I recently made a housing for a small halogen
reflector lamp that is very similar to your plan -
including the threaded bezel. You can hold the bezel
or the tubing from the inside by extending the chuck
jaws outwards until they firmly grip the inside
surface of the work.
Frank Hoose
--- "roylowenthal <roylowenthal@...>"
<roylowenthal@...> wrote:
--- In 7x12minilathe@..., "Neil"
<cobra_neil@a...> wrote:
Hi all,
Here is a sketch of what I need to make (> 20
pieces).
The unit will be used for gauges for my, and a
friend's
car.
This will be my *excuse* for purchasing a lathe,
and other
appropriate tools. Wondering if someone can
assist my
letting me know if I'm on the right track.
The Plan:
=========
BEZEL: Only aesthetic part. I'm using 2.25" ID,
1.75" ID
for the ring, as I can get tubing with these
dimensions from
places like McMaster. I'd need to cut thin slices
(about
3/8" thick) from the tube to make a ring, then use
a lathe
to cut back a part of the inside to ~ 2" ID.
BODY: I'll use 2" OD, 1.9" ID tubing here, cut to
a length
of approx 2". Only lathe work here is the
threads. I can
make the tabs by using a fiberglass cutoff-wheel
or other
saw.
BACK COVER: I'll use sheet-metal for this, but
not sure
what's the best process to cut clean consistent
circles.
My Questions:
=============
- 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.
- 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.
- 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.)
- 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.
- 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.
- 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> 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>)
Roy
I'm trying to make this a science rather than an
art, so
I get consistent repeatable results. So I don't
mind
making jigs where necessary. Any other info
towards these
goals is much appreciated.
Thanks much,
-Neil.
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