Sharp,Very Sharp & Frighteningly Sharp……

(when the hair jumps off your arm in fright atthe approach of the sharp blade)

Sharp tools will give a better finish, require less effort, whether itbe pushing a plane or chopping a joint with a chisel.  Producing more precise joints resulting inmore accurate woodwork.  (also: less riskof slips and accidents which means – less blood in the workshop). 

There is little difference between high and low quality tools if bothare dull.  So money spent on qualitytools is wasted if they are not kept sharp

Most tools for woodworkers are ready to use – right out of the box,except for Planes and Chisels which require honing prior to use, even premiumplanes such as Lie Nielsen require some work.

Definitions:

Bevel Side, of Blade: Side which is Ground and Honed. (Notcalled Front of Blade)

Face, of blade: Flat Side (sometimes called the Back – incorrectly in myopinion)

Bevel can be a single flat face or several facesincluding hollow grind and honed facets

Grinding Angle: Angle at which Bevel Side is Ground.  Either Hollow Grind or Flat Grind - hollowgrind is pictured.

Honing Angle: Angle at which the Bevel side is honed.  Angle at the very point of the blade. 

Can be 2-5^o greater than GrindingAngle or in case of “heel-toe” honing, same as Grinding Angle.

Hone or Secondary Bevel: Sometimes a third angle is added to save time.  Honing may be at 5^o greater thanGrinding,  then a Micro Bevel Hone onfiner Stone at 1-2^o extra

Back Bevel: 1-5^o Honed on the Face side ofBlade.  Not for Chisels, only PlaneIrons.  Used in two situations: when Faceis too difficult to flatten and polish. Also when greater approach angle is required in a bench plane, as inYork Pitch, for hard to plane, difficult grain woods. 

Included Angle: Honing angle + Back Bevel angle = Included Angle

Approach Angle: In Planes, angle of blade relative to the wood.  45^o for Bench plane, 22^o+ Honing angle for Standard Block Plane, (maybe 47^o), 12^o+ Honing angle for Low Angle Block Plane, (maybe 37^o).

The 4 “R’s”

• Ready – to Prepare a new Blade
• Refresh – a quick hone to refresh the edge
• Regrind – when the hone area gets to big and takes too long
• Restore – overhaul of an old abused, neglected or damaged Blade

Equipment for Sharpening

Grinding

Honing

• Oilstones. Aluminium Oxide, Silicon Carbide, natural stones such as Arkansas
• Waterstones.  Either natural, man-made, Japanese, American.
• Diamond Plates.  Monocrystaline or Polycrystaline.  Depending on quality, some are flatter than others.
• Abrasive Paper glued to glass or other flat surface.  Silicon Carbide “wet and dry” glued with thin spray contact adhesive.
• Abrasive particles, carborundum or diamond, loose on a flat surface.  This will not produce a flat face as the particles will cut more at the edges than the middle.

For more info on Equipment, see extra notes

Sharp

What is sharp?  Perfectintersection (meeting) of two polished surfaces.  The finer the polish – the sharper theedge.  This Sharp is different to aButcher’s Knife which has very fine serrations which slice the meat.

There is no “wrong” way to sharpen, just better ways.  Better in that they may be quicker, lesswasteful, easier – different methods suit different people and differentapplications.

The Basics

To create a sharp edge or to refresh a dull edge, we must move metal –hardened steel.  Remove the metal aroundthe damaged area to expose a new, fresh cutting edge.  This extraneous metal is removed by “cutting”on an abrasive surface.  For chisels andplane irons, it works better if the abrasive surface is flat.

There are many choices of abrasive medium:

- a block of natural abrasive (such as Arkansas stones)

- a block of bonded abrasive in a man-made block (such as Norton stones)

- or can be loose abrasive particles (such as silicon carbide ordiamond) on a flat surface (such as granite, cast iron or even MDF). 

The choices are wide and various but whatever we choose, the process ofsharpening - of moving the metal - is the same. We start with a coarse grit and go down through the grit sizes or upthrough the numbers.  Whatever we do toone face – we must do to the other, so if we aim to finish at #1000 (Japanese)then it must be both faces.  If we want afiner edge then #6000 or even #8000 must be done on both faces.  For an extremely sharp edge – use extremelyfine cutting compound such as chromium oxide which has a particle size of 0.5micron (very, very fine).  Why do we gothat fine? The finer the edge – the finer the surface finish of the wood andthe easier it is to use the tool.

Essentials for Sharp Tools:

• The Abrasive Surfaces must be Flat.
• Use the entire surface with an even pressure.
• Do to the other side what has been done to the first side.

 #1 - FLATTEN THE STONE:  Before any Sharpening – make sure the Medium is flat. Slight Convex or Hump is OK but Concaved or Dished Stones must NOT be used.   

- Grey Oil Stones (Silicon Carbide) are extremelydifficult to flatten. 

- Brown Oil Stones (Aluminium Oxide) are softerand easier to flatten with Silicon Carbide paper (wet ‘n dry) glued to a flatsurface, or use an old Diamond Plate – do not use a new diamond plate as itwill cause premature wear of the plate. Use Kero as a wash to remove sludge and rubbish.

- Arkansas Stones and soft Oil Stones same asBrown Oil Stones.

- Waterstones can be flattened using SiliconCarbide paper glued to glass using water as a wash.  About 120# for Medium Grit Stones and180-240# for Fine Stones.  Stones usuallyneed flattening because of dishing in the middle, either flatten the entiresurface or, quickly flatten the ends and use these flat surfaces for the backsof small chisels, then flatten again. This will save flattening time and also save some stone – the high spotsare being used to good purpose rather than being washed down the sink.  Another method is to rub similar-grittedstones together under a dripping tap – 3 stones or surfaces are needed toproduce a flat surface.   Some sharpenersfind this produces a fresher surface than when using Wet ‘n Dry, one answer wouldbe to give the stone a few rubs with another stone after flattening on the Wet‘n Dry.  A third method uses the DressingStone sold by Waterstone Suppliers, After Flattening, abrade a small chamfer on the edges by passing acouple of times at 45^o on the Wet ‘n Dry.  This will reduce crumbling of the edge.

- Note: even though abrasive paper glued to glassis flat when the paper is new but it usually wears in the middle and thusdishes and then puts a hump in the Face of the Blade.

 #2 - USETHE ENTIRE SURFACE – EVEN PRESSURE

To lessen the chance of hollowing the stone:

- Keep the Blade flat on the Stone. 

- Use an even pressure on the Stone – same forforward and back strokes - firm but not too hard – let the Stone do the work.

- Use the entire surface of the Stone – use apattern which moves across the Stone as well as going over the ends. 

#3 - HONE BOTH SIDES TO THE SAME LEVEL

If the bevel is honed superfine on 6000# butthe Face is only 1000#, the resultant edge won’t be much better than1000#.  So the Face must be polished to6000# if the bevel is finished to that level of polish.

When breaking in a new blade or restoring onold blade, rather than spend a lot of time polishing to 6000# for a super edge,a utility edge can be reach in a short time by abrading on coarse then medium1000# on both sides.  Each time the edgeis refreshed, go a bit finer until the required level of polish isachieved.  This way the blade can be usedin utility situations earlier if it goes through full polish to a super edge.

Flatten the Face

Very important for Chisels.  Needa flat Face for accurate work.

Plane Irons only need a few mm of flat, polished area so that theunderside of the Back Iron can contact perfectly.  So if the Face of the blade is hollow – leaveit, no need to polish that hollow out. It will gradually work out as the Tip is ground back and the Face ishoned over the years.

A hump can also be removed by using a Pecking Hammer on the bevel sideof the blade to remove the hump, may even create a hollow.  Or use a Die Grinder (Dremel) to carefullyremove some of the excess metal.

A flat surface is required for flattening the Face.  Start with coarse grit and gradually workfiner.  Working at an angle, say 45degrees, the coarse grit will create lines, work from the other side of thestone to remove those lines and create a new set of lines.  Alternate from side to side until allimperfections are removed and the entire surface is lined.  Then go on to a finer grit and repeat untilthe lines from the previous grit are removed. 

Tip:  Finishingeach grit at 90 degrees will produce a set of lines across the blade whichmakes it easy to see when they are eliminated during the following grit.  Work through the grits until the desiredlevel of polish is achieved.

A very fine edge is required for accurate work but not so necessary forutility work.

Tip:  Save timeby half finishing the blade – maybe only go to medium stone, use it, resharpen,use, and go a bit finer each time it is sharpened.  After a while the blade will have a fine edgeand the task will not have been so arduous.

Back bevels on Plane Blades have advantages:

1. It takes too long to flatten the Face of an old blade with rust pitting or one with a convex, humped blade from honing on a dished stone.  An easy shortcut is to create a very small back bevel on the Face.  1-2mm is all that is required.  1-5^o back-angle.  1^o won’t affect normal planing, 5^o is advantageous for hard or cranky wood.
   
2. To increase the approach angle when planing difficult grains.  Some of the old English and Scottish planes such as Norris and Spiers were available in 45^o, 50^o or 55^o angles.  The HNT Gordon Plane (Aus.) has an approach angle of 60^o . 

For 1^o, place a thin strip, such as a steel rule, along oneedge of the stone to raise the tool up. When polishing 50mm from the strip – 1mm will give 1^o, 5mmwill give 5^o etc..  Note: Don’tuse your favourite steel rule as the graduations will wear – use an old wornrule or a thin strip of plastic.

For Block Planes with 22^obed angle – anything from 5-10^o on the back then hone front to givedesired included angle.  Only 5^ofor Low angle block planes which are usually 12^o bed angle.

Angles

            Grinding angles – 5^oless than honing angle

            Honing angles - 30^ois a good all round angle

                        25^ofor parring

                        25-30^ofor block planes

                        30^ofor chisels and plane irons

                        35^ofor heavy chisels and planing cranky or very hard wood

                        40^ofor very heavy mortise chisels

            Micro Bevels – 1 or 2^ohigher than Honing angle.

Grinding

Grinding is done to save honing time. A small area at the Tip only needs to be honed.  The larger the area, the longer it takes tohone so honing the entire Bevel area is time wasted.  Grinding removes metal quickly so grind mostof the Bevel and just hone the very tip – 1/2mm is all the honing needed.

Rough grind flat or hollow.

Hollow grind on a stone no smaller than 200mm – any smaller makes thehollow too deep and reduces strength at the tip.  Some sharpeners prefer flat grinding for thisreason.  Flat grind by machine or by handon a coarse stone.  Manufacturersrecommend that Japanese chisels should not be hollow ground.

If machine grinding without coolant, hold the tool with a finger orthumb up near the edge so the temperature can be monitored.  Let cool when uncomfortably hot.  Do not dunk in water, best to let air-cool, microcracks can form if dunked in water.

Wheels

Grey wheels (Aluminium Oxide) - for Mild Steel or Cast Iron,

White, Red, Blue (Aluminium oxide) - for Tool Steel, (High Carbon Steel, High Speed Steel)

Green wheels (Silicon Carbide) - for Tungsten Carbide.

For Chisel and Plane Iron Tool Steels: 38A80-H8VBE is ideal.  But any from 60 – 120 Grit is OK

A is for Al. Oxide,

80 is the grit,

H is the Grade (hardness of Grit),

8 denotes Grain spacing,

V means Vitrified Bond,

BE denotes a modification to the basic bond.  A80 is important as well as H8V, the rest isflexible.

Wheels should be kept true and dressed using a diamond or carborundumdresser – dull wheels rub more than cut which will burn the steel and losehardness.  During grinding, the steelshould never be allowed to blue, straw colour is the limit before loosinghardness.

One grind will be good for many hones. Each honing will deepen the area being honed until the honing takes toolong, then regrind leaving a tiny amount to hone.  No need to go all the way to the tip unless achip is being ground out, just go 1/16^th from the tip.

Stones

         Grey Stones – carborundum, crystolon - both trade names for silicon carbide(hardest of all) –                    difficult tomaintain flat

BrownStones – aluminium oxide –less difficult to maintain flat

ArkansasStones – coarse, medium whiteand hard black – easier to maintain flat

India – Norton trade name for aluminium oxide

Wachita/Washita – Another trade name - Norton

Waterstones – usually Japanese but some made in USA.  Some are natural (very   expensive), some man-made.  Easy to maintain flat.

DiamondPlates – monocrystalline andpolycrystalline.  The better ones areusually monocrystalline.  The better onesare flat but must be used “all over” to continue to be flat otherwise they maydish in the middle like any other stone.

Note that Japanese grit numbers differ from USnumbers which differ slightly from English/European.  They dowear out, the cheaper ones very quickly and are false economy.

Other Mediums

           Silicon carbide powderor paste on a flat surface such as glass, granite etc

           Diamond powder or pasteon MDF

Polishing compound such as Chromium oxide,Rouge, “Autosol” on leather, wood, MDF etc. for that final mirror finish.

Note that leather strops produce a slightrounding at the sharp edge; which may be excellent for carving tools because ithelps the tool come out of the cut, but this curve will increase the honingangle which is not wanted for Plane Irons and Chisels.

Lubricants (Wash) –not really a lubricant but more as a Washto remove the excess filings and rubbish so that the pores of the stone don’tclog. It is important to use something and not to sharpen dry .

Oilstone: Light Oil, Kerosene or a mix of the two.  Don’t use heavy oil (Engine oil) or NeetsfootOil as they will clog the Stone.

Arkansas, Wachita or India: Light Oil, Kero or Water.

Diamond: Water or Kero.  I've recently found that White Spirit works well - keeps the Plate clean and floats the rubbish away so that the grit is fully exposed all the time.

Waterstone: Water only.

“Scarey” Sharp System

Uses “Wet and Dry” paper (silicone carbide) on a flat surface, such asglass.  As with all sharpening – gothrough coarse, medium to fine with paper grades of #120, #240 to #600 andfiner if required.  The flat surface doesn’thave to be glass; it can be anything which is flat.  Make sure to use the entire paper surfaceotherwise the surface will hollow in the middle and the resultant blade willhave a hump.

Care of the Stone

Look after your stones and they will look after you.

Grey (Silicon Carbide) stones are difficult to flatten – better to “use”the corners and ends rather than try to flatten out any hollow in the middle.

Brown Al. oxide stones are easier to flatten but still difficult.  Use  anold diamond plate with Kero or White Spirit as a wash.

Waterstones are probably the easiest to maintain because they are thesoftest.  The coarser the grit – thesofter the stone.  (It may actually besofter but it seems that it is easier to form a hollow in the middle).

Waterstones can be flattened using paper glued to glass.  #120-220 grit.  (Use spray glue rather than double sided tapeas the tape can compress resulting in a surface which is not flat).  Then use water to wash away the mess.  Some sharpeners rely on the water to adherethe paper to glass but the paper can lift at the corners so the surface is notflat and the result is not flat.

Store Waterstones in water to avoid distortion.  (If they do dry – don’t flatten when dry,soak for 30 min.s then check for flatness – they can reform back to flat statewhen wet).  Not absolutely necessary tostore the finer grits like #6000 in water all the time but should do for #1000.

Honing Guides

The use of a guide takes the guesswork out of the angles and createsaccurate precise edges.  The absoluteminimum of steel is removed to recreate that fine edge, thus saving time ateach sharpen and also saving steel, so time and money is saved.  Good steel is expensive, smart sharpeningwill extend the life of the tool.

After honing, a few sweeps on the back to remove any remaining burr andfinish the job.

Free-hand Hone of Bevel

Is OK for those that have practised for years but for most of us it iseasier to use a guide.  The old thickblades are the easiest to hone freehand using heel-toe method.  Freehand tends to wear the centre of thestone because the user is reluctant to go over the edge so concentrates on thecentre.

 Two methods:

1.  Place the Blade on the Stone with Toe and Heel of Bevel both in contact.  Don’t change the angle – hone Toe and Heel together.  This will ensure the contact angle stays constant.  When the honed facets get larger and close to meeting, then it is time to regrind.  This method is really easy on very thick Irons – 3/16”/5mm.

2. 2.  Place the Blade on the Stone same as above but this time raise it a little to increase the angle then hone.  Recheck the angle often to maintain the correct honing angle.

Rust Prevention

The oil from Oil Stones is enough but if using water as a wash, extraprecautions should be used.

Inox, CRC Longlife, Lanotec, Tallow, are all good – G15 seems to bebest.  It doesn’t stay wet but leaves athin, heavy, protective film.  WD40, RP7or CRC may disperse a little water but have very little rust preventionqualities.  Take extra care with castiron as it is much more susceptible to rust than steel, especially if thesurface is sanded or ground.

Extra Notes

Old, oil-clogged stones can be cleaned with Thinners.

Sharpen often, don’t leave it too long – the edge will take much longerto restore.

Enjoy your tools and keep them sharp,

Jim Davey