On Sun, 18 Aug 2019 21:09:28 -0700 (PDT), AK
wrote:

The bike is a Huffy Nighthawk Model 56347. The manual does not
specify whether it uses American or metric sizes.

Every bicycle I have ever seen used metric hardware (including Torx).
There are some legacy dimensions that use imperial (SAE) measurements,
such as tire sizes, seat post diameters, handelbar diameters, mountain
bike frame sizes, some wire gauges, and whatever else I forgot.
However, the small hardware seems to be all metric. Methinks it's a
fair bet that your Huffy Nighthawk is all metric.

I have just a set of American hex wrenches but could get a set
of metric wrenches and see if one of them fits the clamp bolt better.

I have the feeling that some of your problems are due to a lack of
proper tools.

Go to any LBS (local bike shop) and look at the tools they have
hanging in the shop. Notice that they're all metric.

I suggest that you hide your American (imperial or SAE) tools, and
replace them with metric.

Try not to drool at the tools or panic at the prices:
https://www.parktool.com/category/tool-kits
Video on one of the basic tool kits showing what each tool is used
for:
https://youtu.be/oEwCT86n3J8

I suspect you can't afford the very best, but you can borrow the list
of tools and buy the equivalent tools online or at your local hardware
store as you need them. I'm lacking quite a few of the tools show
simply because I've never really needed them (and can borrow them from
a real bicycle mechanic if desperate).


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558