The phrase "a usual part" is correct and usable in written English.
It can be used to describe something that is commonly included or expected in a particular context or situation.
Example: "In our meetings, discussing project updates is a usual part of the agenda."
Alternatives: "a common element" or "a regular feature".
Some would say it's a usual part of industrialization and capitalist economics.
Making notes, and drawing, is a usual part of my investigation before I take any photographs.
Another told the investigation that gang rape was a usual part of growing up in her district.
One young person told the inquiry that "gang rape" was a usual part of growing up in the area of Rotherham where she lived.
The report estimates 1,400 children were sexually exploited over 16 years, with one young person telling the report's author that gang rape was a usual part of growing up in Rotherham.
Texting is such a usual part of a teen's everyday routines that he or she may feel as though a precedent has been set, and may be lulled into thinking that texting while driving is normal (read: "safe").
For example, BIND 2 4 means that, in addition to the usual PART rules, atoms in PART 2 may also bond to atoms in PART 4. Negative PART numbers are allowed in the BIND instruction.
Another aspect of the monstrous is embodied in Pat Keck's "Seated Giantess," a monumental figure with all the usual parts in the usual places.
This shot, for example -- part of an usual pair of back-to-back Obama/McConnell shots on the White House Flickr stream (see: White House Flickr Stream: Professional Right In, Professional Left Out) appeared as recently as two months ago.
The man passed comment on all the usual parts of my body, but the unusual as well — my calves, the notch at the top of my spine.
Students typically would have never thought of these ideas as anything more than "the usual" parts of their daily life and identity.
