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Where to find #30 & #27 plexi-bits?

You can take a regular drill bit and run it on concrete to dull it before using on the plex. I used 9/64 bits from the local hardware store. It's a good idea to warm the plex if you're in a cold workshop.
 
You can take a regular drill bit and run it on concrete to dull it before using on the plex.

Before doing that realize that a plexiglass drill has a very sharp cutting edge. It also has a zero rake angle, which means that it doesn't cut , it scrapes. That's how a Unibit works, which is why Unibits work so well on acrylic.

Tony
 
UNIBITs are great on plexiglass and acrylics. As an added benefit, you can carefully use the next hole size step to lightly chamfer the edge of the hole. Find a piece of scrap material and practice a bit to gain confidence in the process. The UNIBIT doesn't have those fancy "numbered" drill bit sizes, so use the UNIBIT's closest next larger size hole (within reason, of course). A slightly larger diameter hole is preferable to too tight a hole when dealing with plastic expansion.
 
Step bit instead of Plexi bit

I ordered a step bit...uni-bit...from Grainger yesterday. Steps in 1/32 increments. As other builders have suggested, I want to make the hole 5/32...just slightly larger than the instructions call for.
 
Something I have had good results from is to use a battery powered drill with regular bits but use the drill at very low speed.


Glenn Wilkinson
 
Where to find #30 & #27 plexi-bits

I found fractional-inch sized plexi bits on our favorite RV tool suppliers' web sites but I haven't been able to find numbered size plexi bits, specifically #30 & #27 (for landing light lens).

Can anyone help me out here? Thanks.
 
Many builders don't obsess about the exact drill size. If you are drilling into plastic (plexi or Lexan), a slightly larger drill size is preferable to better deal with potential plastic expansion/cracking. I used my UNI-BIT drill for most of the holes in plastic - it worked great. YMMV
 
I use the dull drill bit instead. Run a cheap bit on concrete for 5 to 10 seconds so there are no sharp edges to grab the plex. Make sure the plex is warm to reduce the chance of cracking.
 
Plexi Bits

I've used the dulled in concrete method, it worked well. Otherwise, McMaster/Carr has plexi bits.
 
I've used the dulled in concrete method, it worked well. Otherwise, McMaster/Carr has plexi bits.
Ditto modified bits. But practice on some scrap to get the feel. Not too tricky, but it only takes one crack...
 
I'm splitting the difference: I ordered the #27 from McMaster-Carr so I don't crack or chip the lens, and I'll dull a used-up #30 on concrete as suggested.
Thank you all for your replies.

Kevin
 
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