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Discussion Starter #1 (Edited)
The holes in the plastic bases of my craftsman 27683 router are just a gnat's eyelash too small in diameter for a standard guide bushing. The larger diameter part of the bushing does not fit in the hole. How can I make the hole a tad larger? Can I use a circle cutter like this one Carbide Tip Adjustable Circle Cutter ? Looks tricky. I do have a drill press.
Since the hole in the router base is stepped, I need to increase the diameter of the larger, stepped part of the hole. I even thought of just scraping it with a razor knife but don't think I can get it concentric this way (does it matter?).

Related question: when using a centering cone, do I adjust the bushing within the router's base hole, or adjust the base on the router?
To adjust the bushing would require that the bushing be a little loose in the hole, which it isn't. To adjust the base would require that the holes for mounting the base have some play in them. They don't.

What am I misunderstanding here?

As I type this I realize that maybe the HF bushings are just a little too big in diameter. I'll have to check them later.

Background.
I also have a Skil 1835 router and the guide bushing fits perfectly in the hole in its base. When I say perfectly I mean without any play, so no way to adjust. The guide bushing is from a set I bought at HF 9 Piece Router Template Guide Set. I also own a base plate with quick change guide bushings. milescraft set This one has a universal plate and the HF guide bushings fit it just fine.

I took the guide bushing to Sears and tried 4 -5 other routers. All have the same problem. I tried the guide bushing from the Sears set, though, and it fit fine in the Sears routers and loose in my universal adapter. craftsman bushing set

So it looks like the Sears guide bushings and router bases are all just a tad smaller in diameter than 'standard.'

Thanks, again, for helping a newbie.
 

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So, you are talking Porter-Cable style bushings. The flange is 1 3/8" diameter while the threaded part is either 1 1/4" or 1 3/16" (I've seen both sizes listed). I think it would be very tricky to get a hole saw to make a perfectly concentric enlargement. Concentric isn't critical but you do have to get the bushing in. If there was a 3/32" rabbet bit, you could do it but I didn't see one with a quick look. Frankly, I would just make a new base from 1/4" lexan and use 2 forstner bits (1 3/8", 1 1/4") to make the holes. With a pilot hole you can make them concentric and with oversized mounting holes you can center the base. I've done that a number of times.

On the centering question - you loosen up the screws holding the base and move it to center the bushing that is attached to the base. Get it centered and then tighten down the screws.
 

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fit the current hole w/ a forstner bit exactly...
load that bit into the DP...
fit the base to the bit and clamp the base to the tanle...
change fostner bits to the desired hole you want w/o moving the base plate...
bore your hole...
if you want a shouldered hole to comp/place the ring change fostner bits again and cut the shoulder...
 

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Ken - if there is no play in the base's screw holes, they are probably countersunk. They need to have a flat bottom which allow the base to move around the screw. I'm not sure why base plates are made like that, but I experienced the same issued with my Porter Cable 690 - countersunk holes. I checked my local woodworker store and the new replacement plate from Porter Cable still has countersunk holes.

My old Craftsman router also has countersunk holes. My Bosch 1617 does not. I have a cheapie set of guide bushings and found that they did not fit in my PC 690 - the PC690 center hole had a small tab inside that I had to slice off with a utility knife. Not all guide bushings are the same size - slightly off, but just enough to make a difference.

If you don't want to make a new base, you could take a forstner bit and flatten the bottom of the hole on your current base - that should give you enough play to reposition the base as you center the bushing around the bit.
 

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KISS!
Use the universal base plate with the HF guide bushings and don't bother with modifications to the Craftsman base plate.
 
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Discussion Starter #6
@mebcwd

Great idea. I overlooked the obvious. I was too focused on 'fixing' the problem with the bases that I forgot that the real problem was how to use the router with a template.

Thanks!
 

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if you want to change a countersink to a counterbore fit the current countersunk hole w/ a countersink bit that exactly fits...
load that bit into the DP...
fit the base to the bit and clamp the base to the table...
change the CS bit to fostner bit of the desired sized hole you want w/o moving the base plate...
bore your counter bore hole...
or move to the head of the class and go w/ a counter bore bit from the git go....

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Unfortunately I only understand English!
 

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Have I to assume that I'm not the only one who doesn't understand Stick's post?
 

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Harry..
the top bit is a counterbore bit w/ a pilot (tip)...
use it to change a countersunk hole to a counter-bored hole...

the bit on the bottom is piloted also and is for countersinking holes...

a comparison between the two...

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some better views of the bit tips...

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you got it now Harry or is there another post or a part of one that you are having difficulty w/....
 

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I have to agree with counterboring the screw holes instead of having the centre bore large enough to move the bushing around in. There really isn't much to keep the bushing and nut in place but 3 or 4 screws should do pretty well and if not you could add an internally or externally splined lock washer under the heads.
 

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Counterboring holes is a great idea...make sure they are slightly bigger than the flat screw you need. Hole in the center needs to be slightly bigger also...this will then allow for some slight movement when adjusting with the centering cone...
 
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