- In today's video,
we're looking at how to use a patterning bit
for cutting shapes
or cleaning out the bottom of holes, dadoes, or grooves.
As you can see, this project required a lot of holes,
40 to be exact, and the method I chose to make these holes
was to use an inch and an eighth Forstner bit.
Forstner bits, if you don't already know,
are drill bits that are designed
to drill flat bottomed holes.
However, the downside is that they do leave
a small visible hole where the tip of the drill bit was.
In some cases, that would be acceptable,
but for this project, it's not.
So how do we get rid of those marks?
Well, the method we're gonna look at today
utilizes a patterning bit
and a small trim router with a plunge base.
This router's manufacturer gives you the option
to buy a separate plunge base.
So all you have to do to turn this fixed base router
into a plunge router is to remove the motor from one base
and install it in the other.
As far as the router bit itself,
we're using what's called a patterning bit,
which is designed with a guide bearing
that's installed at the top of the bit.
This bearing then rides along a pattern,
which is basically a template made into a particular shape.
As that bearing follows the pattern,
the bit cuts the wood below,
matching or making an exact copy of that shape.
Today, however, we're using this bit slightly different
and that difference is that we're actually using
these existing holes as the pattern.
But before we start cutting,
we have to first determine the right size bit to use.
In our example,
these holes are about a half inch or 13 millimeters deep,
and we only need to remove around an eighth of an inch
or three millimeters to clean up the bottom.
Therefore, we need to use a bit
that has a cutting length of around a half an inch or less
and here's why.
If we choose a bit that's too long,
the bearing will not be able to ride
along the inside of the holes
unless the bit is set to make a deep cut
and that's not what we're looking to accomplish here.
You can, of course, add material above the workpiece
by making a circular template,
but that creates more work than what it's worth,
especially for these many holes.
To make things easy and without any extra work,
let's go with a bit that is a quarter inch long.
As a side note, you'll often see bits like these labeled
with a CH, CD, and a CL.
SH stands for shank diameter,
which in our case this bit has a quarter inch shank.
CD stands for cutting diameter,
which in this case is a half inch.
And CL, which is the cutting length, is a quarter inch.
Moving on with the bit installed into the router,
go ahead and set the depth
to remove about an eighth of an inch or three millimeters.
Start the router and then lower it into the hole.
Once lowered down to full depth, work your way to an edge
and then follow the inside of the hole
in a clockwise direction.
If your hole is large enough
that you have remaining material left in the middle,
you can always clean it out
by working from the bottom to the top
and from the left to the right.
This routing direction ensures that you're always making
push cuts as you remove the remaining material.
However, this routing direction isn't always necessary,
but it is important
if you're just getting started using a router.
And within a few minutes,
all 40 holes are completely cleaned out
and now looking professionally done.
I do wanna make you aware that you wanna make sure
that you understand what your total depth is going to be
before you start to drill the holes.
For example, if you're looking for a total hole depth
of one inch or 25 millimeters,
you first gonna wanna drill about 7/8ths
or 22 millimeters down with the Forstner bit
and then you're gonna switch over to the router bit
to finish off the remaining bit of material
to get to your total one inch depth.
Lastly, I do wanna mention it's very important
to keep the holes clean.
This is a patterning bit
meaning that it's routing along the inside surface.
So if you have some waste material stuck there,
the bit may pattern over that
and leave you with some jagged edges.
It's not that big of a deal.
You can always blow that out
and make a final pass to clean it up,
but it's something I wanted you to be aware of.
Now that you see how the patterning bit works for holes,
cleaning out grooves or dadoes is just as easy.
For those of you who don't know,
dadoes are three-sided trenches
that are cut across the grain of the wood,
and grooves are the same three-sided trenches
just cut with the grain.
Once the dado or the groove is roughed out,
set the router depth
to remove your desired amount of material
and begin routing from left to right
on the furthest side of the trench.
Then to remove the remaining material,
that is if your bit isn't wide enough to do it in one pass,
ride the bearing now on the closest side of the trench,
moving from right to left.
Again, this is in keeping with the best routing direction
for safe cutting.
As you can see,
the sky is the limit when it comes to patterning bits,
but I hope you're able to pick up a few little tips
from this quick video.
If you have questions
or need help with what you're currently working on,
please feel free to reach out to me on Instagram,
send me a picture or video.
I'd be glad to help you out.
Thanks for joining me today,
and I'll see you guys in the next video.
(upbeat music)