Which oil for quenching ?

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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"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

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.

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.

The assumption that wood router cutters would not perform well is possibly counter intuitive.

The was it goes is this. Wood is a soft material compared to metal therefore wood cutters will struggle to cut metal.

The cutting edge of your router cutter is tungsten carbide not because of the hardness of the wood but because of its abrasiveness. It is surprising how abrasive many biological materials are, consider the razor strop fungus used as its name suggests. Wood cutters are habitually used at very high surface speeds and abrasion of the cutting edge becomes the limiting factor in tool life hence the use of hard materials like tungsten carbide.

Admittedly the cutting edge geometry is probably less than ideal for metals and the impact strength of the carbide may be non ideal but for one off jobs they should certainly do the job.

regards Martin

On the flip side, don't try using your expensive milling cutters in the router. I tried using a 6mm slot drill in my router and it turned blue and started smoking very fast. It was a brand new dormer cutter, so not a cheap junk cutter. The wood I was trying to cut, soft building (c14) pine.

Mark

Umm, resin build up, cutter rubs, cutter overheats ?

Martin