Thread: Compound Angles on Butt Joints

http://home.att.net/~waterfront-wood...oundangles.htm

the above may help you Neil.
beejay1

http://community.webshots.com/user/eunos9

Cheers Beejay1 but iv already seen that link, to be honest it doesnt mean anything to me, sorry its probably me just being a bit thick. I will carry on looking on the internet today to see what we can see.Thanks again anyway,

Neil.

Originally Posted by NeilSheffield

Cheers Beejay1 but iv already seen that link, to be honest it doesnt mean anything to me, sorry its probably me just being a bit thick. I will carry on looking on the internet today to see what we can see.Thanks again anyway,

Neil.

try this link Neil.
http://www.cabinetmaking.co.uk/compoundangles.htm
good luck mate.
beejay1

http.community.webshots.com/user/eunos9

Originally Posted by NeilSheffield

Can anyone please give me the formula for calculating compound angles. I'v trawled the internet for days trying to find the answer or should i say trying to find the answer in simplified terms that i can understand.
Im a PatternMaker by trade so I should really know how to work them out but its been that long ago since doing this as an apprentice that iv completely forgotton and dont have any notes.


I am constructing a tapered box with each side angled back at 11.5 degrees and i need to know how many degrees to back off the Butt Joints to make for a perfect fit.

Many thanks in advance,

Neil.

With each side angled back at 11.5*, cant under stand what you mean, is it for the lid to sit on or is it for the bottom floor?
Might need a rough scetch to understand what you mean?
Ok I'll give it a try(may not be correct, prob not!)
Usually you work out by dividing the number of sides into 360* for equal sided construction, but for adding 90* butt joins...
To get a 180* 3 sided arched box lid using 11.5* angled on the sides, you got 2 X 11.5* = 23* - from 180* /2 = 78.5* each way from the centre 90* to cut on the lid for the top centre piece.
Is that what you mean?

Usually you work out by dividing the number of sides into 360* for equal sided construction, but for adding 90* butt joins...
To get a 180* 3 sided arched box lid using 11.5* angled on the sides, you got 2 X 11.5* = 23* - from 180* /2 = 78.5* each way from the centre 90* to cut on the lid for the top centre piece.

say wot!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

If you have a SCMS and if you are making a four sided box. I would set the tilt angle to 45° and the mitre angle to 11.5° and cut, and if it is more than a four sided box just work out the angle for the tillt degrees.

You do that by dividing 360 by the number of sides in the box and divide the result by 2 and that is the angle to set the tilt at.

If you have a one sided SCMS you will have to set the mitre angle to the opposite side and turn the timber around to cut the other side of the side, if all that makes any sense.

From one Patternmaker to another.

Thanks for the response guys but I feel like you dont quite understand my problem, Im hopefully gonna post a diagram so you can see exactly what I mean. Failing this leave me an E-mail address and i'll forward a sheet on to you personally explaining my problem.

Well iv just tried to add a diagram and failed so allow me to send you a diagram with explanations.

Thanks again, I'll get there in the end.

Hopefully.

Neil.

Originally Posted by arms

say wot!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Wotto!
Thats the way I've used for working out multi angled speaker boxes, works a treat(KIS).

This is the box in question that I require the formula for calculating the compound angles on the butt joints. As I said before the angles of all sides are 11.5 degrees.

Thanks Neil.

This is a more detailed diagram

Neil.

Hi Neil,
I think youre looking at basic geometry here so hopefully the attached will help you now,,http://www.gomath.com/geometry/triangle.php
beejay1

http://community.webshots.com/user/eunos9

I maybe wrong but I think if the sides of the box are parallel the sides of the ends would be square.

I think I have an answer that doesn't involve trigonometry but should work.
Firstly if you were to calculate the bevel you would need for the side if it was 90* it would be 0*. If you go to the other extreme and assume the "side" was at 0*, ie like the base or the lid, the bevel or "backoff" would be 11.5*. There should be a smooth transition between 11.5* and 0* "backoff" as the angle of the side changes from "0*" to 90* and therefore you should be able to calculate it as a percentage. OK?
ie, 11.5/90 x100 = 12.78%. Therefore the backoff for 11.5* should be 12.78% x 11.5* = 1.47*
Cheers
Michael

Cheers mate,

I did try that the other day it made a lot of sense but it actually doesnt work, the back off angle doesnt change uniformally. It does require some sort of trigonometry calculation based on the two adjoining angles. If only id taken more note when i was an apprentice.

The angle has been worked out to around 2.3 degrees on a 3D modelling package software, its just that id love to know the actual formula. It cant be much of a formula can it really?

Anyway back to the drawing board, I dont think were ever gonna get to the bottom of this baby.

Thanks Neil..