[Don Clement]

My machines are all in an un-heated shop. On cold mornings, I open the door, walk in, close the door. NEVER leave the door open.
Ray L.

My shop door is right next to the Tormach. I leave the door open all the time and have no rust issues.

Don Clement

[LSM]

For the intermittent user a good coating of way oil is good,
machine tools should be covered with oil anyway.
WD40 isn't really a good long term rust prevented, way oil or some of the protective spray coatings work better.
I use a lanolin based rust preventer.

I use trim emulsion coolant fairly rich mix it actually leaves and oily residue so no rust issues.

[GJeff]

Good quality coolant will work under any conditions,Not just my conditions

I have had my shops in the extremes, were you can see the condensation running off, your parts machines, & never had a rusting problem use the wrong coolant & you can watch the rust forming

Anyone who suggests a water soluble oil for long term rust prevention in horrid conditions such as the gulf coast is ignorant of just how bad rust can be. I will concede, it may be a perfect solution in shop conditions where you are frequently using the machines, but for a hobbyist machinist whose machine may sit for 6 months or more, that advice is dangerous to their investment.

It only takes a small amount of common sense to know that any ratio of water soluble coolant will logarithmically approach 0 as daily condensation runs off the machine. Add the salt content of the air in some places, and you'll soon have a block of metal that looks like it's been at the bottom of the ocean. The chinese don't coat their parts in thick grease before they ship them across the pacific because it's fun. They do it because that is the only way to prevent the rust. If they could just give them a spray of the "right" coolant and get away with it, they certainly would.

[mountaindew]

Imho the tool cost a bit to much money to let it set for a week dirty and wet, yet alone 6 months.
I clean and service it before and after almost every use.
If I planned on letting it set for couple weeks I would clean it , lubricate and coat machined surfaces and a sheet dust cover!
My methods extend the life of more then just tools
md