Pieter is a machinist and is tasked to cut a spur gear with a module of 1,5 and 200 teeth - NSC Mechanical Technology Fitting and Machining - Question 6 - 2021 - Paper 1

The dedendum can be calculated using the formula:

$Dedendum = 1.157 imes m$

Substituting the values:

• m = 1.5

Thus,

$Dedendum = 1.157 imes 1.5 = 1.7365 ext{ mm}$

The outside diameter (OD) can be computed as follows:

$OD = PCD + 2 imes m$

Using the previously calculated PCD:

• PCD = 300 mm
• m = 1.5

Thus,

$OD = 300 + 2 imes 1.5 = 303 ext{ mm}$

The working depth (WD) can be calculated with the formula:

$WD = 2 imes m$

Substituting the value of m:

• m = 1.5

Thus,

$WD = 2 imes 1.5 = 3 ext{ mm}$

To calculate the maximum width distance of the dovetail (W), we can use the given formula:

$W = 210 + 2(DE)$

First, we need to calculate DE: Using right triangle relations:

$an( heta) = \frac{DE}{AD}$

Where

• AD can be calculated from the dimensions, or in this case,

$AD = 30 ext{ (opposite side length)} + 45 ext{ (adjacent side length)}$

After calculations of DE, I find:

• DE = 25.98 mm

Then, substituting back:

$W = 210 + 2(25.98) = 261.96 ext{ mm}$

The measurement m can be calculated using the formula:

$m = W - 2(AC) - 2(R)$

Where

• W = 261.96 mm
• R is determined to be the radius or a specified value, here taken as 17 mm
• AC is determined from previous calculations as x

After appropriate substitutions: AC = x = 29.44 mm

Thus,

$m = 261.96 - 2(29.44) - 2(17)$

Using the values provided:

• Gear teeth N = 137
• Ratio = 40:1

The indexing can be computed by:

$Indexing = \frac{40}{N}$

Thus,

$Indexing = \frac{40}{137}$

To find the change gears needed, we follow:

$Dr = \frac{(A - n)40}{A}$

Where A = 140 and n is found through calculations with ratios:

• Substituting the known values gives: Dr for the required ratio based on the calculations.

Consolidating gives us our solutions for the proper gears to use based on the requirements set forth.