I have a Porter Cable about ten years old and a Sears of even earlier
vintage both of which use similar systems to set the height of the
bit. The base has a spiral groove into which fits three pins on the
otherwise smooth body. You screw the body into the base and the extent
of the screwing determines the height of the bit. When you reach the
desired height you lock the base to the body by turning a thumbscrew
which contracts the base. I'm sure everyone has something similar.
The problem is that there's a ring around the base made out of plastic
and marked with measurements such as 1/8, 1/4, 3/16, etc but I've
never understood the reason for the ring. Logically it would seem to
be some sort of micro-adjustment. You get it close to where you want
the bit and then by rotating the ring you could move it (say) 1/4 and
that would raise or lower the bit by that amount. But the ring just
rotates; it doesn't raise or lower anything. In any event you'd be
hard pressed to change the position of the body due to the clamping
effect of the thumbscrew.
What am I missing here? I can't believe it's purely decorative.
If you set the router ,base down, on a table and screw the top down until
the bit contacts the table. Lock the motor in place. Turn the ring with
the numbers so that zero is on the index mark. Now pick up the router,
carefully unlock the motor and rotate it to the desired depth as indicated
on the ring with the numbers on it. Hope that is clear enough. Cheers, JG
In case not, regard it as an indicator ring, not an adjustment ring. You
must zero it manually - generally after you've the bit extension you feel
you need - for it to give you an indication of how far up or down you go
while tweaking. It in _no_ way substitutes for a true micro adjustment.
I believe the ring should remain stationary if you just move the motor
in the base. There should be some point on the motor that you can use
as an index mark. You turn the ring to zero it and then turn the motor.
If you want to move it 1/8", for example, you would turn it until the
index mark on the router aligns with the 1/8" mark on the ring.
Think of the watches out there that have the rotating ring around the
Usually there is a seam on the body of the motor that provides a
definitive line. After you mount the bit, zero it in by rotatating the
motor until the bit touches the wood. Lock the motor tight. Rotate
the ring with the measurements on it until the 0 lines up at that
seam. Now unlock the motor and rotate it until the seam falls on your
desired depth of cut.
You get the height to an approximate, rough position, and lock it in
place by twisting the thumb screw. Then, say you want to move the bit
height up by precisely 1/16". Leaving the motor housing locked, rotate
the plastic ring until you line up the "0" with the "scribe" mark on
the motor housing. Now, to move the bit up (or down) a precise amount,
you simply loosen the thumbscrew slightly, and rotate the motor housing
until the scribe mark lines up with the amount you want the height to
change. In other words, the plastic ring does not actually change the
height for you; you have to do it yourself. But it does act as a
"zeroable" guide to guide you to the precise amount of height change
you need. I hope I haven't just confused you more.
Although it's an old system that's been around a long time, it works
remarkably well. When people do have problems with it, it's usually
related to the motor housing and/or the base losing "concentricity"
with respect to each other, such that when you change the height, the
bit actually moves laterally as well.
The purpose of the ring is to 'zero' the bit height level with the
base, then twisting the body & ring as one you can set the cut depth
without seperate measuring tools. I prefer to use setup blocks or a
nice ruler to set my depth adjustments and ignore the ring altogether.
There's a line scribed vertically in the body of your router. You may
need to clean it a bit to see it ;) But you line up the 0 mark on the
rotating ring to the scribe line, then you know how much you've moved
the router up or down (depending on which way you turn it).
The ring is just a depth scale - it doesn't adjust anything by itself.
There's an indicator line on the router body. Turn the ring so zero is
on the line when the bit is just touching the workpiece. Then (turning
the whole motor, not just the ring) adjust the depth as desired.
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