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.

Finishing for Non-Finishers, Part V

Before you begin…STOP!

Careful assembly and surface preparation go a long way to making your finishing techniques pay off.  Said differently, no finish can (or will) cover up every blemish you might leave by not preparing the surface carefully.  In fact, most experienced woodworkers would agree that applying a finish tends to magnify poor surface prep rather than conceal it.  That’s why the first four posts in this series haven’t talked about actually applying the finish.  And that’s why this one starts the way it does.

It’s not too late.  You can still give the surfaces one last, careful examination before you start with the finishing.

Okay, Here We Go

Get out the Sample Boards

Once you’re certain all of the blemishes, scratches, swirls, glue squeeze-out and the rest of it are gone, (and this includes your sample boards, by the way) it’s time to work out your “finishing schedule”.  That’s my term, and it doesn’t imply the timing of the steps, but rather the steps themselves.  And all of the work is going to get done first on the sample boards you’ve saved from the project. While it might seem like a ton of additional effort, working out your finishing steps on project remnants will pay dividends in several ways.

First, it saves the project from ruin.  Unless you have used the proposed sequence of colorants and topcoats before, you don’t really know how they will look on your finished project.  The worst possible outcome is that the finish doesn’t provide you the look you had in mind when you began, or that the finish really does damage the appearance of the project.  In the latter case, I refer to instances like pigment stains on pine, or certain oils on cherry, both species that are prone to significant blotching.  If blotches are the look you’re after, terrific – but better to know your wood is going to react this way before hitting the actual project with the stain.

Second, as you build up your finishing samples, you’re building a library of sorts.  Assuming you keep clear notes about your finishing sequence (more on this in a minute) you can refer back to your library when you’re working on the next project and pick out a sample that offers you the look you’re after.  You will build up familiarity with different finishing products and determine what works well in your own shop.  Here is an assortment of the sample boards from my shop, front and back:

Sample boards, front

Sample boards, back

Finishing Schedule Notes

There are any number of ways you can record the steps you’ve taken as you develop your finishing schedule.  Use note cards, a spiral-bound notebook, or do what I do:  record your work directly on the back of the sample.  No matter how you record your work, write down every step in detail.  A small detail like a change in sanding grit can make a difference in your end result.  One small shortcut is to develop shop standards – steps that you perform the same way each and every time you execute them.  For example, in my shop, “scuff sand” means P320 grit paper held in my hand.  So I save a few pen strokes there.  Recording the process on the sample saves me from searching through the shop for the particular card I need to re-create a finish.

At the beginning of this series, I suggested that the time to chose a finish was before you started work.  If you have done that, you’re ahead of the game. If you haven’t yet made those decisions, now’s the time.  Since this series is aimed at non-professional finishers and woodworkers, my advise is to keep things simple at the beginning.  That’s why plain shellac is the first finish I’m going to suggest you get acquainted with.

Getting to Know Shellac

As a top coat, shellac has a lot going for it, which is why it has been around for so long.  It’s natural and non-toxic.  You’ve probably eaten it more than a few times: ever wonder what makes the outside of M & M’s so smooth and shiny?  You’ve probably seen someone wearing it in their hair, too.  Ever wonder what finish preserves the American furniture in the Smithsonian?  There are a lot of reasons its popularity has lasted.  I recently grabbed a few apple boxes from my local grocery store, and guess what is printed on the bottom!

A family-friendly finish....

For the beginning finisher, shellac has a number of other benefits.  Because its solvent is alcohol, each succeeding coat dissolves the preceding one, and they essentially “melt” together.  So as you add coats, you’re really not building one coat on top of another with discrete borders in between.  Instead, you’re just making one layer thicker and thicker.   If you decide that you have really messed up the job and need to start over, a thorough soaking with alcohol will return the shellac to solution and you can wipe it off the surface and start over.  This means that the finish is easily repaired, too.  Of course, being alcohol-soluble has at least one strong drawback: if you spill an adult beverage on this finish, it can be damaged unless you clean it up immediately.  Clearly this could be a limitation for a tabletop, but for boxes, bedroom furniture (dressers, bed frames and so on) shellac might be all you need.  Finally, because you aren’t using any drying oils, there is no risk of spontaneous combustion from oil-soaked rags.  You do, however, want to provide plenty of ventilation to disperse the alcohol fumes, which are flammable and can be explosive in high enough concentrations.

Shellac has several other useful properties that endear it to finishers, professional and amateur.  Diluted concentrations of shellac are often used as a “wash coat” on bare wood.  Depending on the amount of shellac dissolved in the alcohol, the “wash coat” controls (limits) the amount of coloring or penetrating finishes (like oils and pigment stains) that will absorb into raw wood.  For those blotch-prone species like pine and cherry, a dilute coating of shellac goes a long way to eliminating the problem.  More on this later in the post.

In the same way that shellac helps to seal bare wood, it can provide a barrier between different steps in a finishing sequence.  Say, for instance, that you have dyed a project with a water-soluble dye, and being environmentally friendly,  you decide to use a water-based topcoat.  A seal-coat of shellac in between the dye and the topcoat will prevent the water in the topcoat from re-dissolving the dye.  The uses go on and on, and your continued research and experimentation will produce more than I can write about here.

The November/December 2010 issue of Fine Woodworking magazine has a good article on the origins and processing of raw shellac.  It’s interesting reading.  For the purposes of this article, I’ll summarize and condense some of that information and more into a few short paragraphs.  The article is worth the read, if you have time and a subscription.

Raw shellac includes a component of wax, which all by itself is of no concern to a finisher.  However, when shellac with wax is used as an undercoat to some other finishes, there can be a problem with the succeeding layers adhering.  To address this issue, shellac manufacturers have “de-waxed” and then dried shellac into flakes that you can dissolve in alcohol, making your own concentrations of shellac as a finish right at home.  Along with the dewaxing process, the color of the flakes can be controlled, giving you the option of colors ranging from a warm honey-amber hue to nearly colorless.  These options provide you with a lot of control over how the shellac looks on the project.  Shellac can also be tinted, giving you even more precise control.  In its colorless state, it will do little to change the color of the project.

Shellac’s concentration is measured in the number of pounds of shellac dissolved into a gallon of alcohol.  This concentration is referred to as the shellac’s “cut”.  One pound of shellac flakes dissolved in one gallon of alcohol is known as a “one-pound cut”; two pounds as a “two-pound cut” and so on.  The amount of shellac in alcohol is an important factor for a finisher.  The more shellac in the solution, the more you’re applying with each coat and therefore the fewer coats you’ll need to build up the same film thickness on the project.  There is a drawback to using higher cuts of shellac: the higher the concentration, the harder it is to put on a streak-free coat by hand.  A three-pound cut is about as high a concentration as you’re likely to find, or want to mix yourself, and I think you would have better initial luck with a one- or two-pound cut.

Before you decide to start mixing your own finishes, here’s a time-saving suggestion.  Buy a quart (or a gallon) of a product called Seal-Coat, made by Zinsser.  This is a dewaxed shellac in a 2-pound cut, and it does a great job as that “barrier coat” I mentioned a few paragraphs above.  Finishers refer to this barrier as a “wash coat”.  If you’re going to apply a wash coat, dilute some Seal-Coat with an equal amount of isopropyl alcohol, which you’ll find at paint stores and in the paint departments of the big box stores.  Brush the mix on with a natural bristle or Taklon-bristle brush.  Work “off” the edges (in other words, start your stroke a few inches in from an edge and brush off the surface) and keep a wet edge.  Don’t rebrush or try to “tip off” the shellac – put it on and leave it alone.  When it’s dry (allow half an hour) gently scuff-sand the surfaces with P320 grit sandpaper, and you’re ready for the next step in your finishing schedule.

Shellac can also be used all by itself – not as a wash coat, but as the entire finish.  As I mentioned, it’s been used as a finish for hundreds of years.  If you plan to use shellac as the only finish for your project, it’s time to consider mixing your own.  More on that subject in the next post.

So, on your sample boards, either tape off sections or use a table saw, radial arm saw or cutoff saw to cut kerfs across the width of the sample.  Apply a thin coat of your shellac to all but one end section of the sample board.  The end section will be used to judge your first color layer without the benefit of a wash coat.  The rest of the board will start with the wash coat as the first step in the finishing sequence.

In the next post we’ll talk a little about color and the use of shellac as a final top coat.

Here are links to the first four posts in this series.

Finishing for Non-Finishers, Part I
Finishing for Non-Finishers, Part II
Finishing for Non-Finishers, Part III
Finishing for Non-Finishers, Part IV
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Jeff Zens owns and operates Custom Built Furniture in Salem, Oregon.  He is a frequent woodworking instructor and writer.

Finishing for Non-Finishers, Part IV

Now we’re ready to do final assembly operations for the project.

Before you begin, I recommend that you do some serious housekeeping around your bench or your assembly area, if you have a separate spot. If you are like a lot of woodworkers, you might have a tool or two on your bench, along with some sawdust or shavings from your hand plane or scraper. Right now is the time to get all of the debris left over from your milling and smoothing operations cleaned up. Put away all of the tools, vacuum the bench top and the floor. You’re at the point in the project where significant care should be taken to maintain the surfaces you’ve worked hard to create. This additional care during assembly will pay off when you begin applying a finish.

Get your hands on some carpet remnants or a quilted moving blanket to cover your bench or assembly table. Even with a clean bench top, project components can (and do) slip out of your hands and a collision with a hard bench top can ding an edge or round a corner. A bit of padding on your work surface will help prevent damage.

Careful Clamping is Key

Clamping components together is a staple of the glue-up and assembly processes. But clamps can damage components if they’re not carefully applied, and if a big bar clamp slips or slides into your work, you have repair work ahead.

I  use four kinds of clamps in my shop. I have a lot of pipe clamps with Jorgensen heads. The nice thing about pipe clamps is the ability to change clamp length by moving the heads to different length pipe.  Over the years I have epoxied small squares of 1/4″ MDF with rounded edges to the faces of both clamp components,  rounded edges facing the component to be glued up. I have found that it is considerably easier to attach these clamping blocks or pads to the clamp than it is to struggle with loose clamping blocks, the clamps, the glue bottle, and the components. The alternative, which I did for a few years, is to tape clamping blocks to the components before gluing up. Eventually I wised up.  Here’s an image:

MDF pads epoxied to clamp fixtures

The second kind of clamp I use is a Bessey K-body in varying bar lengths. I like the performance of these clamps, but they are expensive, and limited by the length of the bar. I have not found the pads to mar or discolor surfaces, but if I am applying them to relatively soft woods, I will use a clamping block where needed.

The third clamp style is a Jorgensen F clamp, either the heavy-duty or “3700” style clamps.  I don’t use the light duty clamps for glue-ups because there is too much flex in the bar.  The heavy-duty style does an acceptable job in the right circumstances, with one caution: the factory-applied orange clamping pads will stain the work if they are left in place too long.  Some time ago, I removed these clamping pads and replaced them with MDF pads similar to those pictured above.  In my shop, the “3700″ clamps are mostly utility clamps, and see limited duty during glue-ups.

The fourth and final style clamp is a wooden handscrew. These “old-fashioned” clamps can exert a tremendous amount of clamping pressure, and are really quite useful in the right application. They are limited by the size of the jaw opening, and so are not suitable for large-scale glue-ups.

There is at least one trait common to all of these clamps: they must be kept clean.  Furniture assembly is messy business.  Glue gets squeezed out of joints and panels, and some of it is going to find its way to your clamps.  Clean it off as soon as the glue-up is complete.  The drop you miss today will be the one that gets pressed into the surface of your next glue-up.  How do I know this?  If you’re clamping panels using pipe or bar clamps, it is sometimes helpful to put a short piece of masking tape on the bar or pipe directly below the joint being glued.  That way, squeeze-out can be easily removed when the glue-up is complete.

A Last Look and Some Housekeeping

Once the project is completely glued together, do a careful inspection of every surface. You’re looking for any errant glue squeeze-out, as well as any damage or marking caused by the clamps. The best way to look for these assembly remnants is with strong light from a window or from a set of halogen lamps on a stand. You want the light raking off the surface at a low angle and bouncing into your eyes. Take your time and look at every surface and joint. If you find glue use a scraper, a sharp chisel, or a dental pick to remove it. If you notice marks from the clamps, a light sanding or a touch-up with your scraper or hand plane should clean things up. Use care when manipulating the project to preserve all of the surface preparation work you have done. Keep the project on the moving blanket or carpet remnant as much as possible.

I like to clean the finishing area of the shop the night before I plan to apply finish. I will vacuum floors and work surfaces, and also vacuum the project. I also turn off the ceiling fans so that any bit of airborne dust have the chance to settle out of the air. I save the tack cloth for just before the first coat of finish goes on.

Now is the time to get out the project cutoffs mentioned earlier in this series. They should have been planed, scraped or sanded (or all of the above) just like the project components were. They should be vacuumed to clean up what dust has accumulated since you produced them.

In the next post we’ll start applying finish to the sample boards and evaluating the results.

Previous Posts in this Series:

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

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