I'm working on a little project (a spotlight) that is basically a bit
of aluminium tubing, 50mm ID, 5mm wall thickness. I was wondering the
best way to close the end of the tube that doesn't have the light
shining out. I'm hoping to make it water resistant

a) Turn a round plate of 60mm diameter, drill and tap the tube and
screw the plate on - problem being the wall thickness isn't that great
so I'd be limited to about M3

b) Cut an internal thread in the tube and a threaded plug to fit
(probably a 1.5mm ISO thread) - would require some form of sealant/
threadlocker

c) Cut a chamfered plug and bond it to the tube - not sure what
adhesive to use

Any other ideas? I'll be using my Myford Super 7 and indexable tools

Robin wrote:
I'm working on a little project (a spotlight) that is basically a bit
of aluminium tubing, 50mm ID, 5mm wall thickness. I was wondering the
best way to close the end of the tube that doesn't have the light
shining out. I'm hoping to make it water resistant

a) Turn a round plate of 60mm diameter, drill and tap the tube and
screw the plate on - problem being the wall thickness isn't that great
so I'd be limited to about M3

b) Cut an internal thread in the tube and a threaded plug to fit
(probably a 1.5mm ISO thread) - would require some form of sealant/
threadlocker

c) Cut a chamfered plug and bond it to the tube - not sure what
adhesive to use

Any other ideas? I'll be using my Myford Super 7 and indexable tools

Five millimeters? Half the thickness of my pinkie finger?

Or 0.5mm?

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

Robin wrote:
I'm working on a little project (a spotlight) that is basically a bit
of aluminium tubing, 50mm ID, 5mm wall thickness. I was wondering the
best way to close the end of the tube that doesn't have the light
shining out. I'm hoping to make it water resistant

a) Turn a round plate of 60mm diameter, drill and tap the tube and
screw the plate on - problem being the wall thickness isn't that great
so I'd be limited to about M3

b) Cut an internal thread in the tube and a threaded plug to fit
(probably a 1.5mm ISO thread) - would require some form of sealant/
threadlocker

c) Cut a chamfered plug and bond it to the tube - not sure what
adhesive to use

Any other ideas? I'll be using my Myford Super 7 and indexable tools

Turn a plug .002" over and press it in.

Turn a plug that is thick enough to drill & tap. Hold with screws
through the tube. Bob

On Mar 26, 2:29*pm, Robin wrote:
I'm working on a little project (a spotlight) that is basically a bit
of aluminium tubing, 50mm ID, 5mm wall thickness. I was wondering the
best way to close the end of the tube that doesn't have the light
shining out. I'm hoping to make it water resistant

a) Turn a round plate of 60mm diameter, drill and tap the tube and
screw the plate on - problem being the wall thickness isn't that great
so I'd be limited to about M3

b) Cut an internal thread in the tube and a threaded plug to fit
(probably a 1.5mm ISO thread) - would require some form of sealant/
threadlocker

c) Cut a chamfered plug and bond it to the tube - not sure what
adhesive to use

Any other ideas? I'll be using my Myford Super 7 and indexable tools

You've about covered your options except for spinning. A little late
to plan for that. If you're using any sort of high-temp incandescent,
like halogens, it'll cook any sort of adhesive. Heat expansion may
loosen pressed components.

Any reason for making one as opposed to buying one? Around here,
there's any number of cheap track lights about that size at the big-
box home improvement places. Most of those are cast units. Can even
get LED bulbs for those now.

Stan

On Mar 26, 5:20*pm, Jim Stewart wrote:
Robin wrote:
I'm working on a little project (a spotlight) that is basically a bit
of aluminium tubing, 50mm ID, 5mm wall thickness. I was wondering the
best way to close the end of the tube that doesn't have the light
shining out. I'm hoping to make it water resistant
...

Turn a plug .002" over and press it in.

Ditto.

If you are unsure of the proper interference fit you could turn the
plug 0.1mm oversize and then cut a crude thread on it to allow it to
squeeze down into the tube more easily. The thread is less
hypersensitive than a smooth cylinder to removing small amounts for
adjustment, because you effectively trim the groove width rather than
the diameter. Since it makes the plug more compliant than the tube the
OD is less likely to bulge.

You're Robin in England, right? I am also conversing with a Robin in
France about ion thrusters for spacecraft.

jsw

Jim Stewart wrote:

c) Cut a chamfered plug and bond it to the tube - not sure what
adhesive to use

Loctite. Red or Blue.

Wes

On Mar 26, 4:29*pm, Robin wrote:
I'm working on a little project (a spotlight) that is basically a bit
of aluminium tubing, 50mm ID, 5mm wall thickness. I was wondering the
best way to close the end of the tube that doesn't have the light
shining out. I'm hoping to make it water resistant


Any other ideas? I'll be using my Myford Super 7 and indexable tools

d. Turn a plug 50 mm with o-ring piston seal groove. Use o-ring for
seal . Drill thru tube into plug and use roll pin, screw, epoxy,
whatever to keep plug in tube.


Dan

On Mar 27, 6:29*am, Robin wrote:

shining out. I'm hoping to make it water resistant


Any other ideas? I'll be using my Myford Super 7 and indexable tools


How you going to stop it self destructing, probably fairly fast, given
the extreme temperatures its going to achieve.

Andrew VK3BFA.


PS - nice project though - congrats

On Mar 27, 6:09*am, Robin wrote:


If I end up turning a plug, is it better to trepan a 50mm circle from
a piece of flat bar, or part off a wedge of 50mm round bar?

I like the sound of option d - that's why I asked the question! Might
use high temperature silicone instead of an O-ring, though unless
someone can point me in the direction of an O-ring supplier

Robin (England)

The silicone caulk would probably work well. If you use it smear some
on both parts before pushing the plug in.

I have made larger aluminum disks by cutting a slightly larger blank
using a sabre saw , hacksaw, whatever. Then using something kind of
like a live center, but with a fairly large flat end. Put on your
face plate with some plywood fastened to it and then put some rubber
( old intertube ) next to the faceplate, the aluminum oversize disk,
and use the " live center " to apply force to hold the plate against
the rubber. The live center was made from a front wheel bearing from
a car and some steel bar. The wheel bearing provides the flat
surface. Obviously light cuts, but you should not have to take off a
lot if you don't make the blank too much oversize.
If you make the plugs from flat stock, you could make them with a
shoulder so they would seat evenly and use thinner stock.

You might try finding some aluminum at a industrial recycling center.

Dan

On Mar 26, 1:29*pm, Robin wrote:
I'm working on a little project (a spotlight) that is basically a bit
of aluminium tubing, 50mm ID, 5mm wall thickness. I was wondering the
best way to close the end of the tube

c) Cut a chamfered plug and bond it to the tube - not sure what
adhesive to use

How about solder? With the right fluxes and aluminum solder you
get a good tight join. Drawn plug of soft aluminum would be
suitable, too.

On 27 Mar, 18:59, whit3rd wrote:
On Mar 26, 1:29*pm, Robin wrote:

I'm working on a little project (a spotlight) that is basically a bit
of aluminium tubing, 50mm ID, 5mm wall thickness. I was wondering the
best way to close the end of the tube
c) Cut a chamfered plug and bond it to the tube - not sure what
adhesive to use

How about solder? *With the right fluxes and aluminum solder you
get a good tight join. *Drawn plug of soft aluminum would be
suitable, too.

I've got some aluminium solder stuff, Lumiweld or similar, but can
never seem to get the same results the demonstrator shows! Didn't come
with flux - you had to melt a pool of solder and then scratch through
to break the oxide - I think it then reacted with the aluminium to
break the rest of the oxide. Not sure how I'd do it with this
application

"Robin" wrote in message
...
On 27 Mar, 18:59, whit3rd wrote:
On Mar 26, 1:29 pm, Robin wrote:

I'm working on a little project (a spotlight) that is basically a bit
of aluminium tubing, 50mm ID, 5mm wall thickness. I was wondering the
best way to close the end of the tube
c) Cut a chamfered plug and bond it to the tube - not sure what
adhesive to use

How about solder? With the right fluxes and aluminum solder you
get a good tight join. Drawn plug of soft aluminum would be
suitable, too.

I've got some aluminium solder stuff, Lumiweld or similar, but can
never seem to get the same results the demonstrator shows! Didn't come
with flux - you had to melt a pool of solder and then scratch through
to break the oxide - I think it then reacted with the aluminium to
break the rest of the oxide. Not sure how I'd do it with this
application

Try cleaning/saanding the tubing end just before using the stuff.

This will eliminate the oxide issue and enable a better bond.

The demonstrator probably did his demonstration just after giving a spiel
during which he was "brightening" his materials.

On Mar 27, 6:03*pm, Robin wrote:

I've got some aluminium solder stuff, Lumiweld or similar, but can
never seem to get the same results the demonstrator shows! Didn't come
with flux - you had to melt a pool of solder and then scratch through
to break the oxide - I think it then reacted with the aluminium to
break the rest of the oxide. Not sure how I'd do it with this
application

Aluminum solder might work, but the thick walls would conduct the heat
away so you would need a torch. I don't think I would get good
results.

Dan

On Sat, 27 Mar 2010 15:03:42 -0700 (PDT), Robin
wrote:

On 27 Mar, 18:59, whit3rd wrote:
On Mar 26, 1:29*pm, Robin wrote:

I'm working on a little project (a spotlight) that is basically a bit
of aluminium tubing, 50mm ID, 5mm wall thickness. I was wondering the
best way to close the end of the tube
c) Cut a chamfered plug and bond it to the tube - not sure what
adhesive to use

How about solder? *With the right fluxes and aluminum solder you
get a good tight join. *Drawn plug of soft aluminum would be
suitable, too.

I've got some aluminium solder stuff, Lumiweld or similar, but can
never seem to get the same results the demonstrator shows! Didn't come
with flux - you had to melt a pool of solder and then scratch through
to break the oxide - I think it then reacted with the aluminium to
break the rest of the oxide. Not sure how I'd do it with this
application

If you are machining the plugs, on a lath, and if it is a permanent
joint they why not try shrinking them into place? You can easily do it
in the kitchen, stick the plugs in the freezer and heat the tubes in
the oven - about cake baking temperature I think, fish a frozen disk
out of the fridge, set in on a board and grab the tube (with a pair of
pliers) and just set in place over the plug.

An aluminum tube will expand an amazing amount when heated to, say 350
degrees F.

John B.

Robin wrote in

ups.com:

I'm working on a little project (a spotlight) that is
basically a bit of aluminium tubing, 50mm ID, 5mm wall
thickness. I was wondering the best way to close the end of
the tube that doesn't have the light shining out. I'm
hoping to make it water resistant

a) Turn a round plate of 60mm diameter, drill and tap the
tube and screw the plate on - problem being the wall
thickness isn't that great so I'd be limited to about M3

b) Cut an internal thread in the tube and a threaded plug
to fit (probably a 1.5mm ISO thread) - would require some
form of sealant/ threadlocker

c) Cut a chamfered plug and bond it to the tube - not sure
what adhesive to use

Any other ideas? I'll be using my Myford Super 7 and
indexable tools

You didn't say what the enviornment is, but I frequently use
plastic plugs for steel and aluminum, round and square.

Like these: http://www.mcmaster.com/#tubing-plugs/=6ev3vm

Ken

On 28 Mar, 12:42, Ken Moffett wrote:
Robin wrote
ups.com:



I'm working on a little project (a spotlight) that is
basically a bit of aluminium tubing, 50mm ID, 5mm wall
thickness. I was wondering the best way to close the end of
the tube that doesn't have the light shining out. I'm
hoping to make it water resistant

a) Turn a round plate of 60mm diameter, drill and tap the
tube and screw the plate on - problem being the wall
thickness isn't that great so I'd be limited to about M3

b) Cut an internal thread in the tube and a threaded plug
to fit (probably a 1.5mm ISO thread) - would require some
form of sealant/ threadlocker

c) Cut a chamfered plug and bond it to the tube - not sure
what adhesive to use

Any other ideas? I'll be using my Myford Super 7 and
indexable tools

You didn't say what the enviornment is, but I frequently use
plastic plugs for steel and aluminum, round and square.

Like these:http://www.mcmaster.com/#tubing-plugs/=6ev3vm

Ken

The tube is basically a spotlight body, one which I'm hoping will be
waterproof. Since the bulbs (MR16) are halogen, they tend to generate
a fair amount of heat so I wouldn't be comfortable with a plastic
plug. Have always been tempted by the freezing/heating methods - I
suppose once joined, the fact the whole assembly is heating up should
stop it all falling apart although I'd be tempted to screw in place as
well.