An NMRV worm gearbox is a compact right angle speed reducer that uses a worm and a bronze worm wheel to slow a motor down and multiply its torque. It comes in ten body sizes, from NMRV 025 to NMRV 150, and the size number you choose decides how much torque the unit can carry safely.
Pick a size that is too small and the worm wheel wears out early. Pick one that is too large and you pay for weight, bulk and mounting space you do not need. This guide walks through every size, what each one suits, and how to choose without guessing.
What Is an NMRV Worm Gearbox?
The name describes the construction. The worm is a hardened steel screw on the input shaft. It turns a bronze wheel on the output shaft at ninety degrees, which is why the motor and the driven shaft sit at a right angle to each other. The motor bolts straight onto a flanged input, so there is no separate coupling to line up.
That layout is why NMRV units are so common on conveyors, mixers, packaging machines, textile equipment and food lines across Pakistan. They are quiet, compact and easy to mount, and a single stage can deliver ratios from 1:5 up to 1:100. If you also want to compare them with other reducer types, see our full range of gear reducers.
NMRV Size Chart: 025 to 150
The body size number is the centre distance between the worm and the wheel in millimetres. A bigger centre distance means a bigger wheel and a higher torque rating. Across the full range MV Power Drive stocks, output torque runs from about 2.6 Nm to 1760 Nm and motor power from 0.06 kW to 15 kW, depending on the size and the ratio.
| Body size | Centre distance | Housing | Typical use |
|---|---|---|---|
| NMRV 025 | 25 mm | Aluminium | Small automation, light indexing |
| NMRV 030 | 30 mm | Aluminium | Packaging, dosing, small conveyors |
| NMRV 040 | 40 mm | Aluminium | Packaging lines, food machinery |
| NMRV 050 | 50 mm | Aluminium | Light conveyors, small mixers |
| NMRV 063 | 63 mm | Aluminium | Conveyors, general production |
| NMRV 075 | 75 mm | Aluminium | Standard conveyors, mid size mixers |
| NMRV 090 | 90 mm | Aluminium | Heavier mixers, continuous duty |
| NMRV 110 | 110 mm | Cast iron | Heavy duty, high inertia loads |
| NMRV 130 | 130 mm | Cast iron | Heavy mixers, crushers, feeders |
| NMRV 150 | 150 mm | Cast iron | The largest single stage duty |
Torque depends on the ratio as well as the size, so a table of one number per size would mislead you. Always read the torque rating at your own ratio from the catalogue before you finalise an order.
How to Choose the Right NMRV Size
Most sizing mistakes come from starting with the motor instead of the load. Work through it in this order.
- Work out the torque your machine needs at the output shaft, not the motor rating you happen to have on the shelf.
- Apply a service factor. Steady loads need little margin. Frequent starts, stops and shock loads need more, and this is where a size 75 that looks fine on paper often fails in a year.
- Fix the ratio from your target output speed. The same ratio exists in several sizes, so the ratio alone does not settle the size.
- Compare your corrected torque with the catalogue rating at that ratio and choose the smallest size that clears it comfortably.
- Check the input flange, the output bore and the mounting position before you order.
If the load side of that calculation is new to you, our guide to electric motor selection for conveyor systems covers the same reasoning for the motor.
Which NMRV Size for Which Application
Light duty: NMRV 025 to 050
These four sizes suit small motors and light, often intermittent loads. Typical jobs are packaging indexing, dosing units, small food machinery and compact automation. They are light, easy to mount and inexpensive, and they are the natural choice when space is tight.
General production: NMRV 063 to 090
This is where most factory orders land. An NMRV 63 usually pairs with motors from 0.55 to 1.5 kW, an NMRV 75 with 1.1 to 3 kW, and an NMRV 90 with roughly 2.2 to 5.5 kW, all depending on the ratio. They cover standard production conveyors, mid size mixers and continuous duty drives. Go up to the 90 when the load is heavy, runs all day or is hit by shock loads.
Heavy duty: NMRV 110 to 150
The three largest sizes move to cast iron housings and are built for heavy mixers, crushers, feeders and high inertia loads. At this point it is also worth asking whether a helical or planetary unit would suit the job better, since worm gears lose efficiency at the heaviest duties.
Single Reduction or Double Reduction NMRV?
A single stage NMRV covers ratios from 1:5 to 1:100, which handles most machines. When you need a much lower output speed than that, a double reduction unit pairs two worm stages to reach ratios well beyond 1:100. MV Power Drive stocks NMRV double gear variants for this, so you are not forced to use an oversized single unit that was never meant for the job.
The trade off is efficiency. Every worm stage loses some power as heat, so a double reduction unit wastes more energy than a single stage one. Use it only when the ratio really demands it.
Aluminium or Cast Iron Housing
The smaller sizes use die cast aluminium. It is light, sheds heat well and does not rust, which is why it dominates packaging and food equipment. From the 110 upward the housing is cast iron. It weighs more, but it holds its shape under heavy torque and shock loads, which is what those sizes are built for.
Mounting Position, Oil and Maintenance
Smaller NMRV units are filled with synthetic oil for life and can be mounted in almost any position. Larger ones are more particular. According to the manufacturer datasheet, you must state the mounting position when ordering the NMRV 090, 110, 130 and 150, and only the 130 and 150 are fitted with breather, level and drain plugs. The full details are in the MV Power Drive worm gear reducer company profile.
Get this wrong and you end up with oil in the wrong place, which shows up as leaks, noise or an overheating unit. It is one of the most common causes of early failure that has nothing to do with size.
NMRV Gearbox Price in Pakistan
NMRV prices in Pakistan start from Rs 28,000 for the smallest size and rise to about Rs 7 lakh for an NMRV 150. The size, ratio, flange and brand all move the number. See the full breakdown in our NMRV gearbox price in Pakistan guide.
Frequently Asked Questions
How do I choose the right NMRV size?
Work out the output torque your machine needs, apply a service factor, then pick the smallest size whose catalogue torque at your ratio clears that number with some margin. Do not choose from the motor rating alone.
What is the difference between NMRV 063 and NMRV 075?
The 075 has a larger centre distance and a bigger worm wheel, so it carries more torque at the same ratio. It suits heavier continuous conveyors and mid size mixers, while the 063 suits lighter duty.
What ratios are available on NMRV gearboxes?
A single stage NMRV covers ratios from 1:5 to 1:100. For higher ratios, a double reduction NMRV pairs two stages.
Can an NMRV gearbox be mounted in any position?
The smaller sizes can, since they are filled with oil for life. For the NMRV 090, 110, 130 and 150 you must state the mounting position when ordering.
Is an NMRV gearbox suitable for continuous duty?
Yes, when it is sized with a proper service factor and mounted correctly. For continuous heavy loads, choose the larger size even if a smaller one covers the torque on paper.
What does NMRV mean, and how is it different from NRV?
NMRV units have a flanged input that bolts straight onto a motor. NRV units have a plain input shaft and need a separate coupling to connect to the motor.
Where can I buy NMRV gearboxes in Pakistan?
MV Power Drive supplies NMRV worm gearboxes in all ten sizes. Browse the NMRV series or send your size, ratio and application on WhatsApp for a quote.
Confirm Your NMRV Size Before You Order
Send your motor kW, target ratio and duty cycle to MV Power Drive on WhatsApp and we will confirm the correct body size before you place an order. You can also compare against our gear motors if you are deciding between a separate gearbox and a complete unit.