[Shop-talk] Aligning round tubing for mitering?

[Mark Andy]

Howdy,

On Tue, 8 Jul 2008, Obaa wrote:
> I'm trying to build a small rack/platform using some 5/8" round tubing.
>
> I'm planning for it to be rectangular, with the tubes cut at a 45 degree 
> angle (don't have a tubing bender).  I'm going to notch 3 crossbars with 
> a 5/8" drill, to form a nice, flat platform. The problem is, I don't 
> know how to align the tubing to keep all the cuts square with each 
> other.  Is there a simple way of doing this?

Yes.  Use square tubing.

:-)

(actually, I'm somewhat serious on that... Square tubing in general seems 
to be easier to work with, no need to fishmouth tubes, angle cuts are 
easier, etc.)

If you want to use round tube anyway, attach something to the tube that 
will hold it in one orientation against the bench/saw/whatever.  This 
could be as simply as a piece of decently thick sheet metal with a V cut 
in it, tack welded to the pipe.  It doesn't need to be fancy.

If you don't want to tack weld, you could get a set of v-blocks like 
the enco brand ones here: 
http://www.use-enco.com/CGI/INPDFF?PMPAGE=362&PMCTLG=00

For fish mouthing the tubes, I'd recommend one of two methods...  Either 
just buy a cheap tubing notcher like this:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=42324
(you can find them for less I seem to recall...)

or cheat and use a 4.5" grinder with a cutoff wheel.  Cut a "flat arrow" 
shape at the end of the tube like:

    ___
   /   \
  /     \
  |     |

(ascii art... Use a fixed width font like all the cool kids did back in 
the day).

You'll find that it'll fit reasonably close on the tubing, and chances are 
you want some gaps anyway to help with the welding.  The "perfect fit" 
left by most notchers usually is a little too perfect for welding 
purposes.

Mark