Countersink size for #6 screw?

[pilot28906]

I have found the max-min countersink diameter for a #8 screw but can not find the max-min diameter for the #6 screw. I am countersinking the wing spar for the access plates and this info would be appreciated. I am affraid that using a dimpled sample piece will make the countersink to deep.

thanks,
John

[TerryWighs]

My chart says a number 27 dimple die.

[az_gila]

Originally Posted by pilot28906

I have found the max-min countersink diameter for a #8 screw but can not find the max-min diameter for the #6 screw. I am countersinking the wing spar for the access plates and this info would be appreciated. I am affraid that using a dimpled sample piece will make the countersink to deep.

thanks,
John

..0.257 to 0.279 inches will do the job nicely

The screw specification is here....

http://www.av8design.com/Hardware/MS24693.pdf

[TerryWighs]

Sorry John......Misread your question. Was thinking access plate, instead of the spar which is countersunk...

[mcencula]

Hi John,

I believe that if you use the recommended size for the screw head you will not be happy with the results because the access plate will not sit flush. I used a sample plate for all of the countersunk locations in my spar including the rivet locations, tank attach screws, and access plates. In all cases, the countersink is slightly (~.005 for rivets, ~.010 for #8 screws) deeper for the mating skin than if only the rivet head or screw head was fitting in.

Good luck!

[JoeLofton]

The RVator first issue 2005, "In The Shop" section, gives the Van's recommended technique and dimensions for the tank attach countersinks in those beautiful golden spars. These are the outside diameter dimensions:

Tank attach - 0.365” to 0.375” diameter (from the article)
Access plate attach - less than 0.3125" diameter (from later discussion of the topic on the forums)

The technique was to cut the head off a screw to use as a gauge, countersink until the screw head fit flush to the spar, then go two clicks deeper on the microstop.

Using a dimpled piece of scrap as a gauge tends to lead to oversized holes. Also, recheck the microstop periodically - the locking ring can loosen and you can accidentally change the depth.

...Joe

[pilot28906]

I used the < .3125 method and i think they will work out to be fine. I agree with the problem of using the sample piece; I think they will be way too big if the sample piece sits flush.

Thanks to all for the input,

John