I think we're reaching the readability limit for interspersed
replies!
There's a machining manual here:
20Manual%20TC%209-524/
and another one here, for people who can read without moving their
lips (guess which branch I served in):
--- In 7x12minilathe@..., "Neil" <cobra_neil@a...> wrote:
Hey Roy,
Thanks for the info. Comments interspersed below...
- Is the cut on the inside of the bezel easy with a lathe?
I'm still not sure if the cutting tools will get in there
easily.
A boring bar (or boring tool) is designed to do this easily.
I'll assume this is one of the cutting tools available for a
lathe.
- Are internal threads easy to cut with a lathe?
Easier than trying to cut a short, large diameter thread any
other
way. It's less exciting if there's an unthreaded relief at the
blind
end and if you run the lathe in reverse, to have the tool moving
away
from the chuck while making a right hand thread.
After much thought, I've decided to get away from the threads
and make the parts snug-fit, with a small set screw to hold them
together.
- Can I do the bezel w/o damage or marks to the outside
surface?
With difficulty. You'll need to make some sort of fixture that's
softer than the bezel, yet, able to hold it securely &
accurately.
It'd be easier to machine the outside & front after it's
threaded.
(Screw it onto a mandrel for final machining.)
Sound like you're saying that the threading process will
be the problem in this respect. Sounds plausible since
the bezel will need to be gripped tight. Since I'm leaning
away from threading now, I may be okay? If not, I guess I
can lightly machine the outside to clean it up.
- What's a good way to cut thin, clean slices of the rings?
I'd like to avoid manual polishing/cleaning as much as
possible. Is there some way I can cut it on a lathe so
any marks are circular (so it looks more like a pattern)?
The good way is a parting tool and a lathe large enough to pass
the
tubing thru the spindle! The practical way on a 7xX is to rough
out
the blanks with a chop/band/hack saw and face them to size.
Alternately, with lots of waste, part some off a piece of tubing
held
in a chuck/on a mandrel. After a few are done, start with
another
piece of tubing - there's a limited range between too long to fit
the
lathe & too short to hold. You may need to use a steady rest,
which
tends to mark the outside of the tubing.
I'm a bit confused about what you mean here, since I'm not that
familiar with the lathe yet, until I get one. But I'll look it up
in the lathe docs I downloaded.
With a large lathe, the tubing can pass thru the spindle & be parted
(sliced) off a long piece of tubing. The spindle on the 7xX's only
has about a 13/16" bore, so you have to chuck short sections of
tubing, part a few bezel blanks off the section & start with another
section, leaving a waste piece that was held in the chuck. It's hard
to hold large tubing in a chuck without distorting it, some sort of
mandrel works better, but takes up more of the length of the tube to
hold it. Alternately, use a saw and face each bezel on both sides.
- Alternate option is to not use threads, and instead let
the body slide snugly into the bezel. Then I'd use a
small set-screw going vertically from the bottom of the
bezel to hold the body on.
Boring & cross-drilling is easier than boring, threading internal
+
threading external.
Good. This (threading) option eliminated.
- Any easier way to attach the cover to the body? I don't
mind welding (to avoid cutting the tabs), but not sure
how to do this w/o a tig welder, and that's way to
expensive for me now.
Supposedly, you can buy drawn cups. I've never done it, so I'm
just
passing along a shop rumor <g> ...
Have never been able to find this, but I recently realized that I
need the back cover off to assemble the unit (mounting a part on
the cover for use as a heat-sink).
... If the end can be thicker, you can
turn a shoulder on a purchased disc or blank some out of plate
with a
hole saw. If you've got a drill press, a hole saw without the
pilot
drill will produce solid discs (it also howls enough to panic the
cats & annoy SWMBO <G>)
Yep. This was my first thought, but I thought I'd ask otherwise
since I need to experiment with the available standard hole-saw
sizes to see if one fits my app.
It's possible to tweak a hole saw by modifying the tooth set, but
it's tedious. For Al pieces, I just use carpet tape to hold the
blank to a chucked piece of wood, helped by pressure from a live
center, and take light cuts. For a shouldered part, eyeball
centering before turning both diameters is quicker than accurately
centering an existing major diameter before turning the minor
diameter.
Cheers,
-Neil.
