8″ to 6″ Duct Reducer

Description

Overview

A tapered step from 8-inch duct down to 6-inch. Not a plate with two holes — a proper cone, so the air changes diameter gradually instead of slamming into a shoulder.

What it fits

Standard 8-inch duct on the wide end, standard 6-inch on the narrow end. Works with flexible or rigid duct and with the inline fan sizes those correspond to. Every shroud, elbow and port in our line uses those same two collar sizes, so it drops anywhere in the system.

Measure before you order. Fit dimensions in this line are derived from published fan and chassis geometry and are not yet validated against measured production hardware. Check your flange size and the clearance around your machine against the footprint in the specifications below. If something does not fit, tell us — that is how the next revision gets better.

How it is used

The usual place for it is at the end of the run, not the start: keep the trunk at 8-inch for as long as you can and step down only where you have to — at a wall penetration, a window port, or the inlet of a 6-inch inline fan. It also lets you feed an 8-inch shroud into an existing 6-inch installation without re-ducting the building.

Why it helps

Every diameter change costs pressure, but an abrupt one costs several times more than a gradual one, because the flow separates off the step and churns. A taper keeps the stream attached. Given that the whole reason you ducted the machine was to move air, it is worth spending a few dollars on the shape that does not throw that away.

• Gradual taper rather than an abrupt step
• Standard 8-inch and 6-inch collars — fits the rest of the system
• Lets an 8-inch shroud feed an existing 6-inch run
• Single continuous body, no assembly

Specifications

Open source — print it yourself, or buy it finished

Every shroud D-Central designs is released as an open file. The geometry for this part is free to download from our 3D models download center: use it, modify it, remix it, run it in your own shop, sell what you make from it. There is no licence to buy and no design gated behind a purchase. Shared knowledge is the whole reason this industry has open hardware at all, and we are not going to be the ones who stop passing it on.

This listing is for the finished part: made to order in PETG and shipped from Montreal, Quebec. If you would rather have it in your hands than spend an evening making one, buy it here — that is what pays for the next design in the line. You can also support the open-source work directly through D-Central’s fund page.

Works with

• 6″ to 4″ Duct Reducer
• 6″ Duct Coupler
• 8″ Duct Coupler
• Universal Single 120 mm Fan to 8″ Duct Shroud

See the full D-Central shroud and ducting system for the compatibility matrix and sizing guide.

Frequently asked questions