Simplest way to do this (reduce O.D. of copper tubing) WITHOUT a lathe?


What would be the simplest way to reduce the outer diameter of a small length of copper tubing, without use of a lathe (and with minimal special tools, etc.)?

Might help to know the current O.D. and desired O.D.

Hammer. It won't be pretty though.

You can cut down the length of the tube with a saw that will take out some material (e.g. hacksaw, saber-saw, saws-all), then compress tube until gap is gone. If more material needs to be removed, use a double-sided file (will keep joint a perfect match). Once to the correct size, solder the joint and then file of excess solder.

Best wishes.

chuck it in a drill and sand it down


Sorry for the vague question. I was wondering how (or if it’s possible) to do, kind of generically?

What got me thinking about this is I picked up one of these this weekend:

with the thought of making a simple pill in a cheap light (\_p244453.html?). I think the ID of the head is ~5/8” (ok, sorry, vague again), but that cap is just “a smidge” too large diameter-wise.

(don’t laugh) I’ve been putting the cap into a vise and filing it then rotating it, but it’s taking forever. I have a Dremel, but can’t figure how how I could leverage that to maybe spin the tubing or something like that, so I figured I’d pose the question.

Would it be easier (or even possible) to use a circular sanding attachment in the dremel to enlarge the ID of the head instead?

The head has threading on the inside (the light is a twisty), so I can’t just grind/remove the threads on the inside…

I would, if at all possible, enlarge the ID of the head, to match the fitting. It's much harder going the other way.


I actually also have a drill with a 1/2” chuck, but that piece is a cap for 1/2” pipe/tubing, so the OD of the cap is slightly larger than 1/2”. In other words, the cap won’t fit into the 1/2” drill chuck, so I’d need to get a larger than 1/2” chuck?


As I mentioned to gadabout, there’re threads inside the head, so I can’t just grind them off.

so if you were to chuck a piece of 1/2" pipe with the cap on it ...

Try this, Whittle a piece of wood/ dowel to fit. Get a nice snug fit.
drive a finishing nail (has no head) into the wood,chuck nail in drill.
Staple sandpaper to board, bring spinning pipe cap in contact with sandpaper.
(high speed not recommended) WHERE SAFETY GLASSES!!!


How’d you know I had a piece of 1/2” pipe :)? Turns out I picked a 2’ piece up at the same time as the cap… but, unfortunately, the pipe won’t fit into the 1/2” chuck (chuck’s too small, or pipe is too big, diameter-wise.

But, that did give me another idea. I put the cap on the pipe, and am sanding it the cap that way, and seems to be working better than with the cap in the vise. Slow, but I think it’ll work (eventually).

I may try that if my latest fiasco attempt (see above) fails to yield the desired result.

Seriously though, and for the future, in general, is there a better way to do this? Can I buy a larger chuck that goes into the so-called 1/2” chuck?

1/2" wooden dowel, file down one end to fit your chuck. It doesn't have to be round, file 3 flats on it to make it triangular. Put the cap on the other end and soak it in water to swell the wood so it holds the cap. When you're done dry it out to release the cap.

1/2 rubber well plug/nut
Tighten the bolt rubber expands. We used them to attach truck mirrors to the doors.
If you caught the mirror it would pull off without destroying the door
Best sources : Farm store, good hardware ACE etc. Auto parts that does a lot of autobody


It was quite a lot of work, but I was able to get the cap filed down enough to fit tightly into the head, so I’m good for now.

I wanted to get this one done tonight, but I’ll try some of the other suggestions for the next 2 that I have to do.


You could put the dremel in a vise, if you have one, (so it's sticking out flat) and then use the dowel trick, or the pipe, to hold on and run the cap against the dremel. It's one of those things where it takes some time doing it, to master it.

[Long bolt - big washer - copper pipe - big washer- nut]

-Tighten, centre the pipe
-Put threaded end into drill chuck

Turn on, sand paper/file etc.