Attaching BLC-09 fuse holders to the firewall.

[claycookiemonster]

These are the hefty fuse holders for the ANL fuses between alternator and electrical system. For some reason, the bodies come with countersunk holes for #10 screws to hold them to the firewall. In the congested space there, I'm having a heck of a time holding that Philips head screw while turning the bolt on the inside. The screws are already rounding out. I can see that the intent is to ensure the bold head does not extend and interfere with the fuse itself, but I was wondering if anyone had found a way to use an AN4 bolt there? Is there any other way to attach these?

 

[wirejock]

Nutplates

Alternative is nutplates on the inside.
I draft my Sweetie. She puts the mojo on the screwdriver. I tighten the fastener inside.

 

[johnbright]

How about Torx or hex?

 

[claycookiemonster]

Yeah, the idea of a hex came to me afterwards struggling. Out today to look...

 

[JDA_BTR]

Nutplates are the best way by far. Now is the time to put them in. Sometimes a doubler with the nutplate installed flush, with the doubler behind the firewall works best when it is too hard to dimple the firewall or buck a rivet behind.

I did this when I added the oil separator long after the plane was finished. I put the doubler on front of the firewall and drilled for the screw holes and corner holes to hold the doubler with cherry rivets. Doubler off and installed the nut plates on the doubler dimpled in the normal way.

With that done the doubler was brought up from aft, cleco'd at the corners, and the screw holes checked one more time. When everything was right I pulled rivets to capture the doubler, and voila - all maintenance is from the engine side of the firewall.

I used some 24Ga wire to fish the doubler back to the firewall so it wasn't so hard.

 

[wirejock]

Torx

Yeah, the idea of a hex came to me afterwards struggling. Out today to look...

Whichever you choose, standardize.
It's aggravating if you have a mix of torx, hex and phillips.
I chose Torx from McMaster after one hex head stripped. I switched before going too far down the rabbit hole.