LumberJocks

I have no idea how to get these angles correct

  • Advertise with us

« back to Designing Woodworking Projects forum

Forum topic by RickSanchez posted 10-29-2020 11:51 PM 613 views 2 times favorited 10 replies Add to Favorites Watch
View RickSanchez's profile

RickSanchez

11 posts in 105 days


10-29-2020 11:51 PM

Topic tags/keywords: joining angles roofing

Hi Knowers of All Knowledge,

I’m trying to create a pyramid roof for a small japanese bell (don’t ask) and I’m having a problem with angles. I’m tilting my miter saw over to 20* because I want the pitch to be about 5/12. When I make my angled cuts however they always are off. I’ve attached photos. How do you figure this out???

-- Zak, AZ


10 replies so far

View Loren's profile (online now)

Loren

10782 posts in 4559 days


#1 posted 10-29-2020 11:56 PM

These are fun trig problems, but there’s a chart somewhere on the internet or drawing it in Sketchup will give you the exact angles.

This sort of tool may help you out too. http://www.pdxtex.com/canoe/compound.htm

View wildwoodbybrianjohns's profile

wildwoodbybrianjohns

2208 posts in 459 days


#2 posted 10-30-2020 12:03 AM

Use Pyramid angle calculator. Google that. You just put in base length of one side, plus height, plus number of sides, and it will do the magic trigonometry for you. In Inches or Metric.

I am currently working on box with a pyramid top, came out perfect.

If you want precision though, you should use a tablesaw and jigs. I can post some photos of what jigs I used, tomorrow, if you want.

For example, for my project:

-- Wildwood by Brian Johns: The Big Bang: Nothing - exploded into Everything. Thanks to Nothing.

View RickSanchez's profile

RickSanchez

11 posts in 105 days


#3 posted 10-30-2020 12:29 AM

Thanks, WildWoods.

I think I’m getting lost in the terminology. I have no idea what the face angle is etc. I’m new to miter joints.

-- Zak, AZ

View wildwoodbybrianjohns's profile

wildwoodbybrianjohns

2208 posts in 459 days


#4 posted 10-30-2020 01:06 AM

the only one that is really important is:

Triangle segment edge bevel angle.

In your attempt you used 20º for the bevel.

Face angle is Slope, base to top.

-- Wildwood by Brian Johns: The Big Bang: Nothing - exploded into Everything. Thanks to Nothing.

View RickSanchez's profile

RickSanchez

11 posts in 105 days


#5 posted 10-30-2020 02:20 AM

So in my case it says the base should be 6” and the angle you mentioned should be 14°. What should the bottom half of the miter saw be set at? 45?

-- Zak, AZ

View LeeRoyMan's profile

LeeRoyMan

1443 posts in 638 days


#6 posted 10-30-2020 03:04 AM

Use this calculator (Rectangular Pyramid)
http://jansson.us/jcompound.html

Compare the angles given in the charts to my drawing and you will understand which angles to use where so that you can enter whatever sizes you want next time.

View therealSteveN's profile

therealSteveN

6619 posts in 1485 days


#7 posted 10-30-2020 03:36 AM

I remember a time before computers, sometimes it wasn’t pretty.

Killer link, thanks for posting it LeeRoy.

-- Think safe, be safe

View wildwoodbybrianjohns's profile

wildwoodbybrianjohns

2208 posts in 459 days


#8 posted 10-30-2020 07:57 AM

Not 45º

It will be the angle of the triangle segment, relative to base. So, from the example I posted, the angle will be 50.2º.


So in my case it says the base should be 6” and the angle you mentioned should be 14°. What should the bottom half of the miter saw be set at? 45?

- RickSanchez


-- Wildwood by Brian Johns: The Big Bang: Nothing - exploded into Everything. Thanks to Nothing.

View them700project's profile

them700project

272 posts in 1930 days


#9 posted 10-30-2020 12:09 PM

keeping things simple couldnt you cut it like crown molding?

View Sylvain's profile

Sylvain

1107 posts in 3411 days


#10 posted 10-31-2020 09:17 AM

If you don’t like trigonometry, try descriptive geometry. ;-)
I will give you everything graphically. Then you transfer the angle with your sliding bevel.

-- Sylvain, Brussels, Belgium, Europe - The more I learn, the more there is to learn

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com