Full Chisel Blog

May 30, 2008

Back and forth on Reciprocating Bits

Filed under: Drilling,Uncategorized — Stephen Shepherd @ 8:20 pm

Up until this point (pun) I have discussed bits that cut in only one direction, the direction in which they cut, with the exception of the burn auger.  These bits are referred to as continuous action drill bits, in that they cut continuously when rotated in the proper direction.

Now there are a whole class of bits, probably the earliest, well no THE earliest drill bits are reciprocating drill bits that cut in both direction.  These include pump drills, bow drills and Archimedes drills.  Here some of the ones I use.

Back and Forth Drills

Here is a pump drill, the whurl or flywheel adds to the action.

Pump Drill

And here is a bow drill all put together.  Take not of this type of drill, because I have a surprise a little later on involving this drill.  I also use the bow for my watchmakers lathe, interchangable power source for two different tools, imagine that.

Bow Drill

And this is an Archemides Drill, the two in the photograph have a 4 jaw collet chuck to hold the smallest bits.  I have made a few bits from piano wire (that stuff is hards and requires grinding).

Archemides drill

These are fine drills and their bits cut in both direction.  Bits are either flat and sharpened square or they are round and sharpened like quills, with half the circle of the diameter ground off, leaving two cutting edges.  These bits require that the dreck from drilling be occassionally removed from the hole to help in the drilling operation.

Aside from a sharp antler, bone awl or knapped stone drill, the first drills, these are among the earliest forms of making holes.  Versions of these tools with the exception of the last one have been around for millenia and the last one is fairly old as well.  There is something about wood that makes us need to put a hole in it, haven’t figured that one out yet.

Still need to discuss chucks, drills of other types, drills that drill big holes, drills that drill long holes and things that fit in braces and an unusual drill bit.

Stephen

2 Comments »

  1. Stephen, which of the three works best and is your preference, or do you use each one depending on the situation?

    Comment by The Village Carpenter — May 31, 2008 @ 6:37 am

  2. VC,
    I have these around to illustrate the history of drilling, but I do use them especially the Archemides. The pump drill is good for making quick small countersink holes and for shallow holes on thin pieces, fun to watch.

    The bow drill is a little more difficult to use but works great on small holes and hardened bits work well in metal. When using this drill the bow must be kept in alignment with the bobbin in order to track properly. Once you get the ‘hang’ of it, it works very well.

    The two illustrated Archemides drills (I have one I didn’t show, and I don’t know why) are extremely useful tools for very small holes. The bits are either flat sharpened or quill sharpened, I make them from piano wire and old saw blades. The collet chucks are good but the shank of the bit needs to be roughened in order for the little jaws to get a grip.

    Stephen

    Comment by Stephen Shepherd — May 31, 2008 @ 6:49 am

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