Posts Tagged With: Skills

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.

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

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

Finishing for Non-Finishers, Part III


Preparing Surfaces for Finishing

Hand Work Requires Thought

Let’s get down to some basic facts.  Lumber goes through a number of steps on the road to becoming a component in a piece of furniture.  Typically it is sawn, jointed and reduced in thickness.  Additional shaping operations might also be involved.  Each of these steps leaves a signature behind and those machine marks are not a decorative effect.  You really cannot leave them behind and later call them design features.  They all need to be removed.  How you accomplish that impacts how you finish, and what that finish looks like.  Woodworkers generally choose one of two options: cutting (hand planes, scrapers) or abrasion (sandpapers).  As a general rule, do as much of this work as you can after the joints are cut, but before gluing up.  It’s a whole lot easier, for example, to clean up the apron on a table or the rails on a chair before rather than after they’re glued into the legs.

Admitting my Bias

In the interest of full disclosure, I am mostly a hand-tool woodworker.  That is not to say that I don’t use power tools.  I use them whenever they make sense.  There are many times, though, when a hand tool does a  job faster, more safely, and give a better result.  So if the following comments lean a little in the direction of hand tools, you’ll know why.

A Case in Point: The Hand Plane

Students who have taken my classes know I hate sanding.  Detest it.  So I avoid sanding as often as possible.  There are a number of reasons I feel this way, but the one that relates most directly to finishing is that sanded wood and hand-planed (or scraped) wood looks different.  One surface has been abraded to make it smooth, and it looks hazy.  The other surface has been cut to make it smooth, and it looks clear.  If you don’t believe me, do the following demonstration for yourself.  Take a well-tuned hand plane with a sharp iron, and plane the surface of a piece of cherry or oak, or whatever hardwood you have on hand.  Plane it until the milling marks are gone and you have a nice smooth surface.  Now take a piece of sandpaper of the grit you would normally use last in a sanding progression.  Most woodworkers don’t (and shouldn’t) sand beyond P220 grit, so use that.  Sand half the board you just planed.  It will be smooth, for sure.  But look at the difference between the hand-planed surface and the sanded surface, and you will see what I mean.  Hold it up to a window on a bright day and look at the way light reflects off both surfaces.  There is a marked difference, and I think the hand-planed surface is more appealing.

However, using a hand plane forces you to understand wood grain.  Ignore that characteristic at your own peril when you approach the workpiece with a plane.   Plane in the wrong direction and you risk tearing out chunks of wood, adding untold hours to your project as you wonder how to repair the damage.  If you’re a hand tool user, wood grain plays a role in a lot of the decisions you make.  When you’re gluing up a panel for a table top, for example, you want the grain in each part of the top running the same way, or you must change the direction in which you plane.  And if you bookmatch a panel, you have introduced a grain reversal.  Nothing you can do about it, so think it through carefully.

In any event, a well-tuned hand plane with a sharp iron will make short work of marks left behind by saws, jointers and thickness planers.  They are most certainly worth the time and effort needed to learn to use them well.  As your skills and fussiness increase, you will find that scrapers can remove the little marks left by hand planes and yield a beautiful, smooth surface.

Sanding

Sanding will get rid of the machine marks, although it will be slower, noisier and much dustier.   There are some woods that are really difficult to plane; any species with interlocked grain falls in this group.  So plan extra time, make sure you wear hearing and eye protection and carefully plan a way to keep all that dust out of your lungs.  And while you’re at it, plan some extra time to clean up the dust from your shop before you start finishing, so the little dust nibs don’t fall out of the air onto your nicely sanded and now-wet-with-finish tabletop.

If I am forced to do a lot of sanding, I allow extra time in the schedule to account for dust.  Initially I try to minimize as much dust as I can by using vacuum attachments for power sanders, and by constantly vacuuming the surface as I finish hand-sanding.  Typically I will sand one day, allow another day for dust to settle out of the air, and vacuum my finishing area on the third day.  Finishing begins the day after.

As a rule of thumb, P220 is as far up the grit progression as you need to go on the bare wood.  As long as you have done a good job and were careful not to skip grits (remember that sandpapers are a system, and they are designed to work sequentially) going beyond P220 is a waste of time.  I strongly suggest that the final sanding step be done by hand rather than machine.  Sand with the grain, and sand carefully. Your objective is to ensure you haven’t left behind any of those little “pig-tails” that are the telltale of a random-orbit sander.

A Final Inspection

Before you put away the sander, the scraper or the hand planes, wipe down your project with denatured alcohol or naphtha.  Use the brief time before the solvent evaporates to carefully examine the surface for imperfections.  I like to use a bright light to help with this inspection, either a double halogen work light on a stand, or the sun through a window.  The light should come from in front of you, bounce off the work and then reflect into your eyes at a very shallow angle.  This is your last chance to catch a bit of tear-out, some glue that you missed, or any other blemish that will be magnified by finishing and top-coating.

Remember Those Cut-Offs?

If you saved cut-offs from the project, treat them the same way you are treating actual project components.  If you are sanding, sand the cut-offs with the same grits in the same progression.  If you are hand-planing, or scraping, do the same to your remnants.  This step is important, so don’t skip it.  While you’re at it, start making notes about what you are doing, and write them on the cutoff – on the side opposite the one you’re planing, scraping or sanding.  You will add to these notes later, so leave room to document additional steps.

In the next post we’ll talk about the assembly process and the final preparations for applying a finish.

Finishing for Non-Finishers, Part I
Finishing for Non-Finishers, Part II

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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: , , , , | Leave a comment

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