PC 6931 with plunge base off center

[Tom Hammond]

I have a Porter Cable 6931 router with the interchangeable bases. When I have the plunge base on it, the bit is off center by about .015-.020 inches. It wreaks havoc on trying to rout accurate mortises and dadoes. I contacted Porter Cable and received no response. The plunge base has an odd mechanism on one side for mounting that I think is causing this problem.

Any insight on experience and resolution is greatly appreciated.

[Myk Rian]

Try turning the plastic plate.
Put a guide in it and a bit to fit in the guide, or a centering tool.
Then tighten it down.

[Tom Hammond]

Thanks for the advice. Have tried turning the subbase... off center in every case, and in the same direction so I know it's not the subbase. This really isn't a problem unless I'm using bushings, which we are doing more and more.

[Gerry Grzadzinski]

Can you drill new mounting holes to center it?

[Jamie Buxton]

Every plunge router I've owned has been somewhat off center with respect to guide bushings. Over the years, I've had a Makita, a Bosch, several DeWalts, and now a Festool. 20 mils off center is not unusual. I dunno why manufacturers can't get it right, or provide some adjustment scheme.

I do two things to deal with the issue. First, I use bearing-guided bits whenever I can. Second, if I'm using a bushing guide, I don't rotate the router. If I don't rotate the router, the joint will still be tight, but just be off 20 mils from where I wanted it. If I rotate the router, the joint gets loose.

[glenn bradley]

Are you saying that you cannot center the base using a centering pin? Every router I have owned had more than enough slop in the base to adjust the amount of off-center that you have. Oh, except for a Ryobi that used countersunk flathead machine screws that allowed NO adjustment; what were they thinking?

[Bruce Wrenn]

PC makes two types of base plates. One has tapered holes for screws, and isn't adjustable. The other has flat counter sunk holes and is adjustable. The second is harder to find.

[Michael Heffernan]

If you get an aftermarket clear sub-base for the plunge base, one that is larger diameter than the base itself, then you can center it on the spindle/bit and lock it down. Pat Warner makes very good clear sub-bases for the full PC router line. There are others out there that will also do the job.