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2 American Woodturner Winter 2006

WoodturnersFear Factor

How to Avoid a Catch

I t seems simple, but there arecomplicated forces takingplace while you shape arevolving piece of wood with yourturning tools. I want to simplify

the process and put a language tocatches. If you understand whatcauses a catch, you can eliminatethe cause.

There are just four cuts in all ofwoodturning; 1) push cut, 2) pullcut, 3) scrape and 4) sheer scrape.Lets break down these cuts intotwo groups: The push and pull cut require

bevel support to prevent catches. The scrape and sheer scrape

require that you dont violate the 90-degree rule. More about that later.

Start with sharp toolsA primary aid to preventing catch-es is to turn with sharp tools. Asharp tool can sheer off those end-grain fibers cleanly and smoothly.However, a dull tool will push,

grab, and tear out end-grain fibers.You can have all the right tech-niques and still have trouble withcatches if your tools are not sharp-ened properly and often. I am into

easy and I dont like to sand.When using gouges and doingthe push and pull cuts, most catch-es come from allowing the gougeto cut while not being supported

by the bevel. Without bevel sup-port, the cut will dig in violently ina split second. Big chunks of woodare ripped away.

The bevel prevents the gougefrom cutting too aggressivelyit isa controlling factor.

Inside the bowlLets first focus on the inside of a

bowl, since that is where catchesare most apt to occur because theinside of a bowl is where we areprone to loose bevel support.

The direction the gouge wantsto cut is along a line from the heel

By Lyle Jamieson

If youve been around the AAW for a decade or more,you may recall Five Ways to Avoid a Catch, a well-read

journal article Lyle Jamieson wrote in 1996. Lyle hasrevisited this topic with fresh drawings and thoughts totake you beyond the suffocating fear of catches.


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of the bevel to the sharp point ofthe edge, as shown in Drawing 1a. The first approach is to relax andlet the tool go where it wants to go.Relax the tool rest hand and direct

the cut by moving the handlehand. You can get pretty good atwhite knuckling your way througha cut, but the surface left behindneeds lots of sanding, as shown inDrawing 1b .

It is not much fun when a catchruins the shape you intended.Relax and follow the direction thetool wants to go by steering it withthe handle hand.

Find the sweet spotYou will hit the sweet spot for aclean cut with the flute pointingthe direction you want to travelwith your cut. The twist of the toolwill have the flute pointing at a45-degree angle. Whenever pos-sible, maintain this sheering cut tocleanly slice through each grain fi-

ber as it spins past your tool. Yourgouge cuts the shaving at the tip ofthe cutting edge, as shownin Photo 2 .

This may help: Think of the mo-

tion of an ice cream scoop scoop-ing out the inside of the bowl. Youhave one hand on the handle ofthe ice cream scoop and you followthe shape of the rounded scoop foryour ice cream cone.

Now with the bowl gouge, youfollow the little tiny tip of the tool,or the bevel. Swing the tool handleto follow the contour of the vesselwith the bevel.

Ride the bevel is the usual term

to describe this, but it is a terribleterm. You dont ride the bevel, youneed to follow it gently. Ridingthe bevel too hard will result in anumber of problems: burnishingthe surface left behind, creatingvibrations, and bouncing the bevelinto any voids in the vessel. For me,bevel-supported cut is better.

Bevel-supported cutOne of the hardest things to ac-complish is to start in a bevel sup-ported cut. The tool wants to skatein a spiraling manner across theface of the wood when you touchthe wood at a 45-degree angle.

Note the arrow indicates the direction thewood is traveling past the tool. The 45-degree angled line shows the angle thatwill produce a clean slicing cut. To get thisangle, twist the tool on i ts axis with yourhandle hand. The shaving comes off the

right-hand side at the tip of the tool.

RISKY Note the arrow indicating the direction the tool wants togo. Swing the handle slowly toward your body to direct thebevel to travel the path indicated by the dashed l ine.

SAFENote the arrow indicating the direction the tool wants togo. Swing the handle slowly toward your body to direct thebevel to travel the path indicated by the dashed line.

Bowl gouge inside the bowl

x arrow direction


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The bowl-gouge grind can makeit easier to enter a cut. I refine theEllsworth grind slightly to makethe entry into a cut easier for me.

Davids grind has a slight humpnear the tip that attempts to grabthe wood first before the bevelsupport has been established. (Seedrawings on this page.)

What works for me is the sharp-ened edge is almost straight fromthe top to the back corner of thewingthere is no hump whenviewed from the side.

Hollowing systems

When setting up your supportedhollowing system for boring outthe interior of a hollow vessel,make sure the scraper cutting tip isparallel to the floor and on the cen-ter line of the vessel and you willnever get a catch. This set up will

be cutting right at 90 degrees. (Youcan error slightly with the tool-rest

position on the high side but neverhave the cutter below center in ahollow form.)

If you choose to twist the cutter

for a sheer cut, keep this in mind:When you angle one side of thecutter down to sheer scrape, theopposite side of the cutter is point-ing up into the wood and will getgrabble and produce a catch.

Scraper strategy A scraper requires an entirely dif-ferent process. Whenever a cuttingedge touches the wood without the

bevel support, a catch can occur.

(The exception is the edge touch-ing the wood at less then a 90-degree angle, as shown in Draw-ing 4a .) With a scraper positionedflat on the tool rest and parallelto the floor, the tool-rest height iscritical. If the tool rest is high onthe outside shape, (like a spindle) itgets risky. If the tool rest is too low

SAFEThis shows Lyle Jamiesons modication to the David Ellsworth-stylebowl gouge. Note the side view give you a prole of the grindalmosta straight line from the tip to the wing corner.

RISKY A gouge with a hump at the tip cuts into the wood long before thebevel has a chance to give support. This can cause a catch or evenblow up a thin-walled bowl or vessel.

The side prole of Lyle Jamiesons favoritegrind has nearly a straight line from the tipto the wing corner.

Starting a cuttheres an easier way

wing corner


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on the inside shape, like a hollowform, it gets risky, as shown inDrawing 4b .This is why the popularity of

negative rake scrapers came intovogue. The negative rake gives youextra insurance to not violate the90-degree rule. With hand-heldscrapers, you can change the angleat which the tool touches the wood

by raising or lowering the handle.

Move beyond fearAs I teach at chapters aroundthe country, I meet many self-taught students. They settle for

techniques that are difficult anddemand considerable sanding.Some techniques are downrightdangerous.

The fear generated from catchesis suffocating. If you walk up tothe lathe with the fear of gettingcatches, you dont know whatfun you are missing. Do you fear

the foundations right and it opensup possibilities of excellence ratherthat creating obstacles and settlingfor mediocrity.

Now, lets get over your fear ofcatches. The fun and creativitylocked up inside you will take youplaces you never imagined.

Lyle Jamieson (lylejamieson.com)is a full time woodturning sculptorand instructor who lives in TraverseCity, Michigan. He is president ofthe Northwestern Michigan AAWchapter.

HOLLOW FORM

SAFE2

90 o

OK3

1 RISKY

+90 o

-90 o

1 RISKY

SAFE2

OK3

-90 o

90 o

+90 o

SPINDLE

SAFE2

90 o

3. Acute angle,above center,90 degrees.Risky, prone tocatches.

taking one more cut?The fun and enjoyment starts by

being in control. Taking catchout of your vocabulary will make

turning a lot easier and more fun.You can watch others turn orread all the articles available andstill have catch fear. I suggestgetting some hands-on help. Takeyour turning fun to the next level.It is not necessary to pay loadsof money to get some hands-onhelp. All AAW chapters have goodturners to mentor youusually

just for the asking.Recently, I had a chance to speak

with Michael Hosaluk and hemade a statement that summedit up. He asked What is thedifference between a beginnerand an advanced turner? AndMichael answered his ownquestion with, It is what you dowith the basics.

I truly believe this approach. Get

Scraper strategy

1. Obtuse angleabove center,>90 degrees.Risky, prone tocatches.

2. 90 degreeangle on centerline. Safe

3. Acute angle,below center,

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