This File is about nine or ten Inches long, and three or four Inches broad, and three quarters of an Inch thick: The two broad sides must be exactly flat and straight: And the one side is commonly cut with a Bastard-Cut, the other with a Fine or Smooth Cut. (See Numb. 1. Fol. 14, 15.) Its use is to Rub a piece of Steel, Iron, or Brass, &c. flat and straight upon, as shall be shewed hereafter.
In chusing it, you must see it be exactly Flat and Straight all its Length and Breadth: For if it in any part Belly out, or be Hollow inwards, what is Rubbed upon it will be Hollow, Rubbing on the Bellying part; and Bellying, Rubbing on the Hollow part. You must also see that it be very Hard; and therefore the thickest Using-Files are likeliest to prove best, because the thin commonly Warp in Hardning.
¶. 3. Of the Flat-Gage.
The Flat-Gage is described in Plate 10. at A. It is made of a flat piece of Box, or other Hard Wood. Its Length is three Inches and an half, its Breadth two Inches and an half, and its Thickness one Inch and an half. This is on the Flat, first made Square, but afterwards hath one of its Corners (as h) a little rounded off, that it may the easier comply with the Ball of the Hand. Out of one of its longest Sides, viz. that not rounded off, is Cut through the thickness of it an exact Square, whose one side b f, c g is about an Inch and three quarters long; and its other side b d, c e about half an Inch long. The Depth of these Sides and their Angle is exactly Square to the top and bottom of the upper and under Superficies of the Flat-Gage.
Its Use is to hold a Rod of Steel, or Body of a Mold, &c. exactly perpendicular to the Flat of the Using-File, that the end of it may rub upon the Using-File, and be Filed away exactly Square, and that to the Shank; as shall more at large be shewed in §. 2. ¶. 3.
¶. 4. Of the Sliding-Gage.
The Sliding-Gage is described in Plate 10. at Fig. B. It is a Tool commonly used by Mathematical Instrument-Makers, and I have found it of great use in Letter-Cutting, and making of Molds, &c. a a the Beam, b the Tooth, c c the Sliding Socket, d d d d the Shoulder of the Socket.
Its Use is to measure and set off Distances between the Sholder and the Tooth, and to mark it off from the end, or else from the edge of your Work.
I always use two or three of these Gages, that I need not remove the Sholder when it is set to a Distance which I may have after-use for; as shall in Working be shewed more fully.