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Woodwork 

Winter 2013-2014

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9 Tips for Beating Router Tear-Out

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Stop router disasters before they start.

 

by Eric Smith

 

 

 

 

 

 

 

Snap, crackle, crunch! 

 

No, it’s not your breakfast cereal. That’s the sound of router tear-out.

 

Aaargh! 

 

And that’s the sound of a woodworker facing a do-over or repair. 

 

Tear-out can happen cutting across or against the grain, cutting too deeply, using a dull bit or just running into a hidden flaw. One thing’s for sure: It’ll always happen at the worst possible time. Although it can’t completely be avoided, you can definitely minimize the chances of tear-out by following some simple techniques and precautions—without adding a lot of time or expense to your projects.

 

 

 

 

 

 

Pay Attention to Grain Direction

 

 

Visualize a feather cut by a router. It would be a mess, of course, but the point is that when you rout against the grain (see photo, left), the wood reacts just like a feather. The grain is running right into the bit rotation. The wood’s fibers are likely to catch and break apart ahead of the cut, producing tear-out. But when you run the router with the grain (see photo, right), you get a smooth cut. 

 

 

 

Feeding your stock so the grain direction crashes head on into the bit rotation is like running your finger the wrong way on a feather. Nasty tear-out is almost a sure thing. 

 

 

 

 

 

 

 

 

Flip a board end for end to change the direction from which the grain meets the cutter. Now the grain flows in the same direction as the bit rotation. The result will be a smooth cut with little or no tear-out worries.

 

 

 

 

 

 

Make a Very Light Final Pass

 

 

Trying to hog out a clean edge in one pass is asking for tear-out trouble. Instead of gambling with an expensive piece of wood, take the time to make at least two passes: one heavy pass and a very light final pass. 

 

Because the final pass is just a shaving cut, the bit is a lot less likely to catch and tear the wood fibers. You’ll get a smooth surface, even if the grain is going the wrong way.

 

 

 

 

 

 

 

Use a Down-Cutting Spiral Bit for Flush Trimming

 

 

Down-cutting spiral bits push down on the wood’s surface. The result is a clean, tear-out-free shearing cut. Down-cutting spiral bits work especially well for trimming or cutting through delicate veneers, melamine, laminates and highly figured woods. 

 

 

 

 

 

 

Use a Zero-Clearance Fence

 

 

A zero-clearance fence backs up the wood as it’s fed into the router bit, making it difficult for the wood to chip.

 

To make a zero-clearance fence, set the router bit at the height and depth you want. If you have removable subfences, turn the router on and slowly slide the infeed side of the fence into the bit.  If your fence has a fixed face, clamp temporary subfences on both sides. With the router running, loosen the clamps on the infeed fence enough to slowly slide the subfences into the spinning bit.

 


 

 

 

 

 

Rip and Start Over 

 

 

Sometimes you have no choice but to cut your loss and make a new piece. Other times, you can afford to trim the piece and start over. Just rip a bit off the damaged edge and then rout it again. 

 

When I’m working with wood that looks likely to tear out, I try to give myself some wiggle room by cutting a wider piece than I need, then ripping it to size after I’ve successfully routed the edge.

 

 

 

 

 

 

Stop End-Grain Blowouts 

with a Backer Board 

 

 

Rout the end grain first and use a backer board. That’s the best way to reduce your chances of blowing out a corner. The backer board supports the cut so the corner has no chance to tear away. Make sure the backer piece is at least as thick as the piece you’re routing. Clamp the pieces together for rock-solid support. 

 

 

 

 

 

 

Make Some Plunge Cuts  

 

 

Routing against the grain may be unavoidable. On some edges, the grain reverses direction, so you can’t win. If you’re getting tear-out along an edge—or even if it looks like you might—make a series of plunge cuts every inch or two. This will cause the splinters to break off at the cutout before they can ruin your profile. 

 

The best way to make plunge cuts is to hold one end of the board tightly against the outfeed fence and the other end away from the spinning bit. Push the board against the fence, then pull it out. Move the board forward an inch or two and repeat.

 

 

 

 

 

 

Make Shallow Climb Cuts  

 

 

Reversing the normal direction of the router feed is called climb-cutting. Climb-cutting can involve either moving clockwise with a handheld router or pushing wood from left to right on a router table. Climb-cutting almost always eliminates tear-out, but it also makes the router more difficult to control. That’s because the stock is fed in the same direction as the bit is spinning, so the bit wants to grab the wood and pull. This makes climb-cutting potentially dangerous. It’s not recommended for most routing. If you follow a few rules, though, climb-cutting is a great way to get yourself over those pesky areas where tear-out is almost a sure thing. 

 

 

Play it safe:

 

- Always make very shallow, light passes, especially when using a big bit. 

 

- Secure the wood and/or router very firmly. 

 

- Make sure the bit is sharp. A dull bit grabs and pulls, but a sharp bit cuts with less effort. 

 

- On a router table, use featherboards whenever possible to hold the board and keep it from running away. 

 

-When using a handheld router, firmly clamp down the stock. If the workpiece is narrow, add support so the router won’t tip. 

 

- Never climb-cut small or narrow pieces on the router table. It’s better to cut the profile on a large piece and trim it to the size you want later. 

 

 

 

 

 

 

Make a Scoring Cut on Dovetail Jigs

  

 

Face grain can splinter when you run a bit in and out of a board in a dovetail jig. Instead of having wood filler at the ready, start by making a light scoring pass along the entire edge of the board. Gently move the router in and out of the template fingers. Make the cuts about a 1/8 in. deep. Then go back and finish.

 

 

 

 

 

 


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Comments

Bill Ellis wrote re: 9 Tips for Beating Router Tear-Out
on 02-17-2010 10:29 AM

Oh! boy do I like these tips shame I cannot get DVD or somthing simular as I live in Scotland.

Bill Ellis (recently turned 65) so more time to make toys