Tips needed for dimpling completed firewall

[dwranda]

Originally Posted by agent4573

for my own curiousity, would a doubler plate and riv-nuts work? Put the doubler on the inside of the firewall and then use the riv-nuts to hold it in place and mount the oil cooler with a bolt?

The question was for where there is a support angle behind the firewall and you can't dimple the hole. Other places on the firewall where there are no angles riveting in a doubler is not a problem. It is recommended to mount the cooler to those support angles.

[lr172]

You can make die holders for your dimple dies from 5/8 round steel stock. Then use your rivet gun and bucking bar to make the dimple. I also made a dimple die holder from an old 401 style air chisel bit (same configuration as your rivet gun).

Larry

[agent4573]

Originally Posted by dwranda

The question was for where there is a support angle behind the firewall and you can't dimple the hole. Other places on the firewall where there are no angles riveting in a doubler is not a problem. It is recommended to mount the cooler to those support angles.

I totally didn't understand the angled support aspect. Makes sense now. Thanks.

[gasman]

Originally Posted by dwranda

I am trying to hang my oil cooler and would like to put nut plates in so removal will be easier in the future. Want nut plates behind everything on the firewall to ease removing from the front only. I would need to dimple the firewall where there is the angle support behind it. Obviously I can't just use the dimpler that uses the rivet puller. Is it OK to countersink these even though the firewall is so thin?

Just run a tap through the hole, install the bolt and then install a nut on the back side. That would need you to drill the tap size first.

[Ed_Wischmeyer]

Originally Posted by agent4573

for my own curiousity, would a doubler plate and riv-nuts work?

I've never had good luck with Riv-Nuts. You don't have to drill out very many of them to lose faith. Then again, my bad luck was with riv-nuts previous owners had installed.

[abwaldal@gmail.com]

AS for riv-nuts I have installed gobs of them in another life and would never install them in an aircraft again. Junk. Once they loose their grip your screwed. Just try to drill out something that is spinning in the hole that is bigger than any other fastener will fill.
I threw my whole riv-nut kit n caboodle in the trash many years ago.
Anything than a riv-nut
Art

[fixnflyguy]

I would have no issues at all with drilling #40 holes and countersinking for the nutplate attach holes/fasteners..I have done it on mine. The firewall is more "firewall" than load carrying structure, and the fact that your countersink will knife edge the SS and lightly countersink the angle behind it is irrelevant...not something you would like to do on a skin or area transmitting loads where the rivet would start working and cause cracks.

[Draker]

Maybe you could countersink for a NAS 1097 "oops" rivet in order to minimize the amount of material removed and still have a flush rivet?

[dwranda]

I decided to use rzbill's recommendation and make a plate with the platenuts on it. I drilled out a few rivets and will install the plate using those rivet holes to hold it in. Simple and didn't take too long to do. Thanks everyone !!