Centering Router bushing Guide

[Martin Gerber]

I have a Dewalt router and I am trying to center the bushing guide. I am using a pin and cone and hand tighten the brass nut onto the guide while the cone is pressed onto the pin. I have the pin tightened up in the collet. The cone is sitting tight on the pin against the guide while I tighten the nut. The guide appears to be well centered as I cant see any gaps at the guide/cone interface. I am then using a carbide spiral bit (.5") with the .75" guide

When I use the router, I get about 0.020" difference depending on which part of the guide I using as the guide.

I cant figure out what is going on. Any help would be greatly appreciated.

[Neil Brooks]

Is your base/sub-base centered ?

THAT can be much more difficult than centering the bushing, and can have the same negative impact.

[Neil Brooks]

Ah.

Of COURSE, Tom Hintz has an article on this very thing:

www[dot]newwoodworker[dot]com/cntrguidecolr.html

[glenn bradley]

This is all done with the router standing on its head. Loosen the screws holding your base plate enough so that the base plate can shift about. Tighten the template guide onto the baseplate. Lower the plunge to contact your centering cone, tighten your baseplate screws. That is about as good as you will get with a cone centering pin. Also, consider the source of your template guides. The Harbor Freight variety (for example) can have more variance in the sidewalls than the amount of deviation which is bothering you. Even perfectly centered, the inconsistent sidewall thickness adds error. They are fine for rough stuff.

Whiteside (and others) make precision template guides with machined and polished centering pins. The small pin in the foreground is for the template collar shown (9/32") and fits a 1/4" collet. The larger pin is for a template collar mounted in one of my plunge bases for the Mortise Pal (17/32") and fits 1/4" or 1/2" collets. Very nice for precision work.

188404

More discussion on this board here (http://www.sawmillcreek.org/showthread.php?162562-PC-Template-Guides-with-Bosch-1617-Router&p=1669429&highlight=#post1669429).

[michael case]

+1 on everything Glenn said.