How to mitre different size stock

[Powermyster]

Any tips for cutting 40x40 box and 40x20 to make 90 degree angle

 

[London Wrought Iron]

This is tricky.
Try cutting the 40x40 at 22.5 degrees and the 40x20 at 67.5.
I could be totally wrong tho

 

[hotrodder]

I cheated and drew it (too late for maths)

 

[London Wrought Iron]

AAh yea, thats what I ment

 

[piman]

Hello Powermyster,

simply clamp one on top of the other (at 90 degrees or whatever angle you desire) and carefully scribe a line at the junction, then scribe the diagonal.

Alec

 

[Hitch]

Just mark the cut on the material, and eye it through on the saw blade....
Proabably the easiest way.

You may have trouble getting some saws round far enough to cut the 40mm wide mitre on the 20mm though...

 

[Powermyster]

Hello Powermyster,

simply clamp one on top of the other (at 90 degrees or whatever angle you desire) and carefully scribe a line at the junction, then scribe the diagonal.

Alec

I did think of trying to cut through both at once while clamped. But never thought of just marking them while clamped

 

[Powermyster]

I cheated and drew it (too late for maths)

What's the angle on 40x20?

 

[Seano]

Just one of those little questions that you don't really think about....

 

[wheresmejumper]

what's the angle on 40x20?

 

[hotrodder]

I know this won't help but i can't resist... the angle i labelled is for the 40x20 when measuring things the way most saw mitre gauges work (90* = 0) The way i drew it doesn't help picture things
It's the same reasoning behind protractors having two scales like this (actually a set square since that does 0 - 90 while protractors do 0 - 180)

as the angle depends which direction you measure from. Probably explained much better, definately in more depth here http://its.foxvalleytech.com/MachShop1/Inspection/AngleMeas.htm Note in the above pic the corresponding numbers always add upto 90. You want a 90 degree joint, 90 - 63 = 27

As said you'll probably struggle to set a typical saw to cut the 40 x 20 as many don't have enough movement/big enough tables to set the fence and still be able to clamp the work for this sort of cut. If you've got a lot to cut then clamping fixtures can be made (common examples include exhaust merge collectors... http://www.mig-welding.co.uk/forum/showthread.php?t=39832&highlight=merge+collector). If you only need a few then layout the cut on the 40 x 20 as described/with a square and ruler or cut the 40 x 40 in the saw and layout 40 x 20 using that

 

[graffian]

What's the angle on 40x20?

 

[bigegg]

Why measure?
Lay one over the top of the other, mark the edges of each, then draw the cutting line - basically draw what is on the piece of paper above - on each piece of steel

 

[Powermyster]

Thanks for the help guys. Just another case of me over thinking an analysing simple things.