Using Dovetail Bits With Guide Bearing Collar

[Ken Krawford]

I have a Leigh Dovetail Jig that I use almost exclusively for half blind joints and was wondering if anyone uses a bit with a guide bearing instead of a guide bushing collar? It seems that this arrangement would remove the variable of not having your guide bushing centered perfectly on the router base. Most of the drawer boxes I made are with 1/2" stock and this requires an 18 degree bit. I quick Google search didn't turn up any bits like this with the bearing collar.
And thoughts both pro or con would be appreciated.

[pat warner]

The essential negativity to a third bearing (2 on the armature, 1 on the cutter) is vibration/deflection. It's better to transfer all your pulling loads to the subbase/casting via a collar system. With a bearing on the cutter you have the added deflection/forces bending things up, right at the cutting site.
That is somewhat shank sensitive; big cutters with 1/2 shanks are less of a problem. But, if I could, I'd use a well centered collar over a bearing on the shank of the cutter.
Moreover, consider a collar a safety shield. It protects you and the templet from the cutter.
I would add that there are a limited number of bearings to = collar OD's.
However, a bearing can usually be sleeved or ground to get what ever diameter is desired.

[Jamie Buxton]

I don't know the Leigh, but you might have trouble finding the bearing. A rub collar's thickness can be small -- just 30 thousandths or so. Bearings have to be bigger than that.

One of the reasons I use the Keller jig is that it is designed to use a guide bearing, not a rub collar. It doesn't give that annoying offset problem from an offset in the router base. But the Keller only does through dovetails, so it won't help you on the half-blinds.

[Bradley Gray]

I have a Keller dovetail template set. It uses bits with top bearings, a straight bit for pins, dovetail for tails. It does require some care to prevent cutting the template but in my experience the bearing supports the cutting extremely well and results in less chatter than template/ rub collar set ups I have used

[Cody Colston]

My D4R came with an eccentric guide bushing. It can be indexed to keep the bit centered relative to the position the router is held. I do more thru dovetails than I do half-blinds but I have had no problem getting tight joints after making test cuts to "dial it in."

[Ken Krawford]

Cody I have the eccentric bushing but have never used it. Is it difficult to dial it in? Do you just eyeball it or use a centering bit?

[Steve Wilde]

I had a problem centering my bushing when using my leigh jig at first. I needed another bushing so that I wouldn't need to switch out my router bit. I purchased a whiteside bushing that came with a centering bit to use and I got great results with it right from the get go. I would highly recommend one.

[Ken Krawford]

Steve, I searched Whiteside's catalog and couldn't find a centering bit. Might it be discontinued?

[Andrew Pitonyak]

The Keller jig uses a bit like this.Just do a google search with the following text

keller dovetail bit

I think that you will find many results.

That said, I would prefer if it used something else, but, this allows things to just work with any router and an appropriate bit.

[Steve Wilde]

Ken,
I think this is the one I bought. I bought it at woodcraft.
http://www.woodcraft.com/product/148156/whiteside-054038n-precision-38-od-template-guide-bushing.aspx

[Cody Colston]

Cody I have the eccentric bushing but have never used it. Is it difficult to dial it in? Do you just eyeball it or use a centering bit?

The bushing has numbers for indexing it. I go by the instruction manual and orient the bushing to the direction of router travel. I'm at work and can't refer to the manual for details. Anyway, you orient the number (I think it's 10) and make a groove on the router base plate corresponding to that number. Make test cuts and adjust the bushing by rotating it, again refer to the manual. Once you get it right, it will always go to the number that corresponds to the line on your base plate. Note: Obviously the base plate has to go on the router in the same orientation every time if you happen to remove it. Also, you have to use the same router for both pin and tail routing unless you get an extra eccentric bushing and dial it in on a second router.

The instructions in the Leigh manual are a lot clearer than mine.