[HBR] HBR-13 Progress

[Mike Hanz]

Seems to be a delayed echo on this list. :-) Anyway, the step drills go 
up to 1.375" in hole diameter, and as I mentioned yesterday in 
recommending them, are accurate in hitting the desired finish location.  
It also provides a perfectly circular hole, and with a deft hand, 
deburrs the top edge when you're finished.

It is absolutely mandatory to clamp your workpiece on the drill press 
and use an appropriate speed limit as you increase the size - there are 
speed and feed rate tables for machining online, like this one: 
http://www.americanmachinetools.com/images/lathe_table_6.jpg Otherwise 
you risk burning the cutting edge with too high a speed and that's not a 
good thing.

           73,
  - Mike  KC4TOS
www.aafradio.org

On 4/7/2014 8:29 AM, Shoppa, Tim wrote:
> For anything bigger than 1/8 but less than 3/4 inch in sheet metal,  I start with a 1/8 hole then I use a "step drill". E.g.  http://www.mcmaster.com/#step-drills/=rfkfol
> Home Depot also sells step drills. The Unibit brand is pretty good.
> Harbor Freight also sells step drills. I bought some once when I lent out my real Unibit. They harbor freight stuff will work but they just feel like crap.
> I have a mix of Greenlee (inch) and Mouser (Metric) punches for sizes bigger than 3/4 inch (e.g. tube sockets) in aluminum and plastic.