Adding bearings to bits...

[Matt Benton]

Is it possible to add a bearing to a non-bearing router bit, or does it have to come that way from the factory?

I have a number of 1/2" shank dovetail bits, but need one with a bearing. I can get the bearing from Ace, but don't know about the stops. I'm assuming I would need a top and bottom stop to keep the bearing from moving up and down...

Thanks.

[Matt Benton]

It looks like it can be done after all...

http://pricecutter.com/product.asp?pn=199-9641&bhcd2=1184614395

[Matt Benton]

Actually, is this kit only for bits that came from the factory with a bearing, or can one be added?

[Rick Lizek]

I do it all the time. Best place for the bearings and locking collars is www.ridgecarbidetool.com (http://www.ridgecarbidetool.com). I typically turn bits into top beaing pattern cutting bits. A small washer or bushing under the bearing is the only other thing you need. Should be available in a heardware store.

[Matt Benton]

Rick,

Wouldn't I need a top and bottom collar on a dovetail bit to prevent the bearing from moving too high onto the bit?

[Rick Lizek]

Only if you are putting the bearing higher on the shaft. I'm assuming you are putting the bearing just above the bit. The bushing is to keep the bearing from binding.

[David DeCristoforo]

You can slip a bearing onto the shank of the bit as long as the ID of the bearing fits the shank and you have a top mounted bearing surface. However, the bearing can get stuck on bits that have a "fillet" (a small rounded transition between the shank and the bit body). Spacers can be used to position the bearing on the shank or to fill space to keep the bit from sliding up and down the shank. You can also mount different sized bearings in the bottom of the bit but only if the bit has a mounting post for a bearing. You cannot add a bearing to the bottom of a fixed pilot bit or a pattern bit that has no bearing mount.

[Matt Benton]

I think I'm getting more confused here.

The bit does not have a transition of any kind between shank and body, perfectly smooth.

David, what kind of spacers are you referring to? I would like the bearing to go as close to the cutter as possible while still around the shank.

It seems to me that the bearing needs two fixed objects on either side, and that both of these objects must be tightened to the shank.

Ridge Carbide Tool has a 1/2" ID, 3/4" OD bearing that would seem to be perfect.

[David DeCristoforo]

"The bit does not have a transition of any kind between shank and body, perfectly smooth."

Then, there is no need to worry.....

"David, what kind of spacers are you referring to? I would like the bearing to go as close to the cutter as possible while still around the shank."

That's fine. In that case there is no need for any spacers. But the bearing will be a bit loose because when you tighten the collet, there is going to be some "slack". There are collars (spacers) with set screws that can be used to "lock" the bearing so that it cannot move up and down the shank. With the bearing a bit loose on the shank, it can vibrate under load. What is really happening is that the bearing is rapidly moving up until it contacts the collet and then down until it hits the top of the bit. This can cause more vibration and can cause the bit to loosen in the collet or the bearing to fail. So it's a good idea to have the bearing locked in place and/or the collet good and tight.

"Ridge Carbide Tool has a 1/2" ID, 3/4" OD bearing that would seem to be perfect."

As long as your template has the correct offset, this will work fine.

[Matt Benton]

Are you saying that the bearing is held in place by a collar on the side closest to the cutter and by the collet on the other side? Is that really adequately secure?

[Matt Benton]

By the way, this is in a router table...

Do I need two collars to lock the bearing in place?

[David DeCristoforo]

If the bearing is against the cutter and held in place by a collar with a set screw you should be OK as long as the bearing can spin freely. If the bearing rubs against the cutter, you will need a shim (spacer) betweek the bearing and the cutter. If you want to bearing to be higher on the shank (further away from the cutter) you will need more spacers or even two locking collars, one on each side of the bearing.

When I refer to locking collars, here's what I'm talking about:
http://www.highlandwoodworking.com/index.asp?PageAction=VIEWCATS&Category=291

Shims (spacers) can be seen here:
http://pricecutter.com/product.asp?pn=198-9011&cn=56046

[Charles McCracken]

Matt,

I recommend that you do not try this. If for no other reason, you need at least 80% of the shank in the router collet (at least for Freud bits) and the bearing/lock collar combo may not allow for it. its with bearings are designed to provide enough shank and have a shoulder for a stop.

[Art Mann]

I am trying to figure out what the application is that requires an add-on bearing to a router bit that is being used in a table. Can't you just use the fence? I must be missing something. :confused:

[Matt Benton]

I'm building essentially an inverted halfblind dovetail jig to be used on the router table. It will cut both boards at once. I will be able to build any size template I want.

I would prefer to use 1/2" shank bits if possible, as they are more stable than 1/4". I have numerous 1/2" shank dovetail bits, and would prefer to use them as opposed to buying more with bearings.

Charles, my primary concern is what you pointed out. I'm worried that using two collars to secure the bearing to the shank will take up too much of the shank, and I won't be able to insert it far enough into the collet. I also don't want anything against the cutter, as I don't think I'll have enough cutter height for the cut.

[Curt Harms]

I'm building essentially an inverted halfblind dovetail jig to be used on the router table. It will cut both boards at once. I will be able to build any size template I want.

I would prefer to use 1/2" shank bits if possible, as they are more stable than 1/4". I have numerous 1/2" shank dovetail bits, and would prefer to use them as opposed to buying more with bearings.

Charles, my primary concern is what you pointed out. I'm worried that using two collars to secure the bearing to the shank will take up too much of the shank, and I won't be able to insert it far enough into the collet. I also don't want anything against the cutter, as I don't think I'll have enough cutter height for the cut.

Dovetail bits intended for use with Leigh jigs have longer shanks. Somebody makes a dovetail jig for use in router tables and use bits with top bearings. I can't recall the manufacturer right now though.

HTH

Curt

[Matt Benton]

Curt,

Are you referring to Gifkins?

It looks like their bits have a lip at the top of the shank to keep the bearing from sliding into the cutter.

I'll have to look into bits for the Leigh jig.

[Charles McCracken]

Many manufacturers offer top bearing dovetail bits like the ones at the bottom of this chart:

http://timberlinetools.com/description_images/Freud-Catalog-page158.jpg

[Matt Benton]

Charles,

I think my main goals are:

1. 1/2" shank for stability.
2. Be able to use a bit that did not come with a bearing from the factory. I'm assuming I can save some money in the long run here, but that may not be the case.

Thanks!

[David DeCristoforo]

"I'm building essentially an inverted halfblind dovetail jig to be used on the router table. It will cut both boards at once. I will be able to build any size template I want."

In that case I would suggest that you contact a company like Nordic Saw and Tool:

http://www.nordicsaw.com/

and have them make the bit you need. A custom bit can be any size you need with any shank length and whatever size bearing you want mounted over or under as you prefer. Of course, there are any number of outfits that will make the bit for you. I always recommend Nordic because I have been ordering custom bits and shaper tooling from them for many years and have always gotten a good product at a fair price. It's not cheap to have custom bits made but in this situation, I think it would be worth the cost.

[Arvind Srivaths]

I do it all the time. Best place for the bearings and locking collars is www.ridgecarbidetool.com (http://www.ridgecarbidetool.com). I typically turn bits into top beaing pattern cutting bits. A small washer or bushing under the bearing is the only other thing you need. Should be available in a heardware store.

It's been a while, but in case someone is still looking, 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

[Keith Outten]

In some cases this is the best way to provide bearing support for a variety of cuts.
This pin router fixture is sold by Lee Valley and it is the best quality pin router add-on I have ever seen.
The fixture comes with multiple bearing diameters and is easy to adjust the height.