Quenching oil?

[NoraE]

I'd like to try some 2mm O1 drill rod. What would the recommended oil be for quenting? Also would it be used at room temp, or preheated slightly?

Thank you in advance.

 

[sako3006]

You need to heat to about 1,450 - 1,500 deg.F (bright red), quench in warm olive oil (has a high flash point) and then temper it by putting it in a 375 - 400 deg.F oven (toaster oven) for about an hour to get Rc~ 58/60 to keep it from fracturing. Any thin oil with a high flash point will work.

 

[Dr. Jon]

Whatever you have on hand. I do not think it matter a lot what type you use.

 

[sako3006]

Whatever you have on hand. I do not think it matter a lot what type you use.

I agree with you. I usually use the rule of thumb: 1 gallon of oil to one pound of steel of whatever is cheap at the time.

 

[Dr. Jon]

I am thinking of synthetic oil like Modil 1. It is more expensive but I keep a quart of so on hand for my lawnmower and snow blower. I know a very good clock maker who uses it to lub most of the pivots in the clocks he does and I use a lighter grade on watches. These horological applications use the stuff by the droplet so I always have some on hand, It is very stable non flammable and keeps forever in partially sealed containers.

 

[NoraE]

Whatever you have on hand

Boiled Linseed it is then. Most seem to think it stinks, but oddly I like the way it smells.

 

[sako3006]

Boiled Linseed it is then. Most seem to think it stinks, but oddly I like the way it smells.

It doesn't have to be more than ~100 degree F.

 

[sako3006]

I am thinking of synthetic oil like Modil 1. It is more expensive but I keep a quart of so on hand for my lawnmower and snow blower. I know a very good clock maker who uses it to lub most of the pivots in the clocks he does and I use a lighter grade on watches. These horological applications use the stuff by the droplet so I always have some on hand, It is very stable non flammable and keeps forever in partially sealed containers.

I have a paper submitted to the NAWCC about Mobil 1 products. I use 0W-20 (smaller pivots) and 5W-30 (larger pivots) in my cars as well. Not expensive when compared to $30/ 4 oz containers for two brands sold for clocks. And heck, its good for 20,000 miles

 

[Bill Ward]

Boiled Linseed it is then. Most seem to think it stinks, but oddly I like the way it smells.

Linseed oil is a fire hazard because it's a "drying oil", which means it hardens (polymerizes) on exposure to air; this reaction gives off heat, which can cause a spontaneous fire. It's the oil they're talking about when warning of the danger of "oily rags". Most oils, like mineral oils, do not have this property.
Fresh linseed oil is edible, and has a nice odor. But it rapidly becomes rancid, especially if not refrigerated and kept from air, and then it smells horrible. So it's a pain to store, and has a limited life. "Boiled linseed oil" has had metallic salts added to preserve it and accelerate the drying reaction (for example, when it's used in paint) but the salts are quite poisonous.
Chemically, linseed oil is a mixture of various oils (linoleic, alpha linoleic, oleic, etc.) some of which have low flash points or low breakdown temperatures, which is why it's not used for frying. So, it doesn't seem a great candidate for when you're going to plunge red-hot metal into it. When quenching, you always have to be ready for the oil to catch fire (metal container, metal lid, fire-proof gloves) but using a fire-prone oil seems to be tempting fate. Many machinists I know quench in used motor oil- at least it can be re-used for something!

 

[gmorse]

Hi NoraE,

The important factor in steel quenching is the speed at which the temperature is reduced to around 300˚C, (572˚F); once that's reached, the speed no longer matters too much. The quenching effects of plain water, brine and oil are all slightly different.

Plain water generates a jacket of steam, which is a poor conductor of heat and hence slows the cooling process unless it's dispersed in some way, usually by agitation.

Saline in a 10% solution appears to reduce the steam jacket, resulting in a more even but more rapid reduction in temperature, and produces the maximum hardness.

Oil behaves rather differently, reducing the temperature more slowly in the initial quenching, (it has a much lower latent heat than water), but once the vapour blanket starts to form, with agitation, the cooling rate is very similar to that of water, down to 400˚C, after which it cools much slower. This is why oil quenching tends to produce less distortion in complex shapes, and oil-hardening steels are formulated to accentuate this. Which oils are preferred is covered in the following book, but the author recommends a proper cold quenching oil for best results

The very useful little book 'Hardening, Tempering and Heat Treatment' by Tubal Cain, (ISBN 978-085242-837-5), is well worth reading.

Regards,

Graham

 

[glenhead]

One big thing to keep in mind in all these discussions is the size of the things we're talking about. Quenching a 2-inch (50mm) piece of 2mm diameter rod stock is very, very different from quenching a 5mm thick, 50mm wide, 300mm long knife blade.

The following discussion is ONLY about heat treating things that are the size of clock and watch parts, things that are made from very small stock. If you're looking here for heat treating instructions to heat treat a scythe blade or anything else bigger than a pencil, you're in the wrong place. Use common sense. Do your research on heat treating big things.

A coffee can full (say a quart/liter?) of pick-your-oil will 1) provide a huge amount of quenchant for the job and 2) be plenty big enough to where flash point and all the other technical blah-blah is rendered irrelevant. Any oil will do. Lots of people use peanut oil because it smells good. Plunge the piece quickly and deeply (and as vertically as possible to minimize/avoid warping) into the quenchant and swirl it non-stop for fifteen seconds or so. Don't dip it and remove it to watch the fascinating flare-up, don't yo-yo it in and out of the quenchant, don't ease its delicate little toes in and give it time to adjust. Shove it in deeply and leave it completely immersed and move it around. Figure eight, circles, fancy curlicues, whatever - the swirling pattern doesn't matter. Superheated steel cools surprisingly quickly in a quenchant. For 2mm stock fifteen seconds will take the piece to about room temperature. You avoid the threat of fire by the "plunge...quickly" step. You move the piece through the vapor barrier quickly enough that it doesn't have time to flash, you cool the piece very quickly, and you isolate the piece from oxygen. That doesn't mean you don't need to have a fire extinguisher handy just in case - use common sense. The only time you need to heat the quenchant or any of that stuff is when you're dealing with pieces that are several hundred times the size of clock or watch parts. As we've discussed in other threads, tempering doesn't have to be a long process at these sizes. Once an area turns your target color, you're through unless you're intentionally shooting for a measured hardness. You don't need to carefully calculate soak times or any of that folderol. Heat the piece, dunk it, swish it, clean it off, temper it, move on.

I use W1 tool steel and quench 4-inch long (100mm) pieces of 5mm diameter rod stock in a coffee can full of cold-water-tap water. Quenching that big a piece in that much water does a great job of warming the water to a really nice temperature for washing your hands. W1 means no oil mess, and there's not enough difference in performance characteristics between O1 and W1 to cause me to change.

Hope this helps.

Glen

 

[measuretwice]

I have a paper submitted to the NAWCC about Mobil 1 products. I use 0W-20 (smaller pivots) and 5W-30 (larger pivots) in my cars as well. Not expensive when compared to $30/ 4 oz containers for two brands sold for clocks. And heck, its good for 20,000 miles

Mobile 1 is an engine oil and the advantage I'm aware of is its so easy to find. There are a few real disadvantages. First, it may have some EP additives that will over time (pun intended) eat away at bronze/brass alloys causing premature failure of bearings. Secondly, the detergents keep any dirt in suspension. That's quite important for a machine gear box (you don't want contaminants in suspension), perhaps less so for a clock or total loss lathe oil system, however its still sub-optimal.

Not directed at you, but as a general statement, there's a lot of snake oil being sold out there Like hot rodders paying 2x if told its made out of billet instead of 6061 Aluminum . There's also people picking oils because they know someone use it who's an amazing watchmaker....but that doesn't necessarily mean he knows diddly about oils or plain bearings (he may, but one doesn't necessarily impart the other). Poor practices are perpetuated.

Mineral oil comes out of the ground, i.e. dead dinosaurs.... even synthetic oil (mostly). A major market is obviously internal combustion engines, the challenges of which are a dirty environment (burning hydrocarbons), higher pressure, high temps, and a wide range of operating temps (cold start in Winnipeg in Jan to 300C on the bottom of the piston). Our use doesn't face those challenges. At the same time, there are additives to a clock oil that are needed. I don't think you get any value from it being synthetic oil - what synthetic oils do is provide longer life in a high temp environment.

When picking a mineral oil, the properties to consider are purity, viscosity and additives. There are additives in engine oil we don't necessarily want but in a clock oil we want more antioxidants (won't dry out as quickly) and tackifiers (makes it a little bit sticky so it stays in place). On a machine tool slideway, we want lots of tackifiers - i.e. way oil. Really sticky like chain saw or bike chain oil. For other applications like bearings (plain or rolling) we want a really pure mineral oil with some anti-oxidantes, anti-foaming and anti-corrosion additives. Thats your basic hydraulic or spindle oil; they are interchangeable except lower viscosities are easier to find in spindle oils (e.g. Mobile Velocite series). I don't think brand matters much, anyone of the major oil co's competing products will do....it all comes from the same hole in the ground and they all know how to distill and blend it.

Bottom line for me is when I do a bit of research, I've been able to find rational reasons for using motor oil in cars, spindle or hydraulic oil on bearings and clock oil on clocks, watch oils on watches etc

Back to quenching, I agree with the advice given. Any mineral oil will do and that the main thing that's happening is its a different quench speed than air or water. There are special quench oils available, but afaik its just about less smoke/smell. Not an issue if the part is small, and if larger I've never bothered with special oils as I do my quenching in the garage workshop.

W1 means no oil mess, and there's not enough difference in performance characteristics between O1 and W1 to cause me to change.

From air to oil to water the tool steel gets a bit cheaper so it makes some sense to use W1 when you can - and less mess. A difference between the two is that things will more readily crack in a water quench than oil. That will depend on the shape of the part, but becasue of that I keep O1 in stock as the standard

 

[Old Rivers]

One big thing to keep in mind in all these discussions is the size of the things we're talking about. Quenching a 2-inch (50mm) piece of 2mm diameter rod stock is very, very different from quenching a 5mm thick, 50mm wide, 300mm long knife blade.

The following discussion is ONLY about heat treating things that are the size of clock and watch parts, things that are made from very small stock. If you're looking here for heat treating instructions to heat treat a scythe blade or anything else bigger than a pencil, you're in the wrong place. Use common sense. Do your research on heat treating big things.

A coffee can full (say a quart/liter?) of pick-your-oil will 1) provide a huge amount of quenchant for the job and 2) be plenty big enough to where flash point and all the other technical blah-blah is rendered irrelevant. Any oil will do. Lots of people use peanut oil because it smells good. Plunge the piece quickly and deeply (and as vertically as possible to minimize/avoid warping) into the quenchant and swirl it non-stop for fifteen seconds or so. Don't dip it and remove it to watch the fascinating flare-up, don't yo-yo it in and out of the quenchant, don't ease its delicate little toes in and give it time to adjust. Shove it in deeply and leave it completely immersed and move it around. Figure eight, circles, fancy curlicues, whatever - the swirling pattern doesn't matter. Superheated steel cools surprisingly quickly in a quenchant. For 2mm stock fifteen seconds will take the piece to about room temperature. You avoid the threat of fire by the "plunge...quickly" step. You move the piece through the vapor barrier quickly enough that it doesn't have time to flash, you cool the piece very quickly, and you isolate the piece from oxygen. That doesn't mean you don't need to have a fire extinguisher handy just in case - use common sense. The only time you need to heat the quenchant or any of that stuff is when you're dealing with pieces that are several hundred times the size of clock or watch parts. As we've discussed in other threads, tempering doesn't have to be a long process at these sizes. Once an area turns your target color, you're through unless you're intentionally shooting for a measured hardness. You don't need to carefully calculate soak times or any of that folderol. Heat the piece, dunk it, swish it, clean it off, temper it, move on.

I use W1 tool steel and quench 4-inch long (100mm) pieces of 5mm diameter rod stock in a coffee can full of cold-water-tap water. Quenching that big a piece in that much water does a great job of warming the water to a really nice temperature for washing your hands. W1 means no oil mess, and there's not enough difference in performance characteristics between O1 and W1 to cause me to change.

Hope this helps.

Glen

Glen,

What type of torch do you use for heat treating and tempering?

Bill

 

[glenhead]

For reaching quenching temperature I use Bernzomatic TS8000 heads with MAP-Pro (or other propylene, not propane) gas. I have three TS8000s. One is great for really small pieces like winding stems. If you stand a pair of them so their center flame-tips are "touching" and position the piece being heated at that point you can heat a (relatively) large piece of steel quickly enough to get the whole piece hot enough to quench. Granted, stand-alone torches (without some sort of forge enclosure) aren't ideal for plate steel or really big pieces that need to soak, but crossed flames do a great job on things pencil-sized or smaller, say 1/4 inch (6mm) diameter. That's the setup I use for the 5mm x 100mm rod stock I discussed earlier.

For tempering I use a bunch of different methods depending on the piece. For bigger pieces I have a small cast-iron skillet (the same size as my grilled-cheese sandwich pan) into which I put a layer of brass shavings, which I then heat on the stove. For smaller pieces I have a tin egg-separator and fill the center cup with brass shavings. I mount the egg separator in a "third hand" and heat it with a small butane torch or alcohol lamp. I also have a laboratory hot plate sitting in a box waiting for me to have the time to mess with it. I expect the hot plate will be the bee's knees.

Glen