Making a 70° or 130° degree cut

[PeteHB]

I need to put a 70° cut on the edge of a 1.7M long 30mm Birch ply and as my table saw is limited to 50° I am struggling to think how to do it safely. It does need to be a uniform and flat edge and I am not relishing the idea of trying to do it with a plane.
Any suggestions.

 

[PerryGunn]

Tracksaw if you have one
If you don't have a tracksaw, use a circular saw with a sawboard
If you don't have a tracksaw or a circular saw... you should...

 

[Inspector]

Got the ceiling height to cut the plywood vertically?

Pete

 

[PeteHB]

Tracksaw if you have one
If you don't have a tracksaw, use a circular saw with a sawboard
If you don't have a tracksaw or a circular saw... you should...

Tracksaw has the same angle limitation 47° from memory so how?

 

[PeteHB]

Got the ceiling height to cut the plywood vertically?

Pete

Yes but how does that help.

 

[Doug71]

Yes but how does that help.

20 degrees vertically is 70 degrees horizontally.

 

[PeteHB]

Maybe I didn't explain very well. Consider a standard board it has an edge that is at 90° to the face I wish to make a cut at 70° ie a bevel.

 

[PeteHB]

20 degrees vertically is 70 degrees horizontally.

You have lost me.

 

[Doug71]

If you cut the board stood up on edge (vertical) you only need to set the angle of your blade to 20 degrees to get the equivalent of a 70 degree cut with the board laid flat.

 

[Inspector]

I am reluctant to explain any further but I will try. Firstly if you do not fully grasp the concept then maybe it isn't for you and you should set up a router sled.
You make a tall fence (a least a couple feet high) that you either clamp to the table or the fence. I place it so the blade tips into the fence so you can't over cut the bevel if the panel isn't perfectly flat. The waste will be trapped between the fence and blade so be aware it can shoot back out when the cut is done poking a hole in the wall behind you or your gut. Stand aside. Set up feather boards to hold the sheet against the fence and include a piece of wood between to keep the blade area covered. You can't use the saw's guard so you have to make one to protect yourself. Set up indeed and out feed tables to ensure you have control of the sheet and it feed smoothly. This is not a task for a lightweight contractor saw. Tilt the blade to 20º like Doug said. Make the cut and you have your bevel.

Pete

I'll add that you set your blade angle and with the saw running bring it up into the fence. Account for the blade when you set the distance of the fence to get the bevel. Don't try to tilt the running blade into the fence.

 

[Spectric]

How does that work, I have tried it with a sheet of paper and the cut angle remains the same. I am either missing something or losing the plot.

 

[Spectric]

Ok I get it, not the cut I thought but basically a bevelled edge so I can see the light!

Why not just run it through a router table using one of these from Wealdons, T1945 1/2 and you get a good clean edge.

 

[Inspector]

| | becomes |/ when the sheet is vertical and the blade is tilted.

Pete

 

[PeteHB]

I am reluctant to explain any further but I will try. Firstly if you do not fully grasp the concept then maybe it isn't for you and you should set up a router sled.
You make a tall fence (a least a couple feet high) that you either clamp to the table or the fence. I place it so the blade tips into the fence so you can't over cut the bevel if the panel isn't perfectly flat. The waste will be trapped between the fence and blade so be aware it can shoot back out when the cut is done poking a hole in the wall behind you or your gut. Stand aside. Set up feather boards to hold the sheet against the fence and include a piece of wood between to keep the blade area covered. You can't use the saw's guard so you have to make one to protect yourself. Set up indeed and out feed tables to ensure you have control of the sheet and it feed smoothly. This is not a task for a lightweight contractor saw. Tilt the blade to 20º like Doug said. Make the cut and you have your bevel.

Pete

I'll add that you set your blade angle and with the saw running bring it up into the fence. Account for the blade when you set the distance of the fence to get the bevel. Don't try to tilt the running blade into the fence.

Thanks I understand now.

 

[Fitzroy]

I think I may have happened to make the same cut for a bevel edge bench I’m working in on.

 

[Inspector]

That is pretty much what I had in mind except I prefer the blade tips in the fence. I know the waste is trapped but If for any reason the work comes away from the fence the thickness isn't affected. You can always take another pass to take off the thicker bits. Got a picture of the completed bench?

 

[Spectric]

A picture can certainly replace a 1000 words, but I think I still prefer the router for this.

 

[Sideways]

I would be tempted to mark a line along the face of the board showing where the 70 degrer bevel should come to, then take the first 50 degrees using your tablesaw with the wood horizontal, finally remove the remainder of the bevel with a hand plane.
The T,saw will do part of the work for you. Hand planing will give you control for the delicate part and let you sneak up on the line without the risk of error (mostly risk of damaging the piece) of keeping a tall / narrow (?) workpiece tight against the fence.

 

[jcassidy]

I think the safest way to do it is as described above (either with the tips in the fence or not). A bit of work to make a good steady fence. We had shop-made fences of various sizes to handle different jobs of exactly this nature.

 

[Stevekane]

Could he clamp extra timber to the side of the board he wants to cut and using this extra width do the cut along the edge of the sheet with a skillsaw and fence and have a tidy up with the plane afterwards?