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Power Sharpening Equipment
A four-part primer on the tools you really need
to keep your woodworking edge.
Article Contents:
Part 1
- Introduction
Part 2 - Power Sharpening Equipment
Part 3 - Hand Sharpening Tools -
Coming Soon
Part 4 - Sharpening Jigs -
Coming Soon
Part 5 - Books on Sharpening -
Coming Soon
Power Sharpening Equipment
Many woodworkers assume that the place to start their tool sharpening
collection is with power sharpening tools. After all - machines can do it
faster and better, right? This is a common assumption among new
woodworkers. The truth is that power grinders don't sharpen tools better -
they just do it faster. These tools are great for removing large amounts
of materials quickly. In the case of gouges, they are essential for
sharpening. In many cases, if you keep your tools sharp, all you need is a
touch up with a stone to keep on working. Where the grinders do excel is
in major edge re-shaping such as grinding back an entire edge to remove a
nick.
Grinders - An Overview
Most shop grinders are not suitable for sharpening woodworking tools
as they are sold. There are two parts that will need to be upgraded before
they are ready for fine woodworking tools. The first and most important is
to remove the wheel and replace it with one designed for sharpening
woodworking tools. The "stock" wheel is better suited for
sharpening lawnmower blades and general metal grinding.
The second part that should be upgraded is the tool rest.
The rests on most grinders are unbelievably small and difficult to adjust.
It is nearly impossible to control your grinding with these small rests.
There are after-market upgrades available for grinders. However, you can
also build your own shop made grinder rest.
Dry Grinders
Dry grinders are the most common. They are made from a motor with a
grinding wheel attached to the arbor. Fixtures help protect you from the
spinning stone and rests are used to help guide your tools in the
sharpening process. As mentioned earlier you should upgrade the wheel.
Dry grinders are typically setup with the wheel in the
vertical position. When shopping for a grinder you should look for a wheel
size of at least 6" and preferable 8" or larger. This will
minimize the amount of hollow grinding that occurs on the tool. Hollow
grinding is caused when a small wheel grinds a depression into the tool
due to its tight radius.
There are two primary disadvantages to dry grinders.
First, they can overheat the edge of your chisels and turning tools
causing them to loose their strength (known as temper). The second
disadvantage is that materials from the grinding operation can form a
"glaze" on the stone and reduce its effectiveness. A dressing
tool (see below) must then be used to re-condition it.
Wet Grinding
Wet grinding is useful for sharpening tools because; 1) it helps keep the
tools cool and preserves their temper and 2) it helps to wash away the
shavings from the stone. Typically wet stones run at a slower speed than
dry stones. They are available in vertical and horizontal arrangements.
The vertical systems are the most common and many
woodworkers find them easier to use. The stone rests partial submerged in
a trough of water thus allowing a continuous supply of water. Larger
stones are better as they will allow for a flatter finish when grinding.
The horizontal stones lay flat and the grinding is done on
what would be the side of the stone in a vertical system. The advantage of
horizontal grinding is that you can achieve a flatter surface. One of the
biggest disadvantages is that water is typically dribbled onto the stone
from a small reservoir mounded above the stone.
The differences in principal between a vertical and
horizontal wet grinder aren't really all that significant. The real
difference comes in the actual quality and usability of the individual
machine. And that is often illustrated by their price.
Grinding Accessories
Grinding Jigs, Rests & Guides
There are numerous jigs available for grinders. In most cases, the factory
rest is not suited for anything more than general shop grinding or
sharpening axes and lawnmower blades. There are commercially available
grinding rests that can replace the one on your grinder. These rests allow
for more control and precision in the grinding. They typically have a
larger base, are more adjustable for angle, and have guides to allow you
to move the tools without changing the angles. There are also grinding
attachments for the long turning gouges that are especially difficult to
sharpen freehand.
Dressing Grindstones
Dressing stones are used to grind a grinding wheel. The stones are made
from processed materials or metal and are used to flatten the surface of a
grinding wheel. This is very important, as a flat wheel is needed to
ensure a flat true and accurate grind on your tool.
A new stone needs to be properly dressed to ensure it is
"true" on the grinder before use. This important process helps
to eliminate wobble and hop in the stone that can affect the quality of
your grind. Dressing tools are available as stones; diamond tipped rods,
and star-wheel dressers.
Dressing tools can also be used to revive a stone that has
become filled with glaze and other materials. Many woodworkers mistakenly
throw away old grinding wheels and buy new ones at the local hardware
store when all they need is a dressing stone to fix the wheel.
Felt Wheels
Felt wheels are available for fine polishing of chisels and woodturning
tools. They are available in a wide variety of shapes and sizes. They are
often "charged" with an abrasive to help in the process. They
can also be used for polishing of other metals. Felt wheels work better
than cloth wheels, as they are more rigid and hold their shape when a tool
is pressed into them. Specially shaped wheels are also available for
polishing gouges.
The label "polishing" is somewhat of a misnomer.
Polishing is typically a process where the wheel is used to remove a fine
oxide layer from the metal in order to make it shiny. When a felt wheel is
"charged" (or coated) with compound it will actually hone (or
remove) metal from the tool. The amount of removal is typically much
smaller than a grinding wheel and this can be used for finer sharpening.
Sanders
It often comes as a surprise to many woodworkers but sanders are an
excellent way to sharpen tools. Many woodworkers are more likely to have
sanders in their shop than a grinder and it is an excellent place to start
when moving into machine assisted sharpening. There are essentially two
different types of sanders that can be used for sharpening; belt sanders
and drum sanders.
Belt Sanders
Bench mounted belt sanders can be used in the same way as a bench grinder.
The abrasives can be used to quickly remove metal. The large surface of
the belt helps to dissipate heat within itself. Keep in mind that your
tools will still get hot. Belt sanders have the added versatility that
they can sharpen flatter or with a custom curve. This may allow you to
closely match the shape of your tool. Custom curves can be added to a belt
sander by inserting curved blocks between the belt and the sander's plate.
There are now a wide variety of belts available in grits
ranging from extremely coarse to extremely fine grits. Leather belts are
also available in some sizes and can be charged with honing compounds and
used as an electric strop.
Drum Sanding
Drill driven sanding drums can be used to sharpen the inside of gouges and
other curved tools. The drums are most often made from rubber and have a
shaft mounted internally. Quality varies dramatically so watch what you
are buying with these. The drums are available to accept a sleeve or a
sheet of sandpaper. There are advantages to both. The sheet drums allows
you more versatility on your sanding grades. The sandpaper also costs
less. Drums are advantageous as they are quick and easy to use. They are
limited in their grits though.
The drums can be mounted in a drill press or in a hand
drill locked in a vice. Alternately the tool can be locked in the vice and
the drum brought to the tool. The decision on how to mount the drum is
really a matter of personal preference.
Conclusion
Power tools are a great way to sharpen woodworking tools quickly and
efficiently. They remove metal quickly making them efficient at removing
nicks from the edges of chisels and turning tools. Care should be taken
though as power sharpening tools can quickly remove too much metal and
also cause damaging over heating of tools. Bench stones are ideal for
touching up and keeping an edge sharp. We discuss bench stones and tools
in the third part of our sharpening tool series.
Part
1 - Introduction
Part 2 - Power Sharpening Equipment
Part 3 - Hand Sharpening Tools -
Coming Soon
Part 4 - Sharpening Jigs -
Coming Soon
Part 5 - Books on Sharpening -
Coming Soon
For sharpening tools and equipment mentioned in this
article, please visit our online
store.
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