Router tare out on end grain

[ches]

I use alot of exoitc woods, burl and curl, Babinga,Zebra,Cocobolo,ect., in many of my projects. The stock is

1&1/2" thick ( band sawed to with in 1/8" of the template ) and the template 3/4" plywood. Useing a flush trimming bit ( ball bareing on top or bottom ), on a router table, I always end up ruineing the piece with tare out especially on curved and round end grain projects.I mean it's scarey, the piece kicks, jumps and huncks tare out of the wood. Please help, what am I doing wrong???

[DonkeyHody]

Your cut is too deep for the diameter of the bit. As the cut gets deeper, the forces exerted by the bit on the wood get more angled toward the grain direction. If possible, use a larger diameter bit. I have one that's about an inch in diameter. And / or, bansaw closer to the final pattern line on the ends so the bit is taking a shallower cut there. Slow down the feed rate on end grain if you can do that and still avoid burning. A good sharp bit helps too, but the problem never really goes away.

DonkeyHody "In theory, theory and practice are the same, but in practice they are not."

[Joe]

Everything DH said. Also, if you get really close to your line (

[pat]

[Leon]

You should trim the piece as close to the final cut before using a flush trim bit. Additionally when you near a thin spot where the bit is likely to grab the grain and tear it out or near the corner when going cross grain it is best using caution to route in the reverse direction, this creates the situation where the cutter is pressing against the grain rather than wanting to tear it out.

[Edwin Pawlowski]

Are you using good bits?

[whit3rd]

Been there. Straight-flute bits are more likely to grab than spiral bits, and if you have endgrain to deal with, you WANT to do the cut with a good jigsaw or bandsaw instead, because those cut pulling the wood to the table rather than flinging it across the shop.

Either a spiral bit (will help, but not eliminate the problem) or a sanding drum in your router table can do the endgrain trimming. If you need to use the bearing, it MIGHT help to glue the workpiece to a more massive chunk of wood; inertia is your friend.

[Jeff]

I had this problem while routing tenons. I like to take the depth all in one plunge to ensure uniformity. To prevent tear-out I use sharp bit and I tape the work piece with masking tape. After the plunge, I move the router around the work piece very s-l-o-w-l-y. The tears stop splitting out right at the point where the router stops cutting. It still tears out, but the tape serves as damage control. I work mostly with maple and black walnut so I can't ensure this technique will work with your "exotics."

Jeff

[ches]

Thanks, CHES

[Bob]

I didn't see a reply to your question. that was my thought exactly. All the technique in the world will not cure a low quality bit. I got rid of all my burning problems doing roundover edges on end grain by replacing one of my bits with a new quality bit.

Bob