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Calculate taper ratio??
McLannahan - 19/2/08 at 12:39 PM

Afternoon all - Asking this on behalf of someone else, so please excuse my ignorance but...

How do you calculate taper ratio?

I've "Googled" it and not come up with much!!

Thanks all

[Edited on 19/2/08 by McLannahan]


mcerd1 - 19/2/08 at 12:49 PM

What info have you got ?

and what form do you want the answer in ?


McLannahan - 19/2/08 at 12:53 PM

Thanks Mcerd - I'll check and post back!


McLannahan - 19/2/08 at 12:56 PM

Not that this means much to me but....

"It's a taper reamer that's 117mm long and 27mm thick at top. 10mm thick at the bottom"

and to add...

The form - I'd like to know whether it was a 1in8 or a 1in6 etc.. Dimensions may be slightly out!


Does that help?

Many thanks!

[Edited on 19/2/08 by McLannahan]


smart51 - 19/2/08 at 01:01 PM

the difference in radius is 8.5 over a length of 117mm. Thats 1 in 13.76 or 4.155° per side, 8.31° included angle or 1 in 6.88 (both sides)

Edit to say that ball joint tapers are usually 1 in 6 ( or 2" per foot) 1 in 8 (1.5" per foot) or an included angle like 10°.

[Edited on 19-2-2008 by smart51]


McLannahan - 19/2/08 at 01:05 PM

Thanks Smart, I'll pass that on!

How is it actually worked out?


02GF74 - 19/2/08 at 01:44 PM

one number subtracted from antother, then divided by another.

e.g.
major radius minus minor radius divided by distance between them.


McLannahan - 19/2/08 at 01:52 PM

Thanks 02GF74 - That makes sense!


mcerd1 - 19/2/08 at 01:53 PM



A = (D2 - D1)/2

ratio = A / B (or A in B )



in this case:

(27-10) /2 = 8.5

ratio = 8.5 in 117

divide both sides by 8.5 = 1 in 13.76

for the angle between the tapper and the central axis you've got a right angle triangle with:

the side opposite the angle 8.5
and the side adjacent to the angle is 117

so angle = Tan-1 (8.5 / 117) = 4.15°

and the included angle (ie from one side of the tapper to the other) is twice that = 8.31°

[edit]
damm, too slow...

[Edited on 19/2/08 by mcerd1]


McLannahan - 19/2/08 at 01:55 PM

Fantastic - Thanks guys!


mcerd1 - 19/2/08 at 02:13 PM

those sizes could be imperial

at a guess:
10mm = 3/8"
27mm = 1 1/16"
117mm = 4 5/8"

giving 11/32 in 4 5/8

=> 1 in 13 7/16 or 1 in 13.45

=> 4.25° = 8.5° included angle

[Edited on 19/2/08 by mcerd1]


McLannahan - 19/2/08 at 02:28 PM

The plot thickens!

I'll double check!


mcerd1 - 19/2/08 at 03:20 PM

the difference between 8.31° and 8.5° is only due to rounding errors from imperial to metric

and my figures are only a guess, (using your metric measurements to guess at a likely imperial size)
but it does appear to give a half sensable answer - but I could round them another way and get 8° or 9°

the only way to be sure is measure it accuratly (imperial or metric - doesn't matter)


DarrenW - 19/2/08 at 03:23 PM

Ive checked the Zeus book and it doesnt fit a std Morse Taper.


McLannahan - 19/2/08 at 03:33 PM

Thanks so much for all your help guys!

I wish I could begin to understand it!

It's a good thing I've never built a KC...It'd probably resemble a trebuchet!