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A lot of This is Incomplete

   

Polygon Hole Drill

When I heard about the square hole drill I assumed it was a joke, I have drilled triangular holes in sheet metal but a square hole drill sounded like it should be kept in the same draw as the glass hammer.

The first time I bought drills at Drill Service[DS] in Horley, I got one of their drill catalouge's. They have more types of drill than you can shake a stick at. Next time I went there I asked to see a 1 thou drill, they were out of stock but they showed me a 2 thou drill, what can I say, it was very small. I found the polygon hole drill quite fascinating it was so simple, why hadn't I heard of it before. Well that was in 1982 and I still have only seen them in the DS catalouge.

This system for drilling polygon holes was introduced in 1891, it can be carried out in a variety of machines: drill press lathe etc.

 


Figure 1. Complete setup for polygon hole drilling in drill press.

The drill has one less flute than the number of sides to the polygon. the drill is held in a floating chuck allowing radial movement whilst held axialy aligned. One cutter edge is lodged in a corner and the next corner sweeps around untill it lodges in a corner, this is the cutting action.

 


Figure 2. Square hole drill and form plate.
parrot drill bits
Figure 3. Polygon drilling equipment.
To be continued
       

 

 
     
  Cobbled together on the 7th of Feb 2001
by
Richard

{last modified 9th feb 2001}