Hi spitso,
making a transformer yourself requires close watch from purchasing the enamelled copper wire to finally put one winding next to the other, as I recall from the time as radio amateur (ham).
The most critical point is the enamel, which will crack and leave an uninsulated piece of wire if not treated properly.
Purchasing enamelled copper wire at any shop and observing the employee using techniques like grandma uses to coil wool for the next sock to knit is certainly the worst method. (Just slay him/her if he/she does it that way.
)
With every turn the copper is being twisted 180 degrees and the enamal laquer can't stand that stress, breaking and leaving a blank copper wire. (good for a perfect short)
This is the proper way to make a transformer:
Get the seller wind the desired amount of copper wire off the spool directly to another one (which you should have prepared already when purchasing the wire) without any angular change of turns. (This can be done easily using the body you have provided and a chuck of any drill)
When winding the transformer you must keep the same order not to break the enamel. Hand winding the transformer means turning the core underneath the copper wire you have in use. (Turning the wire is absolutely deadly!)
I wound a 1.5KV transformer by hand for an RF-power amplifier without any trouble, but it took me about two days to get it done.
You might use a drill rotating at minimum speed to get one winding next to the other and layer on layer that way. (Don't forget an insulating plastic sheet between layers.)
Boncuk