The heart of running any business is bookkeeping. You need to keep all receipts, log all sales, log all expenses, and have a regular weekly bookkeeping time where all that gets logged into a bookkeeping program ( unless your wife or someone will be doing it weekly). Put a box on a desk or by the computer and drop every receipt, invoice, stub, note, etc. in it.
Many apparently successful businesses close because they don't really make a profit. I knew a restaurateur who closed three popular restaurants because he was tired of making over $1,000,000 a year and keeping less than $15,000 for himself.
Expenses to consider in a hobby business:
All regular expenses should be posted when the money is spent. If you buy $500 in steel or $300 in belts, it is a one time expense ( even though you will use them for multiple knives). That is because you will be constantly using these materials and replacing them. In the course of a year it balances out about right with sales. Obviously, all sales need to be posted only when you get paid. Inventory and orders are great to have, but you can't spend them. You should keep records on inventory if you start getting a fair amount built up, but it isn't money in the bank, ...yet.
All supplies, miscellaneous materials, small tools and parts, etc. are a one time expense ( even though you will use the item for multiple knives).
The best way to work the tools and equipment into the plan is to amortize them. Total all the tools and equipment you currently have, and divide that by 60. That is a monthly amortization for a five year life ( the norm). If you have $6000 in equipment, it cost you $100 a month for those tools. As you buy new equipment, divide by 60 and add that amount to the $100/mo. current. So, if you buy a second KMG for $1800, you will add $30 a month more, making your amortization now $130 a month. This is a monthly expense just like steel and wood.
It probably is a good idea to deduct about 10% of your utility bill for the heat and power in the shop.
Don't forget knife show table fees and expenses, too.
As a hobby business, you don't need to deduct shop space or personal salary, but you should at least know that they would be needed if running as a full time business.
What I left out of this is business expenses. You will have to monitor the bottom line for a year or so and decide if you are running a business or a hobby. If you make more than about $3000-5000 a year on the bottom line, then you need to call it a business and get a business license and pay taxes. Below that, it would be declared a hobby.
Also, if you are selling any dollar amount of knives at all ( regardless of the bottom line), it might be a good idea to talk to your insurance agent about your homeowners insurance.