I don't know either. Maybe it is, one for a hand held router and another for a table mount router. I'll be checking back to find out.

 

a flush trim bit is good for flushing edges to one another a ptern bit is good for template routing and both can be used in either handheld or table mt routers.

 

just a classification difference. I use a flush trim bit when I make a pocket hole face frame. I oversize it just slightly then it can be trimmed exactly flush.

a pattern bit is used when you double stick tape a pattern to a blank and router the shape. this way the pattern can be on top.

when we make adiorndack chairs in the shop classes, we use screws to hold the pattern down, so we use a flush trim bit (bearning on bottom) with a router table. this way the student can see the pattern and the screws are on top and not holding the board up.

 

Also, a pattern bit can cut mortises, a flush trim can't. Both do basically the same thing, but different.

 

A pattern router bit has the bearing on the top of the cutter, and a flush trim bit has it on the bottom. A flush trim bit works best for triming the top of lets say a counter top flush with the edging, where a pattern bit like it says can follow a pattern that can be clamped to the top of the work piece and trim the lower piece to the pattern detail.

 

I use a Rockler bit with bearings on both the top and bottom. I use it for flush trim and pattern following. With bearings on both ends, you have a choice of using a pattern on top or bottom of the piece.

 

As an electric guitar/bass builder, I know that pattern bits (with the bearing between the cutter and the shank) can be used to rout the cavities/pockets that house the electronics and the pickups. They also can be used to make the cavity that houses the neck on instruments with a bolt-on neck design. These are blind (or stopped) cuts that don't go completely through the thickness of the wood I'm routing, therefore I need the bits that only have the bearing on the top.

I'm usually a proponent of avoiding templates and patterns when building my pieces, but when it comes to features that need to be a consistently standard size, pattern bits and a template can be very useful.

 

I saw a video using what was called a bottom bearing pattern bit to joint 3/4 boards in a router table. That bit looked like a flush trim bit to me. In that situation are they interchangeable?

 

A pattern router bit has the bearing on the top of the cutter, and a flush trim bit has it on the bottom. A flush trim bit works best for triming the top of lets say a counter top flush with the edging, where a pattern bit like it says can follow a pattern that can be clamped to the top of the work piece and trim the lower piece to the pattern detail.

- SnowyRiver

This is the way I always understood the difference

 

A flush bits cutting blade is on the shaft, the tip is not normally a cutting blade.. On the pattern bits, the blade on the shaft and tip area are both designed to cut.

 

Jump to the 2:15 mark if you don't want it watch it all.

 

I do a lot of router table template routing. The best bit for this is a bearing on top and bottom. The idea is you can cut all the curved sections that allow for a "downhill" grain cut to eliminate tear out and burning. Flip the workpiece, raise the bit (or lower the bit depending on where you started), then finish the other curves. Win/win!

 

I do a lot of router table template routing. The best bit for this is a bearing on top and bottom. The idea is you can cut all the curved sections that allow for a "downhill" grain cut to eliminate tear out and burning. Flip the workpiece, raise the bit (or lower the bit depending on where you started), then finish the other curves. Win/win!

Keep the template on the bottom of the work piece so you can see the direction of the grain. If you have cut the work piece CLOSE to the dimension of the template, simply "climb cut" those sections which would be against the grain. Much faster and no danger since you are removing so little waste! Also, a top bearing bit will let you shape a thicker work piece by simply raising the bit height. Can't do that with a bottom bearing bit!

- splintergroup

 

Keep the template on the bottom of the work piece so you can see the direction of the grain. If you have cut the work piece CLOSE to the dimension of the template, simply "climb cut" those sections which would be against the grain. Much faster and no danger since you are removing so little waste! Also, a top bearing bit will let you shape a thicker work piece by simply raising the bit height. Can t do that with a bottom bearing bit!

- SFP

True, but I've been burned by doing any small amount of climb cutting on ornery woods (hickory, juniper etc).

I'll stick to keeping things downhill 8^)

Your comment about the top (shaft mounted) bearing being able to cut thicker stock is a good one. I take advantage of that when making inlayed cutting boards.