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Why drill this hole? 25-04 step 1

WayneJ

Member
I must be missing something. The existing #19 (.166) holes to be drilled #17 (.173) are already the correct size for a #8 screw dimple die. Why are they drilled larger?
 
Negate cracking at dimple

“Over drilling” the hole is to prevent cracking at the edges when dimpling. The edges stretch quite a bit and there have been issues with cracks forming. The larger hole size reduces the amount of stretch at the inner edges.
 
“Over drilling” the hole is to prevent cracking at the edges when dimpling. The edges stretch quite a bit and there have been issues with cracks forming. The larger hole size reduces the amount of stretch at the inner edges.

I've heard of dimple cracking problems but have not seen it myself. These are relatively large dimples for #8 screws so they're likely more susceptible to cracking than the more typical rivet dimpling we do.

I contacted builder support at Van's but he could not give me a definitive reason for the need to enlarge this hole by .007".

I drilled and dimpled as instructed. No cracks. Moving on.
 
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