Drill bit angle????

[Kev Godwin]

Can someone enlighten me as to what the pros and cons are for the different cutting angles at the tip twist drill bits?

Some have shallow angles while others are more steep. Are certain angles best for certain wood types due to grain of the wood? Essentially, what applications would be more suited to a certain angle? :confused:

Thanks for any comments in advance.
Kev

[Tom Veatch]

...Essentially, what applications would be more suited to a certain angle?...

Twist drills are commonly available with point angles of 118° or 135°. I generally consider 118° for the kinds of metals I usually encounter, mild steels, aluminum, brass, etc., and 135° for wood.

Here are a couple of recommended point angle tables for various types of metals. I don't think the characteristics of wood varies enough from species to species that the choice of point angle is very critical. However, I usually try to use brad point drills for wood. I don't know what the point angle on those might be considered; close to 180°, maybe.

http://www.carbidedepot.com/formulas-drills-speeds.htm
http://www.sizes.com/tools/twist_drills.htm

[Kev Godwin]

Thanks Tom,
The links you attached were helpful. I didn't give the bit angle any consideration before until I got my Drill Doctor for sharpening.
Kev

[Kyle Kraft]

Generally speaking, you would use a flatter angle like 135 for tougher materials like Hastalloy and steeper angles like 118 for mild steel. In essence softer materials can use a steeper angle. I have a handbook from Cleveland Twist Drill and I think they recommend for wood a 90 degree point angle.