# what are the parts to a router bit?



## allthunbs (Jun 22, 2008)

The other day I was trying to describe to a newbie the difference between a bottom bearing'd bit and a top bearing'd bit. It would have been so easy had I had a diagram showing the different parts and their names.

Ok, there's the shank, and the cutter, and the bearing, and the flute. But what about all of the other parts? What is the cutting end called as opposed to the shank end? The flutes are carved into what -- the body, the shank, the shaft??? What is the carbide glued/welded to? (how can you tell the difference?)

Do different bits have different names for their parts? I.e. does a round over bit with a bearing have different part names than a bottom bearing laminate trim bit?

Allthunbs


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## Ralph Barker (Dec 15, 2008)

Charles (or, someone else) may have better, industry-accepted terms, but I describe the bit bits as the shank extending into the cutter body, into which flutes are ground for the creation of either the cutting edge (e.g. with HSS bits) or to which the carbide cutter is welded. I refer to the shape of the cutter edge as the profile.

Top/bottom bearings are described from the perspective of the botor on top, bit on the bottom as it would be used in hand-held routing. So, one needs to make a mental flip when buying for a table-mounted router.


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## allister (Mar 10, 2009)

*Parts of a router bit video*

Here is a link to a few videos on router bits


http://www.expertvillage.com/video/10739_how-to-use-a-power-router-parts-bit.htm

Just remove the quotes and copy/paste this into a browser


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## allthunbs (Jun 22, 2008)

Thanks Allister and Ralph: but, we've got a long way to go.

Router: a router is a machine tool to which a cutter is attached and spun at high speed. The objective is to remove small amounts of material at a time. The collective small amounts of material removed makes it seem that the router is very efficient. Unlike saws or planes or other cutting machines or instruments, routers can remove material on any plane.

Shank: that part of the router bit that attaches to the armature of the router and transfers the energy from the armature to the cutting edges.

Bearing: on some routerbits, that part that touches a work surface without altering it. Usually used as a guide for the cutting edges of the bit.

Top Bearing: a bearing that is installed on the shaft of the router bit and held in place with a "shaft-bearing locking collar?"? (two questions there. I couldn't find a precident in the english language for this one ;-)

Bottom Bearing: a bearing that is installed on the router bit at the opposite end from the shaft. It is usually held in place with an Allen head machine screw and locking washer.

Flute: that part of a router bit or drill bit used to remove scarf from the cut. Side cutting router bits will have up or down spiral flutes and occasionally both combined. Drill bits will have only up spiral flutes.

"sit?": the flat part of a routerbit at the end of the shank. The shank, when inserted into the collet chuck sits in the "seat" at the bottom of the collet chuck.???

what's it called: the tip of a router bit, that part at the opposite end to the shank. Is this a different partname for a plunge vs. side cutting bit vs. bearing bit???

what's it called: that part of a router bit made of carbide?

what's it called: that part of a router bit where the carbide is _welded_ to the "flutes?" of the bit?

what's it called: that part of a router bit where the carbide is _glued_ to the "flutes?" of the bit? Is there a difference in the part names when welded or glued.

This is just a start. We can't progress unless we know what we're talking about.

Allthunbs


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## Ralph Barker (Dec 15, 2008)

_"sit?": the flat part of a routerbit at the end of the shank. The shank, when inserted into the collet chuck sits in the "seat" at the bottom of the collet chuck.???_

I call it the base of the shank and the bottom of the collet chuck.


_what's it called: the tip of a router bit, that part at the opposite end to the shank. Is this a different partname for a plunge vs. side cutting bit vs. bearing bit???_

I call it simply the tip of the bit. Plunge bits are differentiated by having cutting edges across the entire tip, whereas side-cutting bits don't.

This gets confused, however, by carbide bits occasionally being called "carbide tipped".

_what's it called: that part of a router bit made of carbide?_

I call the carbide insert the cutter. 

_what's it called: that part of a router bit where the carbide is _welded_ to the "flutes?" of the bit?_

Again, cutter.

_what's it called: that part of a router bit where the carbide is _glued_ to the "flutes?" of the bit? Is there a difference in the part names when welded or glued._

I don't think any are "glued". As far as I know, it's a heat bonding process that I'd call welding, with the cutting edges being sharpened after tempering. The idea of razor-sharp pieces of carbide being _glued_ to the flute, and then spun at 20,000 rpm, gives me the heebee jeebies. 

*Note*: these are my terms, not ones derived from some authoritative source, which I have yet to find.


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## Mike (Nov 22, 2004)

I think this is way over complicated. Bits are described by shank diameter, cutter type and dimensions plus the bearing if applicable. By the way, carbide is brazed to the cutter bodies... not welded.


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## xplorx4 (Dec 1, 2008)

Ya, I could keep it simple, I think it is KISS we all know what that means, and I am not implying anyone here is the last "S". Really it is good information for me anyway.

Thanks for the posts and the links.


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## woodshopdemos (Oct 13, 2008)

One minor change: the carbide edge is not welded on. It is brazed. The difference being the temperature and the use of a solder material.


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## allthunbs (Jun 22, 2008)

Mike said:


> I think this is way over complicated. Bits are described by shank diameter, cutter type and dimensions plus the bearing if applicable. By the way, carbide is brazed to the cutter bodies... not welded.


I'm not asking how they are described, that's simple -- you have a straight bit, or a round-over bit or ... 

I'm asking what are the parts to a router bit? It is a simple question. I feel like I have to defend my question? Why is it over complicated?

We have some of the most talented minds in the history of router use on this forum. Do you mean to say that when we discuss something everyone is creating their own vocabulary every time? 

The first thing that happens when manufacture begins is someone identifies all of the components and features of each component. Like that all of the members of the design team know what they are talking about.

I just got my car back from repairs. I was shocked to learn that they no longer welded pieces into place, they use glues. I was told that welds were operator and climate dependant whereas glues were accurate and thorough every time. Do they not use epoxies and cyano-acrylates in router bit construction?

Allthunbs


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## allthunbs (Jun 22, 2008)

Ralph Barker said:


> *Note*: these are my terms, not ones derived from some authoritative source, which I have yet to find.


Exactly, that's my point. Where is that authoritative source? Who is the final authority on all things router? I'm going to shock the bunch of you. In my opinion, YOU are the final authorities on all things routers. Each and every one who puts in their 2 cents worth contributes to the whole body of knowledge about routers. The Ralphs and Harrys and Toms and Nicks and Jerrys and Bobs and Ricks ... provide a focal point to whom we all address our questions and hopefully get some sort of answer. But, each and every one who has an interest in this craft forms part of the whole knowledge base. It just happens that this forum is the focal point of that knowledge.

I look at the books that everyone is referring to and I look for stuff that I see and hear here and I figure the guys who write the books are like TV reporters. The repeat what they saw but seldom create something new.

Could someone please create a drawing of a router bit so we can start naming the parts. I can't get my "Thunbs" around Sketchup or AutoCAD.

Allthunbs


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## Hamlin (Dec 25, 2005)

Hi Ron,

A bit actually starts out as a "billet". From there it begins a long process of becoming a router bit.

IMHO, shank, flutes, edge or cutter, then bearing, rather it's a top or bottom bearing. Just my thoughts.


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## AxlMyk (Jun 13, 2006)

Shank
body
knife or cutter
bearing

Bearing on the shank end of a straight bit is a pattern bit
Bearing on the cutting end of a straight bit is a flush trim bit


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## woodshopdemos (Oct 13, 2008)

Go to any manufacturers catalog and you will fid info. try this one CMTUSA.com

Frankly Ak Thumbs, you have gotten plenty of information. Way more than you need. What you should do is use a real router bit in a real router and cut real wood.


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## Mark (Aug 4, 2004)

woodshopdemos said:


> Go to any manufacturers catalog and you will fid info. try this one CMTUSA.com
> 
> Frankly Ak Thumbs, you have gotten plenty of information. Way more than you need. What you should do is use a real router bit in a real router and cut real wood.


Lets keep this friendly


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## allthunbs (Jun 22, 2008)

woodshopdemos said:


> Go to any manufacturers catalog and you will fid info. try this one CMTUSA.com


I have found very little information in any of the manufacturer's catalogues, which is typical. The only manufacturer to qualify it's tools is LeeValley and even they don't list component details.



woodshopdemos said:


> Frankly Ak Thumbs, you have gotten plenty of information. Way more than you need. What you should do is use a real router bit in a real router and cut real wood.


How do you determine what I need and for what purpose? Do you manufacture custom router bits? If I were to ask you for a specific pattern could you provide it? The biggest headache I have is manufacturers who have lost the ability to produce custom products. There is an art to making molding plane irons and router bits. Knowing the names of the parts allows one to communicate with manufacturers about one's wishes and resolving problems. 

One of the things that bugs me is the price range for router bits. Some are horrendously expensive and others are dirt cheap. But, the best people can say is "you get what you pay for!" Well, it ain't necessarily so. I use cheap bits for "garbage jobs" and expensive bits for cabinetry. However, I visually compare them and I see little or no difference. I go to manufacturer's catalogues and I read the specifications - LeeValley and Rockler for some of their bits share specifications almost word for word yet there is a, perhaps, $10 difference in the price. Why, what's the difference between them? There isn't a standardized terminology to allow one to compare the bits.

There are those who would ask "who cares" and throw money at router bits and think nothing of it. But, there are those who's funds are not limitless and who must, for lack of budget or slim profitability margins, purchase judiciously. How can you compare products unless you can describe it?

Not all of us require custom router bits and not all of us need to know the parts of a router bit. But, there are those of us who do have this information and even others who need it. I'm just trying to bring the two together.

Allthunbs


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## Ralph Barker (Dec 15, 2008)

FWIW, I think it's both healthy and informative to discuss terminology and semantics associated with any field of interest. Of course, doing so may not be of interest to everyone. But, that's OK, too.

For example, welders and machinists probably use tighter definitions for welding, brazing and soldering than do woodworkers. For many of us, "welding" is synonymous with the high temps achieved with oxy-acetylene or arc rigs, steel rods, and essentially melting the edges of the components together. Similarly, brazing usually conjures up a similar operation using brass rods at lower temps, and soldering involves even lower temps where only the (typically, lead-based) solder is actually melted. But, there are manufacturing methods involving high voltage that joins metal parts without the use of rods, and still others that use a joining material of a higher melting point than common lead-based solder - similar to "silver soldering". For many, the line between welding and brazing is fuzzy.


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## curiousgeorge (Nov 6, 2006)

Ok, Ron. Is this what you want? If so, then everybody take a stab at naming the lettered parts and see what we come up with...

A. Shank
B. Flute
C. Body
D. Cutter, Blade, Knife, etc.
E. Bearing (In this case a bottom bearing on a Flush Trim bit)


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## allthunbs (Jun 22, 2008)

*Derek Whats a bit shank in the UK?*



curiousgeorge said:


> Ok, Ron. Is this what you want? If so, then everybody take a stab at naming the lettered parts and see what we come up with...
> 
> A. Shank
> B. Flute
> ...


Marvellous! I've added two elements, the two ends of the bit. 

a: the shank - a router bit is made from a billet of steel. One end is machined called "the cutter" and the other end is left untouched "the shank."

b: chip clearing channels are machined into the cutter to allow chips to move clear of the workpiece and be ejected from the "kerf?" These channels are called "Flutes?"

c: if the entire "business end" of the bit is "the cutter," then this should be "the body?"

d: these could be the blades if they're not part of the body. The "blades" would only be those carbide elements that are braized on. Should the "bolt on" "blades" also be called "blades?" High Speed Steel (HSS) bits have these "blades" an integral part of the body. In this instance, they might not even be considered "blades."

e: this is the de facto standard "bearing." However, there are several styles of bearing mounts: there is a slight protrusion from the "tip" of the bit and inside that protrusion is a socket with threads into which screws an allen head screw to hold the bearing on. On other bits, that protrusion is replaced by a threaded shaft and the bearing slides on a is held by a nut. Should these two techniques (or more?) share terminology?

f: this is an important feature of bits. Depending on whether or not this is a plunge bit or a side cutting bit, this end can either plane a surface smooth, provide a hole with no tearout and clean shoulders or remove material to the side. What brings this to the fore is that some manufacturers make a bottom-cleaning bit, rabbeting bit... To my mind they're all the same thing.

g: this is the top end of the bit. I called this a "sit" that fits into a "seat" in the collet chuck of the router. In one of our earlier posts, it was suggested that I set a plumbing washer in the bottom of the collet. This would give consistent seating on every bit.

Are there other bits with other part names?

Allthunbs


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## AxlMyk (Jun 13, 2006)

A. The part that goes in the collet
B. The music maker part
C. The thicker metal part
D. The sharp part
E. The spin-around part


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## allthunbs (Jun 22, 2008)

AxlMyk said:


> A. The part that goes in the collet
> B. The music maker part
> C. The thicker metal part
> D. The sharp part
> E. The spin-around part


chuckle


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## tomwalz (Aug 14, 2008)

One source generally considered authoritative is the book Chisels on a Wheel. I can't post the address but it is free at carbideprocessors web site.


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## tomwalz (Aug 14, 2008)

The steel that does the cutting is soemtimes called wings and the carbide is called carbide.


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## tomwalz (Aug 14, 2008)

Glues, epoxies, etc. can work but brazing gives much greater strengths. In addtion glues, etc. tend to break down past maybe 300 or 400 F whereas most braze alloys are good to at leat 1400 F.


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## allthunbs (Jun 22, 2008)

Lovely, thanks Tom. BTW, I've bookmarked Carbideprocessors.com and the book (two different indexes for me.)

I do buy BusyBee Cyclone and Woodline USA but I also buy LeeValley and OakPark. People have said that the LeeValley and OakPark are _supposed_ to be good bits. You sell four different brands of router bits. From the worst to the best how do you position them? 

Why? How can I as consumer tap into the knowledge that you have? Translation: how can _I_ tell what is a good bit and what isn't?

Thanks for your participation Tom, it is much appreciated. Your timing couldn't have been better 

Allthunbs


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## SteveSawDust (Mar 18, 2009)

Reading all this gave me headache. Had flashbacks of being in school and cramming for a final in physics.  Might be easier just to keep a bit in your pocket and then pull it out when you need to describe it.


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## allthunbs (Jun 22, 2008)

SteveSawDust said:


> Reading all this gave me headache. Had flashbacks of being in school and cramming for a final in physics.  Might be easier just to keep a bit in your pocket and then pull it out when you need to describe it.


Hi Steve: You're absolutelly right. This is applicable to about 10% of the community but to that 10%, it could make a real difference. I'm beginning to look at the requirements for bits used with skis compared to bits using templates or jigs. Duplicators already have shown they need different bit requirements than other forms of routing. However, what I ran into was that there was no common method of analyzing router bits, the good, the bad and the ugly. This is an attempt to resolve that question.

This all came to the fore when I was using an upsprial bit to do a rabbet. For some reason the floor of the rabbet was never clean. I deduced that my Freud upspiral was flexing under the pressure of side cutting. I switched to a Cdn Tire side cutting bit and I had chip clearing problems and still can't figure out why. The bit looks identical to the LeeValley equivalent but in a slightly different size.

So, how can I discuss this problem unless we know what we're talking about?

Allthunbs


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