There are 2 sizes of hooks and loops, and the shorter ones are for short buffered vehicles so I tend not to use them.
Clean up the loop with the scratchbrush and run a 0.8mm drill through all 3 holes.
The instructions recommend a 0.9mm drill but the idea is to have a nice free pivot but without too much slop or side play so a 0.8mm waggled about in the holes does the trick.
Bend the dropper down at 90Ëšas close to the pivot holes as possible (Pic 13)
Try to avoid bending the pivot tags.
Grip the dropper in the pliers and carefully bend up the pivot tag 90Ëš on the dropper side. The other tag can then be bent up at about 45Ëš ready for the loop to be fitted to the pivot on the hook. Check the slot between the two pivots hasn’t closed up.
The dropper should then be bent about ½ way along its length and a twist put in so that the hole for the soft iron wire dropper is now vertical.
The leading edge of the loop should then be bent upwards at 45Ëšand the front edges slightly rounded to aid smooth coupling.
Pics 17 and 18 explain it better than words!!
The loop is then ready for mounting on the hook.
Re-check that during the bending up process that the slot hasn’t closed up between the pivots and gently ease the loop onto the pivot pin as shown in pics19/20.
The pivot tab at 90Ëš should slide onto the pin and the other one still at 45Ëš should be ready to be bent up to 90Ëš while locating on the pivot pin.
Use thin pliers and gently squeeze the pivot tab up to 90Ëš while locating on the pivot pin (pic21) so that both pivot tabs are parallel.
The loop should now lift up and down smoothly and with minimum side movement
If not, check the gap as shown in pic 22 and also check that the tabs are at 90Ëš to the pin and still parallel. The gap can be carefully eased open with a scalpel blade if necessary.
On the bottom edge of the hook, there is a limiter tab to stop the loop from rising too far. This is tiny and has to be bent at 90Ëšcarefully, and squeezed with the pliers to obtain the maximum projection. There isn’t much of it to bend and the dropper from the loop must be fairly close to the hook to catch it. Ideally it could have been about 0.5mm longer for ease of use. (Pics 23/24)
On odd ones where I’ve clumsily broken it I’ve replaced the tab with a short length of wire soldered to the hook.
The coupling should now work smoothly up to its limit and drop down without binding.
Using the soft iron wire, make a dropper from the loop down towards where your magnet will be in the track and fit it through the loops dropper, checking that it is free to swing. Allow enough length and once fitted to the vehicle, the wire dropper needs to be trimmed so that is about 1mm above rail level. (Pic 25)
The whole coupling can now be chemically blackened in your chosen dip. I have used Carrs blackener for nickel silver on this one. (Pics 26/27)
Note the clean bit where an air bubble kept the fluid off!! Cured by re-dipping.