Drilling plexiglas/lexan

[DeltaRed]

I have a windscreen on my motorcycle('92 Yamaha Virago 535).It was new last year when I bought the bike. It is plastic of some kind.Plexiglass/lexan? what if anything is the difference? Anyway,I need to raise it about 2". Drilling a pair of new bolt holes would be easiest. I have heard that that drilling such would cause cracking. Don't want to ruin it,just raise it 2" so the wind goes over my head,not hit me just about eye level. thanks,Steve. Didn't know I was 'biker trash',did you? LOL

 

[37 chief]

If you drill it, it will crack most of the time,if it's thin. I have had good luck by grinding the cutting edge off just a little. at the high point away from the center. so it doesn't grab. Do some practice drilling first. Stan

 

[Oliver 500 Wa]

You can buy drill bits that are made for drilling acrylic which is the most common plastic used in motorcycle windscreens. They have a sharper point, but a 0 rake cutting edge. One can kind of mimic that by hand grinding a 0 rake cutting edge on a regular drill bit. Old timers call this "dubbing" the drill. Google for images of these type drills and you will see what you need to do.

 

[db4600]

I’ve used masonry bits with good success.

 

[MarkB_MI]

I had a 535 Virago for many years. It was fine for scooting around town, but not enough bike to take on Michigan freeways, where you need to run 85+ if you don't want to get run over. Replaced it with a Triumph Tiger 1050 about ten years ago. This has nothing to do with your question, but a cheap yet essential upgrade to the Virago is heavier springs up front. <a href="https://www.progressivesuspension.com/product/1465/fork-spring-kit">The springs I got from Progressive Suspension</a> made a huge difference in how the bike behaved.

Most aftermarket screens are acrylic (plexiglas), while OEM screens tend to be polycarbonate (lexan). Either can be drilled. You can buy <a href="https://aircraft-tool.com/shop/search.aspx?keyword=plastic+drill">drills intended for plastic</a>, or you can <a href="http://acrylicsbydesign.blogspot.com/2010/10/how-to-modify-metal-working-drill-bit.html">resharpen a regular twist drill</a>.

 

[cannonball]

drilled a golf cart windshield yesterday just used a regular bit but used duck tape on both sides..

 

[showcrop]

Even two inches will put more leverage from the force of the air against it which will stress the new holes more than the original holes were stressed. Could you increase a part of the mount instead of drilling holes?

 

[JF in MI]

You are correct. Done it many times. 0 rake is the key.

 

[Stephen Newell]

If you drill a clean hole it should never crack. I would recommend using a brad point drill bit and clamp a piece of wood to the back side.

 

[Steve@Advance]

The windshield would almost have to be Lexan (polycarbonate) instead of Plexiglass (acrylic).

Polycarbonate drills and machines easily, it can even be run through a brake press! What it does not like is being squeezed down tight with a bolt, especially a flat head bolt. That will over time cause it to crack.

Acrylic though, very difficult to drill or cut. It will crack very easily.

It's advantage is it is more scratch resistant and shows less optical distortion. That said, the windshield could be a blend of the 2 materials. Here's what I found:

"Motorcycle windshields are made from either acrylic or polycarbonate, and each material offers its own advantages. Impact modified acrylic has a glasslike clarity, while polycarbonate windshields that have been hard coated have high impact and abrasion resistance."

So, what to do? As said, raising it will put more leverage on the existing material, plus having the old holes that close to the stress line might put it over the edge. I think I would either raise the mount or buy a new windshield.

What would the consequences of sudden failure at high speed be?

 

[4wdtom]

To drill plastic and other materials that tend to "grab" the drill and make it dig in too much you need to stone the cutting edge different than for metals. With a small stone stone the cutting edges parallel with the length of the drill so the cutting edge is in line with the length of the drill , not slanted back with the spiral. Another way of saying is the cutting edge needs to be perpendicular to the material to be drilled/cut so it scrapes more and doesn't "suck" in as when the edge is sharper. This will spoil the drill for normal use but will save it from digging in and possibly spoiling what you are working on. It doesn't take much to to change the way the drill cuts. Try and experiment if you can on some scrap.

 

[MarkB_MI]

> What would the consequences of sudden failure at high speed be?

None, if he's wearing a full-face helmet. But since he's relying on the windshield, he probably doesn't wear one. A 535 Virago tops out at about 85, so the chances of windshield failure from raising it are minimal. It's probably a universal windscreen that been tested at over 100 mph.

 

[jacksun65]

I've used a soldering iron and melt the hole needed before.

 

[Ellis Kinney]

Shouldn't have any trouble drilling Lexan. Had a lot donated to my school shop over the years. Use a lot of oil as the drill bit will melt the Lexan. Use a backup piece of something to keep from splitting out the back side of the plastic. Ellis

 

[Janicholson]

Use a regular sharp bit. Use a drill press, with a hold down of the plastic to prevent it from pulling into the bit, drill for one second, lift for 10 seconds make each hole take 2 minutes to create. No issues. I also recommend increasing the mount height as an alternative. Putting a piece of Lexan (real, not from menards, as an extension from the bottom would also reduce air flow through the new gap. Wear that helmet, I do. I like your brain and so does Susan. Jim

 

[jddrawbar]

Why would you assume he doesn't wear a helmet just because he has a windshield? I've ridden bikes for over 60 yrs. (long before the helmet laws) & would not set on a bike without a helmet....my choice. I think all my bikes had some sort of wind break....except for the dirt bikes. I had a 750 Virago....good little scooter.

 

[Goose]

I second the helmet.

I dumped a bike once and busted a helmet. When you look at a broken helmet it doesn't take long to put two and two together.

 

[dr sportster]

Two things I've heard Soldering iron -- melt the holes . Grind the drill bit flat on the end like a mill. That being said I mounted my drag bike fairing with a regular drill bit.

 

[Pete in Holland MI]

Drilling any plastic:

1) Sharp tools cut. Slightly dull tools create friction and melt plastic.

2) As the drill starts to break thru, it has a tendency to plunge thru the last bit of plastic, taking too big of bite and chipping or breaking the plastic. Hold it down. Drill with a drill press to control the break thru feed.

3) Keep your tools cool. Taking too long to drill a hole builds up heat in the tool, causing more melting of the plastic than cutting.

 

[Russ from MN]

Like others said, sharp drill, use a drill press, hold down the Plexiglas so it can't lift when the drill breaks through.

 

[37 chief]

It's a law in California to wear a helmet riding a motorcycle. Helmets cut down on the donor body parts. Stan

 

[MarkB_MI]

> Why would you assume he doesn't wear a helmet just because he has a windshield?

Yes, you can certainly have both. I do on my Triumph, but then I routinely make long trips in questionable weather. My assumption is based on Red's concern about the wind hitting him at eye level, which he might not notice with a full face helmet. That and the lack of a helmet law in Colorado. If my assumption is wrong, well I owe him an apology.

 

[MT pockets]

Mr. 4wdtom has the right answer here. I have drilled a couple hundred holes in half inch thick material. A sharp drill will grab. Dull that drill just like he said and you will be good. Steve, in the state that is getting a new flag design.

 

[Texasmark1]

Sheet metal drill and cooling water. Sheet metal drill has the center like other drills but between there and the circumference, the material is removed and at the outer edge is a protruding portion flat at the circumference and 45# angle (more or less) sloped back to the center, flat, recessed area.

The reasoning is that when cutting sheet metal and you break through the drill hangs up and tears the side of the hole, besides sometimes causing the bit to spin in the chuck.

The design of the SM drill is such that, other than the center section, needed to retain the location in the material, the outer diameter connects with the material first and is the first to clear the hole making for a clean cut. Obviously the water keeps the plastic from melting.