Drill bits Question #2

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theoldwizard1

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Newbie confused !

There are sooo many choices


  • 135º split point
  • 118º point
  • Silver & Deming
  • Black Oxide
  • TiN
  • Cobalt

Why so many choices and what should a newbie buy ?
 
theoldwizard1 said:
Newbie confused !

There are sooo many choices


  • 135º split point
  • 118º point
  • Silver & Deming
  • Black Oxide
  • TiN
  • Cobalt

Why so many choices and what should a newbie buy ?
Click to expand...

The 118º point is the most common bit. I buy the TiN coated just because the finish is a bit better.

The Cobalt bits can be used for general use and the 135º split point is a more aggressive cutting edge, and they work great in stainless and some of the tougher steels.

The black oxide are the lower end drills, but they work fine for general use.

Silver & Deming are bits with the shanks smaller than the drill body. Normally the size range is greater than 1/2 inch.
 
Not long after I discovered 135 degree split point drills I gave away all my others. The split points drill on center without skating around, and that feature alone is worth the price of admission. They also drill better without needing a pilot hole.
 
what Frank said :)

For the last 3 points, cobalt is usually the best (stays sharper for longer than HSS generally), TiN works a bit better in alu to prevent galling and chips sticking to the tip, black oxide is a anti-rust coating for general use bits. The last 2 are just coatings on HSS bits, you can get plain uncoated HSS (bright finish) bits too.
 
In case you're thinking of import drills - I used Home-Depot style bits (DeWalt brand, made in China) for a while with increasing frustration, and finally spent the money on a nice US made set.

My recommendation is to start with the US made set to begin with. They cut better, drill straighter & deeper, clog less, and stay sharp far longer; their higher price is forgotten much quicker than the crappy performance of the cheap imports ...

YMMV
 
The "web" at the center of a drill is a limiting factor in starting holes and in achieving round holes . That web is thicker as drill size increases. A pilot drill web is smaller , the force to start the hole is less , and it can prepare a hole so that the larger drill web rests in the hole while the cutting lips work. Just the other day I was hurried and tried to go direct with a 5/8" drill in a center punch dimple. Result- a three lobed hole due to the drill walking around during extreme pressure to force the cut, and the sloppy result I deserved.

A split drill has had the web thinned to produce rake (of a smaller drill). If you practice a grinder can be used to thin a web. Expect to ruin some drills before you succeeed. IMO:))
 
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