DC inductor from ATX transformer core

[ambrozy]

Is it possible to make a DC inductor from an old transformer core of an ATX power supply, and how? I'm not exactly begginer in electronics, but on this particular topic I am. All I know is that I need an air gap in a DC inductor, and I'm having trouble finding some good resources on designing DC inductors with ferrite core, so I would appreciate some links if there are any good online resources on the subject.

[mag_therm]

Basing a design on a given available core does not need the calculations that a production inductor would need.
The inductor does not have to be optimized using Hanna curves etc which is needed for production as the inductors are the major cost.

For hobby, I do similar DC inductors based on surplus NOS cores, just using a simple spreadsheet.
Here is a scrot of the spreadsheet for a hand wound DC filter inductor for a DC~DC converter 250 Volt 1.2 Amp that is presently on  breadboard here.
https://app.box.com/s/a0o4xt1nhovh3wh84ljbz5q2qmrj01io
The choke on test:
https://app.box.com/s/deaoghhngiapjlrv2tpxxtme87suhyke
The calculation uses approximations:
-Core reluctance is negligible
-Fringing factor is a guess at 1.2 based on experience.
-The DC operating position is down from the rollover into saturation, so the a L measurement at signal generator level,
 will still be fairly close to the incremental inductance at operating DC level.
-Conductor size is selected to be conservative by experience, avoiding the need for thermal calcs.

For your specific query about references for ferrite design, I would always recommend the old book by Snelling.
Member TimNJ kindly put up a link, on the ferrite gapping thread,  to a non-pay copy here:

https://ia803405.us.archive.org/1/items/SNELLING__SOFT-FERRITES__1969/SNELLING__SOFT-FERRITES__1969.pdf

Hanna DC choke curves Page 85 on,
Inductor design Page 193