Which oil for quenching ?

[ken king, King DesignParticipant @kenkingkingdesign]

I've just finished making handbrake parts for a 1947 Humber Hawk Series 1, the toothed quadrant and the mating pawl, from 1/4"gaugeplate. After much careful measurement (not easy, given the badly worn state of the originals) I knocked up milling jig No. 1 and set to work producing the quadrant shape.

Jig No.2 then produced the teeth ….

using a carbide tipped routerdovetail cutter, which worked suprisingly well.

Then jig No1 was re-used to check the pawl shape, using a piece of bar drilled at the correct centeres to represent the handbrake lever …

Now I have the machined components and it's time for hardening and tempering. Data on the gaugeplate wrapper suggests 780 – 820 degrees for hardening (held at temperature for 15 – 20 minutes, Tubal Cain), then quenching in oil. Tubal says engine oil gives variable results, so which oil is best ? I don't do much hardening so don't need gallons of the stuff, and I'd like it to be very reasonably priced. Any suggestions ? Your help will be much appreciated,

Thanks,

Ken.

[ken king, King DesignParticipant @kenkingkingdesign]

[Brian HParticipant @brianh50089]

I'd be inclined to try a heat treatment company, who will have the correct oil. In my apprenticeship days it was whale oil but I would guess that is difficult to obtain nowadays!

[Anonymous]

I use brine; seems to work fine. Provided you vigorously agitate the part when quenching it results in a hardness measured as greater than Rc65. Tempering as detailed by the manufacturer results in reduced hardness, in line with the manufacturers data.

Andrew

Edited By Andrew Johnston on 02/08/2015 21:08:34

[Mark CParticipant @markc]

I would agree with Brian – after taking the effort to make it, I would be miffed if it bent or cracked when I tried treating it. The problem with sub con HT is the minimum charge they normally have (circa £50). Perhaps you could get it done by a local machine shop who get regular treating done and bung them a few beer tokens?

If you do try DIY then think about the best way to quench, I would guess it needs to go in bowed edge first with teeth at the top – on it's back so as to speak but certainly edge on, not flat side first.

Mark

[Roderick JenkinsParticipant @roderickjenkins93242]

Ken,

Gauge plate is formulated to minimise distortion. Quenching in oil has a reduced cooling rate compared to water (or brine) which also helps to keep distortion at bay. I've successfully used straight SAE 30 oil (new!) but there are several references on the web to using vegetable oil. I think the cheapest cooking oil in the supermarket will do the job admirably. I don't suppose there was anything magical about whale oil – before the mineral oil industry took off I believe it was the only none gumming commercial oil available in bulk, much used in oil lamps. I would imagine that the most important part of the formulation for commercial hardening oils is to give a long life – something that is probably not relevant to our usage.

Nice bit of machining by the way,

Rod

[ken king, King DesignParticipant @kenkingkingdesign]

Some useful tips there chaps, thanks. Commercial H.T. companies are out; too expensive, so it's a DIY job alright. I like the idea of using cooking oil; I'll look for web references, as Rod mentions, before jumping in. And yes, edgewise immersion too. All good thoughts,

Thanks again,

Ken.

[AjohnwParticipant @ajohnw51620]

I tried veg oil once on a D bit around 3/4in dia with a reduced shank. Not very good as I don't think there was enough of it to cool the metal quickly enough. Personally I would use a lot of water, get it all in quickly and be sure to wave it about.

Thanks for the idea of using a router cutter. I have used them on aluminium a few times but not steel and if they will cut gauge plate it widens their use.

Next time I harden something I am going to try the clock makers method again. Soap. One I talked to reckoned it didn't matter which type but when heating blacken it all first – my way of putting that – it should all fly off when quenched.

John

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[Dinosaur EngineerParticipant @dinosaurengineer]

All British gauge plate I've ever seen is oil hardening to minimise cracking /distortion. Quenching in water/brine is asking for trouble. Gauge plate is not a plain carbon steel & is an alloy steel formulated for oil quenching.

The D bit round stock mentioned is probably "silver steel" which is a plain carbon steel & is water /brine hardening. I've never oil quenched silver steel so cannot voice an opinion on this.

The more exotic "tool steels" have various additives to give high hardness/toughness/min distortion to allow for oil quenching.  

Edited By Dinosaur Engineer on 03/08/2015 02:14:15

[Ian HewsonParticipant @ianhewson99641]

Used to harden hundreds of inch square by eighth thick gauge plate guides with a v cut out in old engine oil that gave a black finish, all came out ok.

[Bob MurrayParticipant @bobmurray]

Had good results with canola (rapeseed) oil from the grocers, preheated to about 35C in a slow cooker for quenching oil-hardening stock. It certainly smells better than old motor oil, and when it's cooled, just pour it back in the jug. The domestic authority knows that containers in the shop are not safe to put in the pantry.

[HomeUseParticipant @homeuse]

In the past our local Blacksmith/Engineering Shop used Castrol R oil for all Quenching/hardening/tempering jobs – Will always remember the resulting smell (like being at a motor meet) – sort of follow along the lines of a vegatable based oil

[David Clark 13Participant @davidclark13]

You should weigh the cost of heat treatment firms against the cost of failure if the part breaks in use possibly damaging the car or possibly killing a bystander if it fails while parked on a slope.

Then professional heat treatment may be the better option.

[Nigel McBurney 1Participant @nigelmcburney1]

I have used old engine oil,it works ok,just do it out doors ,its a bit smokey and can catch fire. I usually harden gauge plate in water,Last tool I made from 3/8 gauge plate was a curved tapered gib head key extractor about 7 inches long,this was hardened and tempered with a Calor gas torch and water quenched, and has taken a few beatings since,its now on the A32 somewhere after I went to help a full size traction with a troublesome flywheel key,and one of the crew must have dropped it.

[AjohnwParticipant @ajohnw51620]

Silver steel is an alloy tool steel. At one time or the other I have seen it mentioned for both water and oil quenching.

I have quenched items at work in oil – it was in something the size of dustbin and nearly full and plenty of room to wave the item about.

The main difference really is the cooling rates. Water is about 3 times faster than oil also boiling temperatures.

As an aside last time I handled one of these things it was pressed steel so why harden and temper it anyway? It's likely to be a lot stronger and more hard wearing than the original anyway. Heat treating the pawl would make mores sense as it has a much harder life but I feel that it would need tempering into the blue so also questionable really.

My driving instructor used to do his nut if I just pulled up the handbrake without pushing the button first. Just shows how quickly they can wear out.

John

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[Ady1Participant @ady1]

Old engine oil is the one I have heard mentioned as much as whale oil. The carbon deposits must make the difference

[AjohnwParticipant @ajohnw51620]

The oil water choice is down to cooling rates. Water is something like 3 times faster but spoiled by boiling to some extent which is why in both cases the parts need waving about. Taking an extreme HSS is likely to crack if quenched in water due to it's hardness and differential cooling through the section. Even more extreme stellite can crack due to quenching because it gets too hot while grinding it.

Where people at home get away with quenching oil hardening steels in water may just be down to none optimal conditions and simple sections. Relatively low amounts of water and space to wave it about etc.

People shouldn't forget over heating can cause problems as well.

John

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[Mark CParticipant @markc]

i seem to recall most hand brake quadrants I have seen (and I have seen a few over the years, but never taken much notice of their manufacture) have had just the ratchet hardened – most likely induction hardened. That's not something you can do at home easily!

Mark

[Dinosaur EngineerParticipant @dinosaurengineer]

I stand corrected Silver steel is an alloy steel – normally contains Chromium and Manganese in addition to the carbon.

Gauge plate is similar in composition but contains further additions such as Vanadium & Tungsten to give improved properties.

[AjohnwParticipant @ajohnw51620]

You can probably get both formulations in bright drawn or black.and save money if they are to be machined all over.

Don't ask me what numbers – I'm an animal I just ask the supplier for what I want. A silver steel equivalent is available in round black bar so probably available in other sections. After all they have to be made out of something in a more raw state.

John

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Edited By John W1 on 03/08/2015 12:54:10

[Neil WyattModerator @neilwyatt]

My driving instructor used to do his nut if I just pulled up the handbrake without pushing the button first. Just shows how quickly they can wear out.

The Mondeo auto-adjusting handbrake won't auto adjust if the push the button in!

Am I the only one impressed that a router bit will mill gauge plate? I thought the received wisdom is that one would chip if used like that.

Neil

[AjohnwParticipant @ajohnw51620]

If needed I intend to give a router cutter a go Neil – on anything un hardened now.

This might help with water hardening steels but note the comment at the top about what also might be added

**LINK**

Frankly the range of the constituents shown makes me think the old brand name style of buying is better than so called standards.

John

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[Martin KyteParticipant @martinkyte99762]

"Reposted on the right thread.

Put this on Ground Flat Stock so it was really off topic. Sorry."

Going partially off topic the way I understand it is the faster the quench the more Martensite is produced respective to Austenite and Pearlite. Water quenches quicker than oil because the layer adjacent to the steel is flashed into steam and the energy required for the phase change cools the steel quickly. With proper agitation the bubbles that form are shaken off and the process repeats until the steel is fully quenched. Adding salt reduces the size of the bubbles that form before they break off which makes Brine a faster quench than plain water. Both water and brine are corrosive to hot steel which for tool production is undesireable. Oil has a higher boiling point than water so bubbles do not form and there is no phase change. Oil cools steel slower than water. Oil hardenable steels have been developed for just this reason. The requirements for the oil should logically then be high boiling point, no nasty additives and relatively clean. I would suggest lower viscosity would work better than thick stuff but that's just intuitive on my part.

I would add that this is just my basic understanding and would welcome any comments that elaborate on this as it's quite interesting.

regards Martin

[jaCK HobsonParticipant @jackhobson50760]

Quench in oil. Almost any oil. Veg, engine old or new etc. Whale is good.

If your guage plate is O1 then you are going to struggle not to get it hard – it is very close to air hardening, especially for thin sections. For your application I don't think you need it really hard and I wouldn't bother hardening at all but if you do then you must temper – stick it in your oven at max temp (250 C) for 1 hour. Temper soon after heat treat as hard 01 is almost as fragile as glass.

Quench vertically and move up and down vertically – do not 'stir' it.

I make sharp things and they can crack quite a while after quenching if not tempered. Cracks are not always easy to see.

There is no need to quench O1 in brine to get it full hard, and the faster cooling rate is an unnecessary risk. I have experienced 01 cracking on numerous occasions.

[ken king, King DesignParticipant @kenkingkingdesign]

Thanks to all respondees and the wealth of your collective experiences. I can now report that the parts have been successfully hardened using Sunflower Oil ! Very cheap and available anywhere, it was chosen after various suggestions and some reading of articles on the 'net. Heated to dullish red for a few minutes, parts were then dunked with vertical agitation. They are certainly hard, and black deposits were easy to clean off, mostly by wipe, then a brief rub of emery. The oil is now back in the bottle but appropriately labelled and permanently removed from the kitchen at my wife's insistence, though in truth I would happily use it for a fry-up (but then I couldn't use it for subsequent hardenings, could I ?). Annealing was carried out at 200C for one hour, in line with the supplier's suggestion, so was simple to do in the domestic oven. Reassembly of the handbrake is scheduled for tomorrow.

I too was pleasantly suprised at how well the router cutter performed. After all, there is a world of difference between a tough wood and gaugeplate, but I thought to myself 'carbide tipped, so worth a try', and glad I did so. The cutter was barely worn at all afterward, even on the outermost sharp corner, which I had expected might quickly be destroyed, but no. It's given me confidence to consider other uses for router cutters, with their fancy profiles, and I hope you too find they help solve a problem.

Regards to All,

Ken.

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