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Old 12-05-2017, 04:58 PM
coffeeguy coffeeguy is offline
Join Date: Jul 2015
Location: Lake in the Hills, IL
Posts: 106
Default What was that countersink set to?

I had to reach for the countersink cage today and couldn't remember if it was set for rivet depth or minus 7 clicks. Argh, I hate to drill a few new holes in angle stock, deburr and test it out. I came up with the idea of using red and green electrical tape wrapped around the cs cage. Green for skin, red for watch out, it's deeper and set to -7 clicks. I realized I didn't have any colored electrical tape, so I went to the junk drawer and grabbed some bread twist ties.

If it doesn't have a twist tie on it, check it. I also had the idea of taking some thicker flat stock (don't have any on hand, though) and making something like a pegboard. One for #30 and one for #40. Drill all of the holes once, then just check your cs depth on one or two holes as you need them.

Jeff Dingbaum
RV-14A empennage, wings
Cherokee 180
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Old 12-05-2017, 05:07 PM
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wirejock wirejock is offline
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 3,030
Default Tip

Good tip but I never trust any of my cages. I take scrap and drill tons of #40 and #30 holes. Before any use, I test the cage. I know they should stay set but those pesky gremlins love to mess with my tools.
Larry Larson
Estes Park, CO
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Donated 12/01/2017. Plus a little extra.
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Old 12-05-2017, 05:37 PM
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Bruce Bruce is offline
Join Date: Feb 2006
Location: ADDISON,TX
Posts: 1,066

+1 on Larrys advice.

Been there.
Bruce (BOOMER) Pauley
Kathy (KAT) Pauley

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EX -KC-135A -------------BOOM OPERATOR #3633
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Old 12-05-2017, 08:17 PM
scsmith scsmith is offline
Join Date: Jan 2008
Location: Ashland, OR
Posts: 1,932

What is the purpose of the -7 click setting?
Steve Smith
Aeronautical Engineer
RV-8 N825RV
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Old 12-05-2017, 09:15 PM
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Bill Boyd Bill Boyd is offline
Join Date: Sep 2006
Location: Landing field "12VA"
Posts: 1,180

I've used 2 different cages over the years and learned with both that the depth of cut is dependent on applied pressure to such a degree that I always "sneak up" on the desired CSK depth by means of multiple passes. It seems to be an inherent weakness of the tool.

I've also earned to give myself grace over the occasional too-deep hole and just live with it. The rivets seem to drive good and tight even when the head is slightly below the surface of the piece. A proud manufactured head is to be avoided far more than one that's just a tad too deep.

That said, it is a horrible feeling to forget to check the setting and hog a hole out way beyond spec. Not sure how I know this, but I've been told
Bill Boyd

Hop-Along Aerodrome (12VA)
RV-6A - N30YD - flying since '98
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Old 12-05-2017, 09:39 PM
coffeeguy coffeeguy is offline
Join Date: Jul 2015
Location: Lake in the Hills, IL
Posts: 106
Default -7 clicks

Originally Posted by scsmith View Post
What is the purpose of the -7 click setting?
Most of the time it is because you will have a dimpled skin at that location, but it could be for any two pieces that are joined with a flush rivet. It needs to be deeper for the dimpled skin to sit in the countersink.

From the construction manual:
Use the appropriate rivet or screw as a gauge when you machine countersink. Stop when the rivet or screw is flush. For a dimpled
skin riveted onto a machine countersunk surface the countersink must be slightly deeper as mentioned earlier. Proper depth is .007
deeper than when the rivet head is flush. This depth correction corresponds to seven "clicks" on a microstop countersink tool
indexed in .001 inch increments.
Jeff Dingbaum
RV-14A empennage, wings
Cherokee 180
2018 dues paid
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