Quenching oil info for newbie

[Joel_BC]

If I want to play around with the making of chisel blades and knife blades, just to get my feet wet and start to get a feel for all of this, what can you tell me (the most preliminary info) about quenching oils?

I've noticed that some petroleum-product companies list quenching oil products on their Web sites. These are obviously supplied to industries. I just want to experiment at the home-shop level, as a complete beginner & amateur.

I've picked up that there are "fast", "medium", and "slow" quenching oils.

What about brands that are favored by knife makers (possibly because of availability, and the possibility of purchasing them in relatively small volume)? I'm in Canada, so brands that are widely available in the U.S. may or may not be available, here. Are there generic types that can be searched for under various brand names?

I've been a participant in an on-line welding forum, and some of the guys there have tried their hands at blade making. A couple of people mentioned using readily-available 20W motor oil. But I don't suppose this may be the best choice, even for a beginner like me.

In any case, I'd be grateful for anything you could pass on to me. Thanks.

 

[12345678910]

Pick your steel first and then match the oil to that steel.

What's your steel preference?

 

[Nathan the Machinist]

If you plan on doing the heat treat yourself, you will need to select a steel that can be processed with what you have. If you don't have a way to hold and maintain a temperature for 10 minutes or more you're not going to be able to soak things like O1 or A2 very well. So if you're looking at steel that doesn't need much of a soak at temp - you're probably going to be looking for a fast quench oil.

A relatively fast quench oil that is easy to come by is the 11 second oil you can get from McMaster for $15 per gallon. With good agitation you can expect good results on even the fastest quench steels such as W1 or 1095 on thin sections like a knife blade.

The other option for fast steels like that is a brine quench. The salt in the water decreases vapor jacket stability, promoting a more even quench. I believe it is 3/4 pound salt per gallon of water.

20 weight motor oil is slow, uneven, leaves burnt on gunk, makes dangerous fumes, and bursts into flames. And is also $15 per gallon.

 

[Stacy E. Apelt - Bladesmith]

If you go by what you read online, and hear from many chatroom sources, anything will work. If that answer is good enough, then look no farther.

However, if you are interested in getting the steel to fully harden, and make the best quality blades and tools you can, then a proper quenchant matched to the steel is required. Read Kevin Cashen's stickies at the top of this forum and you will get a lot of info.

Many things will work as quenchants, you often hear of 20W motor oil, ATF, canola oil, olive oil, peanut oil, and exotic concoctions and goops using everything from bacon fat to bear grease. These all will work to some degree on some steels, and not at all on others. The thing is to understand when you need a certain type of quenchant.

Simple carbon steels, like 1080,1084,1095, W1,W2 need a fast quench. The quenchant has to drop the steel from about 1500F to below 900F in one second. That is called a fast quenchant. ( The number of seconds listed in quenchant types is a different thing. BTW) Water and brine do this well, but are too severe a quench for thin things like knife blades. Blades may warp or crack in them. Fast oils, like Parks/Heatbath #50, will do the job nicely, without the cracked blades.

Lower carbon steels. like 1070,1060 can be water/brine quenched, but fast oil is still preferred.

Alloy steels, like 5160, L-6, O-1 will take a slower quench and use "Medium Speed" quenchants, like Parks/Heatbath AAA. Most home brew quench oils will work for these steels. ( but that does not make them the best choice)

Air hardening steels, like D-2, stainless, and most high alloy steels, can be quenched in still or moving air. They require much higher temperatures to austinitize them, but the cooling time is so slow, that there is no need to speed it up with a liquid. Some can be oil quenched in slow oil. The usual system used on knives is to take them out of the foil packet and cool them by clamping between two large aluminum plates, called quench plates. This speeds the cooling while preventing warp.

If home brew quenchants will work on most steels, why use a commercial quenchant????
Because they are made to do the job and survive. There is a lot more than just cooling of the metal going on in the quench tank. The vapor jacket of gasses that forms around the blade as it boils the oil will insulate the blade and slow the cooling rate if the oil isn't right for the job. Their viscosity can prevent proper convection ( or allow too much). The oil may burn, scorch, acidify, or become useless quickly by decomposing in the heat. ( Motor oil and ATF aren't designed to come into contact with 1500F metal, they are lubricants.) And, the vapors released may be toxic. These backyard oils are usually petroleum products. Commercial quenchants are usually mineral oil based ( mostly parafinic), and will survive much longer. They have stabilizers, and many other things that you need when quenching.

Will the home mix oils work??? - Maybe.... sometimes.
Will they work as well as commercial quenchants???? - Almost never !
Are the commercial quenchants expensive??? - Not really. When you look at the cost of a gallon of ATF, canola oil, etc. and compare it to $15/gal for a proper quenchant that will last for a long time, the savings of a few dollars/gal is wasted money.
Looked at another way, if you spread the cost over the first 100 blades ( it will last a lot longer than that) the cost is 15 cents per blade for the good stuff. A gallon of some cheaper mix may only last long enough to do a few dozen blades, thus costing a lot more per blade. ( and may produce inferior blades)

Stacy