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  #1  
Old 05-08-2022, 09:43 AM
LettersFromFlyoverCountry's Avatar
LettersFromFlyoverCountry LettersFromFlyoverCountry is offline
 
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Location: St. Paul, MN.
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Default 4-40 Countersink size?

What size countersink cutter for the 4-40 screw callout in Section 42 page 1?



I don't seem to see it listed on the Van's RV-12is list of recommended tools.

And thank you.
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St. Paul, MN.
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Beginning RV-12iS avionics
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Last article: "Gonna Finish This Sucker" (Kitplanes)

Last edited by LettersFromFlyoverCountry : 05-08-2022 at 09:51 AM.
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  #2  
Old 05-08-2022, 09:52 AM
jask jask is offline
 
Join Date: Feb 2018
Location: Ramona, CA
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Default countersink

The size of the countersink does not matter, use whatever fits. What does matter is the degree. You can get them in 82, 90, and 100 degree. Aviation uses mostly 100 degree hardware.


Quote:
Originally Posted by LettersFromFlyoverCountry View Post
What size countersink cutter for the 4-40 screw callout in Section 42 page 1?

I don't seem to see it listed on the Van's RV-12is list of recommended tools.

And thank you.
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Free prop balancing for Vanís owners.
RV-6A N665CM
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  #3  
Old 05-08-2022, 02:48 PM
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LettersFromFlyoverCountry LettersFromFlyoverCountry is offline
 
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Default

Any idea what the angle is on a 4-40 screw?
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Bob Collins
St. Paul, MN.
Blog: Letters From Flyover Country
Beginning RV-12iS avionics
N612EF Builder log (EAA Builder log)
Last article: "Gonna Finish This Sucker" (Kitplanes)
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  #4  
Old 05-08-2022, 03:15 PM
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erich weaver erich weaver is offline
 
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Default

If the screws originated from an aviation supply place, they will be 100 degree countersinks. Practice using your micro stop countersink on some scrap until you get the depth setting dialed in
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  #5  
Old 05-08-2022, 03:17 PM
jask jask is offline
 
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Default screws

4-40 is available in 82 or 100 deg
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  #6  
Old 05-08-2022, 04:48 PM
terrye terrye is offline
 
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Location: Vancouver, BC, Canada
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Default 4-40 Countersink size?

AN507 or MS24693 screws are 100* head angle. The "D" dimension of the head diameter to the sharp points is .207/.225".
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  #7  
Old 05-12-2022, 10:13 AM
madmax4499 madmax4499 is offline
 
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I just used my 100 degree deburr tool. It only holds the Maint port and its under the shelf.
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  #8  
Old 05-12-2022, 07:09 PM
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LettersFromFlyoverCountry LettersFromFlyoverCountry is offline
 
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Just to follow up, a 4-40 takes a #43 bit for the hole so there's nothing that will fit in a microstop countersink cage as far I could find online for countersink cutters. I guess enlarging the hole to a #40 is the only way to do this.
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St. Paul, MN.
Blog: Letters From Flyover Country
Beginning RV-12iS avionics
N612EF Builder log (EAA Builder log)
Last article: "Gonna Finish This Sucker" (Kitplanes)
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