# From Marc Sommerfeld's Site - Why not to bottom out your router bit



## BigJimAK (Mar 13, 2009)

I've seen this recommended in virtually every router book I've read but Marc has the most logical explanation I've seen yet. I've attached the file.

Sommerfeld's Tools For Wood


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## bobj3 (Jan 17, 2006)

Hi Jim

Right On,,I have been pushing this for many years  and I have been in some heated discussions over it..


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BigJimAK said:


> I've seen this recommended in virtually every router book I've read but Marc has the most logical explanation I've seen yet. I've attached the file.
> 
> Sommerfeld's Tools For Wood


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## BigJimAK (Mar 13, 2009)

I've been *doing* it since I knew there was no down-side and so many recommend it, but this provides an iron-clad explanation, it makes *complete* sense (to that engineering sense in me) and one I should have figured out myself. 

His grommets make even more sense than o-rings to me.. between the two rings there's room for the rubber to expand into upon tightening.


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## bobj3 (Jan 17, 2006)

Hi Jim

I do have a way that makes no sense to many but if you look at it the way I do, it makes sense to me.. so I now use it in all my routers. 
Some routers have a very deep hole under the collet, so a wooden dowel pin is needed to put the rubber grommet on or just put it in the collet..

see below..

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BigJimAK said:


> I've been *doing* it since I knew there was no down-side and so many recommend it, but this provides an iron-clad explanation, it makes *complete* sense (to that engineering sense in me) and one I should have figured out myself.
> 
> His grommets make even more sense than o-rings to me.. between the two rings there's room for the rubber to expand into upon tightening.


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## Noob (Apr 18, 2009)

Haven't heard of using rubber grommets, but I've seen some recommend using "Space Balls" which are rubber balls .26" in diameter that are used in panel frames. One ball is all you need, and if you lose one, well there are 99 more in the package:

Space Balls


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## bobj3 (Jan 17, 2006)

Hi Noob

Man do I hate the rubber space balls,,all over the floor/work bench once the bag is open  I do use the type below 

200ct. Panelign Strips-Sommerfeld's Tools For Wood

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Noob said:


> Haven't heard of using rubber grommets, but I've seen some recommend using "Space Balls" which are rubber balls .26" in diameter that are used in panel frames. One ball is all you need, and if you lose one, well there are 99 more in the package:
> 
> Space Balls


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## Hamlin (Dec 25, 2005)

Marc also goes into detail on how much of the bit shank is to be "enclosed" in the collet for those deep well routers. BTW, I've been supportin Bj about Marc Sommerfeld's way. I'll admit, at first, none of it made any sense to me. Now, after "studying" Sommerfeld's DVD's. It makes perfect sense. Don't ask how many times I've viewed them. I could go into further detail but, won't. I'd hate to "bore" people.


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## BigJimAK (Mar 13, 2009)

BJ,

Do they bounce like that 60's phenomena (that they outlawed) called "Superballs"? Remember them? They were a blast!



bobj3 said:


> Hi Noob
> 
> Man do I hate the rubber space balls,,all over the floor/work bench once the bag is open  I do use the type below
> 
> ...


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## bobj3 (Jan 17, 2006)

Hi Jim

hahahahahahahahaha the same way, but the little black ones are hard to find and to pickup off the floor or off the work bench, little suckers..LOL ,,,hahahahahaha I think I still have some on the floor some where..after the bag hit the wall,, hahahahaha....

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BigJimAK said:


> BJ,
> 
> Do they bounce like that 60's phenomena (that they outlawed) called "Superballs"? Remember them? They were a blast!


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## TWheels (May 26, 2006)

I was surprised that the Marc Sommerfield video showed the bottom of the bit shank extending beyond the bottom of the collet. I have taken all my router bits, put them into the appropriate collet so that the bottom of the shank is even with the bottom of the collet and marked the shank where it extends out on the bit side so that when I insert the bit I know visually how far to insert it. Is there really something wrong with what I do or do I simply do something differently than others? 

On another point, what are the thermal expansion coefficients of the router bit shanks, the collet and the router receptacle for the collet/bit? Could prolonged use, which does result in heating, cause problems?


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## bobj3 (Jan 17, 2006)

Hi Tom 

You must have great eyes,, .010" is a big deal if you are using a match set of bits, many bits are used as a pair or in both ways (vert. and horz.) on the same board ...once you remove the bit there is no way you can get it back in the same way without some type of device..or replace it with one other that needs to do the same thing but backwards..

Heat ,,,,the bit/shank will always get hot no way around it.speed = heat
,the trick is not to let it get to hot.. 

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mftha said:


> I was surprised that the Marc Sommerfield video showed the bottom of the bit shank extending beyond the bottom of the collet. I have taken all my router bits, put them into the appropriate collet so that the bottom of the shank is even with the bottom of the collet and marked the shank where it extends out on the bit side so that when I insert the bit I know visually how far to insert it. Is there really something wrong with what I do or do I simply do something differently than others?
> 
> On another point, what are the thermal expansion coefficients of the router bit shanks, the collet and the router receptacle for the collet/bit? Could prolonged use, which does result in heating, cause problems?


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## Ghidrah (Oct 21, 2008)

I bought a reversible glue joint from I forget that has a setting marker on the shank, I think it was Price Cutter before they merged with Eagle.

Wouldn't rubber button only be working on a cutter set that guaranteed the shanks were matched for the grommet


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## Hamlin (Dec 25, 2005)

For unmatched sets, you'd still need to reset the height no matter. But, the bit will drop into the router exactly same each time you put it in. It still eases or speeds up the set-up process. As far as I know, Sommerfeld is the only one who has the "matched" sets. I might be wrong though.


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## bobj3 (Jan 17, 2006)

Hi Ken


Many sale them that way 

2pc 1/2" SH Double Round Rail & Stile Router Bit Set - eBay (item 140364565514 end time Jan-01-10 17:29:04 PST)

MLCS, Katana, almost all of the Katana brand come hash marks on the shanks..


Ron

" Wouldn't rubber button only be working on a cutter set that guaranteed the shanks were matched for the grommet"

They have no idea what type of button you are using, it's just a universal "0" stop point for any router bit..


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Hamlin said:


> For unmatched sets, you'd still need to reset the height no matter. But, the bit will drop into the router exactly same each time you put it in. It still eases or speeds up the set-up process. As far as I know, Sommerfeld is the only one who has the "matched" sets. I might be wrong though.


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## Hamlin (Dec 25, 2005)

It would still be difficult to keep them right on the hash marks though. As Marc says, drop them in, tighten and it's exact each and every time.  I'm not against the hash marks, just stating, the slightest movement while tightening the collet...


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## BigJimAK (Mar 13, 2009)

Good question, Tom.. so I've done some research.

The thermal expansion coefficients for common steels are common steels (ignoring superalloys) range from about 8.3 to 8.6 (x10^-6 inch/inch-deg F), and even malleable iron is close, at 7.5, so I doubt the thermal expansion, in and of itself is a serious risk as the bit would tighten in the collet upon heating. What I cannot speak to is any fatiguing effect that (?might?) occur over time due to the deformation of the weakest metal (the collet) repeated heat cycling. This *could* be an issue, but I'd be surprised.

Most spring steels (of which I'd expect collets to be made from, to handle the repeated small bending upon compression) are low-carbon and I'd expect them to be heat-treated not for hardness, but for resilience. I'd expect them to be the "disposable" commodity, expected to give way first (before the bit or collet holder) under stress.

I've read several articles on using old routers (example, Lonnie Bird's book on Routers) recommending replacing the collet due to the amount of stress they take under use. Perhaps this is a contributing factor?


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## BigJimAK (Mar 13, 2009)

I was wondering that too, Ken.. Are the shanks on the other brands milled accurately to the same length, like Marc's are?


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## TWheels (May 26, 2006)

Thanks, Jim. The differences in heat coefficients seem to be so small they will not be a problem under normal circumstances.

Hi Bob, I do not have matched sets of bits; I always adjust the height of the bit for my purpose of the moment. I certainly agree that for some purposes, including for example glue joint or tongue and groove bits 0.01 in or even 0.05 mm would be important. Even with matched sets I do not know if I would trust reproducibility to that extent. How much give is there in the rubber grommets?


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## bobj3 (Jan 17, 2006)

Hi Ron

" How much give is there in the rubber grommets?"

I don't know and I don't care I just know it works very well for me  and has for over 3 years now...it's very easy for me, if it works I use it and if not I drop it..and move on.. 

I don't try and over analyze things to much, I try many things if it works I use it if not I'm done with  

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## TWheels (May 26, 2006)

bobj3 said:


> Hi Ron
> 
> " How much give is there in the rubber grommets?"
> 
> ...


Hi Bj, If it works for you that is all you need. The way I do it, marking the shafts and adjusting the height each time works for me.


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## Hamlin (Dec 25, 2005)

Matched sets such as what Sommerfeld's are, make for above table or even the "pop-out" router table bit changing much easier. Don't change the height at all, just the bit(s). I'm not bashing the hash marks at all. Just trying to point out that, with the grommet, you drop in one bit, change to another without having to worry about "bit adjustments". I don't have any bits that have the hash marks, if I do, I've never noticed them. In fact, never looked for them because, you still have to adjust for each bit, changing the height of the router for each bit. 

When you have a matched set of bits, does it not make sense to make just only 1 adjustment? You can change/switch bits all day long without changing the height of the router and everything matches from the get go.

Perhaps I'm wrong with the assumption that with the hash marks you still have the chance of the bit slightly moving on you while tightening down. I've seen a few of mine move while tightening, never worried about it because, again, you still have to set the height of the router per that particular bit. 

Just my $0.02 worth


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## Ghidrah (Oct 21, 2008)

For exacting purposes, I think the problem with the hash mark/ring setting is in the eye of the beholder, where as the grommet if in good repair doesn't require any interaction with any human body part.

In my limited routing experiences matched sets always meant the yin/yang! stile and rail sets, window sash sets. From this setting blocks came to be to minimize setup time now matching cutter to shank sets.

I may be remembering wrong but I thought the general consensus was that the reason for pulling the shank up a 1/16" to an 1/8" from the router shaft was because the collet pulls the shank down while it tightens on the shank.

If the shank is bottomed out on the shaft and the collet pulls the shank down as it tightens around it, it is putting counter pressure on the collet which is supposed to be bad.

If the collet pulls the shank down, how much pressure does it put on the grommet? If so how much does the grommet distort under that pressure?
If the grommet does distort how reliable can the repeated setting be between one bit change to the other?


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## Hamlin (Dec 25, 2005)

Hi Ron,

I can't really answer the "technical" question of how much the grommet is distorted.

Here's a short quote from the catalog.


> Although the insides of collets are straight to accept the shanks of your bits, when collet nuts are tightened, it's the tapered outside surface that causes the collet opening to close around the bit as it's drawn down into the seat. If the bit is already in contact with the collet seat when you tighten the nut, it's shank won't allow the collet to be pulled fully into the seat. Not tight. Perhaps not precisely straight.


Since Marc Sommerfeld has been using this method for well over 10yrs, there must be something to it.  It is why Bj and myself usually mention his DVD's. The best one for demonstration purposes is, the "Router Tables Made Easy". He switches constantly between the T&G bits, with a slot cutter and a flush trim. Never once did ever change the height setting on the router, just the bits. 

When Bj first mentioned about using a grommet in the router, I was very skeptical, until I ordered Marc's DVD and watched them. IMHO, his system is a more simplified version of the K.I.S.S. method. 

I"m not disagreeing with you at all.


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## bobj3 (Jan 17, 2006)

Hi Ron

When you tighten the collet down it moves the bit down just a very,very little bit..if you put in a bit in your router you will not see it move the norm, if you have a gauge you can check it (with a caliper ) the hole in the collet is on a very high tolerance to match the router bit shank..

Because the grommet is rubber it will bonce back every time to the same place.. the collet locks up on the top part of the collet on many of the routers..that's to say it locks up the bit shank on the end of the collet..not the bottom of the shank..

Setup blocks don't always work,the errors comes into play once the router moves up or down and you need to do that with setup blocks..
The key is not to move the router up or down once the 1st bit is setup for the cut..all the bits dropped into place will always be in the same place..(that's why they make them in the match format ) not for the yin/yang thing so to speak..but they must be the yin/yang on the bits.(male/female thing) as well..

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Ghidrah said:


> For exacting purposes, I think the problem with the hash mark/ring setting is in the eye of the beholder, where as the grommet if in good repair doesn't require any interaction with any human body part.
> 
> In my limited routing experiences matched sets always meant the yin/yang! stile and rail sets, window sash sets. From this setting blocks came to be to minimize setup time now matching cutter to shank sets.
> 
> ...


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## jschaben (Jun 21, 2009)

I've been following this thread and I can understand the reason for the grommet but it seems to me that it leaves an awful lot of shank above the collet. That, or you guys have collets a LOT deeper than mine.
The bits in the picture have shanks about 1-1/2" and looking at the Freud website, the matched bits, #99-267, 268 & 269 have (if my math is right) 2-1/4" shanks. That would seem to me to be an uncomfortable amount.:wacko:


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## BigJimAK (Mar 13, 2009)

How deep is your collet, John? The grommets don't look very thick.


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## bobj3 (Jan 17, 2006)

Hi John

Think about it iike it's a drill bit, lets take a 1/4" bit you chuck up in the drill press ,no need to push it all the way in the chuck the best place is right at the point where the flutes start on the drill bit, the chuck will grab the bit at that point and lock the bit up in place..but you can pull the bit out of the chuck and just grab the top end of the bit in the chuck and it will just do fine...same thing as a router bit all the holding power of the chuck/collet is right at the end of it...


John,,note the picture of the collets I posted the best one for that type of job is the Freud one,it's the deepest one on the market place..note you will see I don't use the rubber grommet I use a rubber faucet washer,it's just the right size for the collet and aging the holding power is at the top of the collet..


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jschaben said:


> I've been following this thread and I can understand the reason for the grommet but it seems to me that it leaves an awful lot of shank above the collet. That, or you guys have collets a LOT deeper than mine.
> The bits in the picture have shanks about 1-1/2" and looking at the Freud website, the matched bits, #99-267, 268 & 269 have (if my math is right) 2-1/4" shanks. That would seem to me to be an uncomfortable amount.:wacko:


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## jschaben (Jun 21, 2009)

Hi guys... Don't get me wrong, I'm not disputing anything here, just trying to find a comfort zone I guess.
Anyway Jim, that is the collet from my Freud 1700. Collet depth is 1-13/32 with the grommet. Grommet is 1/4" thick relaxed and 9/16" in diameter. All ACE hardware had. Probably bulged a bit forcing it in the collet but I also pushed a bit below the collet bottm. Overall length of the collet is 1-27/64" but, of course, the bit extends through the bottom. 
I took the bit measurements off the pedestal bit in the picture, second from the left. Shank is 1-35/64 long and has 23/32 sticking out of the collet with the grommet in place, roughly 50%.

Bob, yeah, I like chucking drill bits up close to the flutes, and I have been known to pull them back out aways also. Broke more than a few that way, usually small ones putting to much lateral pressure on them. Still agile enough to dodge one at 1,000 rpm, not sure about 10,000 though..:sad:
Overall, I think I like your suggestion about dropping a wooden dowel down the armature shaft and letting it set the depth. Should be pretty repeatable if the dowel is close to the ID of the armature. Get 'em back out with an O-ring hook.


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## Ghidrah (Oct 21, 2008)

So, you here an idea, that seems reasonable and accept it as true. You pass the idea along and eventually many believe the idea is true. So one decides to test the validity of the idea and can't reproduce the effect presumed by it.

This morning I went into the shop pulled out the PC, and 3 1/2" collets put bits into them flushed the shanks to the bottom of the collets using the surface of the BS's table. I gently installed each into the same router, tightened them, then released and removed them to the BS table. 

There was no visual change, I sat them down and pushed there was no movement to readjust any difference between the collet and the shank. I repeated the experiment with 11 more 1/2" bits and got the same results.

I then repeated the original process 5 more times but turned the router on (close to a minute) each time and rechecked with the same results, no detectable movement of the shank to the bottom of the collet.

My guess is that the base of the collet can also be used, (like the grommet) as a guage for setting a bit


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## bobj3 (Jan 17, 2006)

Hi John

3/8" dowel about 1/2" long with the rubber grommet glue on the dowel works just fine in the deep hole of the Freud...if you don't want it in place from time to time, just flip the router over and it just drops out easy.


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jschaben said:


> Hi guys... Don't get me wrong, I'm not disputing anything here, just trying to find a comfort zone I guess.
> Anyway Jim, that is the collet from my Freud 1700. Collet depth is 1-13/32 with the grommet. Grommet is 1/4" thick relaxed and 9/16" in diameter. All ACE hardware had. Probably bulged a bit forcing it in the collet but I also pushed a bit below the collet bottm. Overall length of the collet is 1-27/64" but, of course, the bit extends through the bottom.
> I took the bit measurements off the pedestal bit in the picture, second from the left. Shank is 1-35/64 long and has 23/32 sticking out of the collet with the grommet in place, roughly 50%.
> 
> ...


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## jschaben (Jun 21, 2009)

bobj3 said:


> Hi John
> 
> 3/8" dowel about 1/2" long with the rubber grommet glue on the dowel works just fine in the deep hole of the Freud...if you don't want it in place from time to time, just flip the router over and it just drops out easy.
> 
> ...


Great Bob, thanks, hadn't thought of gluing the grommet to the dowel.


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## bobj3 (Jan 17, 2006)

You're Welcome John

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jschaben said:


> Great Bob, thanks, hadn't thought of gluing the grommet to the dowel.


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## sometimewoodworker (Feb 13, 2009)

jschaben said:


> I've been following this thread and I can understand the reason for the grommet but it seems to me that it leaves an awful lot of shank above the collet. That, or you guys have collets a LOT deeper than mine.
> The bits in the picture have shanks about 1-1/2" and looking at the Freud website, the matched bits, #99-267, 268 & 269 have (if my math is right) 2-1/4" shanks. That would seem to me to be an uncomfortable amount.:wacko:


Hi John 

I think that you have missed the point that the grommet/rubber washer/ball does not fit in the collet itself. That would serve no purpose. it fits under the collet onto (in the PDF it is called) the collet seat

All routers allow the router bit to extend bellow the collet 



Ghidrah said:


> So, you here an idea, that seems reasonable and accept it as true. You pass the idea along and eventually many believe the idea is true. So one decides to test the validity of the idea and can't reproduce the effect presumed by it.


Hi Ronald 
Your idea of testing "accepted" ideas is a very good one. But in this you are not actually testing the problem. The problem is when the bit is pushed past the bottom of the collet to the base of the recess that collet fits in.



Ghidrah said:


> This morning I went into the shop pulled out the PC, and 3 1/2" collets put bits into them flushed the shanks to the bottom of the collets using the surface of the BS's table. I gently installed each into the same router, tightened them, then released and removed them to the BS table.
> 
> There was no visual change, I sat them down and pushed there was no movement to readjust any difference between the collet and the shank. I repeated the experiment with 11 more 1/2" bits and got the same results.
> 
> My guess is that the base of the collet can also be used, (like the grommet) as a guage for setting a bit


You are completely correct that if you use the bottom of the collet (pulling and replacing it each time) and the bit does not slip while doing this you will have an exact repeatable setting.

That said (unless you are using 1/2" small diameter bits) it is a very bad way to set a bit because with the majority of bits you will have too much of the shank above the collet.


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## DerekO (Jan 20, 2010)

Very glad I saw the link to this thread. I've never had a problem getting a bit out of full size router yet, but have had the problem with a couple of rotary tools. I will have to get some some thing to make sure I don't drop the bit in all the wall.

RE: Superballs...No more Superballs? How sad.


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## KUMZUM (Jun 19, 2010)

Some great advice and knowledge in this thread. Thanks


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