What's This!!!

This doesn't look like an aircraft part!!!

And it is not.

My wife gave me a weather station for Christmas.  One of the challenges has been to find a place to put the rain gauge and figure out a way to mount it.  It wants to be out in the open, but it requires batteries, so it needs to be accessible.

I decided the best place to mount it would be on a fence post.  So today I fabricated this bracket.

Yes, I did some airplane fabrication, too. 

Cutting Sheet Steel

One of the aspects of building a rag-and-tube airplane is that the primary structural material is 4130 steel, commonly called "chrome-moly".  It is tough stuff and cutting out sheet steel parts can be a challenge.

I acquired the inexpensive (OK, cheap) Harbor Freight power hack saw.

This saw can be used vertically or horizontally.  They recommend that it be used horizontally for metal shapes, like tubing, angle, etc.  I started out switching it back and forth, using the vertical for sheet metal and horizontal for shapes, mostly tubing.

However, I found it just as fast, and almost as easy, to cut the thin wall shapes we use in airplane construction with a hand hack saw and just leave the powered saw in the vertical position.  To lower the saw to the horizontal position, the table must be removed.  Though it is not a big task, it gets bothersome enough to make hand sawing thin-wall tubing attractive.

I am quite happy with this little saw, with a couple of caveats.  The first being the blade that comes with the saw.  It may work fine on carbon steels and non-ferrous metals, but it rapidly  wore out on 4130.  I purchased the Harbor Freight bi-metalic blade with 18 teeth per inch (TPI).  The original blade was a bit more coarse at 14 TPI.  The 18 TPI works much better. If this blade wears out rapidly I will go to Starrett or one of the other higher end blades.

When cutting and drilling steel, always make sure you have adequate lubrication. A good grade cutting oil will help your tools last a lot longer.  Yes, it gets things messy. Live with it.

Another caveat is that the gullet around the small table used in the vertical position is pretty large, abut an inch and half square. With that big a gullet the blade had a tendency to grab the work piece, especially delicate cuts near an edge, and bend the metal down, quite violently.

So I fitted this chunk of wood over the table.

It is held in place with a couple of 8-32 machine screws and nuts. It works just fine, allowing me to cut very fine shapes without the piece disappearing into the inner workings of the saw, or grabbing the piece and cutting my hands to shreds.

Which reminds me of a safety note.  Always wear stout gloves and face protection when working around machinery, particularly when working on small pieces from light gauge metal.
 

Ancient Time Honored Skills

First, just to prove that progress IS being made, here are the three completed aileron hinges.

Three more to go.

But what I really want to talk about today is, what seems to be, the lost art of sharpening drill bits.  This interest was brought on because somehow I have managed to misplace the drill point gauge that I have had since I don't remember when.  At least 40 years.

I grew up believing that, if you wanted to drill holes in things, you needed a small assortment of tools.  The first being some means of turning the drill bit, such as a hand drill or drill press. Back in those days you usually had an "egg beater" style of hand drill, a 1/4" electric drill, and, if really affluent, a drill press.  Obviously, you needed drill bits, too.

But nothing stays sharp forever, so two other tools, a bench grinder and a drill point gauge are necessary.  As observed above, I lost my old faithful drill point gauge somewhere along the way. 

Being the naive type, I trotted down to my local hardware store, which has a very fine inventory, and got blank looks when I asked for a drill point gauge.  Nobody, but nobody, in the store had heard of such a thing and had never heard of anyone sharpening drill bits.  Everybody just assumed that dull bits got thrown away and new ones purchased.  Unbelievable.

On a hunch, I stopped at the local NAPA on my way home.  The gentleman at the counter (with gray hair) at least had heard of a drill point gauge.  However, they did not have one in stock.  The best he could do was offer to sell me a dedicated (made in China) drill sharpening machine at something well north of $100.  For sharpening drill bits?  Give me a break!

I finally found a drill point gauge at L.G. Isaacson.  But first, a brief description on how drill bits are sharpened.  A good bit has four characteristics:

1.   It is straight. That is set at the factory and you can't change it.
2.   The cutting lips are sharp and are raked back from the point at 59 degrees.
3.   The bit slopes back from the cutting lips to clear chips.
4.   The point, where the two cutting lips come together, is centered.

A bit gets dull when the cutting lips are no longer sharp. The process of returning them to a good sharp condition is, with a little practice, very easy.

You hold the bit, as shown below,  with the cutting lips at a 59 degree angle to the wheel, parallel to the floor.

Note that I have drawn a line, with a Sharpie, at a 59 degree angle to help me keep the bit aligned properly.  Just touch the bit to the wheel and then give it a slight clockwise twist while lowering the far end of the bit just a tiny little bit. Flip the bit over and do the same to the other side.

If you did it correctly, and evenly, your lips will be sharp, the rake will be correct, the angle of the lips will be 59 degrees, and the point will be centered.  How do you know if you got it right?

Why with the point gauge, of course.

Here you can see how the point gauge is used. The angle on this bit is slightly off, so it needs to go back to the grinder.  To check the centering of the point, just compare the two sides of the drill to the number etched on the gauge.  You will note that the point on this bit aligns with the "5" line on the gauge.  The other side should do the same (it does).

The final test is to drill into a piece of mild steel. At the right speed and feed rate you should get nice curly chips.  If not, back to the grinder.

See, that is not so difficult.  And you get years of use out of a drill bit instead of just a few holes.

And Then There were Three

Today's task was to finish the third aileron hinge.  There is one more "easy" one.  Then there are two more that start out exactly like the first four, but mount pulley brackets that have to be precisely positioned.

The theme for the next little while is just slogging through the fabrication of aileron hinges.

Another Hinge!

You can expect the above title to be repeated in the next few weeks.  I have one aileron hinge complete, one finished except for primer, and a third started.  There are a total of six.  Two of which are complicated by carrying the aileron pulley brackets.  I will build those last.

There won't be many photos.  They would just be highly repetitive.

Ran out to the hardware store today to pick up a new drill gauge.  I don't know what happened to the one that I purchased sometime in the 1970's.  I was amazed at the blank looks I received. Nobody at the local hardware store (and this is a mill town fer cryin' out loud) had any idea what I was talking about.  The best the local NAPA could do, after receiving a long explanation as to what a drill gauge is and how its used,  was offer to sell me a "Drill Doctor" electric bit sharpener for $100.  Really?

Has the simple, but essential, art of drill bit sharpening been lost?