GOT ER DONE!
Thanks everyone, for all your words of wisdom.
1) Centered hole.
I have a lot of spacers lying around, mostly from mounting extra LEDs on bikes. It turns out that one of them fit nice and snugly in the handlebar end opening:
View attachment 22472
So I left that in, held it in place with some needle-nose pliers, got a big bit out that just fit inside the spacer, and did a little drilling. This allowed me to start the drilling process pretty much exactly in the center of that extra end piece.
(By the way, my guess now is that the extra end piece is essentially a permanent part of the handlebar. That is, I think that it's welded or hammered in there, or something, so that it forms the base -- way inside a bit -- of the female threads that the end bolt connects with.)
(Oh, also by the way, that end bolt is an M6 bolt; I mistakenly said earlier that it was M5, but what I meant was that it took a 5mm Allen key in its head.)
Here's my centered hole:
View attachment 22473
2) Did a bunch of drilling.
I switched to smaller bits, then medium bits, then masonry bits, then larger, then smaller, etc., etc. It was slow going, and even required a battery-pack switch. I sprayed a bunch of PB Blaster while I was working.
3) Kept trying some EZ-Outs.
I used all of these at various points (not shown: some masonry bits and some other twist drill bits):
View attachment 22474
None of the EZ-Outs worked at all. I think the problem was that I was nowhere deep enough when I was messing with them. That is, those female threads in that piece that's inserted into the handlebar end don't go to the end of the handlebar, but are instead just way deep inside.
4) I eventually managed, with a smallish bit, as the Doors sang, to "break on through, to the other side."
5) I then used a larger bit, and got a surprise.
I looked up the value of the proper bit size for an M6 tap (having already located my tap and die set in the garage -- I use that, oh, every three or four years).
As I was working my way up to that bit size, when I had drilled completely through again with that interim bit, I pulled out the drill, in preparation for switching bits, and this is what I saw:
View attachment 22475
That is, the remaining part of the original bolt -- the part that was left behind, when I broke it -- came out with the drill bit! And the drill was spinning clockwise -- go figure. I mean, I was correctly using the EZ-Outs in a counter-clockwise manner, stuff like that.
(By the way, that now-hollowed-out bolt part is still stuck on that bit. I tried to twist it off using some pliers, but it won't budge. I have 100+ bits, so I just left the bolt on, and put the bit away.)
6) The female threads are still there, and work!
I got out a spare M6 x 1.00 x 20mm bolt -- same size as the two broken pieces seem to amount to -- and (gingerly) worked it into the handlebar end. No problem, and it seems rock solid, plenty of threads catching:
View attachment 22476
So I put away my tap and die set, without having to use it. And ordered some black M6 cap head bolts from Amazon.
7) I'm done with my handguard project.
I was only half-hearted in my desire for handguards, anyway, and I am not going through all this on the other side. (I actually ordered some handguards earlier this year for my C 400 GT scooter, and wound up taking them off.)
So I am abandoning this project.
These are Bark Busters that I bought from Hitchcock's, because I wanted to make sure that the particular pieces, and the guards themselves, were fit for an M350 (and I trust Hitchock's more than any other outfit).
If anyone wants the never-been-opened set, no reasonable offer refused. I'll be posting an ad tomorrow.
That's all I got.
