Countersink Drill bits

I use a small, 1/4" diameter, countersink originally intended to be chucked up in a lathe. It has a small pilot and then the countersink. Most countersink bits are intended primarily for wood and tend to vibrate on metal usually leaving an octagonal hole. You want a single or two flute bit, not one that looks like a gear. Moreover you want to use a drill press with the down stop properly set. Trying to countersink metal with a hand drill is somewhat less than an ideal setup.

 

Norseman....available at Fastenal and similar.

 

Hi JBurton, the company that I use is Tools Today a great range of cutters they are US based and I am in Australia ripper range and fair prices

 

It was given to me ~50 years ago. If you go to the Fastenal web sit and search 'countersink bits' ir's the third one down.

 

As you probably know, Aluminum is a soft non-ferrous metal and even the inexpensive Harbor Freight bits will work very well, unless you get the variation meant for wood products. My personal tools are typically the top-shelf and off-limits to the hired help for good reason. Choose your tools based on needs and intended end user in order to maximize the "Bang vs. Buck". Just food for thought....

 

https://www.mcmaster.com/countersinks take your pick for the application