My router has a depth stop and integral back-off wheel so that I can set the
final depth and lock it, and then back off the router for a small first cut,
and the steps on the adjustment wheel allow 1/8" incremental cuts. I do use
this when not confused. It is obviously necessary with larger bits of
understandable geometry, and I have broke a 1/4" Dia. straight bit at a
depth of 5/8", just trying to get a good estimate of the depth I had set in
a test piece, after a short distance. Forget about it with a smaller bit,
or a larger I guess.
I just did a bunch of 1/4" roundover, and also 1/4" rogee at the edge of
some 5/8" mdf. I did it all at the final depth, no increments. These are
small bits, 1/4", so think I just got away with it. I was prepared for it
to let go at any time, but I had already started. I was using the companies
best Ti-C bit set. But I do not know the teachings when it comes to these
kind of profile bits. What is the rule. Is there any difference from other
bits? To be honest the question is a little premature because me ain't even
considered what type of bits need only one pass because of the actual
profile generated, if necessarily possible. If I don't find out I may be in
for a rough ride.
Pat's an instructor at one of the well respected colleges in SoCal, and has
this really indepth website on all things router. Spend a cold evening at
the computer reading Pat's stuff, and you'll be a lot further ahead with
the practical, doable side of routing.
And most of the stuff he sells is first rate, too.
If you are only talking about the depth setting on your router, then several
types of bits that produce beaded profiles, or joints - including dovetails -
cannot be routed in successive passes at increasing depth settings. If you are
talking about mounting the router in a table (or possibly using a guide fence),
then you have more options for making a larger cut using multiple passes.
When multiple passes are necessary depends on the amount of wood being removed,
the type of wood being worked, the size of the router bit and router, and how
good a cut surface you want. All decorative routed edges and routed joints
benefit when the last, or finish, pass through the router removes only a small
amount of material. This produces a smoother surface, better fitting joints,
less sanding, etc.
Router bits that produces joints such as -
or any bit where any part of the cutting profile toward to bottom of the bit
(away from the router) is a larger diameter than a part of the profile nearer
the top of the bit -
cannot have the router depth setting altered in successive passes. However, when
the router is mounted in a table, you can make successive passes using different
Dovetail sockets are routed to size in one pass, but a preliminary cut using a
straight bit that is smaller that the dovetail socket profile can be helpful.
This technique also works with T-slot bits, although here multiple passes can be
used if you need to deepen or widen the cut slot.
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