Worm Gear & Helical Speed Reducers

Speed reducers are gearboxes that cut motor speed and multiply torque between an electric motor and the driven equipment. Texas Belting stocks 650+ Vortex worm gear, inline helical, and shaft mount reducers in Houston, TX - NEMA C-face and IEC inputs, plus adapters and rebuild parts.

Shop speed reducers by type

On this page: Types · Efficiency · Sizing · Identify · Interchange · C-face vs IEC · Mounting & oil · FAQ

Worm, helical, or shaft mount: which reducer do you need?

Three types cover most industrial drive swaps. Worm gear reducers give a compact right-angle drive with high single-stage ratios at 52-93% efficiency. Inline helical reducers run roughly 94-97% and suit continuous duty. Shaft mount reducers hang on the driven shaft of a conveyor and take a V-belt input.

Worm gear reducer efficiency by ratio

Worm gear efficiency falls as ratio climbs: a 5:1 unit transmits 92-93% of input power, while a 60:1 unit transmits only 52-71% depending on center distance. Helical gearing holds roughly 94-97% at any ratio. The table shows typical published values for cast iron worm reducers at 1750 rpm input.

Smaller boxes sit at the low end: at 60:1 a 1.75 in center distance unit runs about 52%, a 3.25 in unit about 71%.

How do I size a speed reducer?

Size a speed reducer in three steps: compute the ratio (input rpm divided by required output rpm), pick a service factor from load class and daily run time, and confirm published ratings meet required torque times service factor. Output torque in lb-in equals HP x 63,025 / output rpm, times efficiency.

Step 1 - Ratio. A 1750 rpm motor turning a head shaft at 90 rpm needs 1750 / 90 = 19.4, so pick 20:1 nominal.

Step 2 - Service factor. Pick from an AGMA-style chart, then multiply required torque by it:

Step 3 - Torque check. Worked example (typical catalog data): a 20:1 unit (actual 19.5:1) rated 4.74 hp at 1750 rpm gives 90 rpm out. Output torque = 4.74 x 63,025 / 90 x 0.86 efficiency = about 2,855 lb-in, matching the published 2,875 lb-in rating within 1%. Required torque x service factor must sit at or under the catalog rating.

Overhung load. If the output drives a sprocket or sheave, divide the published overhung load rating by a K factor: chain 1.00, gear 1.25, V-belt 1.50, flat belt 2.50, variable-pitch belt 3.50.

How do I identify a replacement reducer without a nameplate?

Five checks identify almost any worm gear reducer with a missing tag: center distance between shaft centerlines, ratio, input type, output configuration, and mounting position. Center distance is the master dimension model families are built around, so measure it first.

1. Center distance: input shaft centerline to output shaft centerline. Standard sizes: 1.33, 1.54, 1.75, 2.06, 2.38, 2.62, 3.00, and 3.25 in.
2. Ratio: turn the input by hand and count full turns per one output revolution. 30 turns = 30:1.
3. Input: C-face quill, IEC flange, or solid shaft? For C-face, measure pilot and bolt circle (frame table below).
4. Output: solid left, right, double-extended, or hollow bore? Record bore and keyway. See output mounting accessories.
5. Mounting position: note worm under or over, and which face carried the feet.

Cross-brand replacement and interchange

Single-reduction worm reducers are built around industry-standard center distances, so most brands interchange dimensionally once center distance, ratio, and input all match. Model families encode it directly: a 2.62 in measurement points to a Boston Gear 726, Worldwide HDRS262, or IronHorse WG-262 class unit.

Interchange references are based on manufacturer-published equivalents. Verify dimensions before ordering.

Our Vortex X-Series worm reducers follow the same standard footprint pattern; verify center distance, ratio, and input, then output hand and position. Accessories that complete a swap:

What does 56C mean? NEMA C-face vs IEC inputs

A NEMA C-face motor has a machined face with a male pilot and tapped bolt holes: it bolts straight to the reducer input flange while its shaft engages a hollow quill. 56C and 143TC/145TC share the same 4.5 in pilot and 5.875 in bolt circle - only the shaft differs - so many reducer inputs accept either frame with the correct bushing.

IEC metric motors mount by B5 flange (clearance holes; an IEC 80 frame has a 19 mm shaft, 165 mm bolt circle, 130 mm spigot) or B14 face (smaller, tapped holes). Across our Vortex line: X, XS, and XH take NEMA C-face quill or solid inputs; VMRV takes IEC B5/B14 flanges; VR takes C-face; VXT uses a solid, belt-driven input shaft. To mate one system to the other, use motor mounts and adapter kits.

Mounting positions and oil fill

Mounting position determines oil capacity, fill level, breather location, and seal arrangement - not just bolt orientation. Worm reducers use six standard positions: four with the input shaft horizontal (worm under or worm over) and two with the input vertical. Confirm position when ordering; if you re-orient a unit later, drain, refill to the new level, and move the breather to the highest port.

Oil quantity changes with orientation: published Boston Gear figures show a 1.33 in unit taking 5.5 fl oz worm-under but 7.0 fl oz in the other horizontal positions, and a 2.62 in unit ranging 28-43 fl oz. Makers commonly specify double input seals for worm-over and vertical positions. Two rules never change: the breather plug goes in the uppermost port, the drain at the lowest.

Check the fill state before start-up: some brands ship worm reducers dry, while many metric-pattern units ship factory-filled with synthetic oil. Typical worm gear lubricant is an ISO VG 460 class synthetic; a common schedule for mineral-oil fills is a change at 250 hours, then every six months.

Speed reducer supplier in Houston, TX

Most stocked sizes ship same day from our Houston, TX warehouse; cross-reference quotes typically turn around in one business day. We serve the Texas Gulf Coast and ship nationwide. Call (888) 203-2358 to confirm availability.

Common speed reducer selection mistakes

• Sizing by motor HP alone. A 1 hp motor on a heavy-shock 24-hour drive needs a reducer sized for 1.75 hp equivalent; apply the service factor first.
• Matching ratio but not center distance. Two 30:1 reducers from different families share no bolt pattern. Center distance first, then ratio.
• Assuming self-locking holds the load. Worm drives can creep or run back under vibration; use a backstop where reverse rotation is a hazard.
• Ignoring mounting position at order time. A worm-under unit flipped to wall mount runs its input bearing dry or floods the seal.
• Topping off with the wrong oil. Mixing PAG with PAO or mineral oil can ruin the lubricant; match the fill or flush and refill.
• Like-for-like worm swaps on continuous drives. A 60:1 worm turns roughly a third of input power into heat, a loss an inline helical avoids; run the numbers first.

When to call

Call when:

• Nameplate gone and measurements ambiguous
• Double-reduction ratios, dual outputs, or special output hands
• Vertical or re-positioned drives needing seal, vent, and fill changes
• CEMA screw conveyor drives needing matching shafts and adapters
• Obsolete brands or OEM-only model numbers to cross

Call (888) 203-2358 or send us what you have.

Frequently asked questions

Related products and guides

Last updated: July 2026