SG-250 - Oil Better Suited Than Water?

[Thy Will Be Done]

After extensive use of this stone with water trough, I'm beginning to think that this stone is much more suited to using something like a thick mineral oil on the cutting surface.  That may not even be thick enough because ideally it would not be something that would simply soak into the stone at all.  I suppose that is the issue with oil after all and wondering if there is anything similar one could use to both act as a coolant and a friction reducer to limit wear to abrasive much more than water and also keep the edge from losing temper.

[John Hancock Sr]

Definitely not. It is a water stone and designed to be soaked in water for best results

[John_B]

The Tormek system using water does not heat the blade being sharpened to a point where it will lose temper.

[Ken S]

Has anyone tried using Tormek ACC with the SG? It has cooling properties like water, and also has anti rusting properties.

Ken

[RichColvin]

Ken once told me that grindstones are like brake shoes:  both are meant to be worn down through use.

[tgbto]

If you reduce friction you will reduce sharpening efficiency. In another post, you seem to complain that the stone is glazed and needs refreshing... If the stone wears down it means that new abrasives are exposed, therefore maintaining sharpening efficiency. If the stone wears down too quickly, it means it is not hard enough for the material you're trying to sharpen.

[Thy Will Be Done]

If you reduce friction you will reduce sharpening efficiency. In another post, you seem to complain that the stone is glazed and needs refreshing... If the stone wears down it means that new abrasives are exposed, therefore maintaining sharpening efficiency. If the stone wears down too quickly, it means it is not hard enough for the material you're trying to sharpen.

This is patently false and a myth that needs to die. Friction is nothing more than generating heat.  Abrasives work by cutting, friction actually reduces cutting of abrasives and increases wear of abrasives.  The stone surface wearing is not at all the same as the stone releasing abrasive grains via bond strength being low enough to do so.  You can easily see this in the fact that if you continue grinding on a piece there will be an increase in the level of polish very quickly and noticeably as the surface gets more and more glazed/loaded.  It will burnish more than cut the steel as this progression happens, burnishing is not desirable.

[tgbto]

This is patently false and a myth that needs to die. Friction is nothing more than generating heat.

Thank you for your kind, nuanced words.

Still, from a physics standpoint, in a situation where a solid moves in relationship to another, the friction coefficient is the ratio of the tangential force to the normal force. If there is no friction, there is no tangential force applied to the material being cut, so no work being done and obviously no matter being removed.

In the same fashion, a frictionless action of a knife blade on a tomato will press down on the tomato but not cut it. Our job as sharpeners is to make sure friction happens over such a tiny surface that the cells are instantly sheared in two by the focused tangential force without the tomato being deformed by the normal force.

Heat is a byproduct of friction, heat reduces cutting of abrasives, and increases wear ; hence the need to use a coolant in many situations where friction generates a lot of heat, or to reduce friction using a lubricant where the unlubricated action would generate more heat than the tool (drill/belt/wheel) or piece would be able to withstand locally. Cutting fluids act as both.

[Ken S]

I have seen difficulties which reoccur occasionally, such as frozen EZYlocks and noisy water troughs on T8s. These are frustrating, but can be handled. I don't recall ever reading a previous post recommending oil instead of water with the SG. I am not saying that oil would not work. I am just puzzled that in fifty years of product innovation, Tormek does not recommend using an oillike coolant instead of water. My guess would be that Tormek has good reasons for staying with water. They do recommend ACC as an alternative which offers more rust prevention.

Ken

[Sir Amwell]

Maybe you are asking too much of your SG250 stone?
And looking for an alternative like oil to run it through is not going to get more performance out of it?
The SG250 works just fine, through water with occasional regrading,for most everyday day steels, with correct honing gives good results.
But for harder steels?
It just won't cut it.
I spent a long time on bench stones, hand sharpening.
Eventually found that my trusted ceramic stones just couldn't handle the harder steels, loads of work, glazing on the stones, nagura stones, re flattening etc etc.
Oil addition didn't help either.
Diamond or CBN did though.....
Just my two pennorth.....

[John Hancock Sr]

Friction is nothing more than generating heat.

Indeed, the water actually acts as a lubricant as states by Tormek.

[John Hancock Sr]

Eventually found that my trusted ceramic stones just couldn't handle the harder steels, loads of work, glazing on the stones,

There are different ceramic compounds and they have differing harnesses. It really depends on the MOHs hardness of the ceramic in the stone.

[John Hancock Sr]

Still, from a physics standpoint, in a situation where a solid moves in relationship to another, the friction coefficient is the ratio of the tangential force to the normal force. If there is no friction, there is no tangential force applied to the material being cut, so no work being done and obviously no matter being removed.

The work being done can be measured by the material being removed (bonds being broken within the steel) and the generation of heat. You need to maximise the first and minimise the second. We want as little heat as possible and as much material removal as possible for maximum efficiency. This is achieved by ensuring that the relative MOHs hardness of the abrasive is higher than the steel, the abrasive keeps as sharp as possible (friability helps with this) and the surfaces slide past one another as smoothly as possible, which is done by lubrication. The lubricant also assists in removing any heat that may be generated by friction. Water and oil have both been traditionally used on sharpening stones.

[RichColvin]

I remember using oils for keeping cutting tools cool and working efficiently (e.g., on drills, milling machines, and metal lathes).  I could not remember using oils for this purpose, so I asked Claude.ai.  Whilst AIs are not always right, Claude does seem quite good.  

Question:  What are typical grinding lubricants?

There was a long iteration of options provided, based on, 

• Material being ground (steel, carbide, ceramic, aluminum)
• Wheel type (CBN, diamond, aluminum oxide)
• Precision requirements
• Environmental/health regulations

But it was summarized as:

For most general-purpose surface or cylindrical grinding, water-soluble synthetic or semi-synthetic fluids are the go-to choice due to their cooling efficiency and cleanliness.

I followed this up with the question:
What is most commonly used for aluminum oxide grinding wheels?

For aluminum oxide grinding wheels specifically, the choice depends on the application, but here's the breakdown:

Most Common: Water-Based Synthetics & Semi-Synthetics
These are the dominant choice for aluminum oxide wheels because:

• Aluminum oxide generates significant heat — water-based fluids excel at cooling
• They keep the wheel from "loading up" (pores clogging with swarf)
• Good for ferrous metals, which are the typical workpiece material paired with Al₂O₃ wheels
• Easy to maintain and cost-effective

By Application
General surface/cylindrical grinding (most common use case)

• Synthetic or semi-synthetic water-based fluids are standard
• Concentration typically 3–8% in water

Precision grinding (tool & cutter, OD grinding)

• Semi-synthetic fluids for the balance of cooling + lubrication
• Sometimes light sulfurized mineral oil for very fine finishes on steel

Heavy stock removal

• Soluble oil emulsions — the oil content helps with lubrication under higher loads

Light/bench grinding

• Often run dry, or with a wax stick touched to the wheel periodically

What to Avoid with Al₂O₃ Wheels

• Straight heavy oils — poor cooling, can cause thermal cracking in the wheel bond
• Alkaline fluids with high pH — can degrade certain wheel bonds over time

So, I think we are good with water.

[Rossy66]

Has anyone tried using Tormek ACC with the SG? It has cooling properties like water, and also has anti rusting properties.

Ken

I noticed that when I started using ACC with my SG250, it stopped getting brown spots on it which I assume was some part of metal partial stuck to the wheel.