Bevel Gear Blank (2D Drawing) Method

Below we use a pair of Gleason spiral bevel gear parameters as an example to introduce the general steps for drawing a bevel gear blank.

The method described in this chapter applies to three types of bevel gear blanks: uniform clearance taper, non-uniform clearance taper, and duplex taper.

Let us look at the gear parameters needed for drawing:

For the first example, we will draw the blank of the pinion (small bevel gear).

Step 1: Locate the outer (large) end position of the bevel gear.

It is recommended to use the pitch diameter and pitch cone angle to determine this position.

The pinion's outer pitch diameter is 26, and the pitch cone angle is 20.92 degrees.

The intersection of these two lines is the outer end position. The outer end face is perpendicular to the pitch cone, so draw a line through this intersection perpendicular to the pitch cone to find the outer end face.

Step 2: Addendum and dedendum at the outer end.

The pinion's outer addendum is 2.22 and the outer dedendum is 1.56. The addendum is the distance from the tooth tip to the pitch cone at the outer end. The dedendum is the distance from the pitch cone to the tooth root at the outer end. By measuring the corresponding lengths, we can locate the tip circle and root circle positions at the outer end.

Step 3: Construct the face cone.

Here we need the face cone angle.

The face cone of a bevel gear must pass through the tooth tip at the outer end, so we already have one vertex of the face cone.

We know the face cone angle, so we can directly draw a line. This line is the face cone of the bevel gear.

Note: Only in the non-uniform clearance taper system does the face cone apex coincide with the pitch cone apex. For the other two systems, the face cone apex and pitch cone apex do not coincide. Therefore, you cannot simply connect the outer tip point to the pitch cone apex as the face cone.

Step 4: Construct the root cone.

Using the same method as for the face cone, draw a line from the root cone point.

Note: In the duplex taper system, the root cone apex does not coincide with the pitch cone apex. For consistency, it is recommended to always use the root cone angle and the outer root point as the basis for drawing the root cone. It is not recommended to simply connect the pitch cone apex with the outer root point.

Step 5: Draw the inner (small) end.

The inner end is parallel to the outer end. The distance between the inner and outer ends equals the theoretical face width. So as long as we know the theoretical face width, we can draw the inner end.

After trimming the line segments, we obtain the standard tooth profile of the bevel gear.

Mirror along the centerline to complete the standard tooth profile of the bevel gear.

We often see bevel gear structures like the one below. How are these dimensions determined?

Inner end treatment: Material is typically removed from the inner end. During bevel gear meshing, the contact pattern tends to shift toward the outer end, making the inner end less critical. Therefore, some material at the inner end can be removed.

Generally, we choose a rounded integer value between the inner pitch circle and inner root circle to trim away part of the inner end material.

In this example, I chose 24 mm from the origin as the plane for the bevel gear inner end.

After trimming, the inner end structure looks like this:

The outer end treatment differs from the inner end — the general principle is to add material. Regardless of the final structure, we want the outer end to be fully represented in the bevel gear structure.

Here the outer end face is also a flat surface, so we make a rounded surface slightly larger than the root point.

The outer cylindrical surface radius was chosen as 15.5, and the outer end face distance from the origin was set to 35 mm.

After trimming, the blank structure becomes:

In summary, the key point for processing the gear blank is: remove material at the inner end, and generally preserve the outer end completely.

Presented by ETAGEAR

5/17/2018 7:29:44 PM