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2015-Nov-28 - Wooroloo - Loft Floor Joists #16
During the week I completed the butt welding of the third long beam.

On Friday morning I picked up from DiCandilo my two lengths (approx 2.1 metres each) of SHS 100 x 9 mm.

I think their per metre rates may be slightly higher than Midalia Steel, but they will cut to exact length - meaning I do not have to purchase some multiple of 3 m or 4 m. So perhaps cheaper in some ways.

Plus the cuts were very precise and nice and square.

My main job for the day was to fabricate 4 fishplates to go on the ends of the two SHS 100 pieces.

I sat down the previous night and looked at the design.

I have a supply of 10 mm plate, 150 mm wide.

If I cut 100 mm of this stock then I would end up with a fishplate 100 mm x 150 mm leaving only 25 mm each side for the fixing holes.

The other alternative was to cut pieces at 220 x 150 allowing 60 mm either side for holes but needing work to reduce this back to 220 x 100.

I decided to go with the second, more robust design.

I was not keen to use a 125 mm angle grinder with 1 mm disks to cut off the 220 x 50 mm strips so I played around with using the cut off saw.

I mounted a new disk to allow the longest cut but found that I could not mount the stock steel in to the machine without the disk fouling on the work piece.

In the end I had to resort to using an older, small cutting disk to make the initial cut from each side and then switch to a new disk, threading the work piece over the larger disk.

This is quite a risky approach as the new disk could have locked up on the work piece but I mounted everything carefully and spun the disk by hand before applying power.

Once I had my four raw fishplates I ran a light weld over four faces of the assembled pack, marked up the hole positions on the top piece and drilled the pilot holes in one operation on my drill press.

After this - a bit of grinding to remove the temporary welds and to clean off any imperfections from the cutting process.

Next about an hour's work to drill the pilot holes individually out to 12 mm.

This was followed by another hour's work to grind bevels on to the surfaces to be welded.

At this time, I backed my utility in to our main driveway and offloaded my SHS steel from DiCandilo.

I spent a further two hours manhandling this in to position and grinding welding bevels on to the ends.

Then an hour to tack weld the fishplates in to position, and the rest of the evening to perform all the detailed welding.


Mainly a day of rest today.

However, I was up at 6.00 am and set up mockup of the top stud plates that the beams will be sitting on.

This was two 3 metre beams 4 metres apart levelled off with all sorts of packers inserted underneath to compensate for the slope on our paving.

In the afternoon, as soon as this area had cooled down enough, I positioned the 3 main 4.1 metre beams and started setting up the cross beams.

This all has to be done very carefully - I suspect the 100 SHS x 9 beams must weigh at least 50 Kg - I need to move them around without hurting my back and without knocking the mockup out of alignment.

The end result will be some texta marks on the main beams showing me where to drill the 12 mm holes that will take the high tensile bolts to join all the beams together.

Hopefully, during breaks in work, during this week, I can position the second cross beam and drill the holes.

Perhaps I can even temporarily insert some bolts to check for alignment.

220 x 100 x 10 mm blanks for fish plates

Blanks lightly welded in to a block for drilling

Pilot holes drilled in block

12 mm holes and bevels added for welding

Welded to cross beams

Setting up cross beams for mounting holes