Sharpening Turning Tools Copyright © 2011 John W. Cobb

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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