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What's The Difference Between These Bits?

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Forum topic by Mean_Dean posted 03-02-2010 03:52 AM 7922 views 0 times favorited 14 replies Add to Favorites Watch
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Mean_Dean

7053 posts in 3998 days


03-02-2010 03:52 AM

A pattern bit, and a flush-trim bit?

It seems to me that one has a bearing on top, and one has a bearing on the bottom. So what’s the difference between them, and which one is best for what use?

Thanks in advance!

-- Dean -- "Don't give up the ship -- fight her 'till she sinks!" Capt James Lawrence USN


14 replies so far

View Alexander's profile

Alexander

198 posts in 3961 days


#1 posted 03-02-2010 03:54 AM

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.

-- John at Sugarloft Mountain........Don't argue with an idiot; people watching may not be able to tell the difference.

View bigike's profile

bigike

4057 posts in 4139 days


#2 posted 03-02-2010 04:28 AM

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.

-- Ike, Big Daddies Woodshop, http://[email protected]

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tooldad

665 posts in 4565 days


#3 posted 03-02-2010 04:32 AM

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.

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Ger21

1099 posts in 3981 days


#4 posted 03-02-2010 05:28 AM

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

-- Gerry, http://www.thecncwoodworker.com/index.html http://www.jointcam.com

View SnowyRiver's profile

SnowyRiver

51458 posts in 4331 days


#5 posted 03-02-2010 05:47 AM

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.

-- Wayne - Plymouth MN

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closetguy

744 posts in 4742 days


#6 posted 03-02-2010 07:17 AM

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.

-- I don't make mistakes, only design changes....www.dgmwoodworks.com

View Alex Lane's profile

Alex Lane

575 posts in 4741 days


#7 posted 03-02-2010 03:21 PM

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.

-- Alex...builder of wooden wings for vintage sport biplanes...I'm your wingman :)

View Deadend's profile

Deadend

17 posts in 1064 days


#8 posted 02-02-2019 02:13 AM

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?

-- I might not do good work, but I'm slow.

View AlaskaGuy's profile

AlaskaGuy

5991 posts in 3159 days


#9 posted 02-02-2019 03:12 AM



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

-- Alaskan's for Global warming!

View WoodenDreams's profile

WoodenDreams

1123 posts in 761 days


#10 posted 02-02-2019 06:50 AM

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.

View AlaskaGuy's profile

AlaskaGuy

5991 posts in 3159 days


#11 posted 02-02-2019 07:26 AM

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

https://youtu.be/tPwokpRYBN4

-- Alaskan's for Global warming!

View splintergroup's profile

splintergroup

3988 posts in 2073 days


#12 posted 02-02-2019 04:02 PM

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!

View SFP's profile

SFP

36 posts in 2106 days


#13 posted 02-15-2019 01:17 PM



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


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splintergroup

3988 posts in 2073 days


#14 posted 02-15-2019 09:36 PM


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.

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