I was just wondering if anyone here has ever experimented with using
"full synthetic" motor oil as a heat treat quench oil for hardening
5160 and the like steels?
And if so what kind of results you had.
I have used normal motor oil, and wouldn't see the point of wasting
good synthetic oil instead...
Having said that, I recommend Peanut oil, which you can purchase at
WalMart or anywhere convenient. It has a high flash point and doesn't
smell so bad when quenching.
No matter what you use, make sure that it has no water in it. If in
doubt, heat it to about 220 degrees F and then let it cool before using.
Maybe that goes without saying, but if a red hot part hits water, you
get a dangerous burst as that water turns to steam. Wear eye
protection, at the very least.
I hesitate to give advice about the oil. There are many variables that
go into heat treating. If you are making a cold chisel, I doubt that
the type of oil you use could do much to change the results, since you
ar probably guessing at the quench and temper temps anyway. If I knew
you were making a high quality knife, I wouldn't even say that much for
fear of the reprisal that I would suffer in the face of the experts.
I know a guy would never use anything other than peanut oil. Another
uses olive oil.
Many people just try a thing and, if it works, that's what
I have read that synthetic motor oils can take higher cylinder wall
temperatures than "natural" oils. So, at least, I'd assume that it
wouldn't be any worse at decomposing than used petroleum motor oil.
DAGS on this group - there are some excellent reasons to avoid _any_
motor oil (or perhaps just any detergent motor oil, which is any motor
oil that does not specifically state "non-detergent") as a quench
medium. I recall reading them but don't immediately recall the specifics
- something with the metallic soaps interacting with the hot steel in an
As for used motor oil - ick. Which part of "definitely a carcinogen" do
you fail to read, much less want to breathe in fumes from?
Peanut oil for the high flash point and easy availability (with better
smell), or quench oil (supposedly not too hard to get from any oil
distributor) for even better flash point behavior. And you still want
both enough oil that flashing is unlikely (lots of oil relative to hot
steel means the bulk of the oil does not get too hot), and a
tight-fitting metal lid for the metal container so you can put it out
when it does flash. Make that container very hard to tip over, too.
DON'T. Automotive petro products contain metallic soaps that react
chemically with the work at temp, contaminating the steel. I use vet
grade mineral oil, available at your local Feed & Seed type stores,
usually for about $10 a gallon. It will flash a bit until the work is
totally immersed, wear gloves and eye protection. Once the work is
completely under, the fire goes out. Hold it under until you stop seeing
obvious convection at the surface. On 5160, you can get up to about Rc
62 full hard starting with room temp oil. My quench tank is four feet of
six inch pipe and I use a vertical point first quench. I can usually get
three swords through the tank before the oil gets really hot and the
hardness starts to fall off. Cold oil gives a harder workpiece than hot
oil. Having done over 100 swords and Bhob knows how many knives, the
results are quite consistent, and the scale rubs off with a shop rag
while the blade is still warm. Mineral oil will take the work down to
black in less than a second from 1600F red, and wets quite well, no
Thanks muchly for the advice,
I will tell my Dad to just send the used Mobil 1 that he was saving for
me to the recycler,, I was afraid there might be a situation like the
higher boiling point of the synthetic oil making it bad for a quench
oil,, I hadn't even thought of the detergents and other additives in
As for the safety issues, I'm damn near 50 now and have been a
machinist all of my working life,, I've been called a " saftey fanatic
" by more than one person before,, but then I still have my eyesight,
hearing, and all of my fingers,, if it takes being a fanatic to keep it
that way, so be it.
The safety blurb is reflexive, you never know who might read the post;
don't take it personal. I too learned a loooong time ago to keep my fingers
out of the fan, I've still got all of them.
I know how that reflex is,, and it drives my stepson crazy,, he just
finished his training and got his class A trucker's licence a couple
months ago, and started working for a local trucking firm, if either
his mom or I am awake when he heads out the door, the last thing he
hears is "drive safe",, same reflex,, we both know full well that he is
at least as good a driver as either of us are,, but we still do it.
Keep it up. The one and only time I forgot the 'drive safe' charm, the old
lady's car burned to the ground on the side of the road. Wiring under the
dash, she got out okay but the car was totaled.
It really does work...
Say what? I don't indulge in politics, too much like religion for my tastes.
That reminds me of the afternoon that the JWs showed up in my shop while I was
making a billet. Thay asked me why I made swords, and I told them that there
wasn't much call for plowshares these days, and a man has to stay busy. They
left scratching their heads, and I went back to work. Just another day in
Sorry Niko, no way to get them into the web. The grips are usually hardwoods
bonded with epoxy and banded with brass at both ends, just to be sure.
Scabbards are 12-14 oz veg tanned leather, stitched with .032 aircraft safety
wire and dyed USMC black, then soaked in the mineral oil quench tank to
'prime' them. Not all that fancy, but very functional.
The blades are machined from virgin SAE 5160 stock. Blades are 30" long, 2"
wide and .290 thick, full tang. This gives a weapon that's 35 3/4 long
overall. Hardware is either mild steel, 304 SS, or cable damascus, depending
on the customer's desire and wallet. Blades are heat treated to Rc 55, +/- 1
point (computer controlled oven). All blades are tested against 12 ga steel
before final assembly, any damage or marring and it goes in the scrap pile.
This is a dimensional replica of a 10th C Juttish long sword, optimized to
take advantage of modern materials. They will pull 45 drgrees out of true and
spring back, but you'll need a comealong to do it and a really sturdy vise.
The only thing I won't guarantee them against is a train running over them.
Turn your coupe into a convertible in a half dozen good strokes. The current
'high score' is felling a four inch diameter oak tree in a single stroke.
Granted, the fellow that did this was a Large Lad, but that's a fence post in
anybody's book. The math says it will take 37 tons of shear loading before
structural failure occurs at the shoulder. I don't think there's anyone alive
that can put that much force on it with muscle power.