Dovetail bit not centered in baseplate

Hi,
I'm wondering if anyone can help me? I recently tried to use a dovetail jig and found that my dovetail joints were consistently sloppy on one side of the pin by about 1/16". Everything else fit snuggly when viewed from the side but at the top of each pin there was this 1/16" gap. (and, yes, I tried extending the bit a little but the joint was still sloppy)
After checking everything out, I've concluded that because the bit is off-center in the guide bushing, the bit is allowed to travel a little deeper on one side of the cut. Looking at the bit in the bushing, it is obvious that this is where my slop is coming in.
I removed the bushing and checked the distance from the bit to the edge of the baseplate and then checked the opposite side. There is a 1/16" difference. I tried removing all the screws and rotating the baseplate clockwise a couple of times, but the results are still pretty much the same. (oh, sorry, didn't mention that I am using a Porter-Cable 690 series router with the stock baseplate) I also tried using a baseplate from my plunge router base. Almost the same results. I would have thought that PC would have better tolerances than that. Anyway, can you think of any way to correct this problem so that I can use my dovetail jig?
Could I use a bearing in lieu of the guide bushing? My jig requires a 7/16" O.D. bushing so if a bearing is a possibility, do they come in that size? What would hold the bearing on the shaft?
I'm a newbie to woodworking and not at all comfortable with the idea of trying to make a new baseplate at this point. I'd just be happy to be able to use my jig to make the drawers for the router table I'm building. I know a little further on in the process I'll be pretty much forced to make a baseplate for the table, but I'm just working on little steps at a time. :)
Thanks, Sandy
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Are you rotating the router when you use it? Try to keep the orientation the same at all times. It's a good idea to mark one side of the baseplate with a marking pen and always keep the mark facing you. Also, you will want to remove the three baseplate screws and try rotating the baseplate over one set of holes at a time until you find the holes that get the bit closer to center.
You rarely find a 690 that is dead-on concentric, but if you get it close, and always orient the router the same way, you should be able to get better cuts than you are getting on your jig.
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No
Also, you will want to

Tried that with very little change in the results.

This advice will work well in general but when using a guide bushing it doesn't help that much because when you are routing down a 1/2" pair of dovetail fingers on a template, you can't really keep the same edge against the pattern.
Thanks for your reply, Sandy
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Swingman wrote, wondering if this is really what he meant?

You'd think that one of the top of the line routers, (Porta Cable) could get a measurement right! Sure doesnt say much about Porta Cable when it comes to getting their baseplates in line. Makes me a little leary about my next purchase.
Rich
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Most of us have been confronted by your problem, I'm sure. In my case, I did some modification of the holes in the plastic baseplate. Doesn't take much (1/32) to compensate. Makes it necessary to check concentricity every time thereafter, but you've seen that the results will justify the effort. The counterbores are usually enough oversize; a bit of scraping might be necessary if they're not.

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On Sat, 30 Aug 2003 22:14:55 GMT, "George"

It seems to me that those counterbores are what pull the baseplate out of alignment. What do you scrap them with? A small knife?
Sandy
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If that'll do it. I used a carving gouge, though you might do as well with a Dremel-mounted rotary file.

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I did everything mentioned in this string. I ended up purchasing a DW 610 for my dovetail work. It solved all my problems. :-) I only use my 690 in a router table these days, along with a foot switch for safety.

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Some information on the collar/cutter centricity issue at the http://www.patwarner.com/collarguide.html link. A very common problem. Suspect your error is more like a 1/32nd x 2. As bad as it may seem, doing a 180 with the router when the work is indexed on the right side of the jig may cancel all of the error. Try sample on scrap. ******************************************************************

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