Diagrams-Tooth bearing of spiral bevel gears

The following sketches represent diagrammatically the possible tooth bearing on the gear member of a pair of correctly made spiral bevel gears. The sketches in one column show the opposite side of the tooth shown in the corresponding sketch in the other column.

CONCAVE SIDE	TOOTH BEARINGS ON DRIVEN GEAR	CONVEX SIDE
	Correct tooth bearing position with accurate and rigid mounting
	Out of position bearing Cause:    Pinion too close to cone centre.        Remedy: Move pinion away from cone centre
	Out of position bearing Cause:    Pinion too far from cone centre.        Remedy: Move pinion toward cone centre
	Cross bearing Cause:    Shafts do not intersect Remedy: Line up shafts
	Cross bearing Cause:    Shafts do not intersect Remedy: Line up shafts
	Toe bearing Cause:    Shaft angle too large   Remedy: Correct the shaft angle
	Heel bearing Cause:    Shaft angle too small   Remedy: Correct the shaft angle

Figure 10. Tooth bearing chart

If the amount of backlash is unsatisfactory after a suitable bearing has been obtained, it will be necessary to correct the position of the gear member. In the case of 2 : 1 ratios and higher, the gear member may be moved axially for backlash with very little change in the tooth bearing. However, in the case of miters and low ratios up to 2 : 1, movement of the gear alone will affect the tooth bearing slightly. This can be compensated for by axial adjustment of the pinion in the opposite direction to that of the gear, the relative movement of the two being in proportion to the number of teeth.

Figure 11. Ideal tooth bearing (non-localized) for Straight bevel gears.	Figure 12. Out of position
Figure 13 Incorrect shaft position	Figure 14  Incorrect shaft angle

Gears on center	Pinion up 0.020"
Pinion in 0.020"	Pinion down 0.010"
Pinion out 0.20"	Gear out 0.020"

Figure 15. Effect of relative displacements on Tooth bearing on large spiral bevel gears. These gears were cut on a spiral gear bevel planing generator and the teeth have a lengthwise curvature of approximately 100 inches radius.