Why every shop has a different name for the same tool
Trade language is local. The same object can carry four names inside a single county, and each one tells you something about where the worker learned the job.
Ask five machinists what to call the block of iron with the shaped grooves and holes cut into it, and you may get five answers. The entry in this dictionary is swage block, which is what the catalogues have said for well over a century. On the floor it might be a bolster, a swage plate, or simply the block.
None of those people are wrong. Industrial vocabulary is not handed down from a standards body. It spreads the way any spoken language spreads: apprentice to apprentice, shift to shift, plant to plant. A term that is universal in one region can draw blank looks two hundred miles away.
Three forces pull the names apart
The first is the supply chain. Shops tend to adopt whatever their main supplier prints in the catalogue. Two competing manufacturers with different house styles will seed two different vocabularies into their customer bases, and those names outlive the companies that coined them.
The second is the trade of origin. A part that crosses between trades usually arrives carrying the older trade's name. The rail industry calls the handhold on the side of a car a grab iron, and that name followed the hardware into other industries that borrowed the design.
The third is simple compression. Anything said fifty times a shift gets shorter. Full descriptive names collapse into one or two syllables, and once the short form is established, new hires learn it as the real name and never meet the long one.
What this means when you are writing a spec
Slang is efficient and precise among people who share it, and dangerously vague the moment it leaves that group. A purchase order, a method statement or a maintenance procedure is read by people who did not train in your shop. In those documents, use the catalogue term and the dimension, and treat the local name as a gloss rather than an identifier.
That is the reason this dictionary carries register labels. When an entry is marked slang, informal or regional, it is a signal that the word does real work in conversation but should not be the only identifier in a document that has to survive being read by a stranger.