- Tube is a popular material choice in motorsport fabrication due to its strength and weight,
however joining tube together inevitably results in a somewhat complex intersection that will
require us to perform what's referred to as a notch.
This may sometimes be called a mitre or a cope instead.
Cutting this notch can be achieved by using a few methods that we'll demonstrate in this module.
For our first example, we'll demonstrate the paper template method.
Before we notch our tube, we need to work out a few measurements, including our desired notch
angle, the diameter of the tube we're notching and the diameter of the tube that we're fitting up against.
Here, we'll be notching a length of 38.1 mm diameter roll cage tube with a wall thickness
of 2.6 mm.
To get the angle of our notch, we need to measure the angle between our intersecting tubes
which is easiest to do with the use of a digital angle gauge.
By opening up the angle gauge to sit flat against both lengths of tube, it will display
the required angle of our notch.
Once we record that angle we can mark a few lines of reference on the tube to let us
know which end is which and what direction our notch will go in.
The paper template method uses an online calculator that requires us to input the key
parameters that we now know.
The parent tube diameter and cut tube diameter are both the same at 38.1 mm,
however we can easily adjust these to suit if we're notching different sized tubes together.
We can then enter the wall thickness and the intersection angle and the template will change
to suit.
The calculator will also give us a visual indication of what the completed intersection
will look like as a bit of a sanity check.
Once we've double checked our entries and we're happy with everything, we can download
the finished template as a PDF document and print it out.
It should go without saying but it's critical to ensure that your printer is set to a 1:1 scale,
otherwise the template's going to be useless.
With the template printed, we can then carefully cut along the template line with a sharp pair of
scissors and then wrap our template around our tube before securing it in place with tape.
In this instance, the orientation isn't important when we're notching just one end of a straight
length of tube.
However if we were to notch the other end or our tube has a bend in it then the orientation of
the notch would be critical and the centreline of the template can be used as a reference to ensure
that you have this correct.
Next up, we can transfer the template onto the tube using a sharpie marker which will give us a
visible line to cut to.
From here, we can secure the tube in our vice using aluminium soft jaws to ensure we don't
mark the surface of the tube.
Now we can rough out the shape using an angle grinder with a 1 mm cut off wheel.
Initially we want to cut very slightly outside of the template marks that we have enough
material left to achieve a good fit up.
With the template roughed out using the 1 mm cut off wheel, we can swap to a coarse
flap disc to remove the remaining material and carefully work down to the template line.
This is a process that takes a little time and it's important to be patient.
It's important to understand also that we're not trying to cut perpendicular to the surface
of the tube and instead, our cut will need to be continuously profiled to provide a tight
gap free fit up against the parent tube.
This is why it's a good idea to start checking your fit up against the parent tube once you
get close to the template marks so that you can adjust the notch angle as required.
This is an iterative process that may require several adjustments in order to get your
fit up just right.
Once the fit up is almost complete, you can switch to a half round file to final finish the
notch and ensure a perfect fit up.
The file can also be used to remove any burrs that might still be present.
Now that we've seen how the paper template is used, we'll go through the process using a
specific notching tool.
As we discussed in the tools section of the course, these are available in models that are
designed to fit in a drill press or freestanding, however for our demonstration, we'll be using one
in conjunction with our drill press.
The quality of the completed notch will depend to a large degree on how the notcher
is secured to the bed of the drill press.
In particular, we want to make sure that the notcher is aligned so that the chuck of the
drill press is concentric with the notcher and ensure it's properly tightened so that there's
no chance of it moving around.
It's also important to adjust the bed height of the drill press so that we have sufficient cutting
depth available to get through our complete notch.
I'm going to repeat the same notch that we've just completed, being a 45° notch on a 38.1 mm
length of tube.
In this instance we're intersecting against a 38.1 mm parent tube so this means we need
to select a matching hole saw.
38.1 mm might sound like a pretty specific size and that's because it's the metric
equivalent of 1.5 inches so in this case we'd of course select a 1.5 inch imperial hole saw.
If you can get access to a hole saw with a fine tooth profile instead of the more typical
coarse tooth option, then these are preferable for notching as they tend to provide a more
accurate notch as they don't tend to move around as much while cutting.
Next we need to adjust the notcher to suit our desired 45° notch angle.
It should go without saying but ensuring that the notcher is properly tightened at our
desired angle is critical to ensure it doesn't move as we complete the notch.
Now we can fit our tube into location and tighten the saddle down to securely support it.
As with our last demonstration we need to be mindful of the orientation of the notch if your
tube includes another notch or a bend already.
It's essential to add lubricant to the hole saw and use a low speed to preserve the life of the
saw as well as preventing excessive heat.
On our drill press, the slowest speed we can achieve is 250 RPM which is where we'd want
to be for tube notching.
As with any drilling task, we want to apply light pressure, letting the hole saw do the work
as it cuts through the tube.
Once the notch is complete, we can loosen the saddle, remove the tube from the notcher
and use a half round file to deburr the tube.
Depending on the quality of your notcher and the hole saw, you may find that the
notch ends up slightly oversize which will adversely affect fit up.
If this is the case, you can then fine tune the fit up using your file.
Just bear in mind that this will result in your finished tube being slightly shorter than
expected so if you know that your finished notch will require fine tuning, it's important
to factor this into the length of the tube you're working with.
Regardless of the method you use for notching, a good fit up will make the next step of welding
the tubes together far easier and as a bonus you'll end up with a stronger joint and a
better looking weld so the time spent perfecting your notching will pay dividends.
That was just one module from our Motorsport Fabrication Fundamentals course.
If you're interested in learning how to fabricate components for your vehicle, then this course
is going to be perfect for you.
You'll start by learning about the various tools that you're going to need for motorsport fabrication
as well as how to use them.
You'll learn about techniques such as bending and notching tube, drilling and tapping holes
and how to use dimple dies.
You'll also learn about MIG and TIG welding which are both popular techniques for welding
in the world of motorsport fabrication.
While you don't need to be a mechanical engineer or have a degree to fabricate parts, you'll also
learn some fundamentals of design so that you're able to design and fabricate strong and
reliable parts.
All of this knowledge is then tied together with a range of worked examples so you can
see how these skills and techniques are put to use with real world fabrication projects.
If you're a motorsport enthusiast and you want to expand your skillset so that you can start
fabricating parts for your vehicle, our Motorsport Fabrication Fundamentals course is perfect
for you.
If you'd like to find out more about this course, click the link in the description.