Beam tapping

Some time back Ian offered a limited number of 10mm aluminum wingnet eyes for sale, and I picked up a batch.   After painting the beams it was time to fit the wingnet eyes, first by drilling pilot holes, then the final hole, then tapping, then mounting the eye in an epoxy sealant.    There are approximately 36 eyes to be mounted.

I mentioned in an earlier post that I was learning about tapping - it's not something I've done before.   Here are the first two tapped holes of my life:

Pretty awesome feeling, threading something into that that first hole :).

Here I'm trying to do it for real:

I have been encountering major problems with the backing plates falling off after I remove the tap.   The force required to turn the tap seems to be torqueing the plates more than the 5200 adhesive (used to fix the plates to the inner beam wall, according to Ian) can withstand.     I discovered that I was using a slightly too small tap drill (8.33mm) which seems to have been the primary cause (plans say to use 8.6mm, duh on me).   I used this drill partly because there wasn't any metric drills in my tap-and-die set, and I didn't take the time to figure out what some of the other sizes were for.   Well after doing more research, I figured out that an 'R' drill (.3390" or 8.611mm) was the closest my tap-and-die set could offer to the specified 8.6mm.   Weird - I never knew there was such things as letter-rated drill sizes.

However even after going to the R' drill size, I have still had a couple of plates fall off inside of the beam.  Very frustrating - at some point I am going to have to play a fishing game to see if I cannot recover the plates and get them lined up.   

At one point I tried drilling two small temporary holes to either side of the main hole, just as a means of keeping it in place while I did the main tap:

It worked but was awkward.   

I'll update later on the status of my plate fishing expeditions - I have about 8 or 9 plates to recover :-(.   Not looking forward to that - but I'd rather try than deal with them rattling around.