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Proper Machine Countersinking

Daniel S.

Well Known Member
Okay.
Building trivia question. This just recently struck me a few weeks ago when visiting a fellow -7 builder. There tends to be two trains of thought when it come to proper counter sinking. Some feel that you need to counter sink deep enough to account for full insertion of skin dimples, depth varying with different skin thicknesses... And others believe that you should only counter sink deep enough for a rivet head to sit flush regardless of skin thickness. Who is following proper procedure? ;-)
 
Section 5 of the preview plans, under dimpling and countersinking it states if there is going to be a dimpled skin riveted onto the machine countersunk surface adjust the machine countersunk tool a few clicks deeper than flush. This will make the rivet sit .005 below flush when dropped into the hole. That is Vans recommendation for what it's worth.
 
Ditto. If a rivet is sitting in the machine countersink, I adjust the countersink for a flush rivet. If a dimpled skin is to go over it, I countersink so the rivet is slightly inset. You can tell by noticing a thin bare aluminum ring around the rivet head.
 
+1

Slightly deeper CS when dimpled skin sits in it. Using a rivet to gauge this is the best way IMHO, but it usually ends up being about 4 clicks past flush for me.
 
Slightly deeper CS when dimpled skin sits in it. Using a rivet to gauge this is the best way IMHO, but it usually ends up being about 4 clicks past flush for me.

Wow! 4 clicks seems like a lot to me. I haven't really counted but I would think 2 would do the trick. I use a "dimple" guage. I have various size dimples in some scrap aluminum and I use that to see if the countersink is deep enough by checking for flushness.
 
Wow! 4 clicks seems like a lot to me. I haven't really counted but I would think 2 would do the trick. I use a "dimple" guage. I have various size dimples in some scrap aluminum and I use that to see if the countersink is deep enough by checking for flushness.

The typical small countersink cage is 0.001 inch per click.

So 4 clicks is in the ballpark for Vans 0.005 extra depth suggestion -

http://www.panamericantool.com/countersinks/micro-stop-countersinks-cage-needle-bearing.html

On the above web page -

• All Bronze Bushing Construction.
• .001 Increment Depth Adjustment.
• Positive Adjustment Lock
 
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