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Help - Miter Cuts of unknown angle

5.7K views 15 replies 9 participants last post by  RobDubs  
#1 · (Edited by Moderator)
Hi - I need help making miter cuts where the angle is unknown and changing. I'm making the front of a train to put in my son's room: I'm making the front cattle guard of it and I'm having a hell of a time cutting the slats!! It's angled in two directions/axis'. Does anyone have any tips to help me - I'm pulling my hair out trying to get this right. I got three of them on there but now the angles are getting steeper and I'm not doing so well. Any tips or tricks would be greatly appreciated! I have a table saw and a compound miter chop saw. I'm willing to but whatever tools needed to finish this project up fast! My son is so excited and I can't turn back now! Thanks for your help!

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#3 ·
Put a piece of scrap next to the line/string thing under the blue tape, draw the line and that should be your angle.

You can scribe the top and bottom angles as well on the scrap.

Easy peasy, take your time you got this fords2613 and a belated welcome to Lumberjocks!

You can bandsaw or jigsaw close to the line and then sand or hand plane to it if I understand
the situation correctly.
 
#4 ·
Do you have one of these?
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Hold a board on the outside of your top and bottom, (where your string is) and use the angle finder.The board will give you a flat surface to use the angle finder. Place it against the board and adjust it to be flat with your top piece. Use the angle to mark the piece you are going to cut. Now do the same at the bottom. measure the length that you need from top to bottom and transfer your angles onto the board your cutting.
 

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#7 · (Edited by Moderator)
This is akin to a thorny problem I have encountered
in fitting backs to chairs. I conceived an elaborate
set of jigs for my problem.

I think how I would approach it (if I decided not
to just go back to the drawing board and use
Sketchup or something to know the angles) would
be to make a simple jig in a 3/4" square piece
of wood that I would clamp or screw to the
front of the cow catcher in the position where
I wanted to measure the angles. Then I would
tape, clamp, or screw a scrap block to each end
inside the frame, scribe the sides of the scrap
blocks and very carefully use the miter saw to
cut them off so they fit. Then it's a matter of
using the same miter saw settings to cut the
actual part on both ends.
 
#8 ·
I still think you could just lay a long piece of wood right on top of that string and directly scribe the angle on it. Then cut it on a band saw right to your scribe lines. Or, you could get a good hand saw and cut them by hand if you don't have a band saw.

Brian
 
#10 ·
...sort of.

Another way to do it is just eyeball the angles
and cut a scrap piece for a wedge fit, then
scribe say 1/2" up on each end and then
the scrap is a pattern piece that is 1" short.

The middle 3 bars on the cow-catcher are
the easy ones I think because they aren't
compound angles on the ends. From the
middle 3 out he wants to fan them out and
that makes a compound angle. The maddening
thing about cutting compound angles is
the angles affect each other. There's no doubt
a way to work out the trig if you're real
smart with math or have a lot of time, but
as a practical matter in woodworking the general
approach I've described can work. If the
material is costly, use whatever amount of
cheap wood is required to figure it out.
 
#11 ·
...sort of.

Another way to do it is just eyeball the angles
and cut a scrap piece for a wedge fit, then
scribe say 1/2" up on each end and then
the scrap is a pattern piece that is 1" short.

The middle 3 bars on the cow-catcher are
the easy ones I think because they aren t
compound angles on the ends. From the
middle 3 out he wants to fan them out and
that makes a compound angle. The maddening
thing about cutting compound angles is
the angles affect each other. There s no doubt
a way to work out the trig if you re real
smart with math or have a lot of time, but
as a practical matter in woodworking the general
approach I ve described can work. If the
material is costly, use whatever amount of
cheap wood is required to figure it out.

- Loren
I didn't realize they were angled as well, but just as easy to mark the edges of the board you are going to cut during the same process and set the angle to the lines you mark when you make the cuts.
 
#12 ·
yeah, you're right. duh.

Assuming the planes at the ends are parallel
one should be able to position the workpiece
at the edge and from that position mark
the angles on 3 sides of each end.

It can still be tricky to set a miter saw to cut
these marked angles but once marked
accurately I find I can eyeball parallel off
the end of the workpiece. You have to
fiddle with both the miter and bevel settings
at the same time but your eye can gauge
pretty well an end out-of-parallel to the
the marked line.
 
#13 ·
ok - I put in some hours last night working on it and here is what I did: using scrap, I used my table saw to get the top angle guts; first I set the blade angle, then the miter sled. Once I got the top angle set up so the board rested against the string, I moved onto the bottom cut using the chop saw. once I got the bottom to line up against the string, i then got a real piece of wood and used the two different saws for the two cuts.
 
#15 ·
Do you have one of these?
Image


Hold a board on the outside of your top and bottom, (where your string is) and use the angle finder.The board will give you a flat surface to use the angle finder. Place it against the board and adjust it to be flat with your top piece. Use the angle to mark the piece you are going to cut. Now do the same at the bottom. measure the length that you need from top to bottom and transfer your angles onto the board your cutting.

- jbay
That is what I was going to suggest also or even a digital one. You just take it right to the table saw and match the angle from there. They are called bevel gauges and here are a few links for you.

http://www.grizzly.com/products/Ebony-Sliding-Bevel/T10263?utm_campaign=zPage&utm_source=grizzly.com

http://www.grizzly.com/products/Digital-Angle-Finder/H8258?utm_campaign=zPage&utm_source=grizzly.com
 

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#16 ·
Do you have one of these?
Image


Hold a board on the outside of your top and bottom, (where your string is) and use the angle finder.The board will give you a flat surface to use the angle finder. Place it against the board and adjust it to be flat with your top piece. Use the angle to mark the piece you are going to cut. Now do the same at the bottom. measure the length that you need from top to bottom and transfer your angles onto the board your cutting.

- jbay
This with a marking knife and a handsaw.
 

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