Hi ChipIf you are going to do this multiple times its worth making a jig
Bill's one is very versatile and will do whatever you want, repeatedly, for as many jobs as you can think of.
If you are only going to use it 5-10 times then maybe this jig is easier and quicker to make, if not so long-lasting.
I'm assuming that you want to make 2 cuts in the elbow so it is symetrical when you rejoin the cut bits
Technically this jig is a sub-table on the saw, a piece of 8"x8"x3/4" panelboard (MDF, plywood etc) (needs to be stiff to work well) positioned so it fits between the fully retracted guides.
The table sits on top of the jaws?with a 3 to 4" wide and long by 1"thick cleat fixed to the bottom so you can grab it in the vice.?I hot-melt glued the 2 together.?Play a heatgun over the pieces you want to hot-melt glue before pressing together to get a nice thin strong glueline. (takes longer to set, but its minimal in the overall scheme of things)
Then you hot-melt glue a fence to align the fitting at the correct half-angle and a stops at the end and behind to suit where you want to cut through the fitting, so the fitting always positions in the same place. Should be able to line it up by eye looking down over the sawblade as in pic below. Angle iron makes a good fence that's easy to clamp to but any scrap of wood will do.If you fix the cleat, so the back of the sub-table is parallel to the vice jaws then you can lay out the half angle on the table itself with a protractor then glue the fence over the line??
You'll need to shim under the non-flared part of the fitting so it sits flat. Shim under all of the fitting so the shim gets cut in 2 when making the cut.
With a 1/2" fitting being so small, you'll need to use a thin clamp to clamp it to the fence - toolmakers clamp is ideal but long-nose or large vicegrips maybe would do.??Might have to fit a plug into the end of the fitting if is squashes too much when clamping up?(For a shape you can't clamp easily, just use the hot-melt glue! but its way slower to change over).
To cut the other side of the joint just flip the offcut over and reclamp it in the jig.??
Because the sub-table sits up on top of the vice jaws the blade cuts through the workpiece at quite an angle.? This mean you can cut part-way into the sub-table and get support for the cut on both sides of the blade, which means it doesn't need much clamping force.
Fine tooth blade and hold it up in the cut, since you're cutting thin sticky material.
Rgds - jv
