Fig. 2570.
The best form of template to plane the ways to is that shown in [Fig. 2570], in which b is a side and a an end view. A corresponding female template being shown at d to be used in planing the table V’s.
The length c of the V of the template must not be longer than from 4 to 6 inches, or it will be liable to spring or twist from its own weight. This template is not intended to be used in any sense as a straight-edge to test the truth of the length of the ways, but rather as one to test their width apart, and the correctness of the angles. The top surface a b should be quite true with the V’s, being equidistant from them, so that by testing that surface with a spirit-level it may be known whether the ways are level either crosswise or lengthwise.
The V’s of the template require to have red marking on them so as to mark the ways when the template is moved, and show that the ways accurately fit to the template, which is highly important.
In planing the table or platen it is essential to bear in mind that the area to be planed on the V side is always small in comparison with that to be planed on the other or work-holding side of the table, and as the planing of this latter surface is sure to cause the casting to alter its form, it is necessary to plane it first, so that the alteration of form may occur before and not after the V’s have been planed.
In chucking the table to plane its work-holding surface, the packing pieces must be used as described for the bed, and the bolts placed as there described.
Both bed and table being planed they require to be fitted together (no matter how expertly the planing has been done) if a really first-class job is to be made of them. In doing this it is essential that the bed be supported at the same points as it will be when the machine is put to work, for in large or long casting the deflection or bending from its own weight is sufficient to have an important practical effect. The same fact will also apply to the table and even to the cross slide, even though the latter be heavily ribbed and but, say, 5 feet long.
If, therefore, the bed is to be supported by legs, its guideways or V’s should be fitted after the legs are attached. The bed must be carefully levelled so that the ways may stand horizontally true, which may be tested by placing the template a b in [Fig. 2570] in place and applying a spirit-level first across and then lengthwise of the upper surface of the template.