Dai_The_Eye
Member
Been asked to make a letterbox for a wedding. Constructed a ½ hex body fine but in a complete mess getting the 3 triangles to work for the roof. Can anyone help getting the angles right, pleeese!
Victorian letterbox roof... Aargh!
- Thread starter Dai_The_Eye
- Start date
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What i understand you're trying to make a hexagonal pyramide. It's a 3D structure, can't understand which angles you are asking. I haven't dealt with geometry for a long time, but check the calculations below. Try on a paper first, hope didnt make a miscalculation.
a is the side lenght of base, h is the height of side wall. ( not height of roof top from the center of base). Drawing shows the hexagonal pyramid in open form, side walls torn down.
a is the side lenght of base, h is the height of side wall. ( not height of roof top from the center of base). Drawing shows the hexagonal pyramid in open form, side walls torn down.
Alexam
Bandsaw Boxmaker
Will this help? https://www.google.co.uk/search?espv=2& ... B495%3B613
or anything here http://www.mathk8.nelson.com/math5/pdf/ ... s-CH07.pdf
or anything here http://www.mathk8.nelson.com/math5/pdf/ ... s-CH07.pdf
Dai_The_Eye
Member
Thanks guys for your input, I've added a scan to clarify the problem. If it was cutting just the triangles that would be fine. Its the pesky gaps and mitres thats beating me. Doing it in paper was easy when the material thickness was irrelevant. Any other ways you can think of to create similar?
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Biliphuster
Established Member
Possible problem, you have listed the diagonal as 48cm, but the sides as 23cm. For a regular hexagon the diagonal must be twice the side length.
Assuming a side length of 23cm, this is how I would do it
Mark off 23 baseline, find halfway (11.5) and draw a line 23.2 long. Join either end of the baseline to the end of this line. This should give you a triangle 23 across the bottom with 2 equal sides of 25.8.
Take this triangle and mitre the bottom edge to 31 degrees instead of 45 (preserve the full 23.2 length of the triangle on the exterior surface). When stood on this mitred surface the triangle should now extend 19.9 (from the exterior surface) towards the centre of the hexagon and raise 12cm above the base plane. So that is the bottom mitre sorted.
Next, set a sliding bevel to 60 degrees and place the blade on the surface you have just created, with the stock registering against the exterior surface of the triangle baseline. Slide the bevel along until you reach the corner and mark off the 60 degrees. Plane down to this line, again preserving the exterior surface. This provides the required mitre for the triangles to both meet at the base and all along the long sides.
Assuming a side length of 23cm, this is how I would do it
Mark off 23 baseline, find halfway (11.5) and draw a line 23.2 long. Join either end of the baseline to the end of this line. This should give you a triangle 23 across the bottom with 2 equal sides of 25.8.
Take this triangle and mitre the bottom edge to 31 degrees instead of 45 (preserve the full 23.2 length of the triangle on the exterior surface). When stood on this mitred surface the triangle should now extend 19.9 (from the exterior surface) towards the centre of the hexagon and raise 12cm above the base plane. So that is the bottom mitre sorted.
Next, set a sliding bevel to 60 degrees and place the blade on the surface you have just created, with the stock registering against the exterior surface of the triangle baseline. Slide the bevel along until you reach the corner and mark off the 60 degrees. Plane down to this line, again preserving the exterior surface. This provides the required mitre for the triangles to both meet at the base and all along the long sides.
this link might help you I used it when I built a dovecote/bird nest box
http://jansson.us/jcompound.html
http://jansson.us/jcompound.html
As Biliphuster said for a perfect hexagone radius should be 2 x edge so 46cm. Long edges of traingle has 60 degree miter. Tricky point, miter angle at the base of triangle. Try the 3 steps below, hope no miscalculations made. A shooting board + hand plane would be nice for tight fit but making a shooting board could take more time. I think I'd use track saw for cuts, a litte big for mitre saw, awkward for table saw.
Note: for 31 degree reference outer face of wood. Depending on setup, you might have to adjust your saw either 31 or 59 degree.
Note: for 31 degree reference outer face of wood. Depending on setup, you might have to adjust your saw either 31 or 59 degree.
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It is quite complicated isn't it?
Does it really need to be made of wood? If you can make a template from cardboard, it would transfer easily to a piece of aluminium which you could then make the two folds in, before painting.
Or, seeing that it's presumably a short life item, a bit like a stage prop, just spray paint the cardboard?
Does it really need to be made of wood? If you can make a template from cardboard, it would transfer easily to a piece of aluminium which you could then make the two folds in, before painting.
Or, seeing that it's presumably a short life item, a bit like a stage prop, just spray paint the cardboard?
Baldhead
Established Member
David you may also find this thread helpfulcedarwood":1emfuigr said:
compound-mitre-angles-t77496.html?hilit=Jansson
Baldhead
Dai_The_Eye
Member
Thank you everyone for your suggestions, hopefully I won't be wasting any more sawdust! Cheers
