# Modify router bit to add a bearing below



## asri vaths (Nov 18, 2015)

Is it a good idea to add a bearing below the bit (in my case, a round over bit) and cut a small grove after leaving space for the bearing and put a C ring in the groove to hold the bearing?

Thanks,
Arvind


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## sunnybob (Apr 3, 2015)

Most bits that need a bearing can be bought with "top bearing" (closest to the router) or "bottom bearing" (at the end of the bit. Some are even available with both. Search the bit manufacturers catalogues.

It is NOT a good idea to home modify bits of steel that spin at 30,000 rpm. Youre risking life and limb.


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## harrysin (Jan 15, 2007)

asri vaths said:


> Is it a good idea to add a bearing below the bit (in my case, a round over bit) and cut a small grove after leaving space for the bearing and put a C ring in the groove to hold the bearing?
> 
> Thanks,
> Arvind


I can see no reason why not BUT collars are available held in place with a grub screw. Bits are also available with top and bottom bearings.


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## DesertRatTom (Jul 3, 2012)

Technically you might be able to do that, but even the smallest bit of out of balance-ness of the contraption would put you at great risk. Amiong other things, you will not be inserting the bit almost all the way into the collet. Any shaking will likely destroy your collet, if you are lucky, and fingers and other gear if the collet fails and spits out the bit. You will NOT be able to dodge it if it heads toward you. Collets work by tightening by a few thousandths of an inch. As you can see from the picture, there's not much collet doing the squeezing grip on the shank to start with.


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## mgmine (Jan 16, 2012)

Not sure what you are trying to do. They already make round over bits with bearings below the cutter. There isn't any room at the bottom of the bit to add anything on so it sounds like you are wanting to put a bearing on the top. But by doing so the bit wouldn't be able to cut into the wood. As Harry said you can get collars to fit over the shaft which would be better than cutting a slot in the shaft.




https://www.amazon.com/Round-Over-Edging-Router-Bit/dp/B01I1YQU5U/ref=asc_df_B01I1YQU5U/?tag=bingshoppinga-20&linkCode=df0&hvadid=&hvpos=&hvnetw=o&hvrand=&hvpone=&hvptwo=&hvqmt=e&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=&hvtargid=pla-4583657830358482&psc=1


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## Biagio (Mar 2, 2013)

Arvind, if this is what you are looking for, *do not, repeat do not*, try to make your own. They are readily available and cheap, made in India and made in China. The better quality ones come from Taiwan, EU or USA, but it depends how much/for what you will be using it.
If you were to try and add a bearing below a bearing-less cutter, you would have to cut away part of the bit, including the carbide cutting edges. Even if you succeeded, the chances of a properly balanced bit are less than the chances of your winning the Indian National Lottery. On the other hand, the chances of damage or injury are extremely high.


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## harrysin (Jan 15, 2007)

I've just had a thought, as I occasionally do, I cannot imagine how a round-over bit would work with a lower bearing, that is one with the bearing BELOW the cutter. In fact, I doubt if such a bit is made.


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## Biagio (Mar 2, 2013)

Hi Harry, if by BELOW you mean on the shaft, i.e. between the business end the collet, I have to agree. But I always understood that position to be a top-mounted bearing, or have I got it wrong? I thought a bottom-mounted bearing was the type in the image I posted, very common in round-over bits.


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## harrysin (Jan 15, 2007)

DesertRatTom said:


> Technically you might be able to do that, but even the smallest bit of out of balance-ness of the contraption would put you at great risk. Amiong other things, you will not be inserting the bit almost all the way into the collet. Any shaking will likely destroy your collet, if you are lucky, and fingers and other gear if the collet fails and spits out the bit. You will NOT be able to dodge it if it heads toward you. Collets work by tightening by a few thousandths of an inch. As you can see from the picture, there's not much collet doing the squeezing grip on the shank to start with.
> View attachment 398017


There is an answer to this problem, the MUSCLECHUCK which has several times the grip of a standard collet PLUS it gives about and extra 1/2" depth of cut PLUS no spanners are required, just a half turn of a 4mm hex key to lock/unlock.


Biagio said:


> Hi Harry, if by BELOW you mean on the shaft, i.e. between the business end the collet, I have to agree. But I always understood that position to be a top-mounted bearing, or have I got it wrong? I thought a bottom-mounted bearing was the type in the image I posted, very common in round-over bits.





Biagio said:


> Hi Harry, if by BELOW you mean on the shaft, i.e. between the business end the collet, I have to agree. But I always understood that position to be a top-mounted bearing, or have I got it wrong? I thought a bottom-mounted bearing was the type in the image I posted, very common in round-over bits.





Biagio said:


> Hi Harry, if by BELOW you mean on the shaft, i.e. between the business end the collet, I have to agree. But I always understood that position to be a top-mounted bearing, or have I got it wrong? I thought a bottom-mounted bearing was the type in the image I posted, very common in round-over bits.



Well Biagio, after routing for about 46 years, I'm now totally confused since searching the internet. Can you now answer your question????, I no longer can!


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## mgmine (Jan 16, 2012)

I'm totally confused too. As I said in my original post is what Harry has pointed out that with the bearing at the top(?) anything other than a straight bit won't be able to cut into the wood. What confuses me is what is being considered "below the bit". I have to assume that the top is the part closes to the collet and "below the bit" is the bottom. But if that is the case then there isn't any need to do anything about a bearing because you can just buy a bit like that. Besides, there isn't any shaft below the bit to attach anything on.


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## Biagio (Mar 2, 2013)

As I said. 👍


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## harrysin (Jan 15, 2007)

Biagio said:


> As I said. 👍


What is wrong with MY logic which I've used all my routing career?


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## Biagio (Mar 2, 2013)

Hi Harry, nothing wrong, it is a question of spatial orientation. I don't want to use the word "intuitively", as there are obviously two different possible intuitions, but in my interpretation, the top and bottom you show are applicable to a table-mounted router. In the hand-held configuration, bottom would be the opposite of what you are showing. I can live with either, I just wish we could standardise to avoid confusion.
For example, if the OP wants to fit a bearing to the bottom of the bit (in my sense), I think it is a very bad idea - he should buy a suitable bit. 
If he wants to do it in your sense, eminently doable with a bearing and collar, I have done it myself with straight bits, but as you say, what would be the point of doing it with a round-over bit, which he specifies?
So we have directional confusion compounding confusion of intent.

In no way questioning your experience, which I admire, but I think you can see the source of confusion?


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## harrysin (Jan 15, 2007)

Biagio said:


> Hi Harry, nothing wrong, it is a question of spatial orientation. I don't want to use the word "intuitively", as there are obviously two different possible intuitions, but in my interpretation, the top and bottom you show are applicable to a table-mounted router. In the hand-held configuration, bottom would be the opposite of what you are showing. I can live with either, I just wish we could standardise to avoid confusion.
> For example, if the OP wants to fit a bearing to the bottom of the bit (in my sense), I think it is a very bad idea - he should buy a suitable bit.
> If he wants to do it in your sense, eminently doable with a bearing and collar, I have done it myself with straight bits, but as you say, what would be the point of doing it with a round-over bit, which he specifies?
> So we have directional confusion compounding confusion of intent.
> ...


How on earth would one fit a bearing to what I've labeled TOP. The original poster talked of putting a groove and this could only go on the shaft which is the bottom of the bit irrespective of whether it's in a table or hand held, surely.


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## Biagio (Mar 2, 2013)

Harry, I saw ingenious engineering in my time in India - nothing is impossible there, although I am inclined to agree that he was using the same spatial orientation as yourself, and wanted to cut a groove on the shaft and use a C-ring to retain the bearing. Grooving the shaft is also a seriously bad idea.

Regarding the confusion, here are two images from the same page on Amazon:
View attachment 398067
Described as Freud 1/2" Top Bearing Flush trim bit

View attachment 398069
Described as Baowox 1/4 inch shank Top End Bearing Flush trim router bit.

Amana and others coyly avoid the controversy by just calling them flush trim bits - you pays yer money and you makes yer choice.


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## bfblack (May 2, 2012)

The terms TOP and BOTTOM depend on whether you view the world through the lens of hand held routers or table mounted routers. It appears as if Freud chose hand held routers as the norm.







The attached photo came from Freud's web site.


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## DesertRatTom (Jul 3, 2012)

Top bearings don't have a nut. Just for clarity. Not all straight bits cut a perfectly flat groove. I like to post this now and again just to clarify which is which. Don't forget to clean the cutting tips and lube the bearings every once in awhile.


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## harrysin (Jan 15, 2007)

DesertRatTom said:


> Top bearings don't have a nut. Just for clarity. Not all straight bits cut a perfectly flat groove. I like to post this now and again just to clarify which is which. Don't forget to clean the cutting tips and lube the bearings every once in awhile.
> View attachment 398113


Can anyone dispute this example?


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## Biagio (Mar 2, 2013)

harrysin said:


> Can anyone dispute this example?


No sir, cannot. However, Harry, if you don't mind my saying so, it is not an appropriate example. A tree only grows one way, root and tip are not i terchangeble, and a Xmas tree will only be displayed one way, even if stored upside down at times.
Consider the example of my hourglass, which can be used both ways: would you insist on labelling one bulb as "top", and the other "bottom"? I still maintain it is a matter of orientation in space.

What if you were to utilise the principle of your ingenious router lift, to make an overarm router? Would "raising" the router be applicable even if you were actually "lowering" the router?

Anyway, enough of the semantics, I do not claim any spatial ascendancy, I merely state that there is room for confusion. I bow out of this discussion - the field is yours.


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## harrysin (Jan 15, 2007)

Biagio said:


> No sir, cannot. However, Harry, if you don't mind my saying so, it is not an appropriate example. A tree only grows one way, root and tip are not i terchangeble, and a Xmas tree will only be displayed one way, even if stored upside down at times.
> Consider the example of my hourglass, which can be used both ways: would you insist on labelling one bulb as "top", and the other "bottom"? I still maintain it is a matter of orientation in space.
> 
> What if you were to utilise the principle of your ingenious router lift, to make an overarm router? Would "raising" the router be applicable even if you were actually "lowering" the router?
> ...


No symmetrical item like an hour glass can have a top and bottom, a router bit is not symmetrical!


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## Biagio (Mar 2, 2013)

the bearings used on router bits are generally sealed types, and some are tiny. I understand the cleanliness point, but is it even possibly to oil them?


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## harrysin (Jan 15, 2007)

I've never improved a tight bearing on a router bit by oiling, replacements are readily available in lots of sizes with 1/4" and 1/2" centre holes


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