Thursday, May 23, 2013

FJ Cruiser: The Platform Begins...

My current effort on fixing up the FJ Cruiser is focused on building a platform where the back seats used to be.  This platform will serve two purposes.  First, it provides a level, flat, and elevated place for the dogs to sit behind us at the right height for them to see around.  Second, under the platform is a handy-dandy storage space for tools, winch supplies, etc.

The platform needs to be sturdy and rigid, and strong enough to handle any kind of stress we might put on it while offroading.  I came up with a design that relies on 1/2" thick marine-grade plywood (this means it has no voids on the internal plies) and 1" angle iron to join the pieces.  So far I've fabricated the fore and aft bulkheads, and a port and starboard rib – the basic strength components of the design.  All four of these pieces are bolted directly to factory threaded holes, the same places that the back seats and seat belts were attached.  The pictures below, with their captions, tell the story of what I've done so far (there's much more to go!)...

My "baby" drill press - primitive, but it works surprisingly well.  Curls are from drilling holes in steel angle irons; oil is used to lubricate the drill bit (to keep it from getting hot).

A cut, ground, wire-brushed, and drilled piece of angle iron, forming one "connector" between two pieces of plywood.

Four identical connectors (for connecting the aft bulkhead to the port and starboard ribs).

Two pieces cut from a 10' length of angle iron.

Rough-cut ends.

In the little "pony" vise, ready for grinding...

Yours truly, all gussied up with safety gear: face shield (I'm quite attached to my vision), hearing protectors (ditto), and gloves (those metal shaving and sparks can be very painful and hard to extract!).  The Australian bush hat is there to protect the top of my head from the sun!

The 4.5" angle grinder, armed with grinding wheel, ready to go to work.

What it looks like after grinding - flat end, chamfered edges.

After grinding, I degreased them with this magic stuff.  Probably should have done that before grinding!

Change over to the wire brush, which cleans all the non-grease gunk off the metal.  It also acts like fine emery paper, polishing off all the rough bits.

Quite a difference after being cleaned up!

All three parts completely cleaned up.

Next step is to mark where the holes are to be drilled.  The machinist's square does the measuring, the scribe (long pointy thing) scores lines in the metal, and the automatic center punch (short pointy thing) makes precise little dents in the metal, right where I want the center of the holes to be.

You can see two of the dents made by the center punch, and the scribed line they are on.

Connector ready for drilling, a drop of oil on the center punch dent.

First step is to very lightly "tap" the drill against the work, to check whether you've got the bit centered over the dent.  When you get it right, you can see a faint disk drilled out around the dent (as above).  Sometimes it takes me four or five tries to get the drill in the right place :)

We're at the right place, so it's time to start drilling.  The key with drilling into hard metal like steel is to go slow and let the tool do the work.  I just keep a steady pressure of a few pounds on the drill press handle.  The drill bit does the rest; takes about 60 seconds or so to drill the complete hole.  Above is what it looks like when the hole first gets started.

Here the entire width of the hole is started.  The little curls of steel are what it should look like if your bit is sharp and you have the right pressure on the drill bit.  Time for some more lubrication; don't want my bit to get hot...

The hole is finished, and you can see there are a number of quite large curls lying out.  That's what you want it to look like!  For a 5/16" hole (as above) through 1/8" steel (as above), I generally pause twice for additional lubrication.  For a bigger hole or thicker metal, I'd pause more.  It's all about keeping that drill bit cool, which will keep it sharp much longer (it gets softer when it gets hot).

Done, and degreased again!

Now I need to cut the port rib (the starboard rib is the piece with the angle iron bolted to it, lying down to the left of the router).  I use the router (upside down on the plywood) to do the cutting, not a saw - saws tend to splinter the top side of the wood, plus it's a challenge to make a perfectly square cut with them.  The router against a straight edge (like the big aluminum one above) makes a perfectly square cut every time, with no splinters.  It's a little tricky to control (and I screw up sometimes), but on the whole the result is superior to what I can do with a circular saw.

The router, close up, showing the milling bit (1/4" diameter).  Note the drill-like flutes to pull the wood chips up and out of the cut - key to this technique working.  The router is still upside-down, of course.

Here's my starting piece of wood, with the cuts I need to make marked on it in pencil.  There are five cuts altogether - three horizontal, one vertical, and one angled.

To make the first horizontal cut, first I set up (and clamp) the straight edge exactly 2 7/8" from where I want to cut.

All rigged for cutting.

The first horizontal cut.  Note I first cut through some waste wood to get there.

The second horizontal cut.

The third horizontal cut.

The angle cut (note some of the waste wood now fell off).

And the last cut, the vertical cut.  My piece is done.

And there it is!

Marking hole centers with a scratch awl.

These two holes are getting a counter-sunk bolt in them, so I drill them with the special counter-sink drill bit.

The trick is to counter sink them enough so that the head of the bolt projects ever-so-slightly (perhaps 1/32"), so that when you tighten the bolt, it pulls in flush with the wood.  There's a bit of art to this, as it depends on the size of the bolt and the kind of wood...

The rest of the holes are just 1/4" holes for bolts; there's steel on both sides so no counter-sinking is required.  To make a nice, clean, perfectly cylindrical hole I use a special kind of bit called a Fortsner bit - with a "backer board" so that the bottom of the hole doesn't splinter.  The backer board is just a piece of waste wood placed below the work piece when you're drilling.  The drill bit goes cleanly through the work piece and 1/8" or so into the backer board. 

The Fortsner bit.
Tah dah!  The perfect resulting holes...

The port and starboard ribs, with all their connectors installed.  The two long connectors tie into the fore and aft bulkheads; the short connector on the bottom ties directly into the FJ.

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