Drill bits to drill main spar attach holes.

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Drill bits to drill main spar attach holes.

Postby Rynoth » Tue Feb 04, 2014 12:02 pm

I've read and studied a lot of different methods to drill out the final size of the attach holes, including some creative modification of drill bits to help prevent ovaling of the hole (such as grinding down the tip of a larger bit to pilot the bit through the hole). I believe I just discovered a drill bit that can be purchased and do exactly what most of these drill bit modifications attempt to do.

http://www.panamericantool.com/double-m ... s-937.html

Item #13-250 is a 3/8" double-margin bit with a 1/4" pilot. I haven't purchased one yet and my only question would be how sharp is the pilot portion, as the idea is for it not to do any cutting and only follow the existing hole. The double-margin feature basically helps make the hole have a near-reamer finish.

Right now this is the front-runner for how I believe I'll drill the attach holes, I'm curious what others think of it.
Ryan Roth
Waiex #197 (Turbo Aerovee)
Knoxville, TN
My project blog: http://www.rynoth.com/wordpress/waiex/
Time-lapse video of my build: https://www.youtube.com/watch?v=Q8QTd2HoyAM
First start and taxi video: https://www.youtube.com/watch?v=HNZTuFreZvI
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Re: Drill bits to drill main spar attach holes.

Postby gammaxy » Tue Feb 04, 2014 12:41 pm

I've heard of people using this bit: http://www.mcmaster.com/#29525a53/=qjrex3

It seems like the same thing you posted except yours is a lot less expensive. I wasn't particularly excited about spending $40 on the McMaster one. The Sonex Foundation has a tool loan program that has most (all?) of what you need for wing rigging including one of these bits: http://sonexfoundation.com/Tool_Loan_Program.php

From what I've read, a longer bit would be even better. Both of these seem to be 5".

I hope to drill these holes in a couple weeks, so I'm curious to see what others post.
Last edited by gammaxy on Wed Apr 12, 2017 5:49 pm, edited 1 time in total.
Chris Madsen
Aerovee Sonex N256CM
Flying since September 2014
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Re: Drill bits to drill main spar attach holes.

Postby Rynoth » Tue Feb 04, 2014 4:09 pm

I will probably end up getting one, even if the 1/4" pilot is sharp, it will be a lot easier to dull it than to modify a normal bit.

Pan American tools has a $50 minimum order. I've bought quite a lot of supplies from them though, including all my clecoes (cheapest I could find anywhere that weren't used), most of my drill bits and reamers (including threaded bits and shanks for them), a pneumatic cleco tool and one of their Nova drills (the best quality tool in my whole shop.)
Ryan Roth
Waiex #197 (Turbo Aerovee)
Knoxville, TN
My project blog: http://www.rynoth.com/wordpress/waiex/
Time-lapse video of my build: https://www.youtube.com/watch?v=Q8QTd2HoyAM
First start and taxi video: https://www.youtube.com/watch?v=HNZTuFreZvI
Rynoth
 
Posts: 736
Joined: Fri Jul 26, 2013 1:32 pm
Location: Knoxville, TN

Re: Drill bits to drill main spar attach holes.

Postby Fastcapy » Tue Feb 04, 2014 5:12 pm

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Last edited by Fastcapy on Tue Feb 24, 2015 2:56 pm, edited 1 time in total.
Mike Beck
Oshkosh, WI (KOSH)
Sonex #1145 N920MB
Std Gear, Modified Aerovee, Rotec TBI, Dual Stick, Acro Ailerons
MGL Panel
Airworthiness: 10/24/13, First Flight: 05/18/14
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Re: Drill bits to drill main spar attach holes.

Postby Fastcapy » Tue Feb 04, 2014 5:26 pm

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Last edited by Fastcapy on Tue Feb 24, 2015 2:56 pm, edited 1 time in total.
Mike Beck
Oshkosh, WI (KOSH)
Sonex #1145 N920MB
Std Gear, Modified Aerovee, Rotec TBI, Dual Stick, Acro Ailerons
MGL Panel
Airworthiness: 10/24/13, First Flight: 05/18/14
Fastcapy
 
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Joined: Sun Jan 12, 2014 11:45 am
Location: KOSH

Re: Drill bits to drill main spar attach holes.

Postby sonex892 » Tue Feb 04, 2014 8:45 pm

Or if you're brave enough to trust you're wing attach block measurements. Clamp the completed spars together and updrill them to 3/8" in a drill press prior to wing assembly. The risk of ovaling the holes whilst rigging can be all but eliminated by using a long 3/8" OD x 1/4"ID bush and long 1/4" and 3/8" bits. Need only to hand drill the forward and rear angles whilst rigging. Only 1/8" of material 4 times.

The ovaling a lot of people experience is caused purely by the combination of the drill not being held consistently straight whilst hand drilling the attach blocks, and drilling a large hole through about 3" of soft aluminium takes quite some effort. Making it likely the drill operator will have trouble keeping things straight. The somewhat awkward position the drilling needs to be done in, also doesn't help.

Just need to plan well ahead. The actual rigging process only took about 3 or 4 hours the 3/8 bolts are tight and need to be turned and tapped to remove or install.

Here's a photo of the tools needed and a couple of drawings



IMG_1967.jpg
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IMG_1464.JPG
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pg 2.jpg
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Steve
Sonex 892 3300TD 140 hrs
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Re: Drill bits to drill main spar attach holes.

Postby Rynoth » Tue Feb 04, 2014 9:57 pm

Fastcapy wrote:I looked at those ones from Pan American and you had to buy a minimum of 6 of those bits at $10 ea.


I completely missed that, what a bummer. I might try to negotiate if I get a larger order of other items together.
Ryan Roth
Waiex #197 (Turbo Aerovee)
Knoxville, TN
My project blog: http://www.rynoth.com/wordpress/waiex/
Time-lapse video of my build: https://www.youtube.com/watch?v=Q8QTd2HoyAM
First start and taxi video: https://www.youtube.com/watch?v=HNZTuFreZvI
Rynoth
 
Posts: 736
Joined: Fri Jul 26, 2013 1:32 pm
Location: Knoxville, TN

Re: Drill bits to drill main spar attach holes.

Postby radfordc » Wed Feb 05, 2014 1:16 pm

One way to avoid ovaling the holes is to drill in increments. When I bought my plane the holes were so ovaled that the left wing tip moved up and down about an inch. Rather than rebuild the wing attach fittings I went to a larger size bolt. I drilled from 3/8" to 7/16" using drills that were each 1/64" bigger than the previous one....25/64"; 13/32"; 27/64". For the final 7/16" hole I used a reamer rather than a drill. I also used lots of WD-40 as a drill lube. The new holes are perfectly round and the bolts have to be tapped into place.
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Re: Drill bits to drill main spar attach holes.

Postby gammaxy » Sun Mar 16, 2014 12:34 pm

I attached my wings this weekend.

I used a 6" 1/4" black oxide bit then switched to this one:

http://www.fastenal.com//web/products/details/0350457

double_margin_bit.jpg
double_margin_bit.jpg (50.13 KiB) Viewed 3838 times


Here's a picture I took while doing a practice run that better highlights the stability provided by this drill bit. The contacts with the hole wall are a lot wider than I was expecting.

double_margin_bit2.jpg
double_margin_bit2.jpg (43.71 KiB) Viewed 3815 times


The bit was very stable in the hole due to the double margins. I used an electric drill and stopped about 5 times to remove chips. The last time I removed chips I was almost bottomed out in the hole, so I unchucked the bit and slid it about 1/4" out and was able to make it all the way through without having to switch sides. Both holes seem great.

The biggest "gotcha" I had was my rear spar attachments were only pilot drilled when I started. I thought I was supposed to drill to 1/4" with the wings attached to the fuselage, but was unable to get the drill positioned without interfering with some riveted angles on the fuselage walls. I then decided to remove the wings and attach them resting on sawhorses. This allowed me to attach the main spars solidly together with bolts in the 3 alignment holes. I was then able to attach the rear spar channel and drill up to 1/4" without interference. This is probably a step I skipped somewhere.
Last edited by gammaxy on Sun Mar 16, 2014 4:56 pm, edited 1 time in total.
Chris Madsen
Aerovee Sonex N256CM
Flying since September 2014
Build log: http://chrismadsen.org
gammaxy
 
Posts: 419
Joined: Wed Sep 04, 2013 9:31 am

Re: Drill bits to drill main spar attach holes.

Postby Rynoth » Sun Mar 16, 2014 3:22 pm

That looks like the best solution yet...
Ryan Roth
Waiex #197 (Turbo Aerovee)
Knoxville, TN
My project blog: http://www.rynoth.com/wordpress/waiex/
Time-lapse video of my build: https://www.youtube.com/watch?v=Q8QTd2HoyAM
First start and taxi video: https://www.youtube.com/watch?v=HNZTuFreZvI
Rynoth
 
Posts: 736
Joined: Fri Jul 26, 2013 1:32 pm
Location: Knoxville, TN

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