Short answer: Look at three things: who made the model (KATO or TOMIX), where the coupler is attached (on the truck or on the body), and the shape of the coupler head. A flat hook-and-loop coupler on the truck is an Arnold coupler. A small claw shaped like a real train coupler is a knuckle-type coupler. A box-shaped head on the body of an EMU is a tight-lock coupler: a TN coupler on TOMIX models, a KATO Coupler on KATO models. The drawings below are simplified diagrams, not to scale.
Check in this order
- Maker. Look at the box or the underside of the car. TOMIX’s own couplers are TN couplers; KATO’s are KATO Couplers. TOMIX says TN couplers are not compatible with other makers’ couplers, so the maker alone already rules out many pairs.
- Where it is attached. TOMIX explains that couplers that look the same can be body-mounted (fixed under the car body) or truck-mounted (fixed to the truck, also called bogie). See the diagram below.
- Head shape. Compare the coupler head with the diagrams in the next section.
- Confirm with the product number. Search your model’s product number on this site to see the standard coupler and the parts listed for it.
Body-mounted or truck-mounted?
The coupler types
Arnold coupler
Flat, horizontal hook-and-loop coupler, usually on the truck. Many locomotives, freight cars and coaches have it as standard.
KATO and TOMIX. TOMIX calls it a worldwide standard that other makers also use.
Knuckle coupler (KATO Coupler N)
A small claw shaped like a real automatic coupler. Supplied as a replacement for the Arnold coupler on many KATO locomotives, freight cars and coaches. KATO Coupler N JP A and N JP B are of this type.
KATO. Parts: 11-702, 11-707, 11-721, 11-722.
Magne-Matic coupler
A knuckle coupler with a thin release pin hanging below. Cars fitted with it uncouple automatically when stopped over KATO’s uncoupler track (20-032).
KATO. Parts: 11-710, 11-711, 11-712.
KATO tight-lock coupler (with hook)
Body-mounted coupler used on EMUs such as the E231 series. A hook-shaped part under the head does the coupling.
KATO. Does not couple with the hookless #2 type.
KATO tight-lock coupler #2 (no hook)
Newer, more realistic tight-lock coupler without the hook. It locks inside the coupler head. Sold in long and short versions.
KATO. Parts: 11-730, 11-731. Does not couple with the hooked type or the KATO extendable tight-lock coupler.
KATO semi-tight-lock coupler
A small, body-mounted knuckle coupler. KATO says it couples only with the same type and with no other coupler.
KATO.
TN coupler (TOMIX)
TOMIX’s own coupler, shaped like the real train’s coupler, in three head shapes: tight-lock (EMUs), semi-tight-lock and automatic. It can be body-mounted or truck-mounted. Sold as JC spare parts; check the part list for your exact model.
TOMIX. Not compatible with other makers’ couplers.
Dummy coupler
A coupler-shaped detail, often on the front of a cab car. It cannot couple. TOMIX says a cab car with only a dummy coupler can be coupled only if the manual lists an optional TN coupler for it.
KATO and TOMIX.
Electrical-contact coupler (TOMIX)
TOMIX uses electrical-contact couplers on Shinkansen models. They pass power between cars on long trains.
TOMIX. See our guide to TOMIX electrical-contact couplers.
Which of these couple together?
| Pair | Couples? | Source |
|---|---|---|
| Arnold + Arnold (any maker) | Yes | TOMIX official FAQ |
| KATO Coupler N + KATO knuckle + Magne-Matic | Yes, all with each other | KATO official FAQ |
| Knuckle type + KATO tight-lock or semi-tight-lock | No | KATO official FAQ |
| KATO tight-lock (hook) + #2 (no hook) | No | KATO official FAQ |
| TOMIX TN + any other maker’s coupler | No | TOMIX official FAQ |
This table shows only what the makers state. “Couples” means it couples as supplied, without modification. Drawings are simplified diagrams made by this site, not product photos.
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