Question for mathmeticians - or engineers.

Garry Edwards

Garry Edwards

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An email from my son, I can't help him and would appreciate an answer from anyone who can...

I'm struggling to work out an angle. I need to make a sleeve to fit over a slightly tapered bar, the taper is very, very slight but it needs to be done correctly (I need to make the sleeve on a lathe).

At one end of the bar, the diameter is 14.65mm, the other end is 14.28mm. The distance between the two points (length of the bar) is 38.1mm.

I can't work out how to work out the angle, which I need to set the lathe
 
Pythagoras?

Actually, ignore me, that's for length, misunderstood the question....doh!
 
0.56 degrees

Tan of angle=Opposite over adjacent
Tan of angle= 0.37 over 38.1
Angle = 0.56 degrees
 
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Devide that by two. It is 0.2782º.

Edit:

(14.65-14.28)/2 = 0.185mm


Ɵ = tan^-1 x (0.185/38.1) = 0.2782º
 
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Ooops well spotted. Dave is absolutely right. Little rusty......
 
Many thanks gents - much appreciated.
 
Far cleverer folk than I here - I used a free Google program called Sketchup to produce a very quick and nasty measurement of 0.3 degrees - making Dave's answer spot on...


Skitch by Scgwhite, on Flickr
 
I almost had it with some extensive googling (I last did this over 18 years ago :p)....but you buggers beat me to it.... Im out :p
I even pulled out the calculator I used in my GCSE exams (yes I still have it and its on the same battery :D)
 
Marcel said:
I almost had it with some extensive googling (I last did this over 18 years ago :p)....but you buggers beat me to it.... Im out :p
I even pulled out the calculator I used in my GCSE exams (yes I still have it and its on the same battery :D)
Click to expand...

Well that makes me feel old :eek:. I last did this sort of thing 27 years ago and i was using a slide rule.
 
Spudgun said:
Well that makes me feel old :eek:. I last did this sort of thing 27 years ago and i was using a slide rule.
Click to expand...

I did my Maths O level in 1984, one paper was no calculator but log tables were allowed, the other paper a calculator was allowed. Not that the calculator was much help, it was only used for the final step to put the numbers in to the resulting expression after you'd done the actual mathematics.

I still have the same (Casio) calculator with the same battery.
 
No, I went to Greensward in Hockley.

I actually remember it better from....


So Old Harry
Caught A Herring
Trauling Off America

But people look at me weird if I use it our loud....... :nuts:
 
Come on then, SohCahToa?

I'm getting the Sine, Cosine and Tangent bit, but the others?
 
Sin = Opposite/Hypotenuse

Cos = Adjacent/Hypotenuse

Tan = Opposite/Adjacent

245px-TrigonometryTriangle.svg.png
 
I'll teach you something about trigonometry if you can teach me how to take a decent photo. :D
 
:LOL:
It's looks more complicated than it is because of the scruffy notation. Would look a lot cleaner if the forum had an equation editor built in, but there is hardly a call for that.

Otherwise, it's only GCSE level maths. Just not something which anyone would remember unless you use it reguarly, which I do.
 
I might be wrong but have all the answers so far not been assuming its a right angled triangle? My understanding of the post was that its a triangle with 2 equal sides (whatever thats called) and they would both have the same taper angle. BUT, as far as I remember soh cah toa can only be used for right angled triangles.

Can anyone clarify this/can the OP give more detail?

Might have to get my uni notes out soon lol (which is bad since it was only 2 years ago lol)
 
Yup, with it being a bar/sleeve, I assumed it was a right angled triangle too.
 
wealthysoup said:
I might be wrong but have all the answers so far not been assuming its a right angled triangle? My understanding of the post was that its a triangle with 2 equal sides (whatever thats called) and they would both have the same taper angle. BUT, as far as I remember soh cah toa can only be used for right angled triangles.

Can anyone clarify this/can the OP give more detail?

Might have to get my uni notes out soon lol (which is bad since it was only 2 years ago lol)
Click to expand...

The taper must be same on both sides, so it's part of an isoscleses triangle, which can then be split into two right angled triangles, which means the use of tangents etc is appropriate.
 
wealthysoup said:
I might be wrong but have all the answers so far not been assuming its a right angled triangle? My understanding of the post was that its a triangle with 2 equal sides (whatever thats called) and they would both have the same taper angle. BUT, as far as I remember soh cah toa can only be used for right angled triangles.

Can anyone clarify this/can the OP give more detail?

Might have to get my uni notes out soon lol (which is bad since it was only 2 years ago lol)
Click to expand...

No, I can't clarify anything, I'm just a photographer:)
The question was from my son to me, and as I'm too thick to know the answer I asked you lot...
 
Ah Mortimer that explains it, wasn't sure where yous were getting the division by 2 before. Thanks
 
I've still got my British Thornton sliderule from the 70s. And a set of log tables. When I was at college, sometime around 71 to 73, one of the instructors showed us the first electronic calculator that the college had just acquired. It was a bit smaller than a VCR tape, had a neon-like display, and did just the basic + - x ÷. It cost around £500 - a tidy sum in those days. Let's see - my brand new Honda CB250 bought around then was £375, and petrol was about 30p a gallon, or less.
 
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