Sunday, August 21, 2016

I finally finished my coffee table!

When I left off, I had just tacked the frame together. I finish welded all of the crossmembers, working in sequence to minimize warping and keep the table square.

After welding, it was close but still had to be pulled into the final shape.  After pulling around with some carefully placed ratchet straps, I was able to get the frame square a little better than 1/16" on the diagonals.  Here you can also see that the crossmember welds have been ground smooth.

The next step was to build mounting tabs to hold the top in place.

These are just pieces of 16ga stainless steel welded to the crossmembers and legs.

All finihsed up!

I added some 1/8" thick rubber strip to the top of the frame. This will isolate it from the concrete a bit, provide a grippy surface, and space the concrete away from the stainless just a bit.

The last step before assembly was to seal the concrete surface.  I decided to use an acrylic sealer, which should be more than adequate for a coffee table.

I bolted through the tabs using rubber washers to isolate the stainless from the concrete.  This is strong enough to hold it together, but will not over-stress the threaded inserts I have down inside the concrete.

This photo shows off some of the weld finishing I did on the crossmembers as well.

All finished!  I'm not quite happy that some of the rebar created ghost lines in the surface, but overall I'm happy with the finished product.

As expected... it's heavy.

As I loaded up I realized I don't have any coasters in my apartment.  So I made some in matching 304 stainless!


Now back to the Jetta!!!

Sunday, July 31, 2016

Moving on with my coffee table project, it was time to weld up the legs.

To get started, I clamped all of my cut pieces into the fixture for tack welding.  This is 18ga 304 stainless steel tubing.

After tack welding everything up, I set up a back purge.  Since these welds will be ground flush, I wanted to make sure I get decent penetration and a strong weld all the way through.  To prevent contamination on the back side, I modified a fitting to thread into the 3/8-16 hole and purge the interior with Argon.

Next step: Welding!  I was moving really fast to keep warping to a minimum, so they aren't the best looking welds.  My goal here is to achieve decent penetration, but they will be ground flush.

I was practicing a few different techniques.  Since these aren't critical welds, I tried a few different travel speeds and amperage settings to try and minimize warping.

After grinding, I had to fill in a couple low spots.  Since these will be metal finished, I don't have the luxury of adding putty or filling imperfections with powder coat.

When adding filler to low spots, I kept the welds as cold as possible.  These were just barely hot enough to stick some filler to the surface without getting full penetration since I am no longer back purging.

And after some grinding, it's all flush!

The next step is the fillet welds.

I did this first one with hand files and sandpaper, but it took forever.

I ordered a few of these Metabo unitized felt abrasive discs.  These are 6" diameter and designed for smoothing fillet welds in stainless steel.

These have a special size 1" arbor and are designed to fit their $800 Fillet Weld Grinder.  I don't have one of those, but I decided to make a nut and try them out on my variable speed polisher.

I fired up the lathe and turned an aluminum nut with a 1" arbor.

The best feature of these is that you can dress a shape into the wheel.  I dressed a sharp point so I can get right into a sharp corner.  I just taped a piece of sandpaper to a block and ran the grinder over it. I found that about 2100rpm worked best for smoothing the stainless and shaping the wheel.

This is the only intermediate photo I snapped.  I started by grinding the weld with a cutting disc, then blended with the Unitized Felt disc, then finished it off with hand files, sandpaper, and my Dynabrade orbital sander.

Both hoops are now finished!

Kage approves.

Tonight I got the cross braces tacked into place, I still have to finish weld and then grind all of those.

A table shaped object emerges!!