It is possibly more use to not say you are a trader, but that you are selling old personal items so come under the Capital Gains Tax regulations.
It is some years now since I looked but there is a minimum CGT items value of £5000, below that no tax payable. I was selling books, and it was only if a set of books was over £5k that tax came, if selling 50 books at £50 each then thet were all individual items. I found that throwing away books didn’t offset any other CGT, each individual item was treated individually. In my case I was selling off at auction many books, from my records over the previous 30 years I had spant £34k, and sold about £3k, lots disposed of, but none of the encyclopaedias were anywhere near £5k so nothing paid but also nothing to offset either.
Perhaps you sell the lathe etc as a machine and chucks separately, whilst a complete set, a chuck can be fitted to any machine, it is not specific to that machine, unlike one volume of a set.
Most people on this forum who get to three score and ten will have piles of accumulated things, and that they are treated as individual items is really the only way to cope. A set of castings is a set, but even they will be less than £5k. If you get to pay CGT on every individual item also means that the loss of value on each individual item also also allowed in offset. Just need the receipts!