Modifying a spokeshave for paring leather

By Emma Lau, MA Conservation Studies: Books and Library Materials.

At the beginning of each year, books students participate in a three-day course in knife making and sharpening led by Bernard Allen, a designer-craftsman with 20 years of experience teaching sharpening to conservators. We learned about the principles of sharpening and using basic machineries to produce an English paring knife. I had tremendous fun making my own tool and decided that I wanted to look into modifying a spokeshave.

English trained bookbinders often use a modified spokeshave to reduce the thickness of a piece of leather. While there are a few articles written on what needs to be done in order for it to cut leather efficiently, for a books student, it is rather difficult to wrap my head around how to achieve it.

So this is a time to take advantage of the multi-disciplinary community of West Dean: I had a chat with Sam, a second year FdA furniture student, and he was able to show me how to modify my spokeshave specifically for leather paring. I began with researching around the subject to gain a better idea of the modification process, and consulted my books lecturer, Abby, about the reasons behind these modifications. In addition, I was able to observe a properly modified spokeshave which one of my fellow students, Lauren, had modified during a course she took with Jeff Peachey at the North Bennet Street School, Boston.

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Figure 1: modified (black) and unmodified (grey) spokeshave

The Spokeshave Body

In general, Stanley No.151 or Record No.151 flat-sole spokeshave with two adjusting screws are the recommended models for this purpose.

1. Reducing the bedding angle. The blade needs to be at a lower angle in order to cut rather than scraping the leather. Hewit recommends dropping this angle from 45° to 30°, but we found that approximately 35° is the practical limit because we would begin to grind the bottom of the adjusting screws and cap iron screw hole with anything lower. Conroy also mentioned that a lower angle “distorted the tool’s geometry”.

Figure 2: working out the bedding angle
Figure 3: marking out areas to be removed

Feeling privileged to have access to machinery which a bookbinder normally won’t have, we used a grindstone instead of a file to remove the bulk of the metal to speed things up, followed by flattening with sandpaper mounted on glass with 3M spray mount.

Figure 4: modifying bedding angle with a grindstone

2. Enlarging the mouth. To prevent the leather shavings from clogging, we enlarged the mouth to about 5mm by filing the leading edge. Esser warns that opening the mouth too much can cause problems, because “the leading edge of the spokeshave body stretches the leather in front of the blade for a clean cut. If the gap is too wide the leather can begin to ruck up a bit in front of the blade and not cut as cleanly. Also, the outer edge of the leather can be released too soon, flip up in front of the blade, and get sliced off”.

3. Flattening the bed. It is important to ensure the blade is making good contact with the bed to eliminate vibration and chatter. This surface is often roughly cast and covered with an uneven layer of paint. Instead of filing the bed to achieve a flat surface, we decided to resurface with epoxy (because we don’t get to play with epoxy in books). I flattened the face of the blade with 3M Micro Finishing Film (15 micron) to ensure a good contact surface (note that the blade is installed bevel side down for the purpose of leather paring), filled the surface of the bed with epoxy followed by a piece of paper, laid the blade on to the bed and clamped it down to flatten the epoxy using the iron cap screw while it dried.

Figure 5: a thin layer of epoxy was applied to the bed followed by a piece of paper. The blade is placed on top and tightened with the cap screw to apply even pressure

4. Polishing the sole and cleaning up the mouth. The sole was polished to a smooth finish for good sole-to-leather contact using 3M Micro Finishing Film on glass. Irregularities and sharp edges around the mouth were smoothed with a fine file.
 
5. Smoothing and refining the cap iron. The back of the cap iron was flattened with sandpaper and 3M Micro Finishing Film on glass for good contact between the bottom edge of the cap iron and the blade. This minimises blade chatter and prevents shavings from jamming underneath. 

 

Figure 6: poor cap iron-to-blade contact
Figure 7: uneven surface of the back of a cap iron
Figure 8: initial flattening of the cap iron
Figure 9: polished cap iron
Figure 10: flattening the cap iron

The Blade

It is recommended to replace the blade with a higher quality one (O1, A2 and PM-V11 metals). They are thicker so they chatter less and the harder steel holds a better edge.

We replaced the thin original blade with a Ray Iles spokeshave replacement blade, it is made of 3mm thick O1 carbon steel hardened to RC59-61.

6. Lowering the bevel angle

To modify a blade for leather paring, the bevel angle needs to be reduced to achieve a lower cutting angle. We regrinded the bevel to about 15° (the blade becomes too thin and fragile with anything lower) using a Tormek grinder.

The Tormek is a wet grinding system which can run continuously without overheating the blade. The heat developed through grinding on a grindstone can change the hardness of the steel permanently. Once overheated, the end of the blade will turn blue. This is an indication of the steel losing its temper and thus its hardness and ability to retain an edge. Although the grinding process will be slower, a water wheel can effectively prevent overheating.

Figure 11: regrinding the primary bevel on a Tormek

7. Rounding the corners

The corners of the blade need to be slightly rounded to prevent the sharp edges cutting through the leather. This was done first on a 1000 grit waterstone followed by polishing with 8000 grit waterstone.

Figure 12: rounding the corners of the blade

7. Lapping and sharpening the blade

In order to achieve sharpness, the bevel and the back of the blade needs to meet at a point. For them to meet at a point both surfaces need to be flat, true and with as many ridges removed. To achieve this we need to flatten the back of the blade, this process is known as lapping.

The blade is lapped and sharpen using a progression of waterstones (1000 and 8000 grit) and 3M Micro Finishing Film (15 and 40 micron).

Figure 13: lapping the blade with 3M micro finishing film
Figure 14: original (left) and modified (right) blade

I feel privileged to have access to the rich resources here at West Dean College of Arts and Conservation to learn more about my tools. Not only do I now own a much more precise and personalised tool (it really feels like my tool after all of the blood and sweat that has gone into it!), I have also gained valuable skills in maintaining and customising my tools for specific purposes through the process.

References

References

Conroy, Tom. ‘Tips & Techniques - Tuning a Spokeshave’. Guild of Bookworkers Newsletter 155 (August 2004): 11–12.

Esser, Mark. ‘Some Comments on the Spokeshave Modification Article’. Guild of Bookworkers Newsletter 154 (June 2004): 17.

Hewit. ‘How to Modify a Spokeshave for Paring Leather: A Step-by-Step Guide for Adapting Your New Spokeshave for Paring Leather’. Skin Deep 16 (Autum 2003): 8–9.

Peachey, Jeff. ‘A Few More Thoughts on Spokeshave Modification’. Guild of Bookworkers Newsletter 155 (August 2004): 13.

Peachey, Jeff. ‘An Overview of Leather Paring Knives, Tools and Machines’. Jeff Peachey (blog), 28 February 2017. https://jeffpeachey.com/2017/02/28/an-overview-of-leather-paring-tools/.

Peachey, Jeff. ‘New! Redesigned 151 Spokeshave for Leatherwork with Shaving Collector’. Jeff Peachey (blog), 26 April 2016. https://jeffpeachey.com/2016/04/26/new-redesigned-151-spokeshave-for-leatherwork-with-shaving-collector/.

Peachey, Jeff. ‘PM-V11 Spokeshave Blade for Leather’. Jeff Peachey (blog), 16 June 2015. https://jeffpeachey.com/2015/06/16/pm-v11-spokeshave-blade-for-leather/.

Peachey, Jeff. ‘Towards a Type Study of Stanley 151 Spokeshaves’. Jeff Peachey (blog), 5 May 2008. https://jeffpeachey.com/2008/05/05/towards-a-type-study-of-stanley-151-spokeshaves/.

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