Turkish Cobblers Hammer

This French style cobblers hammer is interesting for two reasons- the very short handle, which actually gives a lot of control and I did observe an iterate street cobbler using an identical one, and the unusual method of head attachment.  Earlier French cobblers hammers often has straps that extended down the handle.  Salamon, in his Dictionary of Leatherworking tools pictures one.  In this case, there is not a wedge that holds the handle in the eye, but a hole is drilled through the wood and the thick wire extending up through the sides of the eye are bent over to peen the metal to the wood.  I haven’t been extremly rough with it, but it seems a fairly secure method. I purchased all of these in Istabul, Turkey in 2008.

Paper Knives

The celluloid paper knife below  is a late 19th or early 20th century and  issued as advertising from the A.N. Kellogg Newspaper Company.  I’m confused about distinctions between paper knives, letter openers, page turners and even bone folders.  Neither Etherington or Glaister define their differences, and a few quick internet searches seem to lead to antique dealers selling Victorian versions.  So here is my first attempt at a definition: a paper knife is a large, special purpose type of bone folder, usually with a distinct handle and sharp blade.  It is often made from wood, bone, ivory or celluloid.  It is shaped to allow the user to rapidly slit paper folds.

The marking on the blade  reads “Proprietors of Kellogg’s lists established 1865″.  Kellogg’s list was a compilation of  ” Family weekly newpapers of a better class”  with price lists for advertising.  The proprietors seem quite savvy with marketing- note the book Google  scanned was donated by the publishers to Harvard College Library in 1897.  The surface of the celluloid contains a grain like structure, presumably in order to resemble bone or horn.  When a new material is introduced, it often contains superficial decoration to make it appear more like the original material, this is called a skeuomorph.  Book structures contain many examples of these as well– artificially grained leather, stuck on endbands, fake raised bands, etc….

 

paper-knife

 

pear-paper-knife

I didn’t want to damage the original, so I made a reasonably accurate reproduction out of Swiss pearwood.  When testing the knife, one feature immediately became apparent due to the gentle curve.  It is possible to use the knife to slit a fold moving towards the left, as illustrated below, or moving it forward with the top edge of the knife. It is not so comfortable for folding, if you are holding the handle, since it is so long and the edges are quite sharp, which also supports my hypothesis that this is a single purpose professional knife, and not a general purpose folder. Whoever used it must have had pre-folded sheets. Given the overall length of 12″, I wondered if it was intended as an in house distribution for the various press rooms that were part of the Kellogg empire.  I am unclear why the end of the handle is so pointed– it seems potentially dangerous– did it have some special purpose, or was it supposed to resemble the end of an horn?  In the original, the handle is chipped at the very tip, possibly it was used to open packages?

Paper knives must have been fairly popular, an introductory text for woodworking has making one as a project, although it looks rather crude and slightly dangerous, with the sharp angles.

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              Schwartz, Everett. Sloyd Educational Trainning Manual . N.P.:Educational Publishing Company, 1893.

The rounded handle on this model seemed more comfortable than the one I made, but there are similarities in the shape of the curve and overall length and width.  If I am recalling my mechanical drawing class from High School correctly, it seems the sharp edge of the knife is only on the top of the drawing, which suggests it would be used by pushing forward. The text, in six succinct sentences, describes the fabrication of this knife.  I’m always impressed by the level of common sense that is presumed in 19th C. and earlier manuals, and by the familiarity with the full range of woodworking tools, from  axe to scraper. Contrast this with a current Utube video tutorial which demonstrates how to apply beeswax to linen thread!

“Have the pupil cut from a 1-2” board a piece 2″ x 11″. With the use of axe, plane, tenon-saw and knife prepare an oblong 9-32″ x 1 9-16″ x 9 1-8″. Place drawing upon one of the sides and with the use of tenon and turning-saws cut to within 1-16″ of the line. Cut with the knife and file up to lines. Round and sharpen edges according to drawing. Finish with file, scraper and sand-paper.” (Schwartz, Project 10)

The coolest paper knife I have found is this patented combo paper knife (C), shears, eraser (D), paper folder (E) and seal (F).  This is supposed to combine all the tools a librarian or clerk normally uses into one, convenient package.  Today, we would likely call the “eraser” a scraper.  I can’t see how the paper folder could be used without grasping the sharp edge of “C”, though the patent says all the functions can be used without interfering with the each other.

scissors

 

A close second is the combined paper knife (c), ink-eraser (a), rubber or pencil eraser (b), twine cutter (D), ruler (C), envelope opener (G), pen-knife (B), newspaper-wrapper opener (H) and hang hole (I). The patent notes the handle (C) can be made of ivory, bone, metal, wood or any other suitable material.

opener

 

Any images of other paper knives, or information on how they were used, or images of them in use would be greatly appreciated.

The Testing of Steel for Leather Paring Knives

[Update 29 Feb 2016: Starrett now tells me their red stripe blades are M2]

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.

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