# My flush trimming split my workpiece



## ScoFF (Aug 20, 2009)

I had a project recently where I tried to flush trim a piece of red oak to match an attached template. I roughly trimmed the 3 foot board lengthwise about 1/4 “ from my pencil line and attached the straight edge template and tried to straighten the edge of the board, the template was on top, the flush trim bearing was also on the top of my table mounted setup (so I guess the bearing would have been at the bottom of the actual bit). I thought this would be a pretty basic exercise.
About ½ way through it snagged the grain and split it inwards beyond my pencil line. I had to scrap it and do it again. I’m not an expert on grain direction but I guess I should have flipped the work piece over and came at it the opposite direction?

What if I couldn’t flip it over, say I was trimming a large table edge (non-table setup) and I had only one choice to go. How do I overcome this?


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## jw2170 (Jan 24, 2008)

Hi Bob,

I am guessing the template was not flat and allowed the bearing to rise above the template.

Even with a 'snag', the bearing would not have allowed the bit any closer to the template/work piece.

Unless the bearing was not riding along the template to begin and it only moved in to the edge of the template?


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## kp91 (Sep 10, 2004)

red oak will chip out like that, and always at the worst time. you can try a couple of different things to help. You're right on track that you should try to feed the stock so that you're running 'downhill' with the grain. (just make sure you always feed on the correct side of the bit, don't climb cut) If you can't do that, you can make a few relief cuts with the router every few inches along your template so that if it does snag it doesn't pull out a big long piece.

Sorry about your project.... hope it doesn't happen again soon.


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## ScoFF (Aug 20, 2009)

The bearing position was fine, the bit just grabbed the grain and ripped it down the direction it was flowing. How do you prevent the tearing down the grain direction? It litterally cracked apart.


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## bobj3 (Jan 17, 2006)

Try using the bit below it will help with rip outs..

Spiral Flush Trim Router Bit

Great for use where chip-out is a concern with plywood, melamine or other laminate surfaces.

MLCS solid carbide router bits

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ScoFF said:


> The bearing position was fine, the bit just grabbed the grain and ripped it down the direction it was flowing. How do you prevent the tearing down the grain direction? It litterally cracked apart.


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## Quillman (Aug 16, 2010)

Use a plunger and collars; take the cut in stages.
There is always a depth of cut, albeit likely shallow, that will not tearout or split stock.
It may be a 1/32, it may be an 1/8th, who knows?
Not withstanding stage plunge cutting is safe, perhaps slow, but offers the greatest number of choices in cutters and your best chance at a quality result.


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## RJM (Apr 11, 2010)

I don't see why you couldn't do a climb cut if the grain warrants it. Combined with several shallow passes, it's not dangerous if you know what you're doing.


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## Mike (Nov 22, 2004)

Bob, the best method for eliminating problems like you had is to make light scoring cuts on the wood. To do this simply push the wood into the bit and pull the wood back. Repeat this every inch or so then make your regular pass.


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## Slimpy1 (Aug 14, 2010)

I agree that a CAREFUL climb cut will help. By using a climb cut the bit pushes the wood fibers toward the board and should not tear out even rd oak. You might try using a larger diameter bit and several light passes if you are not comfortable with climb cutting. The objective is to get the angle between the cutting edge and the cut line as low as possible. Using a 1/2" dia bit and a 1/4" cut depth would put the cutting angle at nearly 90 degrees for the fibers at the rough cut surface. 
Red oak is made up of a thousand potential splits hidden in pretty grain. The late wood is very poorly attached to the early wood.


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## bobj3 (Jan 17, 2006)

Hi

Just to add to Mike's post

This works well for trim bits also  ▼
Router Workshop: Tipb2
http://www.routerworkshop.com/Tipb4.html

Router Workshop: Router Tip Archive

http://www.routerworkshop.net/1726/do-i-cut-in-one-pass-or-not/

http://www.routerworkshop.net/1694/a-simple-picture-frame/

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Mike said:


> Bob, the best method for eliminating problems like you had is to make light scoring cuts on the wood. To do this simply push the wood into the bit and pull the wood back. Repeat this every inch or so then make your regular pass.


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## Phil P (Jul 25, 2010)

I'm with the climb cutters on coarse grained timbers such as oak but I'll add a caution about limiting the depth of cut. With climb cutting it is best to try to jigsaw or band saw to within a couple of millimetres (1/16in) of the finish line before using the router. That way the limited depth of cut will be less likely to start a split. Of course you still need to watch for wayward grain and it may be necessary to machine some parts of the cut using the cutter conventionally to avoid splits. It all depends on grain direction

Regards

Phil


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