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Old 11-01-2017, 01:02 PM
guidoism's Avatar
guidoism guidoism is offline
Join Date: Dec 2013
Location: Louisville, KY
Posts: 46
Default Misshapen match-drilled holes

While match drilling the W-707 doubler plates for the rear spar I'm accidentally causing the original holes to widen and become misshapen. I'm assuming this is because I'm not holding the drill straight, or I'm moving it around, or I'm applying pressure laterally. I'm not sure.

Anyways, two questions:

1. Is the biggie in this pic useable or am I going to have to order a new rear spar?

2. How do I match drill without doing this? Do I need to get a drill press?
Guido Bartolucci - Louisville, KY - Bowman Field (KLOU)
RV-8 (N883G): Empennage Finished, Working on Wings
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Old 11-01-2017, 01:42 PM
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BrianDC BrianDC is offline
Join Date: Mar 2016
Location: Northern VA
Posts: 289

Can?t comment on drill larger or replace. Would talk to Vans.

Drill press may not work in all situations. Maybe look at a drill bushing?
Brian Lester
RV10 Slow Build - #41778
Finish Kit - in progress
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Old 11-01-2017, 01:57 PM
Kyle Boatright Kyle Boatright is offline
Join Date: Aug 2005
Location: Atlanta, GA
Posts: 4,669

Dull bits sometimes wander and create odd shaped holes like that. Try a new bit.

Van's is a sane resource on quality control. My guess is they will tell you you're OK, but you should call and verify.
Kyle Boatright
Marietta, GA
2001 RV-6 N46KB
2019(?) RV-10
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Old 11-01-2017, 04:06 PM
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JonJay JonJay is offline
Join Date: Jan 2007
Location: Battleground
Posts: 4,348

Measure the hole and compare to the mil specs on Vans web site or AC43-1b. You are allowed certain tolerances for a given hole diameter. If it is within tolerance, and you have edge distance, you are probably ok.....

Now, saying that, Vans is the only one who can approve deviations when it is a spar. However, I would rather call them with that information so they know than just sending a picture. It will also educate you.

Make sure you clear your chips on the bit. Sometimes a small chip gets stuck in the flute.
Smart People do Stupid things all the time. I know, I've seen me do'em.

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Old 11-01-2017, 05:23 PM
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wirejock wirejock is offline
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 4,755
Default Pilot

This trick works for most holes and match drilling.
Credit goes to my Mentor, Dave Paule.
Go to the local hardware or hobby store. Look for brass tubing in 12" lengths. Buy one each of each size.
Cut a piece of each starting with the smallest working to largest with each a tiny bit longer.
The smallest one should fit the #41 bit with 1/2" or so of bit sticking out when chucked.
Now you can center a bit without touching the parent hole by selecting the correct tube combinations. Try to drill the pilot hole with the smallest bit you can.
Here's the Kitplanes article.
Lots more on my Blog (see signature)
Larry Larson
Estes Park, CO
wirejock at yahoo dot com
Donated 01/01/2021, plus a little extra.
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I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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Old 11-01-2017, 05:39 PM
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bret bret is offline
Join Date: Feb 2010
Location: Gardnerville Nv.
Posts: 2,828

By looking at the drill shavings and the hole it looks like the drill bit is no good, time for a new one, they are cheap compered to parts.
7A Slider, EFII Angle 360, CS, SJ.
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Old 11-01-2017, 05:48 PM
PilotjohnS PilotjohnS is offline
Join Date: Jan 2016
Location: Southwest
Posts: 1,807
Default reamers

I try and use a #30 and #40 reamer, as appropriate for rivet size, as opposed to a drill bit. Much better hole and this shouldn't happen.
John S

WARNING! Information presented in this post is my opinion. All users of info have sole responsibility for determining accuracy or suitability for their use.

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Old 11-01-2017, 05:54 PM
BillL BillL is offline
Join Date: Sep 2007
Location: Central IL
Posts: 6,311

Originally Posted by bret View Post
By looking at the drill shavings and the hole it looks like the drill bit is no good, time for a new one, they are cheap compered to parts.
+1 looks like a melted hole. I got Pan American cobalt bits (Avery - Cleaveland) and have been very happy with life.

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Old 11-01-2017, 09:20 PM
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G-force G-force is offline
Join Date: Jun 2006
Location: Castaic, CA
Posts: 563

Are you using a high speed air drill? I find they want to chatter as they start. No need to spin the bit fast, I prefer to use a slow turning cordless electric drill.
Mike Sumner
Castaic, Ca
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Old 11-01-2017, 09:28 PM
RVDan RVDan is offline
Join Date: Jun 2012
Location: Frederick, MD
Posts: 942

Originally Posted by bret View Post
By looking at the drill shavings and the hole it looks like the drill bit is no good, time for a new one, they are cheap compered to parts.
+1 on replacing the bit. A lot of folks don?t realize that if you drop a bit on the floor (concrete) and it hits on the point, it is likely trash. I have watched people put their drill down with the bit hitting the floor. Same result. Colbolt drills fair a little better but still not good.
Dan Morris
Frederick, MD
Hph 304CZ
RV6 built and sold
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Retired Aerospace Engineer and A&P/IA
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