Some Thoughts About Flattening Your Tools


Much has been written about sharpening.  I’ve contributed to this mass of sometimes-confusing, often-contradictory literature.  As a frequent instructor on the subject, I have some modest experience with the successes and failures of those learning to tune up their edges.

If any part of sharpening can be called fun, flattening is the least among them.  It is certainly the most time-consuming, and it can be one of the most frustrating aspects, as well.

In earlier posts on my blog, I have recommended that students begin their flattening with a known quantity:  a true, flat reference surface.  Some students listen and take the plunge, purchasing a granite test plate, or one of the more expensive diamond lapping plates, also known to be flat.  Others, for a myriad of reasons, choose to use a piece of glass, or a broken  counter-top.

Many folks believe that these surfaces are fine to use for flattening.  Float glass, in particular, is called the “flattest” glass.  As often as I have looked, I can’t find a definition of “flattest”.  Flatter than what?  The old rippled glass from the late 1700s?  Flatter than a stained glass window?  I just don’t know.  Same for a piece of countertop.  I haven’t found a standard that defines when granite is flat enough to be called a countertop, and if that standard implies true “flatness” the way we need it for sharpening.

I’ve seen folks try to flatten their stones using a small DMT plate, with the long dimension of the DMT held at right angles to their water stones.  If ever there was a sure bet to dish out (or round over) the water stone, that’s it. I’ve had students use all kinds of surfaces as their reference, trusting that these are indeed flat.  Many of these same students are dismayed at the condition of the backs of their tools during the flattening process.

Why does this matter?

It matters because flattening is (at least) one-third of the sharpening process.  The steel from the back of the tool makes up half of the cutting edge.  And creating a true, flat surface on the back of a tool is the only action we can perform to guarantee a tool works the same way, sharpening after sharpening.

It matters even more because of the time you spend with your stones and your tools.  Even a well-manufactured tool takes a while to polish.  A less-expensive tool might take hours.  How frustrating is it to work on the back of a tool, obtain a uniform scratch pattern (one of the telltales that our back is as flat as the abrasive), switch to a finer abrasive, and then discover that you’ve still got a hump or a hollow on the back?  If you make this scary discovery, you are left with few options.  You must make the correction at this point.  All of your previous effort must be corrected, and if you don’t make the correction at this point, all your subsequent work will be wasted.  So you go back, flatten your coarse stone on your reference surface, and try again.

But what it the reference surface itself is the culprit?  What if there is a hollow in it, or a hump?  Then you’re creating the opposite sort of defect in the stone, and your tool will never, ever be flat.

So, back to the beginning of this post.  If you’re using glass, or a counter top, or any other “pretty flat” surface, you’re taking your chances.  It matters not that float glass is “the flattest.”  What matters is how flat your piece of glass, or granite, or steel, or whatever, really is.  Unless you know the answer to this question, you take the chance that all of your efforts at obtaining a flat back will need to be redone.

This is why those of us who sharpen a lot, and teach others to do so – make the recommendations we do.  It isn’t so our students run out and buy something else to clutter the shop.  It’s a lesson most often learned through the painful experience of having to re-flatten tools because we didn’t listen when we should have.

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Jeff Zens owns and operates Custom Built Furniture in Salem, Oregon.  He is a frequent woodworking instructor and writer.

Categories: Woodworking | Tags: , , , , | 2 Comments

The Value of Time


I had a very interesting experience recently when I taught a class for the Guild of Oregon Woodworkers.  The class, named “Selecting Hardwoods for Your Project”, was proposed by Chip Webster, who chairs the Guild’s education committee.  Chip originally floated the idea nearly three years ago to another Portland-area woodworking school, but the school was never able to drum up enough students to make the class economically viable.  So he proposed it for the Guild, and the class was held a few weeks ago.

The first half of the class was a discussion during which we talked about the influence of design on lumber selection.  I was intrigued by the various techniques the students use to pick out their lumber.  As I listened to one of the attendees describe his technique, I realized that the woodworker likely came to this process by reading Fine Woodworking, Popular Woodworking, or one of the other publications delivered to our mailboxes every other month.

His technique involved sketching out each of his project’s workpieces and then assembling the sketches into the shape of a stick of lumber:

   
     

At the lumber yard, he searched for a piece of lumber in the bin that had the required dimensions, and added that stick to his cart.  As I thought through this process, I realized that the publications we subscribe to might be doing a disservice to many readers, because this selection process is a lesson readers take away from some of the project-based articles.  Thinking about this on the drive home after class, I recalled many articles that included the same sort of graphic seen above.  What’s wrong with this technique?  It omits any consideration of the graphics – the “figure” of the wood, and how that figure plays into our design.  It’s just a way to buy enough wood.

I also remembered the recent debate, both online and in one of the publications, about the value of cut lists.  During the class many of the students agreed that they calculate their stock requirements extremely closely – some trying to get within one-half board foot.  I wondered if there was a tie-in between the cut lists and their lumber selection processes.

Wood is precious, yes.  It is also a renewable resource:  every year, every tree gets a little bit larger.  New trees sprout from seeds, and many people – including a great many woodworkers and those who supply wood to us – plant new trees every year.  We’re not in danger of running out of wood.  I do not advocate being wasteful.  I am as guilty as the next woodworker of hoarding wood, holding onto little cutoffs and slivers that clutter my bench and shop that should have found the burn pile long ago.  I have also seen trees that should never be cut down, but allowed to die on their own schedule, and left where they fall.  But through all of this I have come to realize that there is a more valuable commodity than wood.  That commodity is time.

The value of our time is measured in several ways.  For most woodworkers, any time spent with tools and wood is time well spent.  It becomes paradoxical that as much as we love our shop time, we hurry to complete our projects.  Might that be related to the frenetic pace of our non-woodworking lives?  Hurry to work in the morning, hurry home, and rush to get the boy to football or the daughter to dance.  Find the time to change the oil.  Spend time with the spouse.   When the pace of your life is governed by the second hand on your clock, is it any wonder that the same pace continues in the shop?

One byproduct of speed is injury.  We all know that.  Another is a mis-cut workpiece.  And if we have calculated out material requirements precisely, how do we make up for the mistake?  Another trip to the lumberyard.  Often, too much rushing produces work that won’t last.  Work that won’t stand the test of time.  Work that maybe shouldn’t last?

Before we go to select our material, we should take the time to design.  We should visualize what, in the best of all worlds, our project would look like.  We should carefully consider the desired graphics of each of the components.  Are we making a paneled door for a cabinet?  What statement should the panel make?  Are we looking for the relative calm of straight-grained Douglas fir, or a bolder statement?  So many questions to answer.

Questions cannot be answered if they are not asked.  That’s why, for me anyway, shopping for wood is designing, or part of it.  If I have done a good job of visualizing the project, maybe making a small sketch with a little bit of detail, I will have a guide that helps me pick out boards that will help me translate an idea into an object.  If all I have is the project – “cabinet”, “table”, “box” – but no idea what it should look like – then I am lost if I go to the lumber yard.  I need the vision first.  And If I can’t fine the wood I need, what then?  Buy whatever is available?  Go somewhere else?  Go home empty-handed and return another day?  What impact do these decisions have on the final result?  Will I regret the choice, or be glad?

Sometimes it’s the other way around.  Occasionally you come upon a plank of exceptional beauty, and neither you nor the wood knows what it wants to be.  While you can certainly force the issue, you won’t be happy with the result.  An obvious example: flat-sawn wood does not do well as rails or stiles for a panel door.  The graphics of that wood are not well-suited to frame the panel.  Straight-grained, rift-sawn wood is often a better choice.  Use the flat-sawn pieces in the panel instead.   Bring home the beautiful plank, if you can afford it.  Stare at it for a while.  Eventually you’ll know what it should be.

The point of all of this is that a trip to the lumberyard can either be a logical step in the translation from concept to object, or it can be a brick wall that abruptly stops that journey.  You’re either carrying out your design (by thoughtfully selecting the wood to execute it) or you’re constructing barriers between design and execution (your material selection imposes limits rather than possibilities).

Good work requires thought, deliberation and time.  Thoughtful, sensitive wood selection makes your valuable shop time more rewarding, and helps to ensure your effort results in a piece that really should last for generations.

Categories: Design, Woodworking | Tags: , , , , , | Leave a comment

Secrets of Happy Grinding


To many woodworkers, grinding a bevel on their cutting tools is a task filled with fear and disappointment.  The dangers are many:  poorly shaped bevels, burned steel, edges that are no longer square to the sides of the tool being ground.  In this post, I will offer some suggestions to help correct the most common problems.

Problem:  Bevels with Multiple Facets

One of the most common problems faced by woodworkers who are just learning to grind tools is ending up with many facets in the bevel.  This situation is most often the result of changing the grip on the tool, changing body position during grinding, or a combination of these factors.  The situation can be complicated by the relationship between the grinder, the tool rest, and the wheel mounted on the grinder.  Here is what happens.  During the grinding process, if the wheel is dressed flat across its face, it is cutting all the way across its width, frequently ¾” to 1”.  Because so much of the wheel is in contact with the steel, the slightest change in the angle at which the tool is presented to the wheel results in a new facet.  These miniscule changes can be caused by shifting your balance, stopping the grind to observe your progress, changing hand positions, and a dozen other causes.  Rather than try to control all of the variables (hand position, stance, etc.) I have found it much easier to limit the amount of wheel surface area in contact with the steel.  I do this by creating a very slight crown on the wheel.  To crown the wheel I use a diamond wheel dressing stick (mine is made by Norton) and remove slightly more material from the sides than from the center of the wheel.  The very slight crown provides me with a lot of benefit.  First, I know exactly what part of the wheel is in contact with the tool.  I can see the steel being removed; some of it remains on the wheel in the form of a dark grey streak.  When this streak gets too pronounced I need to re-dress the wheel, because the buildup of steel in the abrasive will slow the grinding process and permit additional heat to build up.  The wheel is becoming clogged in this area.   Second, the grinding is a lot slower, and that leads to much more control over the process.  For many of my sharpening students, this one suggestion is the single most effective change to their sharpening routine, and it clears up a lot of problems.

Problem:  Overheating the Steel

The grinding operation generates a lot of friction, which, of course, can potentially build up a lot of heat in the steel.  Managing heat is an important part of grinding tools safely and effectively.  There are several steps you can take to mitigate grinding’s thermal impact on tools.  Crowning the grinding wheel effectively limits heat buildup, because you are reducing the abrasive surface area in contact with the steel.  Proper hand position is also critical; if your fingers are located close to the edge, you will feel the tool heating up in plenty of time to slow or stop grinding well before the metal turns colors.

Understanding how heat moves is also important to preventing damage.  Heat moves away from its origin.  Some is radiated into the cooler air around the tool, but a lot of it moves within the steel through conduction.  More mass (that is, thicker steel) can “cope” with more heat than thinner steel.  What this means to a tool at the grinding wheel is this:  as the grinding operation moves closer and closer to the thin edge at the end of the bevel, there is less steel available to dissipate the heat.  If the heat has nowhere to go, it builds up, and the steel eventually reaches a temperature where physical changes occur.  These changes manifest themselves visually through a change in color, and physically through a loss of hardness.  When the steel turns blue, it has lost harness, and that area must be removed by additional, more careful grinding.

This situation becomes even more critical as the point of contact between the tool and the wheel approaches the corner of the edge.  In these two areas, there is the least amount of steel available to conduct heat, resulting in a much faster heat buildup and increasing the chances of damaging the steel.  Here are steps you can take to stop grinder-related heat damage:

  • Use a white (aluminum oxide) wheel, or other “friable” wheel.  Friable means that as the abrasive particles at the wheel’s surface dull, they will break off and expose new, sharp abrasive particles.  Sharper abrasives are more effective, reduce friction, and consequently limit the amount of heat buildup.
  • Use a slower grinding speed.  If you don’t already own a grinder, or if you are making one yourself, look for one that turns at 1,725 rpm instead of the more-common 3,450 rpm motors.  Yes, this will slow down the process, but slower is better as you’re getting started.
  • Use NO pressure.  Let the wheel do the work.  Advance the steel to the wheel, but don’t push.  Let the wheel do its job of steel removal while you concentrate on a smooth and easy back-and-forth across the tool rest.
  • Keep the thumb of your weak hand on the steel, near the wheel.  You will feel when heat builds up.  When you do, stop grinding, or dip the tool in some water to cool it off.
  • Pay close attention, and be very careful, as the freshly-ground bevel approaches those thin corners near the tip.  Do not let the tool linger on the wheel in these delicate areas.

Problem:  Out-of-Square Grinding

This is a very common problem for woodworkers just learning to grind tools.   Fortunately, the solution is quite easy, and it’s foolproof.  Simply put, once you have a square end on the tool, never grind all the way to the edge.  Get as close as you dare, but always leave the slightest glimmer of shiny steel from the previous honing.  If the previous edge was square, the new one will be, too.  The down-side to this technique is that your first honing will take just a little longer, because you will have just a bit more steel to remove as you hone,  But the time this takes will easily offset the additional time you spend at the grinder, correcting for an out-of-square edge.

What to do if the tool isn’t square when you start?  Adjust your tool rest so the edge of the tool is presented to the wheel at 90 degrees (rather than your usual grind angle of 25-30 degrees) and carefully grind the tip square to the edges.  Use an accurate combination square to check.  When you’re there, stop, readjust the tool rest to your desired grind angle, and proceed.  You’ll have a blunt tip to the bevel, and as you grind, that blunt edge will slowly disappear.  Go slowly, and check your progress frequently.  Save just a little bit of the bluntness and hone it away.  When you’re done, the tool will be sharp AND square.

Practice Makes Perfect

Just like every other woodworking skill, no one is born knowing how to grind.  It is a skill that can be learned, and once you learn, sharpening becomes so much easier.  No messing with jigs or tool holders; when you need a fresh bevel, you step up to the grinder, take care of business, hone, and go back to work.  All it takes is a little practice, and maybe a lesson from someone who can observe your technique and offer suggestions.  Practice is clearly called for – but don’t practice grinding away an expensive chisel or plane iron.  Buy an old junker at a flea market or garage sale for a dollar, and get your technique down using that tool; save the Hock irons and Lie-Nielsen chisels for after the practice session is complete.

There are probably other problems people have run into at the grinder, but these are the three big ones.  If you have your own stories, leave them here.  I’ll try to address any problems with simple solutions.  If there is a way to mess up a grind, I’ve done it – but I’ve also figured out how to correct most every error.

Categories: Sharpening, Woodworking | Tags: , , , , , , | Leave a comment

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