I have used three different styles of Kadee couplers for my H0 scale models:

• The whisker coupler
• The whisker coupler with the 'scale head'
• The NEM coupler

 

You can get a narrower version of the draught gear box and this looks neater on some models, but I haven't yet found an application where I had to use the narrow box instead of the standard one.

 

The whisker coupler with the scale head is my favourite because it looks neatest, but it is only available with a centre-set shank. I end up using a standard head coupler when I need an over-set or under-set shank. The NEM version is a bit of an awkward marriage between a North American standard coupler (the Kadee) and a European standard coupler mount (NEM 362), and I often end up modifying the combination to make it work. Here are some of the coupler installations on my models, beginning with the easiest and working through to the more difficult ones ...

 

When the model has an NEM 362 socket on a well-engineered close-coupling mechanism, the NEM Kadee coupler plugs in and works well, although you don't get the close coupling feature. The success of this solution relies entirely on a cam mechanism with minimal vertical free play, a snug-fitting NEM socket, and of course having the socket at the proper height and distance from the buffer heads:

 

When the original model has a tension lock coupler and this coupler is a flat one (not a cranked one) you can drill a small hole in the shank of a Kadee NEM coupler, cut off the two tails and attach the coupler to the model with the screw from the original coupler:

 

When you are making the model yourself or from a kit you can use some scraps of styrene to set the draught gear box for a whisker coupler at the necessary height:

 

On a Lima wagon (either their open wagon or box van), you can cut off the moulded coupler mount and level off the surface of the floor. If you have changed the original Lima wheels to something more "scale" with a 10.5 mm diameter, a Kadee draught gear box glued straight onto the underframe comes out the right height for a centre-set coupler.

 

If you lower a Lima Mk1 coach onto its bogies (this makes the models look so much better), you can cut a slot in the buffer beam and glue the draught gear box onto the floor; a centre-set coupler will then end up the correct height:

 

When the model has a saggy NEM socket, some kind of rework is essential. For the Mehano class 66,  a styrene shim in the NEM socket and a strip of styrene along the valance keep the coupler at the correct height:

 

The NEM socket on the NMJ Di8 moves away from its proper height upwards as well as downwards and I put strips of styrene both above and below:

 

For this Electrotren ferry van, I settled on a block of wood and a loop of piano wire to support the NEM socket. The floor of this model is made from a very hard steel sheet and defied all my attempts to drill it, so I used this block of wood to hold the wire, with the modification fixed together with Araldite:

 

I hardly ever use an over-set coupler, but it works for the Fleischmann Warship:

 

If you lower the chassis of the Warship onto its bogies, the model needs a centre-set coupler. Regardless of whether you lower the model, you have to grind some metal away from the motor bogie and shorten the draught gear box too:

 

The under-set shank is useful from time to time, such as on this Liliput chassis:

 

Some models come with a NEM 363 coupler mount. There is no Kadee coupler available to fit this mount, but AMF87 do a fret of adaptor pieces to build your own coupler. You take a Kadee NEM coupler, push out the pivot pin and then assemble the head onto the adaptor piece. I bought mine from A&H Models of Bracknell. This is all a bit of a fiddle, the adaptor pieces are smaller than you think they ought to be, but the NEM 363 mount makes for a neat installation and gives you an easy fine adjustment of the height of the coupler:

 

Very occasionally, a RTR manufacturer will provide an NEM socket as a drop-in replacement for a factory-fitted coupler. Roco do such a device for the early version of their English Electric shunter:

 

This NEM socket protrudes well in front of the buffer beam to let the model work with a Roco Universal coupler head. This is one of the very few installations where I have been able to use the Kadee #17 'short' NEM coupler.

 

The most important considerations are these:

(1) make sure the rear face of the coupler knuckle is in front of the buffers;

(2) make sure the sides of the knuckle don't foul the buffers on tight curves - you may need a coupler with a longer shank to prevent this;

(3) set the coupler at exactly the proper height - if you need to adjust the trip pin from its factory position you have probably got the coupler at the wrong height.

 

I made my own height gauge, I find this much easier to use than the Kadee one:

 

Above all: if you are intending to change the wheels of a model, do this before you set up the couplers :-)