Outer Limits 4x4 Board

does any one know if i can get my current rear window cut to miss my roll bar or do i need to get a perspex one

you may get it cut ring a windscreen place that specialises in hot rods etc.I'm unsure as the are hardened glass.
you can definitely get one made in glass and they are usually not that expensive (couple hundred).

forgot to mention its slightly curved

slightly curved with holes drilled in it?

it isn't difficult to back-yard cut holes in glass but it does take extreme patience and a steady hand. if you want to cut round holes you need a piece of soft pipe (copper is perfect) the diameter of the hole, you need to solder (rivet/screw/bolt etc) it to a mandrel that will fit in the chuck of a low RPM drill (cordless in low gear is perfect). it needs to be fairly well centered. set up a square or triangle of timber battens to guide the "holesaw" until it has started to cut a definite circle in the glass so it can be self guiding. coat the end of the pipe in an abrasive paste (valve grinding paste works, there are probably alternatives if you're creative, maybe some fine blasting media in a grease/oil paste). work slowly - heat is the enemy and glass does not conduct heat away from the cut very well, so if you build up a localised hot spot it will crack. it will take an hour or more for a 2 inch hole.

enjoy

I was always taught that a toughened rear screen will shatter when you try to drill/cut or even chip it.

If the rear screen is laminated (and I've never seen or heard of one) you could cut/drill it.

dumbdunce wrote:it isn't difficult to back-yard cut holes in glass but it does take extreme patience and a steady hand. if you want to cut round holes you need a piece of soft pipe (copper is perfect) the diameter of the hole, you need to solder (rivet/screw/bolt etc) it to a mandrel that will fit in the chuck of a low RPM drill (cordless in low gear is perfect). it needs to be fairly well centered. set up a square or triangle of timber battens to guide the "holesaw" until it has started to cut a definite circle in the glass so it can be self guiding. coat the end of the pipe in an abrasive paste (valve grinding paste works, there are probably alternatives if you're creative, maybe some fine blasting media in a grease/oil paste). work slowly - heat is the enemy and glass does not conduct heat away from the cut very well, so if you build up a localised hot spot it will crack. it will take an hour or more for a 2 inch hole.

enjoy

Or you could buy a diamond holesaw for $20 and do it in under 2 minutes.
I cut holes in glass every second day (fish tanks) have never tried toughened glass though. Might give it a shot tomorrow just to see if it can be done.

Curved WILL be toughenend. Good luck cutting or processing any toughened glass.

want33s wrote: Or you could buy a diamond holesaw for $20 and do it in under 2 minutes.
I cut holes in glass every second day (fish tanks) have never tried toughened glass though. Might give it a shot tomorrow just to see if it can be done.

I've tried diamond holesaws a couple of times and have always had the glass crack, maybe I was just doing it wrong - do you go wet or dry?

TOUGHENED GLASS

This is a true Safety Glass to BS 6206. It begins as ordinary annealed glass, is cut to the exact finished size, uniformly heated to 700+ °C then cooled rapidly by blowing air on both sides. The outer surfaces cool faster than the core, and permanent stresses are built up. After toughening, the glass can have up to 5 times its original strength. Toughened glass breaks into small blunt fragments, reducing the risk of serious injury. Typically when broken the whole pane crazes and falls out in pieces. Toughened glass products cannot be cut, drilled or shaped - all such work must be completed before toughening is carried out. Toughened glass can be identified by its edge bevels introduced during preparation to avoid localised stress cracking, characteristic "leopard spots" seen in certain lighting conditions, and a manufacturer's stamp in the corner stating its BS 6206 grade. Various scientific identification techniques use polarised and ultra-violet light sources, or a laboratory Differential Surface Refractometer can compare optical distortions between the "fringes" occurring during toughening. Toughened Glass usually falls out of its frame when broken, and fragments can cause injury and shock if falling from some height. Additional containment is therefore needed in (for example) roofing installations. Toughened Glass is subject to spontaneous fracture, sometimes by the gradual expansion of a Nickel Sulphide inclusion, or perhaps by minor damage of an edge. Thermal movements of frames, or near-invisible accidental damage during installation, can lead to such sudden failures. Improvements in manufacturing processes, particularly the technique of Heat Soaking (Heat Soaked Toughened Glass) have meant that Nickel Sulphide inclusions have been less common in recent years, however the problem is not eradicated and must still be considered a significant risk.

Go wet. Lots of it.
But you still wont cut it if its toughened.

dumbdunce wrote:

want33s wrote: Or you could buy a diamond holesaw for $20 and do it in under 2 minutes.
I cut holes in glass every second day (fish tanks) have never tried toughened glass though. Might give it a shot tomorrow just to see if it can be done.

I've tried diamond holesaws a couple of times and have always had the glass crack, maybe I was just doing it wrong - do you go wet or dry?

I use silicone spray to start with, lots of it, and then water once cut is at least 1/3 of the way through.
Secret is keeping the holesaw square to glass and not using too much pressure. Weight of the drill is usually enough.
Can usually do a 40mm hole through 8mm glass in 40 seconds or less.
Jas.