For 2018 how do I deduct mechanic tools I purchased for work. I am a master mechanic at a dealership

Not if you are a W-2 employee, you can no longer deduct expenses such as your mechanics tools.  The miscellaneous itemized deduction (which included non-reimbursed business expenses) was suspended through 2025 by the Tax Cuts and Jobs Act of 2017.

If you are a self-employed contractor (1099-MISC) they are deductible as business expense on your Schedule C.

You still may be able to itemize and deduct your unreimbursed employee expenses on your state tax return.