Fig. 679.
[Fig. 679] represents Brown and Sharpe’s universal grinding lathe.
This lathe is constructed to accomplish the following ends. First, to have the lathe centres axially true with the work when grinding tapers, so that the lathe centres shall not wear and gradually throw the work out of true from the causes explained in the remarks on turning tapers in a lathe of ordinary construction.
Second, to have the headstock b capable of lateral swing, so as to enable the grinding of taper holes.
The manner in which these results are accomplished is as follows:
The headstock b and the tailstock are attached to the bed or table a, which is pivoted at its centre to a table beneath it, this latter table being denoted by c. This permits table a to swing laterally upon c and stand at any required angle. To enable a delicate adjustment of this angle, a screw a having journal bearing in a lug on c is threaded through a piece carried in projection on the end of a.
The table c traverses back and forth past the emery wheel, after the manner of an ordinary iron planing machine, the mechanical parts effecting this motion being placed within the bed upon which c slides. The carriage supporting the emery frame and table d remains stationary in its adjusted position, while c (carrying a with it) traverses back and forth.
Now, if a be adjusted so that the line of centres is parallel with the line of motion of c, then the work will be ground parallel, but if a be operated to move a upon its pivoted centre and draw the tailstock end of a towards the operator, then the work will be ground of larger diameter at the tailblock end. Conversely, by operating screw a in the opposite direction, it will be of smaller diameter at that end.
But whatever the degree of angle of a to c, the line of centres of the head and tailstocks will be axially true with the axial line of the work, hence the work centres are not liable to wear off true, as is the case when the tailstock only sets over (as will be fully explained in the remarks on taper turning).
To grind conical holes the headstock b is pivoted at its centre upon a piece held by bolts to the table a, so that it is capable of being swung laterally to the degree requisite for the required amount of taper in the work bore, and of being locked in that adjusted position, the work being held in a chuck screwed upon the spindle in the usual manner. The pulley d being removed to enable the grinding of cones, chamfers, or tapers of too great an angle to permit of a setting over to the required degree. The line of cross-feed motion of the emery wheel may be set to the required angle as follows.