Hardening gauge plate (O1)

Sometimes I make edge tools from gauge plate which I think is the same thing as O1 oil-hardening tool steel. I've tried quenching in motor and cooking oils but (according to my hardness testing files) have never got above 50-55 RC. I can get to 60-65 RC by brine quenching, as you would do for silver steel, and I seem to have got away with it so far.

But it's not the right way to do it and that worries me!

I was browsing through Sparey (The Amateur's Lathe) today, and lit on his recommendation to use a 50:50 'soluble' oil / water mix if, like me, you've run out of whale oil.

I'm wondering if anyone has tried this. I'd also be interested to know what oils other folk use - I know that there are commercial quenching oils out there, but they seem very expensive.

Robin.

Hi Robin,

With a tool-making background commencing in 1950, your comment ...

'But it's not the right way to do it and that worries me!' ... was a surprise.

With a similar high-carbon content to silver steel, I have always (rightly or wrongly) heat treated gauge steel (gauge plate) the same way.

Heated to cherry red, I always quenched either of the steels into clean water.

Although it was done with much larger items in the toolroom, into oil never impressed me for the small items I'd made.

Tempering back as appropriate for the end purpose, e.g. cutting tools, etc. would be controlled by a further immersion into water.

There'll be, I suspect, a plethora of further responses, directing you to previous threads.

Cheers,

Sam

Whilst I am perfectly happy to accept Sam’s practical success … I think this needs saying:

There is a big clue in the name of the material : The ‘O’ stands for Oil

Sadly, I note that even this page appears to use ‘0’ in several places **LINK**

https://sheffieldgaugeplate.co.uk/blog/aisi-01-ground-flat-stock/

MichaelG.

Gauge plate is sold as "non-distorting" and is mainly aimed at making jigs and fixtures. The slower rate of quenching in oil stops the distortion but limits the ultimate hardness. So, quenching into water gives a harder result but at the risk of distortion, And, of course, harder means more brittle so some tempering will be needed to give the required properties. I've made acceptable blades for wood planes out of water hardened gauge plate.

Rod

Heat treat was one of my jobs years ago, use clean oil or clean water & I would imagine your temperature control is not going to be spot on? Most small parts can be water quenched but we generally used oil with little problem.

Tony

I use a gas fired furnace to anneal gauge plate or silver steel. I let it soak at 750 centigrade and quench in brine. It is then annealed at the appropriate temperature for its use.

I NEVER quench in oil because it can catch fire. Apart from that it doesn't give the best hardness as you have found. Brine is the easiest quenching agent to use for maximum hardness.

Andrew.

In the 70s when I cut my teeth, it was widely held that both silver steel and gauge plate were to BS1407 - same stuff, different profiles - and were hardened and tempered the same way.

Looking on the net now, it seems there are so many different specs offered that it could be anybody's guess unless you've got some sort of release note or CofC to tell you what you've got.

When parts get large, quenching becomes a more sophisticated process to avoid cracking from differential contraction - even in oil. Don't ask how I know...

But for less substantial parts I'd think processing should be simple and not require precise temperature control, to deserve the name of gauge plate.

I presume you don't mean 'Anneal' but who knows? To quench in oil you need a sufficient quantity that allows the part to be fully submerged and also that the part cannot raise the oil above it's flash point, you will get initial flames & a bit of boiling but nothing too drastic. I used to harden tool steel so heavy you could hardly lift it so carefully does it

Tony

This little book tells you all you ever needed to know about heat treatment

Tubal Cain

this is the real English TC, not the American pretender.

Sorry Tony,

I should have said harden and temper, old age creeping in! I emphasised the fire hazard because I once had a bucket of oil catch fire. I was doing it as per book too ............ so it can happen and it was quite frightening.

Duncan is spot on, Tubal Cain's book on hardening and tempering is a gem. Gives you the essentials without overloading the theory.

Andrew.

I use DIN 1.2510 but as far as I can see it is the same type of steel. Oil hardening goes without problems but small items loose heat very quickly and optimum hardness is then not reached. I hold small parts in tweezers/pliers close to the oil container and quench quickly without hesitation. Niko.

I use DIN 1.2510 but as far as I can see it is the same type of steel. Oil hardening goes without problems but small items loose heat very quickly and optimum hardness is then not reached. I hold small parts in tweezers/pliers close to the oil container and quench quickly without hesitation. Niko.

I have hardened Oil hardening steel (gauge plate) by quenching in vegetable oil or in water, tempering right after quenching . Complex shapes were quenched in oil and I got it hard enough for the intended purpose, simple shaped tools were quenched in water.

Thor

I heat the O1 and gauge plate to hotter than bright red, it is actually an orange colour and allow time for the heat soak etc, then Quench in oil. You need quite a lot of oil, as if the oil heats you will loose it's peak hardness. Getting 63Rc is normal hardness range. This is how I did the hardening of my outer ball bearing races for a bearing that is no longer made.

Whether quenching in oil or water the part must be swirled around in the quench for optimum heat transfer. In water if the part is left stationary it will become covered in bubbles of steam which inhibit heat transfer.

When heating steel without the benefit of a controlled atmosphere there will be some surface decarburization resulting in reduced hardness at the surface. The longer the steel is held t temperature (soak) the deeper the decarb.

Just an idle thought that occurred to me... would there be any advantage in cooling the water / brine / oil in the fridge or freezer before quenching?

Rob

Just an idle thought that occurred to me... would there be any advantage in cooling the water / brine / oil in the fridge or freezer before quenching?

No,

Like several others previously I spent a lot of years heat treating B01 (GFS and Silver Steel) and differing tool steels on a near daily and certainly weekly basis. I don't recall taking B01 over 58 - 60 HRc all tested on a (Mitsubishi if I recall correctly) hardness tester

We always quenched in oil (whale oil). The only time we had anything crack in oil was after a particularly cold period where the oil bath chilled overnight. From that point on, a scrap block of steel was heated at the same time as the first batch of the day and used to take the chill off the oil before the first quench.

We were tasked to make a large batch of small cams from silver steel that had a 5mm hex broached in. The material came from Uddeholm a reknowned tool steel supplier. All our heat treatment was done to manufacturers specifications but virtually all of the first batch of components - quenched in water as so defined - cracked in use at the hex. A second and all further batches were quenched in oil with no further issues. Since then I have never quenched silver steel in water at home.

Personally, despite being an advocate of Sparey book I wouldn't use soluble oil/water mix myself but, like so many things, unless you try you don't find out. Trying to get B01 harder than 60 - 62 HRC at home by overheating and or very cold quenching will, in all probablilty, lead to crystalisation that tempering may not improve.

Regards - Tug

Thanks Tug, good to know.

They used some stuff called Ucon for quenching where I worked many years ago. It is water based with some organic compound dissolved in it. When it gets hot (close to the job you've jusr dunked) the organic comes out of solution and coats the job, so you get a sort of oil quench but no fire risk. Probably stunningly expensive and only available in 50 gallon drums

As a follow up to Andrew and Tony’s comments, I couldn’t resist telling the following story.

I was into my 2nd or 3rd year of my apprenticeship when a rather precarious situation developed.

The toolroom heat-treatment plant (a closed off section of the workshop measuring about 8 metres by 6 metres), was equipped with various gas and electric fired cyanide furnaces. A basic gas torch and a brick hearth, along with a bucket of whale oil were there ‘for personal use’.

Quenching of the major throughput was either into a warm water bath for smaller parts, or a very full tank of oil. This tank measured about 150cm deep and was roughly the same diameter. One of the older toolmakers was responsible for all of the once-a-week ‘serious’ heat treatment.

Almost full, the large oil bath became a considerable (flash) point of interest when a large and very hot piece of tool steel (an insert for a compression mould) was being quenched. For scale, the piece (effectively one of several thick-walled cylinders) measured about 150mm diameter and some 400mm long. It was bored out about 45mm diameter through its entire length.

Transferred with some difficulty from a cyanide bath to the hand-operated hoist, the hoist failed (jammed) while the hot insert was half in and half out of the oil. It doesn’t take much imagination to visualise what happened next.

During the initial struggle to free the jammed hoist, the oil began to boil and instantly caught fire. Flames quickly crept across the surface and out to the edge of the tank. Within seconds, flaming oil was dripping onto the floor.

Of greater concern was what was on the other side of the brick wall and thin cement sheeting. It was the powder room known as the drugstore. It supplied measured amounts of rubber, sulphur, and powdered coal to several Banbury mixers and two-roll mills.

Having, for a short while peered through the open door as a not particular welcome spectator, it was time to make my exit. The foreman and a couple of others succeeded in releasing the jammed hoist, quenching the steel, and extinguishing the fire with sand etc. The fire brigade arrived to find the toolroom filled with smoke.

I suspect the other cylinders were subcontracted.

Perhaps that's why I prefer a water quench

Cheers,

Sam