I got started on the M100 floor replacement today – the last day I am off until next week, of course. I started out by deciding on how to replace it. I (along with the advise of my brother) decided to leave a 1″ border around the edge of the tub and cut the edges of the replacement floor to fit inside the tub and spot weld (plug weld) the new floor to the ledge. The front lower edge of the tub was pretty much rusted away, so I have to leave the lip of the new floor and weld a patch panel in place in that area.
I had a 2′ piece of 1/8″ x 3/4″ piece of scrap steel that I used for a straight edge. This, added to 1/2 the diameter of my plasma cutter’s tip came out to right at 1″ – perfect for the ledge I wanted to leave! Man, am I glad I bought that plasma cutter years ago! It only took about 10 minutes to cut the floor out – with PERFECTLY straight lines! It took me about 15 minutes more to decide on how to cut the rusted front out of the tub and to cut it.
After that, I went around and straightened all of the edges and ledges and used a flap wheel to take the red oxide off of the ledges.
Lastly, I cut some sheet metal I bought from Tractor Supply ($10 for a 12″ x 24″ piece, and it wasn’t even 18ga!). Again, I sure am glad I had the plasma cutter! I tacked them in place, then filled in with more tacks. I will have to do more work on this after I get the floor in place and it is more sturdy to work on. I didn’t do anything with the seam on the inside yet – it WILL show, so I will have to use filler or something to make it look good.
I cut the new metal a little wide, so I will have to grind it down to match the height of the floor once it is in also. The original front and rear panels have a 1/2″ bead in them, but I didn’t have anything to make this bead – so a flat piece is what it got on the replacement. It probably won’t be noticeable.
The last thing I did was to spray all the bare metal down with a zinc weld through cold galvanizing coating. This will keep it from rusting until I can get back on it and get the floor in next week. Plus, it will let me plug weld the floor in without having to grind it back to bare metal, so these areas shouldn’t rust years from now.
The plan is to grind the lips off of the side and one end of the new floor panel so that it fits tightly between the tub walls. Then I will drill holes and install sheet metal screws all along the 1″ ledge of the tub to pull the floor tight to the ledge. Then I will remove them one by one and plug weld the floor to the ledge. Then I can come back and grind away the welds. Hopefully the gap between the new floor and tub walls will be so minute that I won’t have to do anything else, but if I have to, I will use seam sealer to cover it up.