Fig.6. - The new toolholder with height adjustment

Thirdly, there is the question of convenient holding of boring bars and tools, and all of these methods are subject to limitations in respect of their ease of tool setting.

All these points are successfully dealt with in the new design toolholder. It will be seen that the toolholder itself is clamped to the cylindrical post or pillar which is cast integral with the topslide, and thus all clamping stresses are confined to the toolholder itself. Only the normal cutting stresses are carried by the topslide, which itself has additional strength owing to the extra metal just in the right place which the post gives.

The toolholder itself consists of a hardened steel block cut from the solid with a central hole a sliding fit on the topslide pillar. The block is split so that it may be clamped to the pillar by means of a hardened clamping bolt. The tool itself is carried in aa square hole through the toolholder, and is held by means of two hardened setscrews. It will be seen from the two illustrations reproduced here that that this toolholder is quickly adaptable to turning or boring operations, and it has a complete range of movement round its pillar.

Perhaps the greatest feature, however, of the new toolholder is that it provides for height adjustment of the tool relative to the lathe centres. A range of movement of about 3/8 inch is provided, the tool being clamped firmly in its square hole all the while, and one quick movement of the spanner on the clamping bolt being the only action required for locking the holder in any position.