My husband is a diesel mechanic, can he claim all his tools if he has never claimed them before?

[AmyT]

Since these expenses were directly related to employment, they may be deductible as job-related expenses.  

However, if you are referring to purchases made prior to 2016, it is important to note that expenses are only deductible in the year that they are paid.  You will only be able to claim expenses paid in prior years by amended the returns for those years.

Unreimbursed job-related expenses are deductible on Schedule A (Itemized Deductions) and are subject to the 2% floor for miscellaneous itemized deductions.  To input your job-related expenses (TurboTax Deluxe edition or higher is required to file itemized deductions):

https://ttlc.intuit.com/replies/4800418