I've got three Machinery's Handbooks. It is hardly a collection, and I use each copy. There is a lot of truth to CSIP's note about " those who belong to the ages". The first Machinery's Handbook I got was the 17th edition. My parents bought it for me new, as a gift. It was required that students in the junionr & senior years of the Mechanical Course at Brooklyn Technical HS have a copy, as it was what we worked out of in Machine Design and shop courses. We also sat a two-day open book comprehensive examination on our mechanical course work to graduate. Machinery's Handbook was the "open book". My copy still has notes in the covers from those days ( 1966-68). My regret is my folks did not sign or write something to me in the cover of flyleaf. Dad has been gone 22 years, and mom at age 92 is going strong but it would seem odd some 40 years later to be asking her to write something in my Machinery's Handbook.
I've used that 17th edition ever since and used it when I sat my licensing exam as a Professional Engineer in 1977.
I've got a later edition at the powerplant, (22nd, posibly, I'm home as I type this). It was given to me by an acquaintance whose mother worked for the publishers. He repaid a favor by giving me a new Machinery's Handbook. That was in 1986. I use it often, but it has never had the same fel or familiarity that the 17th edition my folks gave me has.
A few years back, I got a used copy of the 11th edition. A friend had it in a load of used tools he was selling at a blacksmith's event and "taligate flea market". I am not sure why I bought the Machinery's Handbook, but it seemed to need a home. It turned out to have belonged to two men previously. The first man is a name in the cover. The second man was named Ray Beardsley, and there are all sorts of slips of paper- toolroom checks with calculations on them, odd slips with notes- in the pages of the book. No indication of where Mr. Beardsley worked, or the years. The 11th edition has come in handy for me on steam locomotive boiler calculations. It has data on boiler staybolt threads and staybolt taps as well as tapered threads used on studs tapped into the boilers to hold fittings or manway covers. This is data the later editions do not have. Out of respect for Mr. Beardsley, I've left the slips of paper in the Machinery's Handbook, and I never fail to wonder who he was and where he worked.
Would I get more editions of Machinery's Handbook ? Depends on price, edition, and what jumps out at me at the moment when I might find one at a sale. I've seen some offered in antique tool places and they seem to think the pages are coated with gold leaf. Being someone who uses his copies of Machinery's Handbooks fairly often, and having sufficient copies, I would say I am not a collector. OTOH, were I at a yard sale or similar and there was more of a sense of who owned the Machinery's Handbook ahead of me and connection with the previous owner (or his/her heirs), I'd be hard put NOT to buy it. I suppose the idea I was maintaining some kind of continuum would cause me to "collect" another copy or edition of "Machinery's Handbook".