What is gear undercut?

Undercut – Gear Terminology

The undercut of gears is also called deeper cutting and indicates the phenomenon of cutting the root of the gear deeper than the involute

involute

In an involute gear, the profiles of the teeth are involutes of a circle. The involute of a circle is the spiraling curve traced by the end of an imaginary taut string unwinding itself from that stationary circle called the base circle, or (equivalently) a triangle wave projected on the circumference of a circle.

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Involute gear - Wikipedia

tooth curve. This can happen when there is interference between a tooth cutting tool and a gear or between the two meshing gears.

What is gear interference?

When two gears are in mesh it is possible that an involute portion of one will contact a non-involute portion of the other gear. This phenomenon is known as "interference" and occurs when the number of teeth on the smaller of the two meshing gears is less than a required minimum.

What is interference in gears and how it can be avoided?

Interference can be eliminated by under-cutting of tooth. A portion of teeth below the base circle is cut off. When teeth are produced by this process, the tip of one tooth of a gear will not contact the non-involute portion of the tooth of other gear, hence, elimination of interference.

What is gear tooth flank?

The Tooth Flank Fracture, TFF, is a failure mode observed in the surface-hardened of gear tooth flanks. There is a fatigue phenomenon which initiates from a subsurface crack that occurs in the transition zone between the hardened layer and the core structure of the tooth.

What is a back cut transmission?

“Undercutting”, or “back-cutting” is a process where these square shaped drive dogs and slots are cut at a small angle, so that when they are meshed together, the power applied to them actually forces them together and it's impossible for them to slip free while under load.

Explaining Undercut in Spur Gears

What is a cut transmission?

A straight-cut transmission is inherently more efficient than a helical gearing system. The axial load produced by helical gears only detracts from the output energy from the transmission along with an increase in friction and therefore losses of energy due to heat occur.

What is pitch point in gear?

Pitch Point. When a pair of gears are operating in mesh, the point of tangency between the two pitch circles is called the pitch point. Root Diameter (R.D.) is the diameter of a circle around the bottom (root) of the gear tooth spaces.

What is root clearance in gears?

The distance between the outside circle of a gear and the root circle of its mating gear (the gap) is called the root clearance. This distance (the gap) is also called the root clearance, top clearance, bottom clearance or simply the clearance.

What is pitch circle in gear?

Pitch circle: The circle, the radius of which is equal to the distance from the center of the gear to the pitch point. This is where the gear's speed is measured.

How do you prevent gears from undercutting?

To prevent undercutting without changing the number of teeth, a method called profile shifting is used. Profile shifting means changing the depth of the cutting tool and in the case of undercut, a positive profile shift is used. In this case, the root of the gear tooth becomes thicker.

What are the methods to avoid interference and undercutting?

How can we avoid interference?

What are the 4 types of gears?

What is law of gearing?

The law of gearing states that common normal must always pass through the pitch point at the point of contact between a pair of teeth and the angular velocity ratio of all gears must remain constant throughout the gear mesh.

What is root and backlash?

Backlash is a play between tooth surfaces of paired gears in mesh. Mating gears also have a clearance (play) vertical to tooth depth. This is called Tip and Root Clearance (c), the distance between tooth root and the tooth tip of mating gears.

How can I improve my backlash?

The simplest and most common way to reduce backlash in a pair of gears is to shorten the distance between their centers. This moves the gears into a tighter mesh with low or even zero clearance between teeth. It eliminates the effect of variations in center distance, tooth dimensions, and bearing eccentricities.

What is lead and profile?

The Lead Profile Test is used to monitor exposure to lead and aid in the diagnosis of lead poisoning. Lead and organic lead compounds are found in a number of industrial products including paints, plastics, storage batteries, bearing alloys, insecticides, and ceramics.

What is lead & profile in gear?

In spur gearing, gear profile is the most sensitive feature. In respect to effects on noise, lead has little to no effect. In helical gearing, lead is the most sensitive feature—with profile, it is second. This is due to the way each type of gear meshes (Figure 3).

What is a gear tooth called?

PITCH CYLINDER is the cylinder of diameter equal to the pitch circle. PINION is a machine part with gear teeth. When two gears run together, the one with the smaller number of teeth is called the pinion.

Can you daily drive straight cut gears?

While straight cut gears are a cost effective, high performance addition to your car, they are not without their disadvantages. Straight cut gears are somewhat limiting in that they do not have practical use for your everyday car. That is because they are extremely loud.

Can you shift without the clutch straight cut gears?

It's also important to keep in mind that although you can shift without using the clutch, there must be a momentary release of power to shift [because the dogs are back-cut so they'll stay engaged once you take your hand off the shifter] so you can either tap the clutch or lift off the gas a bit when shifting.