Diamond Stones vs Oilstones

Most sharpening comparisons pit waterstones against something. This one does not. Diamond plates and oilstones are the two surfaces you reach for when you have decided you want low maintenance and long life, and the question is only which of those two suits you. They are the durable end of the category, and they answer slightly different versions of the same wish.

If you have not yet settled the maintenance-versus-speed question at all, start with waterstones versus diamond stones, which frames the wider decision. This page assumes you have ruled waterstones out and are choosing between the two permanent options.

How each one works

A diamond plate is industrial diamond grit bonded to a steel base. Diamond is the hardest abrasive there is, the steel does not wear, and nothing is released or consumed as you work. The surface stays exactly as flat as it was made.

An oilstoneis a hard, dense block — natural Arkansas novaculite, or manufactured India and Crystolon — used with a light oil. The binder is hard, so it does not release spent grit the way a waterstone does. It cuts with the same particles for its entire life, which is why it is slow and why it barely wears.

Both, then, are permanent bodies that do not consume themselves. Nearly every difference below follows from diamond being far harder and far more aggressive than the abrasive locked in an oilstone.

The comparison at a glance

Cutting speed

Diamond wins clearly, and the gap widens on hard steel. Diamond is harder than any tool steel, so it abrades even A2, PM-V11 and hard laminated Japanese blades quickly. A diamond plate cuts fastest when new and then settles to a slower steady rate after the first weeks as the tallest diamonds wear in, but even that settled rate outpaces an oilstone comfortably.

Oilstones are the slowest common sharpening surface. On simple carbon steel they are perfectly pleasant; on modern alloyed steels, reprofiling a bevel is an exercise in patience. If you value your time and sharpen hard steels, this alone often decides it.

Flatness and permanence

Diamond plates never dish — the abrasive is bonded to steel that does not wear, so the surface is permanent. That is their headline virtue, and it means no flattening, ever, which is a real relief compared with the ritual described in how to flatten a waterstone.

Oilstones dish too, but so slowly that a hard Arkansas used for decades shows barely any hollow. When one does eventually need truing, it is a rare event rather than a habit. For practical purposes, both keep their surface. The nuance is that a diamond plate is flat by construction and stays that way indefinitely, while an oilstone is merely very slow to move.

Maintenance and lubricant

Diamond plates ask almost nothing of you. They work dry or with a splash of water, need no soaking, and store anywhere. A rinse and a wipe is the whole routine. That freedom is a large part of why a buy-it-for-life buyer gravitates to them.

Oilstones need oil, and oil is the practical friction point. It floats swarf away and keeps the stone from clogging, but it gets on things — and petroleum oil on a surface you are about to glue or finish is a genuine nuisance. Once a stone has been used with oil it is committed; the oil is in the pores. It is not a hard obligation, but it is a permanent one, and it is the main reason many workshops moved away from oilstones. Diamond's water-or-dry option is simply cleaner to live with.

Feel and polish

This is where oilstones answer back. A new diamond plate can feel harsh — some people dislike the aggressive bite, and a coarse plate can be grabby on a narrow blade — though it mellows as it beds in. An oilstone has a smooth, controlled, almost buttery feel that many sharpeners genuinely prefer, and that hard surface is forgiving of a wobbly freehand stroke in a way a soft stone never is.

On final polish, a fine oilstone such as a hard black Arkansas reaches a keener edge than a diamond plate can on its own, because the finest practical diamond grades are coarser than the finest stones. The equalizer is a strop: a diamond plate followed by a charged strop closes most of that gap for a few dollars, which is covered in sharpening grits explained where the fine end of the range is set out.

Longevity and cost over decades

This is the reason both are on the shortlist, and it is close. A diamond plate has no consumable element at all; it loses only its initial aggression in the first weeks and then holds a stable cutting rate for many years. An oilstone barely wears and, in the case of a natural Arkansas, is the one sharpening object where “my grandfather bought this” is a routine sentence. A cheap India combination oilstone lasts essentially forever, which makes its cost per decade about the lowest in the entire category.

Neither will need replacing in a normal working life, so this is exactly the kind of purchase the site's cost per decade lens rewards. The difference between them on cost is small; the difference on speed and lubricant is not.

Which to buy

Diamond plate if you sharpen modern alloy steels, you want speed and zero maintenance, and you would rather work with water or dry than manage oil. It is the more versatile choice and the easier one to live with, and it doubles as a flattener for any waterstones you keep.

Oilstone ifyour tools are traditional carbon steel — vintage irons, O1 chisels — you sharpen freehand and value a forgiving surface, and you want the single most permanent object in the shop with the lowest lifetime cost. The speed penalty largely disappears on the steels these stones were designed for.

Both, if you can.A coarse diamond plate for fast repair, reprofiling and flattening, plus a fine oilstone for a controlled, high-polish finish, is a genuinely complementary pair. Between them you cover fast metal removal and a keen final edge, with no waterstone maintenance anywhere in the setup — and every piece of it will still be working in thirty years. Both feature in the best sharpening stones roundup.