Q. Are you allowed to cut an old shaitel during the 3 weeks?

A. Shulchan Aruch (O.H. 551:7) rules not to craft new clothing during the nine days. Mishna Berurah (ibid. 68) explains that even the beginning of the design is included in the prohibition.

However, many Poiskim maintain that this applies only to new clothing, and not to repairing used one (Kaf Hachaim ibid. 107, Bigdei Yesha 68, Moadei Yeshurun quoting R”M Feistein ZT”L, Shoine Halochos p. 128).

See question 280 on this forum in regards to cutting ones hair during the period of Sefiras Haomer, were it was explained that a shaitl or hairpiece is seen only as an article of clothing and not part of the body.

Horav Shlomo Miller Shlit”a rules that since this is an adornment article that beautifies the wearer and not a simple piece of clothing, when possible cutting the shaitl should be avoided during the nine days, however, it is permitted during the three weeks period.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a