# Pattern/Trim Router Bits



## tvman44 (Jun 25, 2013)

Thinking about a Pattern/Trim Router Bit for a upcoming project and have a couple of questions for the experienced people here:
1: Is a 3 flute bit any better then a 2 flute bit? Seems like it might stay sharper a little longer?, Don't know who makes a 3, but I have seen a picture of a 3 flute trim bit.
2: Does the diameter of the bit make any difference, or any diameter will do? 

TIA
Bob


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## Semipro (Mar 22, 2013)

Bob
The diameter of the bit would depend on the pattern you were cutting,lot of tight corners smaller diameter


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## Mike (Nov 22, 2004)

Bob, as a rule these bits will be 1/2" diameter and 3/4" is available. The size question is two sided: a larger bit will clear the dust and chips quicker but the smaller diameter bit allows for tighter curves. (either will work fine) In theory the three flute bit will cut cleaner but I have not seen much difference and the two flute bits work fine.

There are very handy bits available that have a bearing on each end of the cutter so it can be used for patterns or table mounted. One bit doing the job of two bits.


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## kp91 (Sep 10, 2004)

tvman44 said:


> Thinking about a Pattern/Trim Router Bit for a upcoming project and have a couple of questions for the experienced people here:
> 1: Is a 3 flute bit any better then a 2 flute bit? Seems like it might stay sharper a little longer?, Don't know who makes a 3, but I have seen a picture of a 3 flute trim bit.
> 2: Does the diameter of the bit make any difference, or any diameter will do?
> 
> ...


Bob,

I think Freud and a couple of others make cutters with more than 2 flutes. I have a bunch of flush trim bits and pattern bits from a handful of makers, and they all work about the same. My favorite pattern bit set is one from Grizzly

Grizzly.com

It's about $20 on sale, and the finish is about as good as some of the others that are twice the price. I have some porter cable and oldham Viper flush trim bits, they work very well. The PC set has a tiny 1/4 inch flush trim bit that I use for small inside cuts.

Porter Cable PC03TRM Router Bit Set, Flush Trim, 3 Pc

I picked up some bits with square bearings on advice of another forum member, and I really like them. 

https://www.routerbits.com/square-euro-bearing-trim-bits/


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## jw2170 (Jan 24, 2008)

kp91 said:


> Bob,
> 
> I think Freud and a couple of others make cutters with more than 2 flutes. I have a bunch of flush trim bits and pattern bits from a handful of makers, and they all work about the same. My favorite pattern bit set is one from Grizzly
> 
> ...


Hi Doug, how do those square bearings work in tight corners or circular templates (inside)?


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## Dmeadows (Jun 28, 2011)

jw2170 said:


> Hi Doug, how do those square bearings work in tight corners or circular templates (inside)?


A 3/4" bit can't cut an 1/8" radius... no matter the shape of the guide bearing! The limitation is the diameter of the bit. However I think the square bearing would limit the radius even more, but only a little.


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## JOAT (Apr 9, 2010)

I have some masters I use that have some pretty tight spaces. So first go around is with a 1/2" bit, then 1/8" to get the finer details. Don't do that often, but works out well when I do.


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## kp91 (Sep 10, 2004)

I've only used them for trimming laminate or edge banding, as that is all they are designed for. They have a short depth of cut, so they're not useful for pattern routing.

They get anywhere you can bend formica, except for a hard inside corner, where a round bit won't work anyway.


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## Capt Caveman (Oct 15, 2013)

What is about a square bearing that works better? I'm trying to see how it would be any different. Seems like it would take outside corners the same way as circle bearings.


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## Quillman (Aug 16, 2010)

"Does the diameter of the bit make any difference, or any diameter will do? "
********************************
Deflection causes chatter.
Chatter = bumpy cuttings that need sanding, and yield tearout and tool breakage.
Skinny bits, .500" or less, will deflect. 
Take out (grind) more of its (a trimmer) body for a 3rd flute and it will deflect even more than a 2 flute bit.
Moreover, there is no practical advantage to a 3 flute trimmer except to the selller.

Effect of cutting diameter: Whence the body of a cutter has not been ground below its shank diameter it has deflection resistance. Cutters > ~.6" are much stiffer than cutters < or = .5 when the shank = .500". 
Diameter matters.


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## bobj3 (Jan 17, 2006)

Hi Bob

I must have 50+ trim bits from the very small to the very big ( 3/16" to 2" OD ) and one or two of the 3 cutter ones, and they do stay sharper long than the 2 cutter type, the square ones are made for counter top jobs (the glue will jam most bearings on most trim bits) the normal trim bit jobs,,,out of all the trim I have I like the 1/4" OD trim bit it gets in all patterns/templates and it turns at 20,000 rpm's the norm,it will make a quick job of any trim job..


==


tvman44 said:


> Thinking about a Pattern/Trim Router Bit for a upcoming project and have a couple of questions for the experienced people here:
> 1: Is a 3 flute bit any better then a 2 flute bit? Seems like it might stay sharper a little longer?, Don't know who makes a 3, but I have seen a picture of a 3 flute trim bit.
> 2: Does the diameter of the bit make any difference, or any diameter will do?
> 
> ...


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