rec.woodworking Frequently Asked Questions
James Roche
Archive-name: woodworking/faq/faq
Last-modified: 04/26/96
Copyright (c) 1994 by James J. Roche. All rights reserved.
I have been reading and archiving rec.woodworking since its inception
as net.rec.wood back in 1984. Below are some of the topics that seem to
come up frequently.
If you have any constructive comments please let me know. If there is
something you would like to see added please pass it on to me.
TABLE OF CONTENTS:
1). Should I buy a table saw or a radial arm saw?
2). Which type of dado blade should I buy, the dial (wobble type) or
the stacking (chipper type)?
3). How do I cut the perfect dado if both types of dado blades have
shortcomings?
4). Should I buy a Sears blurfl?
5). Should I buy a Taiwanese clone blurfl?
6). How do I remove paint?
7). Should I use a hot melt glue gun for my next project?
8). Where can I get plans for the New Yankee Workshop projects?
9). What is the best woodworking magazine?
10). What is a board foot?
11). What is the correct way to handle the glue squeeze out problem?
12). What books should I purchase to learn about various aspects of
woodworking?
13). How do I finish toys so that they are non-toxic?
14). What size drill bit do I use for a wood screw?
15). How do I finish the edge of plywood?
16). Which saw blade should I buy?
17). Where are the archives for rec.woodworking?
18). Where can I find cradle plans?
19). Where can I find futon plans?
20). Where can I get information about particle board?
21). What are some of the common woodworking terms/abbreviations?
22). How do I finish a cutting board?
23). What is snipe and how do I eliminate it?
24). How is lumber graded?
1). Should I buy a table saw or a radial arm saw?
Table saws work best for ripping. Radial arm saws work best for
crosscutting, but are limited by their arm's length. Both
saws will perform both tasks. The radial arm is more adaptable for
non-sawing tasks. For instance, overhead routing, surface planing, and
drum sanding attachments are available for some radial arm saws. You
can buy a disk sanding attachment for use on most table saws.
Ripping on the radial arm saw is difficult because it is necessary
to push the lumber under the motor housing. This problem can be
minimized by use of pushsticks and holddown wheels. Maximum rip width
is normally limited by the length of the arm. Building a secondary rip
fence on the other side of the table from the column will enable you to
rip wider pieces, but the off-cut piece width is then limited. Radial
arm saws are more prone to overheating during rips in thick wood since
the teeth stay in the cut longer, unless you cut substantially into
the table top and even then there is no place for the sawdust to exit.
Crosscutting on the table saw is difficult because it is tough to
keep a board much longer than 4 ft square to the blade. This
problem can be minimized by building a good sliding panel cutter. Some
table saws have built-in sliding tables, and aftermarket sliding table
attachments are available for most saws. A couple of saws have sliding
arbors, enabling them to work as inverted radial arm saws. The arbors
typically don't slide as far as the length of many radial arms (for a
review of 2 of these saws, see the April 1992 issue of FWW).
Both saws are capable of accurate work. The radial arm saw, with its
cantilevered arm attached to a cantilevered column, is typically less
rigid than the table saw, which usually have their arbor trunions
bolted to the table in a wide pattern. Worn arm bearing in radial arm
saws can also contribute to wander in the cut. In table saws, play of
the miter gauge bar will adversely affect accuracy.
Both table saws and radial arm saws need to be aligned to work
optimally. There are more aligning tasks to be performed on a radial
arm saw than on a table saw. Radial arm saws typically require
realignment more frequently than table saw, perhaps because of the
stresses put on the cantilevered assemblies.
Radial arm saws don't need as much space around them as table saws for
performing equivalent tasks. On the radial arm saw, boards are always
oriented the same way whether you are ripping or crosscutting, so you
need space to the left and right of the blade, and only as wide as the
widest board you're cutting. On the table saws, boards are oriented at
right angles depending on whether you're ripping or crosscutting. Thus,
you need space in front and in back for ripping, and to the left and
right as well for crosscutting.
It seems to be easier to engineer and manufacture a table saw than a
radial arm saw, which has more moving parts that must withstand large
forces without deflection or play. It can therefore be argued that if
you're on a budget, a cheap table saw may work better for you than a
cheap radial arm saw.
Some people say the radial arm saw is more dangerous because the blade
is exposed above the work surface, and because the blade's location
varies as the cut progresses. Angled crosscutting is particularly
dangerous since the blade is now cutting where one normally holds the
work. The spin direction of the blade tends to lift the work off of
the table when ripping, and can pull the carriage into the work
(resulting in binding of the saw or serious injury to a careless
operator) in the crosscut position. So-called "safety-blades" have
a shoulder in front of each tooth, thus limiting the amount of pull
generated and reducing these tendencies.
Some people say the table saw is more dangerous because you can't
see where the blade is like you can with the radial arm saw. On the
other hand, the blade is always in the same spot on the table. The
spin action of the table saw's blade tends to keep the work down on
the table, but it can also throw the work, and off-cuts, back at the
operator.
Both machines are very dangerous and should be treated with much
respect.
As with all tool buying decisions, you should consider your intended
applications, both now and in the future. The general consensus is that
if you're building things like jungle gyms, house additions, or trim
work (moldings), a radial arm saw may be best. If you're building
things like fine furniture or cabinets, a table saw may be more a
more appropriate choice.
A number of people have reported that the addition of a motorized
miter box to a table saw is a satisfying combination.
Taunton Press publishes a softcover book titled "Fine Woodworking on
The Small Workshop." It contains a number of articles on designing and
buying equipment for small shops, but is geared to furnituremaking.
The majority of the recommendations are for getting a table saw first,
with one writer claiming a bandsaw is the first tool to buy.
2). Which type of dado blade should I buy, the dial (wobble type) or
the stacking (chipper type)?
The wobble type is very simple to use with infinite settings
between approximately 1/4 inch and 13/16 inch. It does not produce
true right angle cuts because of the design.
The chipper type doesn't have the same infinite setting for width.
You can achieve nearly infinite settings by adding shims with
thicknesses of 1/32, 1/64, 1/128, etc. It will cut a square bottom
on the dado, but it will also leave 2 grooves on the edges of the
dado. The reason for this is that the blades are slightly larger
than the chippers. The larger blades are to reduce the splintering.
The blades can be reground to be equal to the size of the chippers
at the possible cost of increased splintering. Some say the grooves
are a benefit because they provide relief for gluing joints.
Many people claim that the wobble type is easier to set up.
The August 1991 Fine Woodworking further studies the features of
the various types of dado blades.
3). How do I cut the perfect dado if both types of dado blades have
shortcomings?
Your best bet would be to cut it with a router.
4). Should I buy a Sears blurfl?
Most people agree that the Sears stationary power tools sold today
aren't the same quality as the Sears tools sold 20 years ago.
It can be argued that if you can't afford to buy a Delta, then
you should be looking at one of the Taiwanese clones rather than
looking at Sears.
5). Should I buy a Taiwanese clone blurfl?
It depends on how much money you have. If you can afford the
Delta blurfl you should probably get it. Buyers should be
wary that not all Taiwanese clones are quality machines. The
general consensus is that Grizzly has good quality control.
It should be noted that some of Delta tools are now being made
in Taiwan. One would hope that Delta quality control is better than
some of the cheaper imports.
6). How do I remove paint?
There are many ways to strip paint from wood.
Paint can be removed by scraping and/or sanding.
Paint can be removed by using chemical paint removers.
Paint can be removed by using heat.
Paint can be removed by sandblasting.
Paint can be removed by a new product known as Peel-Away.
Rumor has it that oven cleaner also works.
If you know of another way to remove paint please feel free to pass
the information along.
7). Should I use a hot melt glue gun for my next project?
The general consensus is that hot melt glue is not adequate
for woodworking projects. However, hot melt glue guns can
have a place in the shop. Many people like to use them for
tacking items together such as when building forms or jigs.
8) Where can I get plans for the New Yankee Workshop projects?
Plans for any of Norm's projects can be ordered for $7.50 from
(project name)
New Yankee Workshop
P.O. Box 645
Bedford, MA 01730
Videos, which include a copy of the plans, cost $24.95 plus shipping
and handling, from 800-272-0280. Both the address and phone number
are given at the end of each show.
Most of the projects from the first two seasons are in the two
New Yankee Workshop books. For the workbench, one important
dimension is *not* given in the book, though it can, I think,
be calculated.
9) What is the best woodworking magazine?
There are many good woodworking magazines. Two that are frequently
recommended in this group are Fine Woodworking and Woodsmith.
Fine Woodworking is a bit on the artsy side and more for the
experienced woodworker. It does not get into the small details
of a project.
Woodsmith provides much more details for projects. Woodsmith is
well suited for both the amateur and experienced woodworker.
10) What is a board foot?
A board foot is a common unit used in the measurement of wood.
It is equal to 1 foot length x 1 foot width x 1 inch thick.
It should be noted that the thickness is nominal thickness.
After drying and surfacing the usual thickness of a 1 inch
board is 13/16.
A board 10 feet long x 1 foot wide x 2 inches thick would be
equal to 20 board feet.
11) What is the correct way to handle the glue squeeze out problem?
Use the right amount of glue. The (obvious) danger is a glue
starved joint.
Wipe off the excess glue immediately with a damp sponge or paper
towel. This method gets mixed reviews. Some claim the water-glue
mixture will soak into the wood and show up when the piece is finished.
Others say that this is not a problem. The effectiveness of this
method probably depends on the type of wood and finish that are used.
Allow the glue to harden somewhat (1/2 - 2 hrs) and then
chisel/scrape it off. Some recommend removing the glue after it
begins to film over.
Either finish the pieces ahead of time or apply paste wax. This
should prevent the glue from sticking. The problem with this is
removing the paste wax prior to finishing.
Use a plastic drinking straw cut at 45 degrees to scoop the glue
out of the inside corner. As the straw fills up, it can be trimmed to
provide a fresh surface.
12) What books should I purchase to learn about various aspects of woodworking?
Thanks to Ken Smith (kens...@cs.Buffalo.EDU) for providing the
ISBN numbers along with a couple of additions to the list.
GENERAL WOODWORKING
Cabinetmaking and Millwork - John L. Feirer
ISBN 0-02-675950-0
New Yankee Workshop - Norm Abram
ISBN 0-316-00454-5
Classics From The New Yankee Workshop - Norm Abram
ISBN 0-316-00455-3
Mostly Shaker - Norm Abram
ISBN 0-316-00473-1
Encyclopedia of Furniture Making - Ernest Joyce
ISBN 0-8069-6441-3
FINISHING
The Woodfinishing Book - Michael Dresdner
ISBN 1-56158-037-6
INTRODUCTORY WOODWORKING
Basic Woodworking - Sunset Books
ISBN 0-376-0-1628-0
JOINERY
Tage Frid Teaches Woodworking: Joinery Tools and Techniques
- Tage Frid
ISBN 0-918804-03-5
Tage Frid Teaches Woodworking: Shaping, Veneering, Finishing
- Tage Frid
ISBN 0-918804-11-6 (out of print though)
Tage Frid Teaches Woodworking: Furniture Projects
- Tage Frid
ISBN 0-918804-40-X
TOOLS
Router Jigs and Techniques - Patrick Spielman
ISBN 0-8069-6694-7
200 Original Shop Aids & Jigs for Woodworkers -Rosario Capotosto
WOOD
Understanding Wood - R. Bruce Hoadley
ISBN 0-918804-05-1
13) How do I finish toys so that they are non-toxic?
a. Behlens Salad Bowl Finish. This product has been approved by
the FDA for use on objects that will come in contact with
food. It produces a nice, semi-gloss finish.
(Apparently the can no longer states the FDA approval, but
product is still safe for food contact after appropriate
drying time - 12/30/94).
b. Any vegetable oil. Could become rancid after a period of time.
c. Walnut oil. It reacts with the air and hardens into a true
finish. It works particularly well when the oil is heated
and the item is dipped into the warm oil. Available at health
food or large grocery stores. Don't buy the gourmet stuff!
d. Mineral oil or vaseline.
e. Water-based polyurethanes. These are new products which are
very different from the more familiar oil-based
polyurethanes. They are totally non-toxic, dry quickly, and
have no strong odors when applying.
f. Pure Tung Oil. It has no driers or solvents. It is essentially
just a vegetable oil but produces a nice finish that won't go
rancid. Use only Tung Oil that is "pure".
g. Rumor has it that shellac is also safe once it dries. I have
been unable to verify this.
h. Watco claims its oils are suitable for food or baby use if they've
been allowed to dry for 30 days or more. They claim that it takes
this time for full polymerization.
i. Paint. Some paints claim to be non-toxic when dry.
h. Leave items unfinished.
If you are unsure about any finish you plan to use, contact the
manufacturer and request the information. You can also request
an MSDS (Materials Safety Data Sheet).
14) What size drill bit do I use for a wood screw?
Screw Gage Shank Shank Pilot Pilot
Number Hole Size Soft Wd Hard Wd
0 1/16 .060 1/64 1/32
1 5/64 .073 1/32 1/32
2 3/32 .086 1/32 3/64
3 7/64 .099 3/64 1/16
4 7/64 .112 3/64 1/16
5 1/8 .125 1/16 5/64
6 9/64 .138 1/16 5/64
7 5/32 .151 1/16 3/32
8 11/64 .164 5/64 3/32
9 3/16 .177 5/64 7/64
10 3/16 .190 3/32 7/64
11 13/64 3/32 1/8
12 7/32 .216 7/64 1/8
14 1/4 .242 7/64 9/64
16 17/64 .268 9/64 5/32
18 19/64 .294 9/64 3/16
20 21/64 .320 11/64 13/64
15) How do I finish the edge of plywood?
a) Wood tape. It comes in 2 forms, one that can be ironed on, and
one that can be contact cemented on. The tape is approximately
1 inch wide, and can be trimmed with a plane, router, or knife.
b) Glue strips of wood, either purchased or cut from lumber.
16). Which saw blade should I buy?
There is an excellent article on evaluating carbide tipped
sawblades in issue #72 of Fine Homebuilding (March 1992).
To summarize the article:
An expensive blade will typically last longer than a cheap
blade and the cost difference is made up by the number of
extra sharpenings available from the investment.
A blade that has been tensioned will run truer and cost more
than a blade that hasn't been tensioned.
Carbide blades will last up to 60 times longer than steel blades.
17). Where are the archives for rec.woodworking?
There are 2 archives that I know about.
The first is <ftp://ftp.cs.rochester.edu/pub/archives/rec.woodworking>.
Currently it contains summaries of past discussions of tools, some
safety related notes, and some of the FAQ postings. Below is
the current list of files available for ftp from cs.rochester.edu:
15496 Sep 28 14:48 address
128083 Oct 7 11:36 bandsaw
51637 Sep 28 15:21 biscuit_joiners
6125 Oct 28 09:13 crib_safety
42264 Oct 1 09:05 dust_collect
106944 Sep 29 09:29 jointer
15746 Sep 28 16:03 miter_saw
16610 Oct 5 13:39 motors
52704 Sep 29 10:51 planer
44905 Oct 1 14:15 radial_saw
140134 Oct 6 13:01 routers
54977 Feb 19 11:19 ryobi.bt3000
48837 Oct 27 10:35 sander_belt
42432 Oct 27 10:39 sander_misc
47661 Oct 27 10:40 sander_random-orbit
7975 Feb 5 12:44 sawzall
34745 Oct 1 09:23 scrollsaw
27066 Nov 12 11:27 shop_heat
26377 Oct 28 09:17 toy_safety
The second is petroglyph.cl.msu.edu (or 35.8.3.50).
FTP: /pub/woodwork/images/furniture
URL (World Wide Web client):
Use your favorite WWW client to open the URL:
http://petroglyph.cl.msu.edu/~tigger/WoodWorkPhoto.html
For example using Mosaic, you could type:
Mosaic http://petroglyph.cl.msu.edu/~tigger/WoodWorkPhoto.html
18). Where can I find cradle plans?
1. Garrett Wade
$9.95 for plans for a "rocking cradle
item number 14A03.SA in their 1993 tools catalog
2. The Woodworkers' Store
$4.95 for plans for a "four post cradle"
item number 40360 in their 1991-2 catalog
3. The August 1990 issue of Fine Woodworking has an article about
making a cradle.
4. Bartley offers a cradle kit for $199. If it's up to the quality
of their other kits, this should be good.
5. Woodsmith issue #48 - cradle with frame and panel ends with
arched-top panels.
19). Where can I find futon plans?
1. TODAYS WOODWORKER JULY/AUG 1989, VOL 1 NO. 4
Queen size futon folded in half length wise.
Very attractive Futon sofa bed frame for queen size
futon (possibly Swedish modern). Unfolds to make bed,
breaks down for moving. Elegant design with lots of
mortise and tenon joinery.
2. WOODWORKER'S JOURNAL NOV/DEC 1992 VOL 16 NO. 6
"Standard" futon frame for standard 2 fold futon.
Classic bi fold futon frame for queen size futon. The
plans claim to be (and appear to be) appropriate for
"even beginning woodworkers".
3. Fine Woodworking July/August '89 NO. 77
4. Specialty Furniture Designs (800-892-4026)
Design "WSN-15" $14.95
Catalog $2.00
Attractive (modern) Sofa like futon frame fro singe fold
futon (futon folds once (the long way)). Plans for both
twin (39 x 75) and full (54 x 75).
Plans are a large single sheet of blue print like drawings
with associated text, construction looks reasonable and
pictures of the finished project look good, but the plans
are a bit intimidating
5. Popular Woodworking SEP 1992, issue #68
"Knock-Down Couch"
Attractive Mission / Craftsman like design for a sturdy,
knock-down couch. The plans are not specifically for
futons but could be easily adapted to a single fold futon
(might not need to be adapted).
6. Today's Woodworker, Volume 26, Page 8
Contemporary Futon Sofa Bed
7. The Family Handyman Volume 6/94, Page 72
Double Bed Futon Sofa
8. Wood February 1996, issue #86
Fantastic Futon
20). Where can I get information about particle board?
The following was provided by Stavros Macrakis (macr...@osf.org)
and was added to the FAQ with his permission.
*********************************************************************
For technical information on particleboard (PB), the National
Particleboard Association puts out some very nice free pamphlets,
which I summarize below. Although they are basically addressed to
industrial users, they cover particleboard joint techniques quite well
for the rest of us. Some of the facts about joints are very surprising.
I've tried to summarize the essential information below, but you can
also order copies from: NPA, 18928 Premiere Court, Gaithersburg,
MD 20879.
Specifier's Guide to PB and MDF
Abstract
There are 15 ANSI grades of particleboard, with diverse
properties. For instance, face screwing strength varies from 90-450
lb, stiffness from 80,000-500,000 psi. Recommendations are given
for matching grade to use.
Dowel Holding Strength of PB and MDF
Abstract
Dowels joints are one of the cost common adhesive-based
furniture assembly joints. Dowelling is a simple, inexpensive, and
reliable means of making butt and miter joints. Joint strength is
largely determined by the holding power of the dowels. Use good
quality dowels, diameter <= 0.5x the stock thickness. The longer
the dowel, the greater the strength. Holes should be 0.005"
oversized for edges, same as dowel on faces. Use 60%+ solids
content PVA adhesive, applying glue to both dowel and hole wall,
with slight squeeze-out.
Adhesive-based Corner Joints for PB and MDF
Abstract
The thicker the panel, the stronger the joint. Simple butt
joints' strength is limited by delamination; glue blocks or edge
banding help. Dowel joints are standard, and work well; they should be
glued only at the dowels, NOT between edge and face (!). Four dowels
for 18" are standard. Biscuits have equivalent strength, but are
easier to align at assembly. The strength of a well-made simple miter
joint without reinforcement (dowels, etc.) is generally comparable to
that of dowelled butt joints (!); dowels add little strength, but
splines and biscuits do. Rabbets 1/3-1/2 the depth of the panel make
strong joints, but tend to split. Dados are better, but less
attractive. Rabbet and dado butt corner joints (= dado and tenon =
dado box corner) combine a dado on one panel and a rabbet on the other.
Dowelled butt joints are stronger (!). Dovetails are excellent, but
require precise and time-consuming machining. Molded polyurethane
joints (plastic splines) are as strong as or stronger than dowel
joints.
Metal Fasteners for PB and MDF
Abstract
Screws, nails, and staples are widely used. Screws are
strongest. The type of screw affects strength by only +-10% (!), but
PB screws are less likely to break. Screw diameter affects strength
little, but screw length directly affects it. Screw diameter should
not exceed 20% of stock thickness. High internal bond strength PB
holds screws better. Edge screws have half the strength of face
screws. Use full-length pilot holes; shorter holes do not increase
strength. Ideal tightening is 3/4 turn past flush on the face; 3/8
past flush on the edge. Applying glue in the hole can increase
strength as much as 45%.
Staples are used for attaching fabric, etc., and to hold glued
joints.
Nails split panels, so should be >3" from a corner, and >6"
apart. Ring shank nails hold better, plastic coated best. Drive
them at an angle.
Mechanically-based Corner joints for PB and MDF
Abstract
Most bolt and cam joints are 20-50% weaker than dowelled joints.
Screw joints are comparable. Plastic corner block units can be much
stronger in outward bending, but only comparably strong in inward.
Even when they are equally strong, mechanically-based joints are often
less rigid. These systems are most useful for ready-to-assemble
manufactured kit furniture.
Particle Shelf Systems (Builder's Bulletin #1)
(not seen)
All the above are free. They also sell:
Particleboard from Start to Finish $12.50
Abstract (theirs, I haven't seen this)
Ten chapters (120pp) of useful information for users of PB.
Includes information on material handling and storage, sanding,
machining and tooling, laminating, wet finishing, edge treatments,
assembly and fastening, construction products, shelving and
formaldehyde.
MDF from Start to Finish $7.50
Similar abstract, 42 pp.
*********************************************************************
21). What are some of the common woodworking terms/abbreviations?
HVLP - high volume/low pressure
RAS - radial arm saw
ROS - random orbital sander
S2S - smooth 2 sides - surfaced 2 sides
MDF - medium density fiberboard
22). How do I finish a cutting board?
See the answer to question 13.
23). What is snipe and how do I eliminate it?
End snipe occurs when the wood looses contact with the infeed roller
and allows it to rise slightly from the bed of the planer. Snipe can
also happen on the beginning of the board as well. Snipe can be
minimized or eliminated by providing support along the full length
of the board on both the infeed and outfeed sides of the planer.
Proper tuning of the planer is also important in minimizing snipe.
Another way to minimize snipe is to do all of the planing before
cutting pieces to length. This way the only snipe loss in confined
to the end of 1 piece of wood.
24). How is lumber graded?
The following was provided by David R. Mount
(dmo...@bigcat.missouri.edu) and added to the FAQ with his
permission.
*********************************************************************
The "Encyclopedia of Wood" from Sterling publishing is a good
source of this information, a synopsis of which I'll provide here.
As I recall (don't have it in front of me) Bruce Hoadley's book
"Understanding Wood" has a comparable treatment.
I'll give a brief summary of dimensions and grading as follows:
Softwood Construction Lumber
Most softwoods (though certainly not all) that are made into finished
boards are intended to be construction lumber. This material is
generally sold according to it's "nominal" dimension, typically 1 by
something or 2 by something. Mininum thickness for planed, dry 1-by
material is 3/4"; dry means average moisture content of 12%, maximum
of 15%. Minimum thickness for 2 by material (planed and dry) is
1-1/2". For wet or "green" lumber (this includes formerly dry
material that has been allowed to take up water and has not re-dried)
minimum surfaced thickness is 25/32" and 1-9/16" for 1-by and 2-by
material, respectively. For widths, the rules are the same for
both 1-by and 2-by material. For widths up through 7 inches, the
minimum dry, planed width is 1/2" less than the nominal dimension.
So, dry 1x6 and 2x6 material should both be 5-1/2" wide. For
widths of 8" and above, the width should be 3/4" less than the
stated dimension (e.g., 1x10 should be 9-1/4" wide).
Grading softwoods is complex (though not as bad as hardwoods) and it
depends on the use (boards versus structural lumber), and the type
and distribution of defects (tight knots, loose knots, spike knots,
wane, shake, etc.). There are several different grading authorities,
but the board grades most common in the U.S. are (in decreasing order
of "quality") finish or select, #1 (common), #2 (common), #3 (common),
and #4 (common). Structural lumber generally uses different
terminology including such things as #1, #2, and #3 structural,
superior, stud, utility, and several others. Ask your lumber dealer
to explain the system by which their lumber is graded; there is a
lot of variation from dealer to dealer. The "Encyclopedia of Wood"
has pictures of the board grades; Hoadley's book may also, I
don't recall.
Hardwoods
Standard thicknesses for hardwood lumber are as follows (in inches):
Nominal (green) Dressed (dry and planed)
Thickness Thickness
-------------------------------------------------
2/4 5/16
4/4 13/16
5/4 1-1/16
6/4 1-5/16
8/4 1-3/4
Notice that 2/4 lumber is officially listed as only 5/16" planed. In
practice, hardwood stores I've been to generally sell material they
call "2/4" that is actually surfaced to either 1/2" or 7/16". I
don't know why. In my experience, the thicker sizes are typically
sold as I've listed above.
Hardwoods are generally sold as random widths, unlike construction
lumber that has width controlled as tightly as thickness. In
general, according to the Encyclopedia of Wood, dry hardwood is
sold as the next highest inch down to 3/8" shy of the nominal
dimension for less than 8 inches and 1/2" shy for greater than
8 inches. In other words, a 6" wide board may be as narrow as
5-5/8", a 10" board as narrow as 9-1/2". In practice, hardwood
dealers vary in how they figure width into the board foot
calculation; some go to the nearest inch, some to the nearest half
inch, some to the exact dimension. Don't be shy to ask a dealer
how he/she makes the calculation; you have a right to know.
Grading hardwoods is *really* complex. Grades are determined by
number, width, and length of clear (free of knots and other defects)
cuttings that could be obtained from the board, which is in turn
determined by the number and location of defects, primarily knots.
The top three grades are "firsts", "seconds", and "select(s)".
Hardwood dealers typically sell these grades together as "firsts
and seconds" (known as FAS) or "select and better" (SAB). In
short, if all the defects were cut out of these boards, they
should yield between 83.3% and 100% of pieces with at least one
clear face. The specific grading rules are much more complex,
but this is the general idea. Note that there has been a movement to
relax the requirements somewhat for black walnut. I also believe that
many dealers sell wood as "FAS" that actually contains some select
material; it's not a big deal usually, unless you need big wide long
clear boards and are buying sight unseen.
After these top three grades follows #1 common and #2 common. These
grades allow a lower percentage of the board to yield clear cuttings
(BTW, "cuttings" means smaller boards) and allows the cuttings to be
narrower and shorter than in the better grades. #1 common should
yield 66.6% to 100% clear cuttings (depending on the board size)
while #2 common will yield 50% to 66.6%.
A couple notes about #1 and #2 common boards. First, they are often
not displayed right out front by a hardwood dealer; if you are
interested in lower grades, ask about them. #1 and #2 boards can
sometimes be a better buy; they are generally 20 to 70% cheaper
than FAS boards so the cost per square inch of clear lumber may be
lower if obtained from lower grade boards. Of course, this requires
that you can use smaller pieces; you also have to figure in the cost
of your time to cut around the knots. On the other hand, in more
casual pieces I often leave some knots in the finished piece if
they won't cause structural problems. Some of the most beautiful
figure occurs near knots. Each person will weigh these variables
differently.
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Jim Roche
ro...@cs.rochester.edu
University of Rochester Computer Science Department Rochester, NY 14627