Drilling acrylic

[FRY]

[FONT=Arial, Helvetica, sans-serif]Drilling holes in Plexiglass:[/FONT]
[FONT=Arial, Helvetica, sans-serif]The drilling of holes in Plexiglass seems to be the big bugaboo among many aircraft mechanics. The principal difficulty lies in that drills as sharpened for steel are used, it is near impossible to drill a hole in Plexiglass without cracking using a drill that has been sharpened for drilling steel and especially so if the hole is much larger than 3/16 diameter. Drill sharpening for Plexiglass is relatively simple, in general take the drill as sharpened for steel and just grind off or dull the cutting edge. The object is to sharpen the drill so that it scrapes its way through the plastic. Sharpen your drill as shown below, try it out on some scrape plastic first.[/FONT]
[FONT=Arial, Helvetica, sans-serif]Dubbed-off to zero rake[/FONT]

[FONT=Arial, Helvetica, sans-serif] [/FONT][FONT=Arial, Helvetica, sans-serif] Slow Spiral-Polished Flutes [/FONT]

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[FONT=Arial, Helvetica, sans-serif]Cross-section of drill used in drilling steel. This will not work for drilling Plexiglass, due to the fact that it digs in, causing cracks.[/FONT]​

[FONT=Arial, Helvetica, sans-serif]Cross-section of drill sharpened for Plexiglass. The Drill does not dig, but scrapes it's way through the Plexiglass[/FONT]

 

[loismustdie]

Hmmm, I use spade bits all the time and never had a problem. Built a DIY sump, calcium reactor, carbon reactor, drip trays and I actually prefer them. Last week I drilled 14 holes in 1/2" thick acrylic with a 9/16" spade bit. No chips, no cracks. As far as the other one you are talking about, I use a Bosch hole saw set that I got from HD. Grinded the tip of the pilot bit, kind of what is shown above and no problems. No need to go from both sides.
Along with my own DIY projects, I also drilled Mike's sump (slamajama) and some one there said it couldn't be done with the bits I used. Let's just say that some were impressed with how clean the holes were drilled.

 

[LeslieS]

Thanks to everyone for their advise. I just wanted to let you know that it was put to good use. I drilled 2 holes in my sump and created a ledge for my skimmer to stand on.

It took me all afternoon, and I am covered in acrylic shavings...by the end, I was getting much bettter

 

[FRY]

very good leslies what did you end up useing to make the hole any pic.

 

[LeslieS]

I tried to tak a pic, but the return is in the way so you cannot really see it. I bought 3 dif types of bits, and ended up going with the hole saws.

Here's what my project was.

Because an eco system has a permanent cover over the intake area and a big ledge around the pump area, my skimmer (remember I have the deltec HOB) was returning to the refug and stirring up my miracle mud.

Because of my cabinet limitations, my only option was to drill a hole in the side of the intake area. I would have rather had my skimmed water being pumped back to the tank, but this is still better than the miracle mess that I had going.

I had a few problems. For example, the hole saw was painted orange and some of the paint melted into the acrylic so now I have a few little orange flakes Anyway, it doesn't look as professional as most of you guys's work, but it functions really well

Thanks again for all of the advise!