Thanks for sharing the details with us, @MLFD1.
Having one item in different categories isn't possible in QuickBooks Desktop (QBDT). As a way around, you'll want to enter a description on an invoice stating the item is for Machine 2 or 3. This way, you can keep track of the categories you sell on one item.
I've attached a screenshot below for your visual reference.
Another way is to go to the App Center menu and look for a third-party app that lets you set one item into different categories. You can also visit our Apps for QuickBooks Desktop page for reference.
Let me also add this link that you can utilize for reference on how to adjust your inventory quantity seamlessly: Adjust your inventory quantity or value in QuickBooks Desktop.
If you need more help with inventories or with your QuickBooks, you can always tag me in your response. I'll be here to back you up!