I’ve never drilled Lexan before. Searched this website and didn’t turn up an answer to my question.
I’m making a router base out of 5/16″ lexan and need to drill a 1-1/2 inch hole in it. What’s the best bit to use. It seems like a forstner bit wouldn’t work well. A hole saw? High or low speed?
Any input is appreciated.
Replies
It usually machines well so I would go with Fostner at the slowest speed setting the trick is to keep it from heating and melting the plastic.
I'd use a holesaw after predrilling the centerpoint. As Gulfstar says, try not to get melty. If the teeth clog you can let them cool and they'll clear pretty easily. Holesaws for tile have wide carbide teeth that will keep the body of the holesaw from heating up and grabbing in the slot.
Bilyo's comment below reminded me: stop the holesaw before you break through and flip the lexan, then finish the cut from the back side to avoid an "exit wound".
Either a forstner or hole saw will work. Of course, the hole saw is less expensive if you don't already have either one. As gulfstar said, go slow to avoid heat. The forstner will cut a bit cleaner, but may have a bit more tendency to grab the work piece. Best to have your work piece clamped down and use a drill press if you can with either type of cutter.
I've use a multi-spur bit (similar to a Forstner, but with teeth around the edge rather than just a sharp rim, and a bit more of a center point.) I have both types, and usually reach for the multi-spur unless the small center point is a problem.
You can use a router with a guide bushing and a spiral up cut bit. Make a template out of MDF with a hole drilled using a forstner bit taking into account guide bushing size and router bit size (guide bushing diameter - router bit diameter + desired hole size) = template hole. ex 1/2" guide bushing - 1/4" router bit + 1 1/2" hole = 1 3/4" hole in the template...
I have used this technique to create a router base that accepted guide bushing, by figuring out what combination of bushing, template hole, and two router bits... one router bit cuts a circular mortice and a smaller router bit to cut the through hole. since I just changed the bit without moving the template the smaller hole is centered inside the large mortice, creating a small step to accept the guide bushing. I don't remember the exact guide bushing size, router bits, template hole, speed of router, etc..
I also don't remember how bad the cut was with a router bit but it was a better result than a forstner bit and was more accurate in my application, and worked great with guide bushings. I did drill the mounting hole with forstner bit/ drill bit which gummed up and needed some clean up with a razor knife and sandpaper.
There are router bits specifically for cutting plastics, o-flute bits, but I have never used them...
https://www.whitesiderouterbits.com/collections/o-flute-spirals
Video describing the benefits of the o-flute bits with plastics:
https://www.youtube.com/watch?v=YOaKnH0jeZY
Do you have extra? Try a practice cut on a piece of scrap. Use a bit you already own.
A forstner bit is the only bit with that diameter. You'll need to run it very very slowly and with as little press pressure as possible or the plexiglass will chip and crack. You probably dont need a 1.5" hole for a hand held router base though?? The hole in the base only needs to be large enough to pass the bits shank through...and so a 3/4" hole is much less complicated, especially as there are such things as Plexi drill bits. Worth a few bucks, especially in just a few key sizes as they cut cleaning chip free edges. You can order them from WL Fuller in RI, or from McMaster car. A piloted countersink works great in conjunction too.
https://wlfuller.com/html/plexi-point.html
@mattk41, I would say in most cases the opening needs to be as wide or wider than the cutter's diameter. Besides a deep mortise I can't think of a common occasion using a handheld router to have the entire cutter projecting beyond the router's baseplate.
Personally, I would use a hole saw.
Using a forstener bit is simply making the drill work harder and heating up the lexan. Since you're cutting a through hole, there is no need for a forstener, if that's all you have fine.
A hole saw (from both sides) will be quick and easy.
Lexan works very differently from plexi in my experience, so if something works for plexi I wouldn’t assume it will also work for Lexan. It’s super tough, which means that a cutter that takes a big bite can grab the material. As noted by others, secure it well to the table. I would go with the hole saw as I think that the chippers on a forstner risk being really grabby.
I can offer only negative advice - avoid carbide forstner bits. They tend to catch, causing them to wander or even break off pieces.
Standard forstners cut plastic well but I've never drilled Lexan specifically.
Thank you one and all. I appreciate the inputs. I do have extra and was going to make a test cut. With what you’ve all provided I’ve sorted a plan. I hadn’t considered routing the hole and nor not making the hole so large. I won’t be running large bits with this base. Very helpful. I’ve both forstners and hole saws. It’ll be oue or the other. And slow. I’ll get back into the shop in a couple of days and see what works. Merry Christmas to one and all and may you and yours aphave a safe, happy and prosperous New Year.
Use lots of tape on both sides of the Lexan to prevent chipping. Slow speeds to reduce heat. A few shallow cuts are better than one deep cut.
Regards from Perth
Derek
Definitely use a hole saw, go slow, and spritz it with water frequently to keep everything cool. This works for me.
Warren
Hole saw at low speed is probably best and safest. For 5/16" it should go pretty easy. In thicker plastic you risk seizing the saw from friction. That said, using some water as a lubricant and coolant is still a good idea. If you are in snow country, packing some snow around the saw before you start the cut works well also. We would do that in the shop I worked at in college. Just make sure there isn't any sand or dirt in it.