Router Trim Bit

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Forum topic by BigD1 posted 03-01-2010 01:18 PM 1127 views 0 times favorited 5 replies Add to Favorites Watch
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79 posts in 2918 days

03-01-2010 01:18 PM

Knowing how a router “flush” trim bit works, is there any one who makes a router bit, that the cutter extends past the guide bearing about a 32nd or 64th, so you can clean trim an edge without having to use a pattern? Would that be the difference between a “trim” bit and a “pattern” bit? Thanks for feed back. Don

-- Donald Baty

5 replies so far

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661 posts in 2984 days

#1 posted 03-01-2010 05:13 PM

DaveR, more than likely he is thinking that a flush trim bit will hit the veneer below what he is trimming. BigD1, that is the reason for the bearing. It runs on the veneer below keeping the blades away from it, allowing you to remove the excess overhang. You can’t push the bearing through the lower veneer. And like DaveR, if this isn’t what your looking for than we don’t understand what it is you are wanting to do.

-- Methods are many,Principles are few.Methods change often,Principles never do.

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79 posts in 2918 days

#2 posted 03-01-2010 05:40 PM

I guess in part, what I’m thinking is, that I would like to take my board, that I just cut out on my band saw with my 1/4” blade, about 1/16” from my line, with curves, half circles, some straight lines, a few waves, and clean up the edge by just touching it off with a router bit, on my 36” square, open top router table, or my hand held router. I don’t have an oscillating sander to run my nice piece of Bolivian Rosewood across and get a smooth edge. I hope that helps. Don

-- Donald Baty

#3 posted 03-01-2010 05:45 PM

Some woodworking suppliers offer replacement bearings for straight patter bits. If you installed a bearing slightly smaller than the cutting diameter of the bit, you would accomplish your goal. You will be basically turning it into a subtle rabbeting bit.

As stated above, please let us know how you plan to use this trim bit!! If I understand correctly, this is what I think you meant:

Let’s say for example, that you have just cut a long S-shaped curve in a 1” thick piece of wood, using your bandsaw/scrollsaw/jigsaw. You now want to clean up the blade/burn marks. But you don’t want to have to make a pattern of the final curve you want on the workpiece, so you use a straight router bit with a slightly undersized bearing. The router bit has a cutting length of 3/4” inch. If you set the depth of your hand-held router so that the bit cuts 3/4” down from the top surface of the workpiece, your bearing will rest somewhere in the lower 1/4” of the workpiece’s edge.

Here’s the potential problem: the bearing will be riding on the very surface that you want to get rid of. It has that rough, bumpy finish left from the saw blade. As the bearing guides the bit while you make the cut, the resulting finish on the edge of your workpiece will also be bumpy, although maybe not as rough as it started. The larger diameter bit you use, the smoother the surface will be, but every time the bearing goes over one of those small “bumps” of the saw marks, the bit will follow it.

Also you’ll still have 1/4” of on that edge that never got smoothed by the router bit.

My suggestion is (and please do consider my suggestion because I’m a custom guitar builder and have to deal with smoothing curved surfaces often):
Purchase an Oscillating Drum Sander or a sanding drum attachment for your drill press. This allows you to smooth out the edge of a workpiece WITHOUT USING A PATTERN. I do this all the time. Just sand it carefully until the edge looks good to your eye. Who cares if you used a pattern!! If you make another project like it in the future, it doesn’t have to be exactly the same as the previous one, just as long as it looks good TO YOU. That’s the beauty of custom woodworking: NO two pieces are identical. They’re one-of-a-kind.

Now, if you’re dealing with a STRAIGHT edge that you want to smooth, a well-tuned jointer plane can beautifully smooth any rough edges left by a saw blade. If you really want to get into the high-dollar equipment, look into Oscillating Belt Sanders.

Once again, please let us know about your project, so that we can better understand your objectives and techniques in the shop. We’re all here to learn from each other and offer help when possible.

-- Lane Custom Guitars and Basses

#4 posted 03-01-2010 05:49 PM

Sorry, I must have been typing while you responded. If you don’t want to deal with oscillating drum sanders, look for some drum sander attachments for your drill press. They’re pretty economical and easy to use.

-- Lane Custom Guitars and Basses

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79 posts in 2918 days

#5 posted 03-01-2010 05:55 PM

Bingo!!! Right on!!! You got my drift!!! What a guy. Thanks for the info. Don

-- Donald Baty

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