NH35 Rotor Compatibility: Which Custom Rotors Fit, and How to Swap One

The P1083, one of the four Seigaiha rotors.

The rotor, also called the oscillating weight, is the half-moon weight that swings on top of an automatic movement. Each time your wrist moves, it turns and winds the mainspring. The NH35 is what most Seiko mods are built on, and its stock rotor is plain. That's fine behind a solid case back, where nobody sees it. Fit a sapphire case back, though, and the rotor is the biggest thing in view.

So the question we're asked most about rotors is simple: will an aftermarket rotor fit my NH35? Here's the full answer: which movements take our rotors, what you need to see one, the ten designs we stock, and how the swap is done.

Does an Aftermarket Rotor Fit the NH35?

Yes. Every rotor below lists the same four movement families on its product page:

Movement family	Where you'll find it	Takes our rotors?
NH: NH35, NH36, NH34, NH38, NH70, NH71	The movement most Seiko mods are built on	Yes
4R, e.g. 4R35, 4R36	Seiko-branded watches. The same calibre as the NH	Yes
7S, e.g. 7S26, 7S36	The original SKX007, SKX009 and SKX013	Yes
NE	Seiko's NE calibres	Yes

That NH row covers every NH movement we stock: the NH35A, the NH36A, the NH34A GMT, the NH38A open-heart and the NH71. They all share the same rotor.

The reason they all fit is family history. The NH35 is the NH-coded twin of Seiko's own 4R35: one is supplied to modders and other brands, the other goes into Seiko-signed watches. The 7S26 came before both, and it's what ticks inside an original SKX007. All of them take the same rotor. So if you're keeping the 7S26 in an old SKX for now, a rotor bought today moves straight across when you upgrade to an NH35 later.

Before You Buy: Make Sure You'll See It

A rotor upgrade is a visual upgrade. Behind a solid steel case back nobody sees it, you included. To actually see it, you need a sapphire case back, also called a display or exhibition case back: the see-through cover that turns the back of the watch into a window.

A sapphire case back is what puts the rotor on show.

For an SKX007 or SRPD case, or a replacement case running an NH35 or NH36, our pick is the C0361 SKX007 Sapphire Case Back - NH Movement. If you'd rather have a slim profile or a coloured finish to match your rotor, try one of these:

• C1051 SKX007 Slim Sapphire Case Back - NH movement - Gold
• C1052 SKX007 Slim Sapphire Case Back - NH movement - Rose Gold
• C1076 SKX007 Slim Sapphire Case Back - NH movement - Black

Every case back we carry, solid and sapphire, is in our case back collection.

Our Ten Custom Rotors: Three Designs, Four Finishes

All ten fit every movement in the table above. The only choice is how you want the back of the watch to look, so they're grouped below by design.

Seigaiha: The Japanese Wave Pattern

Seigaiha is the traditional Japanese wave motif, made of rows of overlapping arcs. Here it covers the whole rotor, with an S on the weight. This design comes in black, gold, rose gold and silver.

Textured, With the S

A finely textured surface inside a plain outer rim, with the S set low on the weight. This design comes in silver, black and gold.

Stepped Rings, No Logo

Concentric stepped rings, and no logo at all. This is the one for a sterile build. It comes in silver, gold and rose gold.

Matching metals is the easy way to choose. A gold rotor behind the C1051 gold case back, rose gold behind the C1052, black behind the C1076. All ten are also in one place in our rotor collection.

How to Swap an NH35 Rotor

Our video shows the whole swap on an NH movement in an SKX007 case, fitting a black rotor to match the case, in 77 seconds. The rotor sits on top of the movement, held by a single screw through its centre, so nothing under the crystal is touched.

A black rotor going into an NH movement in an SKX007 case, from our Mod Beginner Series.

1. Open the case back. Use a case back wrench with the right tips, or a rubber ball if the case back isn't too tight.
2. Undo the screw at the centre of the rotor with a wide jeweller's screwdriver.
3. Lift the old rotor out with tweezers and put it somewhere safe, in case you want to go back to stock.
4. Line up the new rotor's mounting hole with the post the old one sat on.
5. Screw it down securely, then check it still swings freely. Make sure the case back gasket is clean and seated, and close it up.

Never opened a case back before? Our guide to basic watch building tools covers what you need.

FAQ

Do aftermarket rotors fit the NH35?

Yes. Every rotor we sell is listed for 4R, 7S, NH and NE movements, and the NH35 is an NH movement.

Will an NH35 rotor fit an NH36?

Yes. The NH36 is from the same NH family, and our rotors are listed for the whole family.

Will your rotors fit the NH34 GMT, NH38 or NH71?

Yes. They share the NH35's rotor, so any of our ten fits.

Will your rotors fit the 7S26 in an original SKX007?

Yes. Every one of our rotors is listed for 7S as well as NH movements, so it fits your 7S26 now and moves across if you upgrade to an NH35 later.

Do I need to take the movement out of the case to change the rotor?

No. The rotor sits on top of the movement and is held by a single screw through its centre. With the case back off it's right there, and the dial, hands and crystal aren't touched.

Does the rotor come with its bearing?

Yes. Each rotor arrives with its bearing and centre screw already fitted in the hub, so there's nothing to move across from your old rotor. Unscrew the old one, screw in the new one.

Is a custom rotor worth it with a solid case back?

Not really. A rotor is a visual upgrade, and a solid case back hides it. Pair it with a sapphire case back such as the C0361 so you can actually see it.

Ready to choose? See all ten NH movement rotors, and the sapphire case backs that show them off.