What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Reamer for canopy/rear window

LettersFromFlyoverCountry

Well Known Member
Was all set to start drilling the rear window on the RV12iS (even got my wife to actually come to the hangar to help) when I realized I need a #27 and #36 reamer (Van's does not recommend using plexi bits to enlarge a hole).

Does anyone have a source for these?

I miss Bob Avery.
 
Enlarging plexiglass holes

I have found that unibits are the best tool to enlarge holes in plexiglass. Also, it doesn’t hurt (and is probably a benefit) to make the holes a bit over sized to account for thermal expansion & contraction.

Consider going up to 5/32 for the #27 .
The next fraction up from a #36 is 7/64 and the smallest step drill I have is a 1/8th. I don’t think they make unibits smaller than 1/8.

What is the #36 used for?
 
I have found that unibits are the best tool to enlarge holes in plexiglass. Also, it doesn’t hurt (and is probably a benefit) to make the holes a bit over sized to account for thermal expansion & contraction.

Consider going up to 5/32 for the #27 .
The next fraction up from a #36 is 7/64 and the smallest step drill I have is a 1/8th. I don’t think they make unibits smaller than 1/8.

What is the #36 used for?

The #36:enlarges the #40 holes in the rollbar, which are then tapped in both the window and rollbar.
 
Later you will enlarge those holes in the plexiglass to provide clearance to the screws The tapping through step is to make sure you are nice and square with the roll bar when the screws go in.
Cheers DaveH
 
The manual says #27 if I remember correctly. I went slightly larger to allow for expansion. 5/32 I think, as that was the plexiglas drill provided in the Avery tool kit. There are a lot of holes, so it will align nicely, even if the holes are marginally larger than #27.
Cheers DaveH
 
I plan to use a 5/32" Unibit to enlarge the #30 holes on the sides and aft bow of the canopy (which will have 6-32 screws). But I read in an earlier thread that the holes in the front bow should NOT be enlarged to 5/32" since they will be countersunk for rivets and that will leave too little contact area for the CSK rivet heads. So I'm planning to enlarge those holes with a #27 reamer instead. I asked Van's tech support about it and they said the #27 reamer would be a good choice.

Question for anyone that has done it this way: did you use the #27 reamer directly in the #30 holes, or did you use an intermediate step such as a #29 reamer first? Technically #30 to #27 is too big a step for a reamer, but I thought maybe this would work fine in the softer acrylic material versus metal.
 
I ran a drill bit on concrete to dull it and used it to drill my holes. I learned that trick on a previous build when I didn’t have a plex bit. I enlarged the holes just enough for the screws to turn freely and tightened the nuts just short of not being able to rotate. I replaced my original back window after about 4 years due to crazing unrelated to the screw holes, and used the same method on my current window (molded plex) with no issues after 8 years. Just make sure the plex is warn when you drill it. I learned that the hard way on a previous build..
 
Bob,

You're making the right call. It's a little time consuming and costs a few bucks, but using a reamer to up-size the holes makes the job very easy. Based on fear of cracking the canopy, I used multiple reamers to get to the final size. Other than time, it was a very easy task.

Looks like out of all the responses, only thiggens answered your question.

I believe McMaster-Carr may also have what you need. Link below:

https://www.mcmaster.com/reamers/high-speed-steel-round-shank-reamers-10/

FYI - Used a straight fluted reamer.
 
Last edited:
Reamers

Reamers work very well on plexi. I bought a bunch to get to the final size for to canopy latch hole.
 
Back
Top