Linseed oil for cutting oil

[AllenH59]

You guys probably knew this, but I found out tonight. I am making a small part for my old boat motor, the gear that goes at the swivel point of the handle. It is a weak point in old Evinrudes, and I was unable to buy one. They are cast brass, so I am naturally making one out of a piece of mystery stainless, which I think is Monel. Whatever it is, it is difficult to cut with HSS tools. I drilled a pilot hole with an aircraft bit, and was torture... I am out of rapid tap, and looked around the shop for something to use, knowing that petroleum lubes are horrible cutting oil, I tried linseed oil. It did not smoke, nothing got hot, the tool kept cutting, nothing got dull. it may not work well on everything, but it worked well on that. There was also some slot cutting involved, with a cheap (shars) HSS 4 flute 3/16" end mill, and it was painless.

[Harold_V]

Interesting, and certainly nice to know, but I'd use it with caution, as it is a drying oil and creates heat in the process of drying, so improperly disposed of residue (like shop rags) can lead to fires. The other negative is any residue not removed will harden, which may or may not be an issue.

Harold

[Steggy]

I am out of rapid tap, and looked around the shop for something to use, knowing that petroleum lubes are horrible cutting oil...

By "petroleum lubes," are you referring to motor oil or petroleum-based cutting oil?

I have used petroleum-base cutting oils with both austenitic and martensitic stainless steels (including the extra-tough 440C alloy) for decades and have never had any complaints. For drilling, milling and turning work, I use the cutting oil straight out of the jug. I use a mixture of 10 percent mineral spirits and 90 percent cutting oil for tapping. Works like a charm.

Incidentally, for working with most aluminum alloys, I use a "reverse" mixture that is 10 percent cutting oil and 90 percent mineral spirits.

[curtis cutter]

Interesting, and certainly nice to know, but I'd use it with caution, as it is a drying oil and creates heat in the process of drying, so improperly disposed of residue (like shop rags) can lead to fires. The other negative is any residue not removed will harden, which may or may not be an issue.

Harold

Agreed on the potential fire hazard of organics and breakdowns causing fires.

This brings to mind a very sad event I responded to when a father and son passed away due to a strange series of events. The two had been hired to construct a chain link fence around a business. While cutting the steel posts with a abrasive chop saw the sparks went into an adjacent businesses dumpster. The sparks ignited the contents of the dumpster, which unfortunately for the two contained Magnesium turnings. Not being knowledgeable about extinguishing combustible metals, the two grabbed a nearby garden hose. A horribly painful death.

[neanderman]

I'm with Harold. Linseed is a drying oil -- it will not only form a film if not removed, but it presents a significant fire hazard if any combustible materials are used in application or cleanup.

[pete]

Modern cutting fluids are an effort to try and duplicate what the old ones did that used animal fats. A long time ago I had a few very old machinists tell me that nothing then performed as well as those fat based cutting fluids could. Bacon fat is supposed to be very good but with all the additives and salt in it I don't use it. The fat going rancid and getting into the normal shop scrapes and cuts on your hands plus attracting vermin and bugs are probably the main reasons the more modern ones were developed. I do use pure baking lard and fill the flutes with it while reaming. An idea stolen from one of Guy Lautards bedside reader books. I haven't found anything that works as well especially on stainless. It doesn't seem to do so well with aluminum.I do keep the lard refrigerated to keep away from the other problems. But I've heard of people using common butter in a pinch. The animal fats do smoke pretty good if your speeds are fairly high. But I wouldn't have thought of trying the linseed oil so one more for the already full memory banks. Whale oil is supposed to be really good but seems to be a bit tough to find today.

[John Hasler]

Pure neatsfoot oil (not neatsfoot oil compound) works pretty well and has the advantage of being liquid at room temperature. You can get it at tack shops.