The following requirements are of greatest importance in twist-drill grinding: (1) equal and correctly sized drill-point angles, (2) equal-length cutting lips, (3) correct clearance behind the cutting lips, and (4) correct chisel-edge angle. Figure 5-22 shows the results of correct lip grinding and how equal drill point angles and two equal length cutting lips help achieve correct drill results. Y20 Hand-held Rock DrillModel Y20 Hand-held Rock Drill is intended for drilling downward and inclined blast holes in medium hard and herd rock (f=8~18):┬ĚThe rock drill is mainly used small quarries. Y19A is mainly used for drilling work in small quarries, coal mine, limestone mine, rock blast in road construction work, as well as water conservancy construction project. Product Features Light in weight and small in size, lower air consumption, it can be used together with FT100A pusher, which is a lost cost alternative for multi-purpose drilling applications. 1931 — as above, but trademarks display Greenfield, rather than Millers Falls location.
The drill-point gage is being held against the body of the drill and has been brought down to where the graduated ed^e of the gage is in contact with one cutting edge.

This means that you look at the drill point and approximate the lip-clearance angle (see figs.
DIYTrade accepts no responsibility whatsoever in respect of such content.To report fraudulent or illegal content, please click here. By the latter 1960s, catalog copy had become so vague that a detailed description of features is not possible.
Rotatable cap on end handle provides access to eight drill points, each in its own compartment.
Speed change controlled by knurled ring shifter; two pinions and shifting device are enclosed. In this way, both the drill-point angle and the length of the cutting edge (or lip) are checked at the same time.
The incorporation of FY200B Line Oiler with transparent casing provides automatic lubrication during operation during operation.

While the company typically stressed new features in its catalogs, it seldom mentioned the disappearance of a feature or the addition of a feature that had become so commonly accepted that it was no longer noteworthy. The lip-clearance angle is not necessarily a definite angle, but must be within certain limits.
Whatever angle in the range is used, however, lip clearance should be the same for both cutting lips of the drill.

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