If someone needs to shave during Sefirah or Three Weeks because of work, should he also shave before Shabbos?
It seems strange to shave for M-F, but to go into Shabbos with stubble. On the other hand, there's a dispensation for his job, so that might just be how it turns out.
First, let's address the issue of shaving during the 3 weeks generally. According to R' YB Soloveichik, Shiurei HaRav Al Inyanei Aveilut V'Tisha B'Av, pp. 20-21, there is "a basis for shaving one's beard during this period. He contends that the observances of the three week mourning period are patterned after the twelve month period of mourning that one observes when losing a parent. A mourner during this period may shave or cut his hair when he has reached a state that his friends note his unkempt appearance. Nowadays, when people shave on a daily basis, this state is attained after a day or two. Once that state is reached, one may shave his beard and continue to shave for the rest of the mourning period. However, this leniency will only apply to the three week period [and not to the nine days leading up to Tish'ah BeAv]." - Quoted from: "The Laws of Bein HaMetzarim" [brackets added by me for clarification] http://www.yutorah.org/_shiurim/The%20Nine%20days.html
The opinion of the Rav isn't the only one out there, but he is well known for this opinion, and the following anecdote may be the source for the (now) well established, and possibly erroneous, practice among Yeshivah Bahurim to shave every Friday during Sefirah but not during the week. (By the way, since I'm recalling this from memory, if anyone sees any factual errors in my version of the anecdote, please point them out in the comments!)
When R' Aharon Lichtenstein became Rosh Yeshivah of Yeshivat Har Etzion, his father-in-law, RYB"S, told him that his opinion (which I referenced above) probably ought not apply in Israel, since it was much more acceptable there to wear a few days' growth of facial hair. Since, because of RA"L's position, he wanted to maintain a dignified look, the Rav advised him to shave Friday LiChvod Shabbath instead of daily.
Nowadays, in my own opinion, even in Israel it is much more expected that one shave daily in the workplace. However, there still may be a problem for Bahurim to shave 'Erev Shabbath, since there is no societal expectation in a Yeshivah setting that one shave in the first place, much less during Sefirah or the Three Weeks.
Now, getting to the workplace, assuming one has an expectation of looking well groomed during the week, then, borrowing from the Rav, it would seem it is appropriate to shave on Friday as well, just as one might if, Lo 'Aleinu, one were in the 12 month mourning period for a parent.
EDIT: Unfortunately, the link at YU Torah to the Shi'ur where I found the quote is dead. If I find a new link online for the Shi'ur or for the quote, I will add it.
The link now works. I will keep a copy of the Shi'ur on hand. If I can find a new site to host it, perhaps a blog, I will provide that link in a future version of this answer.
In O.C. Siman 551, the Rema, who extends the issurim of the week of tisha b'av to the previous Rosh chodesh, permits wearing "linen garments" for the honor of Shabbos. [ The Magen Avraham (14) extends this to washing clothes on Thursday for Shabbos. The Magen Avraham then brings the Darkei Moshe who says that the practice was not to wash in honor of Shabbos and implies the same for laundering. The MA concludes that one may be lenient if he has no clothes for Shabbos and alternatively, one may have a non-Jew wash it for Shabbos.]
At the end the MA quotes the Hagaos Ashri that haircuts are forbidden for Shabbos. The MA says that the reason seems to be that we don't normally haircut "every week" (b'chol shavua). The simple reading of this MA is that the HA holds that which is normally done weekly to honor shabbos is not restricted, and only forbids haircuts because they are not a weekly activity.
The Chasam Sofer wants to read the MA as we normally don't haircut except on erev shabbos (perhaps reading it similar to "b'chol *ha*shavua), and it isn't recognizable that he is mourning if he continues to shave on erev shabbos. To me, this would circumvent the DM, since the DM would only forbid once-a-week honors. (See the Chasam Sofer for a further heter for beards.)
So, the Chasam Sofer (if he would sanction shaving year round), would permit shaving on Friday even during the 9 days, if the one shaving would shave more than once a week so that the mourning is recognizable. However, (it seems to me) if one is shaving daily for work, Friday would not be permitted since there, too, his mourning would not be recognizable.
It is unclear whether the MA agrees to the CS's reading of himself, or if the MA would permit shaving as long as it was a normal erev shabbos activity. I have only seen those who follow the Chasam Sofer's reading.
