How to cut thick rubber ?
 

I am thinking about making some landscaping borders using a product called " ECO BORDER" this is a thick heavy rubber product made from old tires, cross-section 3" 1/2 , I got a piece and tried cutting it on a chop saw, as expected it melted the rubber and gummed up the blade quickly, hand saw coarse blade? Sawzall coarse blade , no set , low speed?,, looking to make miters, TIA

Possibly an electric kitchen knife? Or maybe just a very hot/heated sharp knife?

I would try a sawzall, multipurpose blade (wood and metal), low speed and use water from a portable hand sprayer as lubricant. I had the same problem cutting some Plexiglas (material melting), and the water solved the problem. You may want to have a helper spraying the water.

EcoBorder Installation Instructions
Notice - These products are 99.9% steel free. Wear gloves when installing.
Positioning
Carry pieces to the install location by draping them evenly over your arms, with arms extended out in front of you. It's best to install dry EcoBorder products on dry ground. Position the product high on ground that may settle. Simply rake some soil underneath to position pieces higher in the bed. Installations are easiest when you let our products guide you in forming the curves around your
beds. Place the pieces down just inside the edge of the bed flush with the lawn and then connect
them using the provided connector rods. Slide the pieces forward or backward just slightly to close the gaps so that they match the channels over the top of each piece.

Staking and plugging holes
Once in position, stake the pieces down starting with the holes next to the connections. Then come back and use the remaining stakes to hold down the areas in between. More stakes will be used on the curves and less on the straight runs. Please note that the stake holes are tilted toward the front of the edging to maximize the holding power. If using a hammer with a large head or if it is difficult to finish the stake you can use a second stake or a tap in the dimple to finish the stake firmly into place. Use the provided plugs if wish to hide the stake holes. Push the shallow part of the plug in and towards the front of the edging, then push the rest of the plug down into place.

Turns
Please note that the EcoBorder can bend up to 90 degrees. Do not over-bend the product; let it guide you in making natural, gradual curves around your beds. When making sharp curves the product will naturally tilt forward. This is by design, let the product bank the curves for a dynamic effect in your landscape.

Cutting
If a cut is needed, cut with a handsaw, hacksaw, or electric saw. Use a miter box for a more accurate cut. If using an electric saw, give the blade a light spray of lubricant to aid in the cutting. If the connector holes need to be deepened or adjusted, drill with a 3/16" bit. The connector rods are 3" long so the end hole in each piece is 1.5" deep. Drilling templates for the end holes are available on our website. Square corners may be miter cut just like moulding; with a 45 degree cut at the end of each piece.
For more info, please visit our website at EcoBorder and/or simply email us

i put down a rubber floor and used a small curcular disc hand saw
similar to link i pasted .. cutting is slow but did a nice job.. make sure you know the thickness of rubber needed to be cut before buying anything
20V 3-3/8" WORXSAW Compact Circular Saw - WX523L.9 | WORX

Try a hack saw.

Landscaper here... 40+ years. Sounds like you are trying to make a material do more than what it is designed to do. But with that in mind, you can purchase or make a wood miter box to hold the product and saw at the angle you want. Then a slow speed sawzall. Probably will go through a few blades. Try coarse and fine to see what works best. Just search wood miter box on Amazon.

The Ginsu knife can do it all!

If you live in TV make sure that you get ARC approval