Tc 9-524 fundamentals of machine tools

7-36

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TC 9-524
The formula for calculating the tailstock offset when the
taper is given in taper inches per foot (tpf) is as follows
Offset = TPF x L
2 4
Where: Offset = tailstock offset (in inches)
TPF = taper (in inches per foot)
L = length of taper (in feet) measured along
the axis of the workpiece
For example, the amount of offset required to machine a bar
42 inches (3.5 feet) long with a taper of 1/2 inch per foot is
calculated as follows:
OFFSET = TPF x L
24
OFFSET = 1/2 X 42
24
OFFSET = 0.5 x 42
24
OFFSET = 21
24
OFFSET = 0.875 inch.
Therefore, the tailstock should be offset 0.875 inch to
machine the required taper. The formula for calculating the
tailstock offset when the taper is given in TPF is as follows:
OFFSET = TPI X L
2
Where OFFSET = tailstock offset
TPI 
= taper per inch
L 
= length of taper in inches
For example, the amount of offset required to machine a bar
42 inches long with a taper of 0.0416 TPI is calculated as
follows:
OFFSET = TPI X L
2
OFFSET = 0.0416 x 42
2
OFFSET = 1.7472 or rounded up 1.75
2
2
OFFSET = .875 inch
Therefore, the tailstock should be offset 0.875 inch to
machine the required taper.
If the workpiece has a short taper in any par of it’s length
and the TPI or TPF is not given. use the following formula:
OFFSET = L X (D-d)
2 X L1
Where :
D = Diameter of large end
d = Diameter of small end
L = Total length of workpiece in inches diameter
(in inches)