6″ to 4″ Duct Reducer

Description

6 inch to 4 inch duct reducer for mining exhaust lines

A 6 inch to 4 inch duct reducer is the fitting that lets you use a hole the building already has. Houses are full of 4-inch penetrations: dryer vents, bathroom fans, retired range hoods, basement make-up air. Being able to step a 6-inch line down to that size cleanly is frequently the difference between a heat-reuse project that happens this weekend and one that waits until somebody is willing to cut masonry.

This is the small end of the reducer family. The bore tapers from the 6-inch collar down to the 4-inch collar in one continuous cone, 89 mm deep, so the contraction happens over a length rather than at an edge.

Drawn in-house to the same collar standard as the rest of the D-Central ducting line, which means it also serves as the adapter between the main run and any 4-inch branch you are running alongside it.

What it fits: 6-inch line, 4-inch termination

Standard 6-inch duct on the wide end, standard 4-inch on the narrow end, flexible or rigid. The 4-inch collar matches the branch size on the 6″ to Dual 4″ Y-Splitter, so the two parts work as a pair when you are collecting a small auxiliary line into a main run.

Understand what 4-inch is for. It is correctly sized for power-supply-level airflow, small inline boosters and auxiliary branches. It is not the size to terminate a full ASIC exhaust in. If you are looking for the fitting that steps a big trunk down one size, that is the 8″ to 6″ Duct Reducer.

How it is used

Three jobs cover almost every install. First, terminating a 6-inch line into an existing 4-inch wall or window penetration, so no new hole gets cut. Second, feeding a small 4-inch inline fan from a 6-inch run. Third, taking a 4-inch auxiliary line, typically a power supply or a cabinet fan, and bringing it up to the 6-inch trunk. Slide, clamp, done: a band clamp on each collar and the joint is mechanical rather than adhesive.

Why a cone beats a step at this size

The proportional contraction here is larger than on the 8-to-6 part, which makes the shape matter more, not less. Cutting the bore area to well under half in a single edge forces the flow to separate and recirculate right where the velocity is highest. Spreading the same contraction over the depth of a cone keeps the stream attached and hands the smaller duct air that is still moving in the direction you wanted it to.

• Reuses an existing 4-inch building penetration instead of cutting a new hole
• Tapers the whole contraction over the depth of the body rather than at a shoulder
• Matches the 4-inch branches on the 6″ Y-splitter for auxiliary and power-supply lines
• Clamps mechanically on both collars, over rigid pipe or flex helix
• Prints as one continuous body in PETG, which shrugs off exhaust-side heat that softens PLA

Specifications

Open source — the drawings are free, the part is made to order

This reducer is D-Central Technologies’ own design. We drew the taper, we set the collar depths, and we released the drawing open source under CC BY-SA 4.0 at the 3D models download center — ours, not a remix of anyone else’s file. Its card is the 6″ to 4″ reducer model: download it, change the collar depth, scale the taper, run a batch on your own machine, sell what you make. Nothing here is gated behind a purchase, because a fitting standard that only one shop can make is not a standard.

The download is reducer_6_to_4.zip — STL, CC BY-SA 4.0 licence, and the installation and safety guide, in one file. What you are buying on this page is the finished cone: made to order in PETG, in black or orange, and shipped from Montreal, Quebec, ready to clamp. The drawing stays free; buying the part, or giving through D-Central’s fund page, is what pays for the next design in the line.

Works with

• 6″ to Dual 4″ Y-Splitter
• 8″ to 6″ Duct Reducer
• 6″ Duct Coupler
• 6″ 90° Duct Elbow (Compact)
• Antminer S19 Full-Wrap Dual 120 mm to 6″ Shroud

Shroud, elbow, reducer, gate, port — the entire run comes from one place. See the D-Central shroud and ducting system.

Frequently asked questions