Tag Archives: bookbinding knives

Old Style Olfa

Adam’s Practical Bookbinding has an intriguing passage regarding knives to cut binders board:

Instead of sharpening the knife, the tip is broken off, exactly the same as modern Olfa type snap-off blades, except that there were no score lines to make the snap. The description of the knife makes it sound similar to a mill knife. I’m not sure why a broken edge would be sharper or hold the edge better when cutting something as abrasive as boards. Recently on the Book Arts Listserv there was a discussion about resharpening Olfa knives to save a few pennies. Could the original broken edge be superior?

Adam, Paul. Practical Bookbinding. London and New York: Scott, Greenwood and Co. and D. Van Nostrand Co., 1903. (p. 86)

For Sale! Wide Round Knife With a Secondary Bevel

The cutting edge of this knife is slightly wider than the narrow Swiss and French knife that I currently make, but the length of the blade is wedge shaped so the area that is gripped is still comfortably narrow.  Also, it has a secondary bevel, which accounts for the strange looking, extremely acute 8 degree primary bevel.  The advantage of a secondary bevel is that there is much less metal to remove when resharpening or stropping. This is especially the case with a thick and wide knife like this. The primary bevel is fairly roughly ground: only half a millimeter of the secondary bevel, which is the cutting edge, is fully sharpened and polished. In a normal knife of this thickness, the length of the bevel would be about ten times this amount. Although I don’t think the time spent sharpening the bevel corresponds one to one, it does take significantly less time.

The drawback of a secondary bevel is that there is not really enough metal to feel it resting on your sharpening system, so this knife is recommended to those that have some experience in sharpening.  This wide cutting edge is useful for hogging off leather for edge paring and also used in a scraping manner for headcap and spine areas. The slight wedge shape on the leather handled knife, and the rounded thumb holds on the wood version provide excellent control.

A2 cryogenically quenched steel, HRC 62. Length: 6.75 inches (171mm).  Width: 1.875 inches (48mm) at cutting edge, tapering to 1.375 inches (35 mm). Thickness: .094 inches (2.4mm). Weight: about 5 oz (142 g). Primary Bevel: 8 degrees. Secondary  Bevel 13 degrees.

ITEM# WRKL: Leather Handle $125.00

ITEM# WRKW: Wood Handle $225.00

New Lifting Knives

These are the newly designed set of lifting knives, available for sale in the tool catalog section on the left.  Both of the knives are made from 01 steel, hardened to about Rc 59.  This hardness results in a durable edge for the prying and cutting.  The knives are polished, with no handle, so they can be used under water for backing removal.  They are based on a Roger Powell design, are perfect lifting covering material, splitting boards, and mechanical backing removal. They can used by right and left handers.  These knives will pay for themselves the first time you successfully lift something without having to do additional repairs. Both are 6″ long, and 1/16″ thick, half the thickness of the previous model.  The large knife is 1″wide, and perfect for lifting covering materials, splitting boards and mechanical backing removal.  If you are a paper conservator, and normally remove backing material with a scalpel, you will find this knife much more efficient, and safer for the user and the artifact.   The small 1/2″ knife is perfect for smaller books, turnins, lifting spines between raised bands, etc….  The rounded, beveled corners allow you to twist the knife when cutting through slips, for example. These knives are the perfect union of quality, simplicity and functionality.   The set includes two knives and a folding leather case, held together with magnets and protects the blades when not in use.    $225.00

Going Cryogenic

 

a2logo

 

Above is an example of blind stamping, using just water and the heat of the type to create the impression on a piece of vegetable tanned horsebutt leather.  The font is Edinburgh, brass type from P & S Engraving in the UK, the top line 14 point, the bottom two 10.  I’ve had these letters for 20 years, and the wear, especially on the “Y” in “PEACHEY” is evident- time to get some replacement letters!  This is the stamp on the blade cover for the new, A2 knives which has been cryogenically treated.  For more technical information about cryrogenic treatments check out nitrofreeze. Please read more about the new knives in  the new tools page on the right, and the results of testing in the post below which convinced me to use this new steel for leather paring knives.  

 

 


The Testing of Steel for Leather Paring Knives

As the result of my own experience,  feedback from some of my colleagues, and the results of scientific testing, I’ve become convinced that A2 cryro and machine hacksaw blades (M2 or M3 steel) are the best steel types for bookbinding knives.  By best, I mean they offer what I consider an optimum balance of edge retention, initial sharpness, ease of resharpening and price for a leather paring knife.

Four leather paring knives were tested by Cutlery and Allied Trades Research Association (CARTA), located in Sheffield, England. The knives were tested for Edge Angle, Hardness, Initial Cutting Performance  and Cutting Edge Retention.  The steels tested were O1, A2, Machine hacksaw blade, and T15.  All the steels rated very good to excellent, overall.  O1 is a popular, standard knife steel, which I make many styles of knives out of, and it works very well on regular, vegetable tanned goat.  Machinery’s Handbook recommends it when extreme sharpness is required. A2 is a newer, high tech steel gaining favor among woodworkers, since it holds an edge longer than O1.    Most large woodworker blade suppliers make both O1 and A2 versions of plane blades, so there is some personal preference involved- do you like to spend a slightly longer time sharpening (A2) or sharpen more often (O1).  Some type of overall time analysis might be conducted, but I can’t imagine it would be very informative given the wide range of unique variables the affect knives in use and when resharpening.  Some bookbinders also use knives made from D2- but I find the high chromium content and coarse carbide structure (up to 50 microns!) make it cut poorly, more like stainless steel than a tool steel.  Fully hardened machine hacksaw blades are traditional metal (starting mid. 20th C.?) for bookbinders to make paring knives from, I assume since it can be purchased already hardened and shaped by stock reduction. Starrett told me their “Red Stripe” blades are made from M3 steel, and I have read the English Eclipse ones are made from M2.  T15 is a super expensive, very high tech steel that outperformed all the other blades, but the inital cost to me, and the number of grinding belts it ate up and time it took when shaping would result in a $750 knife, and  I doubt anyone would purchase a $750 knife.  And you would almost require a set of diamond stones to resharpen it.

I shaped and sharpened all of these knives by hand to a 13 degree angle.  I suspect it is one of the first times that these types of steel were tested at such low angles– at typical woodworking blade is usually 25+ degrees.  The blades were shaped on a 2 x 72″ Cootie Belt Grinder, progressing through US grits of 36, 100, 220, followed by hand sharpening on 3M microfinishing films of 40, 15, 5  microns, then stropped on vegetable tanned horsebutt with a .5 micron chromium oxide and finished by stropping on the flesh side of undressed vegetable tanned calfskin.  The sharpness was tested on a pack of test cards containing 5% silica for 60 cutting cycles, 50N test load and 50mm/sec. test speed.  CATRA has invented and sells many machines for sharpening and knife testing.

1. BEVEL ANGLE

Although I was attempting a 13 degree angle, the edge angled measured between 14-16 degrees for all of the knives when measured with a laser goniometer.  I think this is the result of not being able to hold the knife angle consistently enough when sharpening and the result of stropping.  There also was a general tendency for the angles to be slightly more acute (.5- 1.5 degrees less) at the sides of the cutting edge as compared with the middle.  This is most likely the result of natural hand motion when sharpening, since I usually sharpen parallel to the cutting edge. I suspect if I was in the habit of sharpening perpendicular to the cutting edge, the edge angle would be even more obtuse.

2. HARDNESS

Average from three testing points near the cutting edge in Rockwell C scale.

A2 – 62

Hacksaw (M3) – 64

O1 – 64

T15 – 65

3. INITIAL CUTTING PERFORMANCE (mm)

This is how “sharp” the knife is; how far it penetrated into the cards during the first three cutting strokes.

Tested in accordance with BS EN ISO  8442-5: 2004, Part 5 (Clause 3.4- Cutting Performance)

A2 – 107

Hacksaw (M3) – 107

O1 – 98

T15 – 116

4. CUTTING EDGE RETENTION (mm)

This is how long the edge lasted– ie. the ability for the edge to resist wear.  This is the cumulative depth of  60 cycles of cutting the test pack.

A2 – 522

Hacksaw (M3) – 586

O1 – 395

T15 –  921

CHART OF CUTTING EDGE RETENTION RESULTS

A2 is light blue

Hacksaw is green

O1 is dark blue

T15 is red

CONCLUSIONS. Initially, A2 has a slightly slower rate of dulling, which may be an advantage, but later in the test the Hacksaw slightly surpasses it.  The O1 seems to have a very constant, predictable rate of dulling- the graph is very smooth.  The T15 is incredible- even at the end it was still cutting quite deep, and each cut it still quite deep.  Since O1 is about 400, and A2 is about 600, does this mean A2 is 20% better?  Given all the complex variables in use, it is hard to accurately  observe.  As with most scientific testing, a primary conclusion is the need for more testing.  I would like to compare bevel angles at 2.5 degree increments, add a number of different types of steel, like some of the M and S tool steel classes, maybe some of the new high carbon stainless steels and instead of testing with a sample card containing silica, test actual tanned and tawed leather.  Also the pressure on the blade may be much more than is necessary (or possible) to pare leather, and the sawing motion of the testing machine is different than a more static blade motion that bookbinders use.

knife-shart1