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Jan Rowland

8. Per Step 1, you will now have exact "CW" and "T" values for your core. You can now make a hardwood spool per the dimensions shown on the accompanying sketches. By adding that 1% of size to the wooden spool core, you ensure that your finished winding will slip easily over the iron (or, that the iron laminations may be easily slipped into the winding's opening.) If, however, you intend to spiral wrap the winding with cloth tape before final assembly, you will have had to allow for the tape. So, you must add another few percent to the CW and T of the wooden spool center, so that the opening of the coil, when slipped off the wooden spool, is a bit larger, yet, allowing for the cloth tape. Common sense, but one must remember such details, or waste much material and time before discovering what you did, after all the work!

This is a sketch of a home-brew transformer coils winding spool. For each size of transformer, i.e., different E-I lamination measurements and stack thicknesses,T, a new spool like this must be made. Anyone with rudimentary woodworking skills and a table-saw, even a small one, can make such spools with acceptable success.