Design Of Circular Form Tool When Diameter Is Given

DESIGN OF FORM TOOL Graphical Method when Tool diameter is given

1′, 2′and 3′

1′, 2′and 3′

1. The profile of the work piece is, first, drawn. 2. Next, the basic points of the profile on axis 1-1 are projected, drawing them perpendicular to the work piece axis. The 1′, 2′and 3′ projected points are 3. From point O2 as the center, circles corresponding to i.e .radii r1 , r2 and r3 are described. 4. After assigning definite angles γ and α and the outside diameter of the tool, determine the location of the centre O2 of the circular form tool. It is on line II-II which is drawn a distance, Ht = R1 x sin α above the center of the work piece.

Material

Hardness (BHN)

Rake angle (Deg.) (γ )

Mild steel

Up to 150

25

Hard steel

235.290

Soft cast iron

Up to 150

15

Hard cast iron

150-200

12

Aluminium, copper

-

20 - 25

Bronze, leaded brass

-

0-5

12 - 20

The relief angle (α ) depends upon the type of form tool. On circular form tools it is 100 to 120 and on flat form tools it varies from 120 to 150.

Centre O2 is found by setting a compass to the outside radius R1 of the form tool and drawing an arc from point 1 which is the intersection of horizontal axis I-I with the circle of radius r1. Point O2, the intersection of line II-II with the arc drawn from point 1, is the center of the circular form tool.

Draw a perpendicular from O2 to the line drawn at an angle  =200. This perpendicular line will be O2M.

Next, draw line aM along the tool face. For this purpose, draw a line from point 1 at an angle γ to line I-I.

The perpendicular distance from o2M is called as “H” and is calculated by formula H= R1 Sin 

1.

By connecting points 1, 2 and 3 (points of intersection of the line representing the tool face with the corresponding circles of radii r1, r2 and r3) with center O2 of the form tool, obtain the corresponding radii R1, R2 and R3 of the form tool.

Show the angles 

0 0 0 32 ,  37 and  =47 1= 2= 3

Next, to construct the tool profile in a radial cross-section, it is necessary to draw radial line N/N and to lay off dimensions to the right on a line perpendicular to line NN (in the case when the axis of the work piece and circular tool are parallel to each other). The dimensions are equal to the corresponding axial dimensions of the work piece.

From the end point of the axial dimensions, lay off dimensions P2 and P3 in a direction parallel to line NN. Dimensions P2 and P3 are equal to the differences between the corresponding radii of the form tool ( R1- R2 and R1 – R3, respectively). On the intersections of the lines corresponding to dimensions P2 and P3 with the lines determining dimensions , obtain points 2” and 3”.By connection points 1” , 2” and 3” by straight lines, one obtains the profile of the form tool in a radial cross-section.

Connecting points 1,2,3, etc. with centre O1 of the work piece we have series of right angle triangles 1aO1, 2aO1, 3aO1etc.

Show A1,A2 AND A3 which are distances between point “a” and point 1,2 and 3 respectively.

Show dimensions C2,C3, B1,B2 and B3 as well as ht