1. Sharpening Turning Tools
Copyright © 2011 John W. Cobb

2. Grinding ALWAYS wear eye protection Most grinders rotate too fast
3600 rpm is normal
‘Slow’ grinders rotate at 1800 rpm
For grinding turning tools, either will work but a slower speed is preferred for 8” wheels
Copyright © 2011 John W. Cobb

3. Grinding Presenting The Tool To The Wheel
Four ways to present a tool to the grinder:
a Perpendicular to the cutting surface – for squaring up the edge
b In-line with the rotation – produces a hollow grind
c Square-on to the rotation – produces a flat grind
d To the side of the wheel – produces a flat grind
Grinding Modes.bmp
Copyright © 2011 John W. Cobb

4. How To Grind Always use a light touch Keep the tool moving
Perpendicular to wheel to square up the profile
In-line to remove excess material
Square on to flatten the bevel on a gouge
(If preferred)
In-line grinding produces a hollow grind. This can be removed on a stone.
Hollow grind can also be removed by gently presenting the tool square-on.
Copyright © 2011 John W. Cobb

5. Grindstone Codes 1 Typical code: 38 A 80 – H 8 V BE 38 A 80 – H 8 V BE
Indicates type of abrasive
used in this wheel
Indicates aluminum oxide abrasive
Typical abrasives are:
A Aluminum Oxide Typically white
C Silicon carbide Typically gray
D Diamond
Copyright © 2011 John W. Cobb

6. Grindstone Codes 2 38 A 80 – H 8 V BE The grit size ( from 8 to 500 )
Use 60 grit for rough grinding
Use 80 or 100 grit for finish grinding
Copyright © 2011 John W. Cobb

7. Grindstone Codes 3 38 A 80 – H 8 V BE
Letter indicating wheel grade/softness
ABCDEFG Very soft
HIJK Soft
KMNO Medium
PQRS Hard
TUVWXYZ Very hard
Use an H grade for woodworking tools
We use a soft wheel so that fresh grains are exposed constantly resulting in cooler grinding.
Slow speeds also greatly reduce heat in grinding.
Copyright © 2011 John W. Cobb

8. Grindstone Codes 4 38 A 80 – H 8 V BE Specifies grain spacing
0 through 12 ( Dense to Open)
Specifies the bond
V is ‘vitrified’ and is used for tool grinding
Copyright © 2011 John W. Cobb

9. Grindstone Codes 5 38 A 80 – H 8 V BE
An optional manufacturers designation for some modification to the bond
Copyright © 2011 John W. Cobb

10. Grindstone Codes 6
The best aluminum oxide wheels for grinding turning tools are, in my opinion
38A46H-8VBE
38A80H-8VBE
60 or even 46 grit for rough grinding
80 or 100 grit for finish grinding, sharpening and re-sharpening
Copyright © 2011 John W. Cobb

11. Spindle Roughing Gouge
Grind the bevel at a 450 angle
Grind the nose with a flat-across profile
A short grind on the side of the wheel will allow the tool to be used as a parting tool on the ends of blanks – very useful
Copyright © 2011 John W. Cobb

12. Spindle Gouge Grind the bevel at 300 to 400 Grind a fingernail profile
Grind a long and narrow fingernail profile for detailing
A low bevel angle makes the wood easier to cleave.
Too low a bevel angle makes the tool too aggressive and subject to catching
Copyright © 2011 John W. Cobb

13. Bowl Gouges
Grind the bevel to about 400 to 500 for bowl gouges with a standard grind
Grind a square-across or fingernail profile
Grind the bevel to 650 or 700 for high-angle bowl gouges
The fingernail profile is used for most purposes.
A square-across profile is useful for dealing with grain that picks up badly or is torn
High-angle gouges are useful for getting into the bottoms of deep bowls
Copyright © 2011 John W. Cobb

14. Skews Ground with two flat or hollow ground bevels of equal length
Move the tool from side to side and back
Bevel length should be about twice to 2 ½ times the thickness of the tool
The tool is MUCH more useful if the cutting edge is slightly curved rather than straight
Copyright © 2011 John W. Cobb

15. Scrapers Ground with two bevels
Long bevel of about 450 to allow getting into tight places
Second short bevel of about 100 to prevent catching
For very hardwoods a narrow shallow bevel on top of the tool edge
(negative rake)
Always remove the burr on the top surface prior to sharpening
A third bevel on the top of a scraper creates negative rake and this feature will prevent a scraper from self-feeding.
This feature is a must on extremely hard exotics such as African black wood, lignum vitae etc.
Copyright © 2011 John W. Cobb

16. Parting Tools Present the back of the bevel to the wheel first
Rotate the tool toward the wheel until sparks come over the cutting edge
Repeat on the other side
Keep the bevels about the same length
Copyright © 2011 John W. Cobb