2023-07  July

“Sharpening Chisels”

by Member: Bruce James

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[ This article is a documented version of a talk by Bruce James (pictured above), who brought his TORMEK wetstone grinder and an 8" white wheel/linisher grinder to the club for a hands-on session.  There are a good number of points he raised, to have Members think about the geometry of the 'grind' and the care needed to not overheat the tool being sharpened.   The risk of manually sharpening at wrong angles, speeds and lack of accuracy without proper jigs and holders, well demonstrated why it is prudent to invest in the right equipment to do the job quickly, safely and repeatedly the same for each tool.    It was indeed a worthwhile talk, and lead to many questions and light-bulb moments for newbies and long time hobbyists alike.       Gary. ]

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Introduction

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Following a chat to the Committee, Rodney asked if I would come along and share with you what I do when sharpening edge tools. I said yes. I am still learning and by no means an expert. I’ll start by passing around some samples of what can be achieved using these grinders and jigs.

 

Note 2 labels (on the top of the tool, example far below).  At the Club we don’t have many sharp planes or chisels and has been the case for a long time. As a new member it was suggested to me, that I bring my own tools. This was OK with me, but I notice new and old members alike reluctant to commit to this and possibly think all items should be supplied. It has been said that (I can’t find the reference) that as many as 70% of all woodturners quit because they can’t sharpen their tools. One member told me that he hadn’t successfully sharpened his Stanley smoothing plane in fifty years. My own experience of sharpening has necessitated using jigs to get a satisfactory result. This is my near 60-year-old plane iron and chisel jig. In golf there are textbook swings and there are variations of that; the same applies to sharpening. The golf handicapping system helps a golfer, but not so with us.

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Four topics & some discussion points.

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1. Dangers / Safety

Loose clothing, long hair, jewellery can be extremely dangerous. My grade five/six woodwork teacher dangled an old school tie near a whizzing bench drill. The drill bit grabbed the tie wound it around the bit in a nano second which would have had his throat on the drill. Safety glasses / goggles are a very good idea and, when dressing the wheel, I believe a P2 / N95 mask is essential re silicosis.

 

 

2. Sharpening Methods

In modern times we have had all sorts of stones from, Arkansas, slate, marble: oil and water stones; wet, compound and sandstones grinders, typical bench grinders, and now CBN (cubic boron nitride) steel wheels which don’t wear, can’t explode and cut quickly and at reduced temperatures). These all come in various abrasive compounds and grits (particles per sq inch). CBN can be used wet/dry.  An eight-inch grinder @ 2850rpm is travelling at the point of contact with the tool at 1800 metres per minute or 30 metres per second as opposed to Tormek’s  1mtr  per second. Apparently, (internet says) overheating HSS does not ruin the hardness, but Tormek disagrees! They also say dunking extra hot steel in water will develop invisible hairline cracks which will present problems. I try not to go past the faint rust colour. Your finger is a good temperature gauge. I have not seen a professional or any book presenting blue/black tools.   Axiom: The harder the steel the softer the wheel. 

 

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3. Techniques - Freehand vs Jigs
 

Shortening shaping and sharpening all tools.

To sharpen freehand on a bench grinder takes years to perfect. Jigs dramatically simplify the process. Shortening is a waste, whereas shaping is ultra important to the sharpening process. Initially setting up the jigs can be time consuming and frustrating. Shaping takes time, (10-40 minutes) whilst the sharpening can be done in seconds. Richard Raffin says often he won’t turn the bench grinder off because he may need to sharpen every minute or two and doesn’t have time to turn the grinder on/off. Refer parting tool re wheel bearings. I now, after years, can only just do freehand grinding on parting tools, scrapers, and roughing gouges using the copy method.

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4.  Equipment.

The Tormek system allows the grinding formulae to be taped onto the ferrule. My idea is to make a basic set of chisels (6) for each lathe, ground & labelled to standard Club/Tormek formulae’s, or to locate chisels by type and grind on shadow board. Members wanting special grinds should bring their own or create Club chisels and label that grind. Once shaped, sharpening could become a dream for all. I would like the Club to review resources available to members. 

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Discussion points

 

There is a need for both grinders for 1. shaping (fast removal) and 2. sharpening ultra fine cut.
 

There is a need for accurate (Tormek style) jigs that have formulae’s that can be repeated.
 

The Harder the Steel the Softer the wheel: Fast Grinder Wear = Finer cut.
 

Describe EDGE TOOLS (any 2 edges coming together). Sand / polish out grain in effect gouges, polish out back of chisels plane irons. Use oilstone to remove corrugations which are not ideal. E.g. Highly magnified,  it is like sharpening the end of corrugated iron
 

LATHE - wood comes to the tool / GRINDING - wheel comes to the tool.

Pushing in can force the tool up the up the wheel thereby creating a new angle. Jigs can prevent this.

Grinding wheel diameter, reduces with wear, as does a (ground) shortened chisel and needs adjusting to formulae by re-setting in jig. That was my original mistake. How to overcome without reshaping chisel but  avoid changes to the grind angle.

Tormek original wheel SG 250 is 200 grit up to 1000 grit. Their claim: the perfect all-rounder.

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Stanley plane irons and firmer chisels CAN have single grind only as opposed to typical:

- Primary/Bedding grind say 25 degrees  and then

- Secondary/Bevel grind say 30 degrees only on the last 1/4mm in the tip edge

When the secondary bevel exceeds 50% of the primary bevel re-grind primary.

Cardboard between grinding wheel and circular washer/clamp will help  avoid wheel disintegrating.

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Marking method. Freehand grinding.

Let's Explain.  Mark bevel with texta and adjust tool rest until thin vertical line forms on all of bevel (a line being the removal of the texta mark), turn grinding wheel by hand until perfect. This avoids losing prescribe shape.
 

6’’ vs. 8’’ grinder. (1350 metres vs1800 metres per minute) Professionals prefer 8’’ for “polishing” effect but as always it gets down to pressure applied. Same applies to individuals own turning speed on lathe.   Bit of an art form!

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Possible to shop-make all sorts of jigs, distance spacers for variable grinds, or timber cut to angle placed on tool rest etc., All too hard!!  Much smarter and easier to buy a machine with all the right jigs!

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More resources

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TORMEK product guides can be read at:  https://www.carbatec.com.au/product-manuals/tormek

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TORMEK TTS-100 'Setter"Selection Chart (Angles and profiles)   
https://tormek.com/download/18.7be5b7f4182e91609ae1f5cb/1664442858180/TTS-100%20Selection%20Chart%20EN-SV.pdf

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For more tips and examples of Grinding, refer to the four sections related to Grinders, Wetstone, Lathe tools and Chisel sharpening midway through this other KDWC Technical article:   https://www.knoxwoodies.org.au/2022-09-largeprint

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Happy woodworking!   

Authored by KDWC Member: Bruce James       

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images below:
Label showing ANGLE-TO-CUT (ie: 45degrees for this one) on ferule of tool.

Top and side profile of a small gouge demonstrating the angles to cut.
TORMEK in action, using the swivel jig for a perfect rounding of a gouge, by fellow Member: John Wolff having a crack at it.
TORMEK wetsonte unit showing the linksher on the left and wetstone on the right, with the brackets for ogs fitted

Another Members' version of an ANGLE METER made on white plastic, with a gouge being checked

Close up of the swivel JIG on a TORMEK.    A pair of accessories: A flat chisel holder and a TORMEK gouge length gauge.

                                                          

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