Tower Damage Repair Update

Strictly my repair to one of the tower legs, since my last update, last Saturday.  As I said at the end of that post:

To the previous posts, several people suggested tapering a steel bar and driving that up that leg to both open it back up and straighten it.  I intend to try that with a back up of cutting off that bottom ~ 2" and putting a smaller, heavier wall tube into it's place. 

Later that evening I decided on the second option and ordered a 12" long piece of 1.375 Outside and 1.125" Inside diameter aluminum tube along with a piece of 2" on a side, 1/4" thick angle aluminum from one of the online sellers I use regularly.  I have one drawing from the tower company that gives dimensions for the upright tubes; it says the OD is 1.50", the wall thickness is 0.065" and those say the ID of the tower leg will 1.370."  With an ID that's .005 smaller than the tube that's supposed to go into it, that told me I pretty much needed to prepare a way to reduce the diameter of the tube I bought down to about 6 to 8 thousandths less than the tube ID.  That looks like this on my smaller lathe, the Sherline, where every tool is about at its limit for the largest things they can handle. 

That thing just right of the lathe's chuck is called a steady rest, and they're pretty commonly available for all lathes.  It's awkwardly positioned in this view, barely doing anything, but while most people think of a steady rest as more appropriate to skinny stock, like 1/4" diameter rods 6" long, they're really appropriate any time the stock's length is several times its diameter.  What they do is reduce the amount the work flexes away from the cutting tool when it applies force to the metal.  That reduces the chances you'll cut a taper onto whatever you're turning.

It may not be obvious, but no cuts reducing that tube's diameter have been made.  I started asking myself if the wall thickness on those tubes was actually .065" and decided that before I reduce the diameter of that tube, I should know what it needs to be.  I took out my jigsaw and cut about the last two inches off that bent tube to better inspect the area I need to work on.

If you look at the top of this cutoff piece, the most important thing about it is that the profile isn't circular.  The side closest the camera was still badly bent.  Most importantly, it allowed me to measure the wall thickness and see that it was very different than that one drawing.  Instead of .065" the readings were around .058 - making the ID of that leg tubing more like 1.384 (1.500 - (2*.058)). That should mean my 1.375 pipe (which I measured at closer to 1.373) would be a comfortable sliding fit. 

Except it wouldn't slide into the tower leg.  I went to measure it with my telescoping inside diameter gauges (like these but not these) on two diameters at 90 degrees to each other (top/bottom and left/right).  I could see the tube was still flattened out top to bottom. 

After taking off another half inch or so from that leg, it measured closer to the same diameter in both directions, but the test piece of tube still didn't go into the leg.  It seemed like it could be a burr, so I used a brake hone, which I first bought to hone the cylinder on my first internal combustion engine, along with files to reduce any burrs along the cut edges, inside and outside curves.  That did it.

That's the way it sits right now, but I'm not sure if it's ready to proceed.  There's more work to be done before the tower is ready to go back up.  That tube will be secured in the leg with two 1/4-20 stainless bolts and then a replacement for the square bracket that secures the tower to the slab will be made and  put in place. 

Again, this is not being looked at as a permanent fix, just a way to get through the next few months.