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  #11  
Old 10-04-2009, 06:42 PM
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BJohnson BJohnson is offline
 
Join Date: Jun 2005
Location: Federal Way, Wa
Posts: 264
Default Tapered Drill Reamers work well

I have been testing a Tapered Drill Reamer, often used for drilling composite materials, with good success on plexiglass. I have been trying to abuse them by pushing hard and moderate speeds, and even drilling plexi I just pulled from the freezer. With limited testing, I have yet to crack a test piece. The picture below is the tapered drill reamer. I do not have a good source for these unfortunately. Perhaps one of the RV tool suppliers can start carrying them. I did find them advertised at http://www.avitecnet.com/cutting_tools/tapered.htm, but I have no idea if they sell small quantities.



The picture below is taken about a minute after I pulled a scrap of plexi from a 10 minute cold soak in a freezer and immediately drilled two 5/32 holes at moderate force and speeds. No backup material was used. The condensation is still visible on the plexi even after wiping it once. So the material was cold when drilled.


The last picture is of the is from the same scrap after reaching rool temperature. The middle hole was drilled at room temp, pushing hard, with no backup. The left two used standard drill bts pushing moderatly with moderate speed on the drill with no backup. Both show rougher hole sides and some chipping on the backside.


In general, the holes sides are very clean, with no chipping or burrs on the entrance or exit of the hole. The material cuts like a reamer in a controlled fashion, with no apparent tendency for a flute to grab the edge of the hole on exit. I am planning on using these to open up the holes in the canopy when I get to that point. Your results may vary.
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  #12  
Old 10-05-2009, 11:40 AM
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Brice, that's beautiful...nice contribution!
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  #13  
Old 10-05-2009, 02:03 PM
CMW CMW is offline
 
Join Date: Mar 2007
Location: Livermore, CA
Posts: 167
Default Source for Tapered Drill Reamers

Here's a supplier for the tapered drill reamers.

http://www.starliteindustries.com/pdf/c120/12w.pdf

I just ordered a 5/32" x 4" reamer for $25.70.

-Chris
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  #14  
Old 10-21-2009, 09:05 PM
OldTee OldTee is offline
 
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Location: Centrerville, MD
Posts: 13
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This is from AC 41-13.1B

While not addressing the problem exactly, it gave me a chance to cut and paste from my PAMA copy of the CD.


(a) The drill used on acrylics must be
carefully ground and free from nicks and burrs
that would affect the surface finish. Grind the
drill with a greater included angle than would
be used for soft metal. The rake angle should
be zero in order to scrape, not cut. (See figure
3-18.)
FIGURE 3-18. Drill having an included angle of
approximately 150?, used to drill acrylic plastics.
(b) The patented Unibit (see figure
3-19) is good for drilling small holes in aircraft
windshields and windows. It can cut
holes from 1/8-to 1/2-inch in 1/32-inch increments
and produces good smooth holes with
no stress cracks around their edges.
FIGURE 3-19. Unibit drill for drilling acrylic plastic
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  #15  
Old 10-21-2009, 09:31 PM
CMW CMW is offline
 
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Location: Livermore, CA
Posts: 167
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I received the tapered drill reamer that I ordered from Starlite Industries. I used it to drill a bunch of holes in 1/8" acrylic with no backing and with and without pilot holes. It make beautiful holes clean holes with no chipping that look just like the ones in Brice's post above. I really tried to get it to crack the plexi by getting way too close to the edge and pushing way too hard and never got it to crack. Thanks Brice for an excellent find and post. I highly recommend this tool.

-Chris
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  #16  
Old 10-22-2009, 10:46 AM
koda2 koda2 is offline
 
Join Date: Mar 2007
Location: West Texas
Posts: 282
Default Followup

Well,
The canopy is drilled and the front installed and so far nary a hitch.

I never used the plexiglass bits I got from Brown Tool.

My technique:

Made the frame. I put in all the pilot holes, spacing, etc. before assembly and up drilled to #40. (The parts were replacement parts for a 6 and had no prepunched holes.)

Installed, cut, fitted and clamped the canopy on gently with soft clamps.

Back drilled the plexiglass with a homemade #40 bit made using instructions by www.plasticmag.com and Dan H. Its easy to get "dead on" the frame hole if you do it carefully and check the hole location a couple of times during the slow drill. I clecoed each hole as I did it to keep alignment. Chamfer both sides of canopy with a zero flute c-sink.

Countersunk with 110 degree 3-flute in a microstop while the canopy is installed and clecoed and the frame holes help keep the sink from wandering around. The edge of the countersink was made just slightly wider than the #6 dimple or the #6 Tinneman washers.

By this time I could no longer make a decision between 5/32 or 3/16 up drilling so I took a new 11/64 bit and converted it to plexiglass configuration and enlarged the canopy holes.

Rechamfered the back side of the plexi and drilled up the frame to #25

All screws installed in the front and no cracks yet.

If I had known about it in time, I would have used the tapered drill reamer shown by the other members. Would have saved a lot of time.

I still believe 80 F+ temp is the key. I warmed the canopy carefully with a small electric heater under the canopy and a blanket over the top and monitored the temp closely

Dave A.
6A rebuild
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  #17  
Old 10-22-2009, 11:12 AM
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BJohnson BJohnson is offline
 
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Location: Federal Way, Wa
Posts: 264
Default Yep

Chris

Pretty amazing little drill. Takes all the worries out of drilling the plexi. I tried to abuse it too without any cracks, chips, and the inside walls of the hole are very clean with no scratching.

Funny thing is when I started drilling my canopy, I was still very carefull despite being reckless on scraps with the same drill.
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