two things.
1) I can do this.
2) Make the top of the transition a little smaller than you think it should be. It has to fit inside the four inch collar.
I found that the part may still be available, but it’s on back order. And I didn’t want to wait. Besides I always did like tinkering and fabricating. And my Dave Gingery books had to be useful for something right?