Yes. There is an FAA advisory circular which permits "owner produced parts". The gist is that the owner must make it or have it made by others to the factory spec's. The AC number is 21-29.
Here's a synopsis:
http://150cessna.tripod.com/parts.html
The biggest thing in that synopsis is, some must return it to service. They are the ones on the hook for the safety of the repair. The safety inspector will not talk to who built the part, they will hold the person responsible for the return to service entry, responsible for the accident.
FAR 43.
43.9 Content, form, and disposition of maintenance, preventive maintenance, rebuilding, and alteration records (except inspections performed in accordance with part 91, part 125, § 135.411(a)(1), and § 135.419 of this chapter).
(a) Maintenance record entries. Except as provided in paragraphs (b) and (c) of this section, each person who maintains, performs preventive maintenance, rebuilds, or alters an aircraft, airframe, aircraft engine, propeller, appliance, or component part shall make an entry in the maintenance record of that equipment containing the following information:
(1) A description (or reference to data acceptable to the Administrator) of work performed.
(2) The date of completion of the work performed.
(3) The name of the person performing the work if other than the person specified in paragraph (a)(4) of this section.
(4) If the work performed on the aircraft, airframe, aircraft engine, propeller, appliance, or component part has been performed satisfactorily, the signature, certificate number, and kind of certificate held by the person approving the work.
The signature constitutes the approval for return to service only for the work performed.