Router bushings -- how much clearance between bit and bushing?

[Tom Henderson2]

Greetings everyone.

I've used router bushings from time to time, but this time I need to try an minimize the gap between the bit and the ID of the bushing.

How close is too close?

I'm using a 1/2" bit, and the closest bushing is 17/32 ID.

So... that gives me 1/64" (0.016") gap between the bit and the bushing. (1/32 difference in diameter, so 1/64 difference in radius)

This is a core box bit being used to rout a groove. So I can take light cuts, etc to minimize bit deflection.

I realize I'll need to be careful when installing/centering the sub-base and bushing.

Is 1/64 gap too small? I'm wondering how small a gap you more experience folks feel comfortable with.

Thanks in advance for your help!

-TH

The next option is 21/32 ID bushing, which give me 5/64 gap (5/32 difference in diameters, so 5/64 difference in radius)

[Paul F Franklin]

What shank diameter? If 1/2" you shouldn't see much deflection, especially if the cutting depth isn't too much. 16 thousandths clearance should be ok as long as the bushing is reasonably well made and, as you say, you are careful centering the bushing.

[glenn bradley]

I run with a 64th of clearance without issue. Obviously you could cut too much or move too fast and cause problems but, we can do that without bushing too ;-)

[Tom Henderson2]

Glen & Paul -- thanks for your thoughts.

I should have mentioned that it is a 1/2" shank bit.

I'll give it a go after giving the bushing a careful centering and close inspection to ensure I have clearance between the bit and bushing.

I appreciate your thoughts!