NMRV Worm Gearbox Motor Selection 030–150

When choosing a motor for an NMRV 030–150 worm gearbox, the size number is not what decides the fit — the input adapter is: IEC input size, B5 or B14 flange, input bore (motor shaft diameter) and the motor power permitted at that ratio. The DRG Motor 4-pole aluminium models that can be compared against these inputs run from frame 71 to 160M, 0.25–11 kW, with shafts from 14×30 mm to 42×110 mm.

Grey DRG three-phase aluminium housing electric motor – illustrative image for NMRV gearbox motor selection

Motors for gearbox mounting are listed on the electric motors for worm gearboxes page and in the online shop; the full range is in the three-phase asynchronous electric motors category and aluminium frames in the aluminium housing motors group. DRG Motor sells electric motors only; it does not supply gearboxes.

What does the NMRV size number mean?

The figures 030, 040, 050, 063, 075, 090, 110, 130 and 150 give the centre distance in millimetres between the worm and the worm wheel axes. An NMRV 063 is a gear set with axes 63 mm apart. The number indicates gearbox capacity, but it does not tell you which motor frame fits.

A gearbox of a given size is often offered with several input adapters; which IEC frame can be mounted depends on the adapter, the ratio and the gearbox maker's catalogue. That is why this article gives no "this size takes that frame" table. The reliable way is to read your gearbox input and compare it with the DRG dimensions below.

What to read on the gearbox nameplate and catalogue

If you have a working gearbox, the nameplate and the input side give enough information. For a new gearbox, take the same data from its order code and catalogue.

Item to read	Where to find it	What it is compared with on the motor
Size (030…150)	Gearbox nameplate, cast housing	Not comparable on its own with any motor dimension
Ratio (i)	Nameplate, order code	Rated speed vs output speed: n₂ = n₁ / i
Input adapter IEC size	Nameplate or order code (e.g. size + IEC frame + flange type)	Motor frame (71, 80, 90…)
B5 or B14 input	Outer diameter and hole type of the adapter flange (clearance / tapped)	For B5: P, N, M, S; for B14 send us the dimensions
Input bore and keyway	Bore in the worm shaft, measured with a caliper	Motor shaft D and key width F
Permitted motor power / input power	Gearbox catalogue, row for the ratio and input speed	Motor power (kW) and rated speed

Ratio and output speed are related simply: n₂ = n₁ / i. As an example, a DRG-90L-4 (rated speed 1445 rpm) on a hypothetical i = 30 gearbox gives about 48.2 rpm at the output. Use the speed on the motor nameplate, not the 1500 rpm class. For other calculations, see the electric motor calculator.

DRG 4-pole aluminium models: power, speed and torque

The rated torque in the table matches the formula M = 9550 · P / n (P in kW, n rated speed). Compare this power value with the input power limit in the gearbox catalogue.

Model (4-pole, aluminium)	Frame	Power	Rated speed / rated torque
DRG-711-4	71	0.25 kW / 0.37 HP	1340 rpm / 1.78 Nm
DRG-712-4	71	0.37 kW / 0.5 HP	1340 rpm / 2.64 Nm
DRG-801-4	80	0.55 kW / 0.75 HP	1400 rpm / 3.75 Nm
DRG-802-4	80	0.75 kW / 1 HP	1420 rpm / 5.04 Nm
DRG-90S-4	90S	1.1 kW / 1.5 HP	1445 rpm / 7.27 Nm
DRG-90L-4	90L	1.5 kW / 2 HP	1445 rpm / 9.91 Nm
DRG-100L1-4	100L	2.2 kW / 3 HP	1450 rpm / 14.5 Nm
DRG-100L2-4	100L	3 kW / 4 HP	1450 rpm / 19.8 Nm
DRG-112M-4	112M	4 kW / 5.5 HP	1450 rpm / 26.3 Nm
DRG-132S-4	132S	5.5 kW / 7.5 HP	1460 rpm / 36 Nm
DRG-112M-4K	112M (compact)	5.5 kW / 7.5 HP	1460 rpm / 36 Nm
DRG-132M-4	132M	7.5 kW / 10 HP	1460 rpm / 49.1 Nm
DRG-160M-4	160M	11 kW / 15 HP	1465 rpm / 71.7 Nm
DRG-132M-4K	132M (compact)	11 kW / 15 HP	1465 rpm / 71.7 Nm

Every frame from 71 to 160M here is in the 1500 rpm class; models up to 3 kW are 230/400 V, larger ones 400/690 V. In frame 63 DRG has a single model, the DRG-632-2 (0.25 kW, 3000 rpm class), so it is not in the 4-pole list.

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Shaft and B5 flange dimensions of aluminium frames 63–160M

The input bore in the worm shaft must equal the motor shaft diameter D, and the keyway must suit key width F. The values below are taken from the IM B5 rows of the DRG catalogue (mm).

Frame	Shaft D×E (mm)	Key F / shaft end thread	DRG models
63	11×23	4 mm / M4×12	DRG-632-2
71	14×30	5 mm / M5×12	DRG-711-4, DRG-712-4
80	19×40	6 mm / M6×16	DRG-801-4, DRG-802-4
90S	24×50	8 mm / M8×19	DRG-90S-4
90L	24×50	8 mm / M8×19	DRG-90L-4
100L	28×60	8 mm / M10×22	DRG-100L1-4, DRG-100L2-4
112M	28×60	8 mm / M10×22	DRG-112M-4, DRG-112M-4K
132S	38×80	10 mm / M12×28	DRG-132S-4
132M	38×80	10 mm / M12×28	DRG-132M-4, DRG-132M-4K
160M	42×110	12 mm / M16×36	DRG-160M-4

On a B5 input adapter, the four flange dimensions are checked separately: outer diameter P, spigot diameter N, pitch circle M and hole diameter S.

Frame	P flange outer diameter (mm)	N spigot diameter (mm)	M pitch circle (mm)
63	140	95	115
71	160	110	130
80	200	130	165
90S	200	130	165
90L	200	130	165
100L	250	180	215
112M	250	180	215
132S	300	230	265
132M	300	230	265
160M	350	250	300

Frame	S flange hole diameter (mm)	T spigot length (mm)	LA flange thickness (mm)
63	10	3	10
71	10	3.5	10
80	12	3.5	12
90S	12	3.5	12
90L	12	3.5	12
100L	14.5	4	13
112M	14.5	4	14
132S	14.5	4	14
132M	14.5	4	14
160M	18.5	5	15

The B5 table for all frames is in the B5 motor flange dimensions table, and shaft diameters by power in the motor shaft diameter by kW table. For the small B14 flange often found on NMRV inputs, the DRG catalogue has no dimension table; if you need B14 or B34, send us the adapter's flange outer diameter, pitch circle, spigot diameter and thread size on WhatsApp and we will confirm. General information is in B14 flange electric motors, and the clearance vs tapped hole difference in B5 and B14 FF/FT difference.

Same flange, different shaft: situations that cause wrong choices

Frames 80 and 90: the B5 flanges are the same (P 200, N 130, M 165, S 12 mm), but the shaft is 19×40 mm on 80 and 24×50 mm on 90S/90L. A flange that seats does not mean the motor fits the gearbox; measure the input bore.
100L and 112M: flange and shaft (28×60 mm) are the same. The DRG-100L2-4 (3 kW) and the DRG-112M-4 (4 kW) can seat on the same input; the decision then depends on the power the gearbox permits.
90S and 90L: same flange and shaft, different overall length (L 336 / 361 mm). A longer motor hanging on the gearbox increases the overhung load.
Compact models: the same power comes with a different shaft in standard and compact frames.

Power	Standard model / shaft	Compact model / shaft	Consequence at the gearbox input
5.5 kW	DRG-132S-4 — 132S, 38×80 mm	DRG-112M-4K — 112M, 28×60 mm	different input bore and flange required
11 kW	DRG-160M-4 — 160M, 42×110 mm	DRG-132M-4K — 132M, 38×80 mm	different input bore and flange required

Ratio, efficiency and motor power: common mistakes

Overlooking efficiency at high ratios: in a worm gearbox, efficiency drops noticeably as the ratio increases. Calculating output torque as motor torque × ratio assumes torque that does not exist at high ratios. Take the efficiency from the matching ratio row of the gearbox catalogue.
Oversizing the motor "to be safe": a motor larger than the input power permitted for that ratio overloads the gearing and bearings. A larger motor usually means a larger shaft and flange, so the adapter changes too.
Using a bushing to fit a smaller shaft and more power: a reduction bushing closes the bore difference but does not change the permitted power.
Mixing up B5 and B14: for the same IEC size, B5 and B14 flanges differ in outer diameter and hole type. Settle the flange type before ordering; mounting types are compared in B3, B5, B14 and B35 comparison.
Relying on self-locking: whether a worm locks itself depends on ratio and conditions; for vertical loads, assess the need for a brake with the gearbox catalogue.

General steps for connecting a flange motor to a gearbox are explained in flange motor selection for gearboxes.

Why is a 4-pole motor usually preferred?

Most worm gearbox catalogues give power and torque ratings for the input speed of a 4-pole motor; check the input speed column in yours. With a 2-pole motor the worm turns about twice as fast, so sliding friction, heating and noise increase. A 6-pole motor needs a larger frame and shaft for the same power, which means a larger input adapter. In most applications the 4-pole motor is the balanced point between the two. Use the motor current chart to select protection and cables.

Frequently asked questions

Which motor frame fits an NMRV 063?

There is no single answer. The same size can take different IEC frames with different adapters. Read the input IEC size and input bore on the gearbox nameplate and compare them with the shaft and flange tables above.

What if the input bore is larger than the motor shaft?

Either choose a frame whose shaft matches the bore, or use a suitable bushing and adapter on the gearbox side. Which one is suitable depends on the permitted power and the flange type.

Does the compact 112M model suit a gearbox with a 112M input?

The DRG-112M-4K has a 28×60 mm shaft in the data; shaft and 112M B5 flange dimensions are read from the same row as the standard DRG-112M-4. Still check that 5.5 kW is within the power the gearbox permits at that ratio.

Can you give dimensions for a B14 input gearbox?

The DRG catalogue has no B14 dimension table. Send us the adapter dimensions and we will confirm suitability.

Technical confirmation

DRG Motor is a manufacturer, supplier and seller of electric motors. Send a photo of the gearbox nameplate, the input bore diameter and the flange dimensions; we will compare them with DRG data and choose the suitable model together. 2D dimension drawings are on the DRG Motor technical drawings page and all models in the technical and product catalogue.

Send a photo of your current motor nameplate and we will find the suitable DRG model together.Send on WhatsApp

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Electric Motors Related to This Topic — Models and Current Prices

Suitability is not decided by power alone: compare the speed, voltage, mounting, shaft and fixing dimensions of your machine with the product data; if unsure, send us the nameplate of your current motor.