coak

If we estimate the coak by its comparative heating power, it represents 65 per cent.
A Dictionary of Arts, Manufactures and Mines|Andrew Ure
The coak which remains in the retorts constitutes about 60 per cent.
A Dictionary of Arts, Manufactures and Mines|Andrew Ure
When the coak is used for heating the retorts, about one half of the whole is required.
A Dictionary of Arts, Manufactures and Mines|Andrew Ure
By the seventh operation, the central hole in the coak for the pin, on which the sheave turns, is drilled out.
The Ports, Harbours, Watering-places and Picturesque Scenery of Great Britain Vol. 2|William Finden

So truly are those grooves formed, that the slight tap of a hammer is sufficient to fix the coak in its place.
The Ports, Harbours, Watering-places and Picturesque Scenery of Great Britain Vol. 2|William Finden