Q. Can I give my Rabbeinu Tam tefillin to be checked, painted and fixed to a sofer who doesn’t put on himself Rabbeinu Tam’s tefilin, since following his minhag they are not necessary, so he will not doing lishmo properly the painting and placing new retzuos?
A. Kesses Hasofer (Lishkas Hasofer 26: 1) indeed rules that a Sofer that does not don Rabbenu Tam’s tefilin himself, should not write them for others, since he does not recognize that there is a mitzva to put them on.
A similar shaila is addressed by Chashukei Chemed (Pesachim 50b). he recommends that the sofer should put them on at least once a month, to be able to work on them lishma.
Horav Shlomo Miller’s Shlit’an opinion is that it is not necessary, since the Sofer understands that there are different Halacha views on that respect and he writes with that intention.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a