Best Fasteners for HVAC Contractors
HVAC fastening is sheet metal all the way down: self-piercing screws that assemble ductwork, worm-drive clamps that seal flex duct, straps that hang it all, and concrete anchors that hold condensers and air handlers to pads and walls. One 1/4 in hex driver runs nearly the entire trade.
What to Look For
- #8 hex-head self-piercing screws for duct — the Zip-in pattern the whole industry standardized on.
- One 1/4 in hex driver for everything — screws, clamps, and straps share the same drive.
- Worm-drive clamps for round and flex duct — adjustable, strong, and removable for service.
- Straps sized to the duct with screws rated for the structure — framing screws for joists, concrete anchors for masonry.
- Vibration-rated anchors for equipment — condensers and handlers shake; the anchors must be rated for it.
Top Picks
1. Malco Zip-in self-piercing screws, #8 hex head Best overall
The best-selling sheet-metal screw in HVAC for decades — pierces layered duct without walking, seats flush every time, and runs on the same 1/4 in driver as everything else in the bag.
Check price on Amazon →2. Worm-drive hose clamp assortment Best for flex duct
Flex duct lives and dies by its clamps — a stainless worm-drive assortment covers every residential diameter and survives rooftop UV and attic heat.
Check price on Amazon →3. Galvanized duct strap hanger roll Best for hanging duct
Pre-punched galvanized strap wraps any duct size and screws to framing in seconds — the universal hanger for both rigid and flex runs.
Check price on Amazon →4. Zinc wedge anchor kit, 1/4 and 3/8 in Best for mounting equipment
Condensers, mini-split brackets, and air-handler platforms bolted to pads and block walls need wedge anchors — rated, removable, and vibration-proof.
Check price on Amazon →What to Avoid
Avoid
- Drywall screws in ductwork — they rust, back out under vibration, and leave sharp points inside the airstream.
- Crushing flex duct with over-tightened clamps — snug plus a mastic seal, not strangled.
- Mixed metals on outdoor units — aluminum, copper, and plain steel in contact corrode fast in weather.
- Undersized straps on long flex runs — sagging flex kills airflow; support every 4 ft or better.
Also in the toolbox
- Reversible 1/4 in hex driver — the one driver that runs the whole trade
- Aviation snips set — left, right, and straight for duct and strap
- 12V impact driver kit — overhead duct screws without the arm pump
FAQ
What screws are used for ductwork?
#8 hex-head self-piercing sheet-metal screws (the Zip-in pattern), usually 1/2 in long — they pierce layered galvanized duct without pre-drilling and seat flush so insulation wraps flat.
What is the difference between Zip-in and TEK screws?
Both are self-drilling, but Zip-ins use a self-piercing point tuned for thin layered sheet metal — faster starts and less walking in duct gauges. TEKs with true drill points suit thicker steel; for ductwork, Zip-ins are the trade standard.
How do you hang flexible duct?
With wide straps (1-1/2 in minimum) every 4 ft, hung with slack so the duct keeps its round shape — tight wire or narrow strap chokes airflow. Support long horizontal runs so there is no sag between hangers.
What anchors hold an AC condenser to a pad?
Wedge anchors or concrete screws through the unit mounting feet into the concrete pad, sized to the local wind code — in hurricane zones, code specifies the anchor size and embedment, so check the condenser installation manual.
Keep Reading
- Self-Drilling Screw
- Self-Tapping Screw
- Concrete Screw
- Wedge Anchor
- Best Screws for Sheet Metal
- Best Concrete Anchors
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