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.