machine countersinking in .032 material.

[CalKid]

RV7 left elev. counter sinking - riviting trim spar to root rib.

Plans say to machine counter sink here. I find machine counter sinking in material this thin is difficult. Can't seem to counter sink deep enough to get the mgf. head flush with the surface without expanding the dia. of the hole. As I look at this location, can't see any reason not to dimple here.

What say you?

Thanks

[Spike]

The minimum thickness you can machine countersink for 3/32" rivet is .032" thickness. If you do it then it is best to put a backstop material down (such as wood) with matching holes to hold the cutter guide. As you noticed you will get some hole expansion doing this. This is acceptable depending on how well you capture the rivet with the other material. I would say go with the plans.

Generally if something like this is explicitly called in the plans they either want you to learn something or there is a clearance issue.

-- Spike

[CalKid]

Thanks for the advice. I called Vans and said that I just can't seem to counter sink .032 without enlarging the hole to accept the dimple. They said you shouldn't increase the hole size and after you cleco down the skin to the elev. trim tab spar it would tuck in nicely - NOT! Quite a few of the countersunk holes are just not deep enough and there is a thumnail's width gap at those holes. Many say that "in reality" you can't avoid opening the holes when countersinking .032. Well anyhow, I can't seem to avoid it. Any advice or assurance appreciated.

[Midnight Sun]

While I cannot vouche for this I have heard of people dimpling .032 then giving it a little "kiss" with a machine die.

[bullojm1]

Doesn't the hinge for the trim attach under this spar? So the spar will be sandwiched between the top skin and the hinge? If so, don't worry about enlarging the hole a little too much. The hinge will add all the strength you need.