Kerfing Different Materials

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In addition to kerf spacing and depth, the material you choose also affects how tight a radius you can bend and still get a smooth surface. Most materials used in the shop can be kerf bent. And with some materials (such as plywood and particleboard), it may be the only way to bend them successfully.

SOLID WOOD

As you might expect, the solid woods that bend the best using steam or thin laminations are also the best choice for kerf bending. Woods such as oak. walnut, mahogany, and ash are flexible and bend well.

Whatever type of wood is used, choose pieces for bending with grain that runs in a fairly straight line, see photo (A). Highly figured woods which have unpredictable grain patterns often break as they're bent.

QUESTION: Does it matter how the kerfs are oriented in relation to the direc-tio7i of the grain?

To minimize breakage, it's best to cut the kerfs across the grain« see Fig. 4. Then the fibers of the wood will hold the whole piece together as they wrap around the curve. If you cut the kerfs with the grain, the piece may break along the grain lines as it's bent.

PLYWOOD

Hardwood plywood with softer inner cores bends easier than softwood (fir) plywood. There are two reasons for this.

First, the face veneer on softwood plywood is thicker than that used on hardwood plywood, see photo (B). And these thicker veneers aren't as flexible as the thin ones.

Second, many hardwood plywoods use lauan for some inner plies, see photo (C). Lauan (also called Phillipine Mahogany) is more flexible than the fir plies used in most softwood plywoods and bends easier.

QUESTION: Should the kerfs also he cut across the face grain of plywood?

Yes, but for different reasons. It has to do with the ply that lies beneath the face veneer, see Fig. 5. After plywood is kerfed, the web that remains consists of the thicker second ply and the thin face veneer, see photo (C).

If plywood is kerfed across the face grain, the grain of the second ply runs with the kerf. Usually, cutting with the grain weakens wood. But with plywood, the face veneer holds it together (and allows it to flex).

COMPOSITES

Composites such as particleboard and hard-board (Masonite is one common brand name) have an advantage over both solid wood and plywood — there's no grain direction to worry about, see photo (D).

Since it's flexible to begin with, Masonite bends easily when it's kerfed. Particleboard, on the other hand, doesn't kerf bend as well. It's made with larger, more loosely compressed particles and can break easily when stressed — especially if the particleboard surface is scored (such as when kerfing).

The composites do have another advantage over solid stock and plywood. They bend better in both directions. Since there's no dominant grain to split along, you can bend the piece so the kerfs close in or open up. This means you can actually form an S-curve, (see Fig. 6 and the Tambour Clock).

KERF DEPTH

QUESTION: Now that I've selected the material I want to bend, how deep should I cut the kerfs?

Fortunately there are some simple rules and guidelines for kerf depth. Generally, the deeper the kerf is cut, the tighter the radius you can bend. At the same time, the deeper the kerf is cut, the weaker the webs will be. What you want to do is cut the kerf as deep as possible without weakening the wood.

KERFED SOLID WOOD

KERFED SOLID WOOD

Kerf Bending Wood
IF KERFS ARE CUT ACROSS GRAIN, WOOD IS FLEXIBLE
Cutting The Kerfs
IF KERFS ARE CUT WITH THE GRAIN, WOOD CAN BREAK WHEN BENT

For solid woods, this means leaving a web that's about an W-thick, see photo (A). For plywood, the general rule is to cut deep enough so you just barely score the second ply (the layer under the face veneer), see photo (C). And for Masonite, the kerf depth should be about one-half (or a little more) of the thickness of the material, see photo (D).

Mdf Curving
FIRST PLY PREVENTS SECOND PLY FROM CRACKING IN OUTWARD BEND

- MASONITE DOESN'T HAVE

A DOMINANT GRAIN, SO IT CAN BEND BOTH WAYS

- MASONITE DOESN'T HAVE

A DOMINANT GRAIN, SO IT CAN BEND BOTH WAYS

SECOND PLY

Kerf Bending Plywood

IF KERFS ARE CUT ACROSS THE GRAIN IN SECOND PLY, SECOND PLY WONT BE VERY FLEXIBLE

KERFED PLYWOOD

Kerfed Plywood

IF KERFS ARE CUT THE SAME DIRECTION AS GRAIN IN SECOND PLY, SECOND PLY WILL FLEX EASILY

KERFED PLYWOOD

SECOND PLY

IF KERFS ARE CUT ACROSS THE GRAIN IN SECOND PLY, SECOND PLY WONT BE VERY FLEXIBLE

FACE PLY KEEPS SECOND PLY

FROM CRACKING

IF KERFS ARE CUT THE SAME DIRECTION AS GRAIN IN SECOND PLY, SECOND PLY WILL FLEX EASILY

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Responses

  • david
    How deep should kerfs be?
    8 years ago
  • steffen pabst
    How to cut kerfing by hand?
    8 years ago
  • FLORIAN MAHLER
    How to kerfing bending mahogany?
    8 years ago
  • Klaus
    How tight a curve can you get with bending ply?
    7 years ago
  • ulrike
    How tight can you bend masonite board?
    7 years ago
  • reija
    How to kerf bend solid?
    7 years ago
  • hanna
    Can kerfed ply be rebent?
    7 years ago
  • Niamh
    How close together do you cut kerfs and how deep?
    7 years ago
  • napoleone
    What is the rule for deep kerfing?
    7 years ago
  • violet
    HOW DEEP TO CUT A KERF FIR?
    6 years ago
  • Nestore
    How deep to cut for kerf in wood?
    6 years ago
  • kaarlo
    How many kerf cuts to bend board around radius?
    6 years ago
  • mackenzie
    Can you kerf particle board?
    6 years ago
  • Markus
    Can you kerf black walnut to make a radius?
    6 years ago
  • fatimah
    How tight radius using kerf core material?
    6 years ago
  • Ave
    How many kerf cuts to make?
    6 years ago
  • mirin
    Can you kerf hardwood?
    6 years ago
  • keeva
    What wood bends the best for kerfing?
    5 years ago
  • kaarle
    Which timber grain orientation for kerfing?
    4 years ago
  • taimi
    What materials can you kerf bend with?
    3 years ago
  • Pearl
    What materials can be kerf bent?
    3 years ago
  • raymond nicholson
    Can plastic be kerf bent?
    3 years ago
  • samuel
    How deep a kerf to bend a wood board?
    2 years ago
  • eila
    How deep kerf plywood?
    2 years ago
  • sarah
    How deep kurf cut for arcs?
    2 years ago
  • gilly
    Does kerfing wood make it more flexible?
    2 years ago
  • Taina
    Why does grain break in ply?
    2 years ago
  • kaarle tuukkanen
    How deep to score plywood?
    2 years ago
  • roosa
    How to score wood to make it bend?
    2 years ago
  • sara
    How to bend partical board?
    2 years ago
  • selma
    Can you bend or stretch particle boards?
    2 years ago
  • TAMMY
    What cut of timber best suited fir making kerfing?
    2 years ago
  • russom
    How to bend thin plywood?
    2 years ago
  • amaranth
    Can luan be kerfed to bend?
    2 years ago
  • Henry
    How to kerf a wooden board?
    1 year ago
  • kimberly
    What type of wood to kerf?
    1 year ago
  • daniela
    What material shouild be used for kerf cutting?
    1 year ago
  • CONSUELO
    How to Kerf 360 degrees?
    12 months ago
  • SHUKORNIA
    How to bend wood Kerf Cutting wood method?
    11 months ago
  • awate
    Can you kerf normal wood?
    10 months ago
  • ryan
    Why is mdf not good for kerfing?
    10 months ago
  • caragh
    Are kerf cuts parallel or perpendicular to the wood grain?
    10 months ago
  • ofelia
    What qualities are required in timber used for solid bend wood curve?
    10 months ago
  • russom
    What materilas are good for kwerfing?
    10 months ago
  • mebrahtu
    Can you kerf cut studwork?
    9 months ago
  • isla
    How to make a round wood shelf with kerfing?
    7 months ago
  • selina hayward
    How to bend pressboard?
    7 months ago
  • ruth
    How to bend wood using kerf cuts?
    6 months ago
  • Judy
    How deep should a kerf cut be made in a large timber beam to keep it fro cracking ?
    6 months ago
  • seth watt
    What type of wood makes for the easiest kerfing?
    6 months ago
  • Antonella
    What types of wood are best for kerf bending?
    5 months ago
  • Hana
    Can you kerf bend knotty pine?
    5 months ago
  • bradley
    What is kerf in construction materials?
    5 months ago
  • AMINA
    What kinds of wood can you kurf?
    4 months ago
  • Matthew
    Can you kerf bend solid wood?
    4 months ago
  • Hayden
    How to curve wood by kerfing?
    3 months ago
  • Largo
    How much material to leave for kerfing?
    2 months ago
  • Jamila
    What is kerfing timber compoments?
    1 month ago
  • Joseph
    How tight a radius can wood be bent?
    1 month ago
  • ROGER
    How to radius plywood 15ft for guitar?
    26 days ago
  • Peter
    What is kerfing laser cutting?
    6 days ago

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