Thread: needing help from a draughtsman/math

A bit of help from the segmented turning world is needed.
After all, you are only making a bowl with straight sides

This site will give all the info you need.

Originally Posted by jchappo

A bit of help from the segmented turning world is needed.
After all, you are only making a bowl with straight sides

This site will give all the info you need.

Thanks for above link, however I do not have a lathe and equipment to cope with the segments internally (using those tables),
I want to build round a former and have smooth sides internally.

I have bookmarked the site and posted at the uk forum for turners which I am sure they will appreciate.

360°/16 segments = 22.5°

So the edge angle of every strip is half that, giving... 11.5°

Perimeter = Pi x Diameter, so 90 x Pi = 28.27cm all the way around. Divide that by 16 strips and each one needs to be 17.67mm at their widest point.

It's not rocket science.

Thanks Skew, you made that so simple, I had that lesson at scholl around 60 years ago and my brainbox has become cluttered since.

My next thought is that I will cut the top off along its longest length and loose that 3.2mm so I suppose I shall have to cut replacement lenths to maintain the line. I shall most probably put the tube on my small lathe that I use for pen turning.

Sorry jow, I wasn't having a dig at you with that last line.

I meant that my calculations aren't spot on: the 17.67mm is for the "arc length" per segment and not the width of the slats. But it gives you a ballpark figure that errs slightly on the side of "too wide." Which I reckon is way better than "too thin."

If you want the accurate figure, I'll have to find my calculator. I remember the formula to use, but don't have the head for plugging numbers into 'em any more.

Busy at the moment, but zenwood gave a thread on this subject a fair while ago. Search......zenwood...coopering........ that may do it. Accurate as all get out.

January last year!

Thanks

https://www.woodworkforums.com/showth...wood+coopering

Correct, except half of 22.5 is 11.25 degrees, if you can measure that close. Similar for width (to accuracy of 0.05mm?!!!)

Measure three times, cut twice, sand to fit.

Cheers,
Joe

Jow
here's a pair of templates, designed for printing on A4 paper



ian
I needed the practice

Thanks all.

I have decided to try and build the coopered box inside a former.



A cardboard whisky bottle holder in card, so it should peel away from the timber strips which will be laid and glued internally.

The inside diameter is 87mm (that was a bit of luck) which should total about 273.1 mm circumference, 16 segments would be 17.07 width but 14 segments would be easier 19.5.

angles would be 16 = 11.25
or 14 = 12.85

So will start a new thread over at boxmaking shortly.

Originally Posted by ian

Jow
here's a pair of templates, designed for printing on A4 paper



ian
I needed the practice

Thanks Ian, sorry about that, I was working on the thread whilst you were posting so the posts have crossed.

no worries

as I said, I need the practice.
would you like a second template?

also, I'd be very leery with working inside a former.
glueing and clamping would be much easier if you clamp from the outside.
I suggest building a former from 5mm ply or MDF



ian

Originally Posted by ian

no worries

as I said, I need the practice.
would you like a second template?

also, I'd be very leery with working inside a former.
glueing and clamping would be much easier if you clamp from the outside.
I suggest building a former from 5mm ply or MDF



ian

Thanks again Ian, a template would be an additional luxury.
I'm still inclined to build inside and will fit temp. bulkheads, also I have the idea that I might be able to stop at the three quarter level and then start again so creating a llid.

Its pis ing of rain and cold today outside and I have an appointment tomorrow so roll on saturday.

Is this what you are seaking?