Twist Drill Bit

Terminology for multi-facet grinds

General Guidelines for 4-Facet Grind
Drill Bit SIze Point Angle Clearance Angle Notes
Inch
Decimal
Inch
Fraction
Metric (mm) Wire Number Letter Mild Metal, Wood Hard Steel
< 0.125 < 1/8 < 3.0 > 31 118º 14º 11º Can't use the Tormek DBS-22 Drill Bit Sharpening Attachment with these bits -- they are too small. However, one sharpener has used a precision pen vice (like the Starrett 166C ) with the Tormek DBS-22 to hold bits as small as #61 (5/128 in. / 1 mm).
0.125 - 0.250 1/8 - 1/4 3.0 - 6.0 31 - 1 A - E 118º
14º
11º
Bits as small as 1/8 inch can be held in the Tormek DBS-22, but they can flex easily. A pin vice can assist with reducing this flex.
0.250 - 0.500 1/4 - 1/2 6.5 - 12.0 F - Z 118º
11º

0.500 - 0.875 1/2 - 7/8 12.5 - 22.0 118º


> 0.875 > 7/8 > 22.0


Can't use the Tormek DBS-22 Drill Bit Sharpening Attachment with these bits -- they are too large

Material-Based Guidelines
Material Type Point Angle Clearance Angle Notes
Recom. Range Recom. Range
Aluminium 118º
90 - 130º
(as above)
12 - 15º
Clearance angles based on drill bit size should be used.
Armour Plate 135º
135 - 140º

6 - 9º
Brass 118º
118º
(as above)
12 - 15º
Clearance angles based on drill bit size should be used.
Bronze 118º
110 - 118º
(as above)
12 - 15º
Clearance angles based on drill bit size should be used.
Bronze, High Tensile 105º
100 - 110º
(as above)
12 - 15º
Clearance angles based on drill bit size should be used.
Cast Iron, Soft 95º
90 - 100º
(as above)
12 - 15º
Clearance angles based on drill bit size should be used.
Cast Iron, Medium 105º
100 - 110º
(as above)
12 - 15º
Clearance angles based on drill bit size should be used.
Cast Iron, Hard 110º
100 - 118º

8 - 12º
Cast Iron, Chilled 118º
118 - 135º

5 - 9º
Copper 118º
100 - 118º
14º
12 - 15º
Iron, Malleable 95º
90 - 100º
14º
12 - 15º
Magnesium and Alloys 95º
70 - 118º
14º
12 - 15º
Monel Nickel 120º
118 - 125º
11º
10 - 12º
Nickel Alloys 135º
135 - 140º

5 - 7º
Plastic, Hot Set 90º
60 - 90º
11º
10 - 12º
Minimum point angle on the Tormek DBS-22 Drill Bit Sharpening Attachment is 90º.
Plastic, Cold Set 125º
118 - 135º
14º
12 - 20º
Steel, Low Carbon 118º
110 - 118º

7 - 9º
Steel, Medium Carbon 118º
118 - 125º

7 - 9º
Steel, High Carbon 130º
118 - 145º

7 - 9º
Steel, Forged 130º
118 - 145º
11º
7 - 12º
Steel, Alloy 118º
118 - 125º
11º
10 - 12º
Steel, Stainless 115º
110 - 118º
11º
8 - 12º
Steel, Stainless, Hard 125º
118 - 135º

6 - 8º
Steel, Manganese 145º
140 - 150º

7 - 10º


Notes & Comments
Information regarding Grindstones


Good videos showing the use of the Tormek DBS-22 Drill Bit Sharpening Attachment:

Sharpen drill bits with Tormek Drill Bit Sharpening Attachment
Tormek DBS-22
Tormek Drill Bit Sharpening Attachment


Tormek is a copyrighted logo of Tormek AB. Its presentation on this site is used to help the user quickly understand when specific Tormek tools, jigs, or setting are being used. For specific information regarding Tormek AB, or its products, please refer to the www.Tormek.com.


About this site
Remember : The goal of sharpening is to produce sharp tools, and these tools can injure you if mishandled. Safety measures should be followed to protect yourself and those in your shop. Be sure to read and follow all instructions from the manufacturer, and and utilize proper safety equipment. Never consume alcohol or anything that could impair your judgement before sharpening tools, or using sharp tools. Comments can be sent via eMail to me at SharpeningHandbook@Gmail.com.