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Cutting and drilling plexi

R

rgmwa

Well Known Member
I'm just installing the RV-12 landing light in the wing and needed to trim the plexi to fit the cutout and also drill some holes in it. Not having done it before I read Section 5 which says do NOT use a saw of any kind to cut plexi. Another builder loaned me a copy of his HomebuilderHELP wing building video, and that had the same warning - don't use a band saw.

So I carefully tried a Dremel with both a diamond and normal cutting disk. The result was a pretty ragged looking cut, so off to the the EAA website to see what videos they had on the subject. The only one I could find was a Sonex canopy being trimmed on a bandsaw without any problems. :confused:

I have a band saw with a 1/4" 14 tpi blade and decided to try to trim some of the excess off the lens. Found it makes a very fine, smooth cut and I can easily and consistently shave fine slices off. Problem apparently solved!

Next step is drilling holes. I have a #40 and a #27 plexi bit. The #27 has a sharply pointed tip and cuts a neat hole. The #40 has a blunt tip and pitted surface and drills a ragged looking hole. However, I need a #30 hole, so I blunted a bit by drilling into concrete and tried it on some scrap, but it also made a ragged, untidy hole. Then decided to try a normal #30 bit (another no-no) at slow speed. Result - a row of neat holes.

So far, I seem to be getting much better results by breaking all the rules. OK, it's summer over here and pleasantly warm, but what am I doing wrong? :confused:
 
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rgmwa said:
So far, I seem to be getting much better results by breaking all the rules. OK, it's summer over here and pleasantly warm, but what am I doing wrong? :confused:
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As long as you're getting good results be a maverick! Break all the rules!:D

Actually I think your success is likely to be tied to the warm temperatures. When I did my canopy and other plexi work it was in the winter time up here, so I just threw some extra wood in the stove, took off my shirt, and had at it. Despite all the dire warnings on the forum all went perfectly.

Enjoy the summer, while we suffer in the snow!
 
John

Thanks. Guess the old saying about rules must be true. :) Seems to be working for me so far anyway. And it's another sunny day tomorrow, so I'm off flying and then visiting another RV-12 builder to see what progress she's making with her empenage kit. Should be a good day!
 
rgmwa said:
Thanks. Guess the old saying about rules must be true. :) Seems to be working for me so far anyway. And it's another sunny day tomorrow, so I'm off flying and then visiting another RV-12 builder to see what progress she's making with her empenage kit. Should be a good day!
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A woman building an airplane...good for her! I've always been surprised there aren't more women homebuilders in the U.S. They do everything else as well or better than men and they are certainly more fun to hang out with!
 
A band saw is OK - I've seen professional shops band sawing glider canopies, just holding the canopy by hand with no table on the band saw.

The secret is to ensure that the plexi is angled downwards so the saw teeth don't "catch".

As long as the blade is smoothly going through the plexi it's probably the quickest cutting method. No rules broken...:)
 
Has anyone tried installing the bandsaw blade backwards for cutting plastic? Have not tried it myself.
Joe Gores
 
Mich48041 said:
Has anyone tried installing the bandsaw blade backwards for cutting plastic? Have not tried it myself.
Joe Gores
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I don't think this would be possible on my bandsaw without cutting then rewelding the blade, lest the teeth ride on the backup bearings.
 
Take a close look at a plexi bit. All of them I have seen have the very leading (cutting) edge ground back just a bit, parallel with the length. I have ground a couple bits that way using a Dremel cut-off wheel. They worked fine, and made clean holes. Use an old, dull bit in the proper size and save yourself a buck or two. Paint a stripe on them, so you can recognize them in the pile...

Bob
 
Peterk said:
A woman building an airplane...good for her! I've always been surprised there aren't more women homebuilders in the U.S. They do everything else as well or better than men and they are certainly more fun to hang out with!
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Agreed, and this is her second plane. She (with some help) has also built an RV6!
 
rgmwa said:
Agreed, and this is her second plane. She (with some help) has also built an RV6!
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Hi Robert, Does Shirley have a builders site we can follow? I am keen to show my Wife!! Re :-Breaking the rules with plexi, I did too! I practiced on an old 737 window and found that an unmodified drill broke the back out of the hole when I jammed it in hard, (sort of like a shattered countersink!), but was able to make repeated nice smooth holes if I took it nice and easy. Then made a #30 Plexi drill and found that it didn't seem to break the back out as badly, but was slightly easier to make neat holes. Keep up the building... Talk soon, Marcus.
 
Woman builder

Hi gentlemen. Apologies for the thread drift, but thanks for the encouragement :)

Sorry Marcus, I do not yet have a site but I could put my Kitlog online if you think it would be of interest to others.

Regards
Shirley
 
Part of our product line includes manufacturing aircraft canopies and various other windows, light covers etc. We routinely use a band saw to cut acrylic without any problem.
Take your time, use a moderately fine tooth blade (no big chunky wood blades!) and keep the acrylic flat down against the bed when cutting to prevent any adverse vibration. Larger items may need an extra pair of hands for better control. Edges can be fine trimmed using a hand held disc sander, with final finish sanding done by hand to remove any cutting marks.
As mentioned in an earlier post, holes are best drilled with a modified drill bit or a step drill. You can 'usually' get away with a standard drill for small holes (say #8 or smaller) but not recommended. Anything bigger than that without regrinding the cutting edges of the drill bit is risking an expensive crack and much bad language.
You warmer temperatures at this time of the year would definitely help.

Clive Whittfield
Auckland NZ
RV6 electrics
 
Thanks all

Thanks everybody for all the helpful information. Good to know that the right way is not always the only way.

O/T
Hi Shirley. Great to see you here. Looking forward to you showing all these guys how to build an RV-12 :)
Robert
 
landing light lens cut with bandsaw

I used my bandsaw to trim the landing light lens with no problems at all.
I rounded the corners and smoothed the edges with my oscillating drum sander.
 
redrv6 said:
Hi gentlemen. Apologies for the thread drift, but thanks for the encouragement :)

Sorry Marcus, I do not yet have a site but I could put my Kitlog online if you think it would be of interest to others.

Regards
Shirley
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Shirley
I would be very interested in being able to see your Kitlog to help me in my build.
John
Melbourne
Australia
 
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