Hey everyone justing wondering who has cut a Lexan polycarbonate shield and with what and how? I'm thinking of cutting my National Cycle Switch Blade. I know many of you have done this so why try something that might not work when someone has made it work. THANKS ahead of time.

 

I have only done one shield, but it turned out great. I taped off both sides of the shield with the really good blue 3M masking tape. I then used a protractor to make the lines to cut on. I put a new sharpie in the protractor and set it about 2"s from point to point, hold the steel point against the top edge of the windshield and trace it along the edge. You should now have a line 2 inches lower than the top edge. You will have to play with the ends to get a curve that looks right. I used a dinner plate to make a nice radius that matched the original. I then put a fine toothed blade in my jig saw and taped up the base of the saw with the blue tape also. GO SLOW and follow the line EXACTLY, HEAT IS YOUR ENEMY, it will make the lexan glob up. When I was finished, I took all the tape off and used a very fine toothed file and gently shaped the rough cut edge. You can put a small amount of acetone on a rag (just damp it) and gently rub this across the cut edge it will "melt" the saw lines and should look like the rest of the uncut edge of the shield. YOU MUST BE EXTREMELY CAREFUL WITH THE ACETONE, IT WILL RUIN THE SHIELD IF YOU GET IT ANYWHERE BUT THE CUT EDGE................ Hope this helps, Brian

 

When I replaced my airplane windshield I used a saber saw to make the basic cut about a quarter inch outside of where I wanted the cut. Then I used a belt sander to get it down to the line. I rounded the edges to give the edges a little extra strenght. Go slow and use a slow speed. Try not to generate a lot of heat. When you drill holes, use a special bit for plastics or it will crack and split.

 

If you've access to a router, use that.

 

I have cut my MOCO shield twice. The first time i trimed the top off 2 inchs and then I cut the headlamp opening after adding a "08" Fat-Bob headlight. I also used blue tape on both sides and used a fine tooth blade in a jig saw. Go slow and leave 1/16 for finish sanding. Use 100 grit on a sanding block to remove the saw marks and get down to the excact line. Finish up with finer grits untill you end up with a perfect edge that matches the OE. Its just that easy ! I prefer using fine grit paper instead on acetone.

 

Good video.
http://www.youtube.com/watch?v=hQj05Db-C3c

 

Emphasizing again, heat is your enemy. Assuming you already know how and what to tape up with 3M painter's tape for protection from surface scratching from the machining....

Use a saw blade with fairly large tooth spacing, approx. 24-32/in. Keep saw blade speed steady but slow. Don't force the blade. It will immediately heat up and start melting the plastic, producing a nasty looking edge finish and cease cutting. Watch your blade position at all times. Cut 1/2 - 3/4" at a time until you get familiar and comfortable with what you're doing.

Keep the saw blade perpendicular to the shield surface at all times. (Remember you're cutting a compound contoured surface.) The jig saw should remain in contact with the shield on both sides of the blade at all times. Try to cut as parallel to your cut line as possible, (I try to stay within 1/16" oversize to allow for finish shaping / sanding with a block), which allows sufficient cleanup of the edge for a professional looking finish.

Using a sanding block, start with 80 grit, progress to 120 until you're satisfied with the new cut contour, (ie; you've achieved the desired shape and a beveled, champhered or radiused edge), and the saw marks have begun to all but completely disappear.

Begin finish sanding with wet / dry grits, (sanding wet with a sanding block to keep the edge square), starting with 400, 200, etc. progressing out to 1500 - 2000 to smooth the edge to a hazed finish that is approaching a clear appearance.

Finish by buffing the edge with Meguire's plastic polish using a blue sponge bonnet moistened with water and spinning between 750 -1000 rpm's. This will produce a finished edge that is transparent and is as clear as the rest of the shield.

With patience you can easily produce professional quality results. Take your time, plan the step by step process and stick to it. I've done several shields confidently only because I've used similiar materials and this basic process I've described to fab custom gauge clusters for show cars and high end performance boat dashes.

It's not as difficult as it seems, however planning the job out and sticking to the process plan is key. It helps to have a helper's extra set of hands, adequate work space and the extra set of eyes to observe what's going on in order to achieve the best possible results.

Remember, patience is key. Each cut you make will make you more and more aware of what the saw and material will tolerate. Remember just 1 "Oh shiit" can trash the whole shield. Take your time. You'll be glad you did.

Good luck! Enjoy your new "DIY" windshield.

V1

 

thanks for the info---i make alot of the oh **** comments -lol
but sounds like a good project on an old scratched shield to make it usable again