Motorsport Composite Fundamentals: Cutting, Drill & Material Removal

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Cutting, Drill & Material Removal

06.31

00:00	With our cured parts out of the mould, we almost always need to perform some type of material removal from the parts, which is a fairly general term that could mean anything from cutting, trimming, drilling, sanding or shaping.
00:13	Usually, we'll leave a wide flange on our parts around the perimeter, which helps us to release the part from the mould, and also provide some excess material which we can trim back to the desired edge.
00:24	There may also be windows in our parts that we need to cut out, for example air vents in body panels, or holes in dash panels for switches.
00:33	Before we get started, it's important to note that proper PPE should be worn when working with these tools, as the risk of being cut, getting debris in our eye or inhaling dust is extremely high.
00:45	To efficiently cut composite laminates, the go to is an abrasive cutting disc.
00:49	If you've ever done any fabrication work, you won't be surprised that an angle grinder is a good option here.
00:55	And a standard metal cutting disc will make relatively easy work of cutting through composite parts, even with metal core materials.
01:04	Smaller rotary tools like die grinders and dremels offer some more manoeuvrability and are much lighter and easier to hold for more control.
01:11	For cutting straight lines and getting into sharp corners, we might also consider using a jigsaw.
01:17	Standard metal cutting blades will burn out relatively quickly though, specifically when working with abrasive carbon fibre, so be sure to use something designed for composites.
01:27	These often have a high teeth per inch count, known as TPI, or use an abrasive grit, rather than a toothed blade.
01:34	Using a blade with a higher TPI or finer abrasive blade, as well as a backing material underneath the composite part will give us a cleaner cut and prevent the edges of the part from tripping or fraying.
01:46	Or if you're looking for a simple non-power tool solution, then hacksaws are a great alternative.
01:52	Again, rather than using a blade with teeth, we'll often use an abrasive grit blade in these, which opens up the use of a rodsaw blade.
02:00	These are cylindrical with grit all around them, rather than being the typical thin hacksaw blade with grit on one edge.
02:07	This helps them to cut more complex shapes with smooth curves.
02:11	Once the edges are cut, they'll still need some finishing, or we might choose to work up to an edge when trimming.
02:18	For this, we'll use sanding and filing.
02:20	Filing would typically remove material faster, but leave a rougher finish, where sanding would be used to achieve a smoother finish and a more accurate edge.
02:29	Sanding can also be used to smooth and finish the surfaces of the part, which we'll be discussing in the next module.
02:36	However, for now, we're mostly interested in removing relatively large parts of material from the edges, rather than the surfaces.
02:43	We'll cut this short here, as the chances are we're all well aware of sanding and filing tools.
02:49	Put simply, they're available in different shapes and sizes, as well as different grits to suit whatever parts we're working on.
02:55	We recommend getting a sanding block to make this work easier, it'll take a lot of the stress off your hand and allows the application of stronger and more even pressure.
03:04	You might be wondering about the specific materials of the abrasive grits on the surfaces of these tools.
03:10	It's important to reiterate here that carbon fibre itself is extremely abrasive, so many of the conventional inox based aluminium oxide abrasive grits will wear away very quickly.
03:21	Tungsten carbide, while being significantly more expensive, is seen as somewhat of the gold standard here.
03:28	It's renowned for its durability and lasts significantly longer.
03:31	Often these tools will last for years, depending on their use of course.
03:35	This brings us to drilling into our composite parts, which might be done to create fixing points, install components like switches, or create a starting point for cutting out an internal window with a hacksaw.
03:47	Drilling straight into our parts with general drill bits as we would for metal parts is going to get the job done, but even if we drill a smaller pilot hole and then step it up to the nominal size, we're still going to get less than ideal results.
04:00	There are a few reasons for this.
04:02	First is that composite parts are prone to chipping and delamination, especially on the back side of the hole, just like how a piece of wood might chip around the edge.
04:12	One way around this is to use a backing material like wood behind the part when we drill through it.
04:17	The type of drill bit plays a big role here.
04:20	Our conventional jobber or twist drill bits tend to cause some chipping and a somewhat inaccurate hole.
04:26	For many jobs, like mounting thin carbon fibre body panels for example, this will be completely fine.
04:32	The chips will be minimal if any and the hole probably doesn't need to be perfect diameter.
04:38	A bit of clearance is usually a good thing for aligning body panels.
04:41	But for composite parts that need perfect holes, we'll turn to something like a tapered drill reamer.
04:47	The tapered lead in allows us to start the hole and open it up to the nominal size, while the straight edges of the reamer are designed to cut a very clean hole.
04:56	Even better is a straight flute spade or dagger drill bit.
05:00	These are best for preventing chipping and delamination, while the straight flutes also cut a clean and accurate hole size.
05:08	Like before, the material of the tool is also important, because again, carbon fibre is very abrasive.
05:14	If we're drilling lots of holes with regular high speed drill bits, then they tend to go blunt very quickly.
05:20	Using cutting lube or drill bits with coatings like titanium nitride does help a lot, but investing in some quality solid carbide drill bits would be ideal.
05:30	Just like our tungsten carbide grits, solid carbide drill bits are extremely hard wearing, helping them stay sharp and last a long time.
05:39	The main points to remember from this module are that wearing PPE is critical when cutting composite parts.
05:45	These cutting processes are often done with rotary cut off discs, jigsaws, hacksaws and rod saws.
05:51	Other material removal, shaping, trimming and finishing is usually done with sanding blocks or files.
05:57	For drilling holes, conventional jobber or twist drill bits can cause chipping and delamination in composite parts, so for the best results we recommend looking into tapered drill reamers and spade or dagger drill bits.
06:10	The straight flutes on these can help cut clean holes and accurate hole sizes.
06:15	While tool materials designed for working with metal do get the job done, we'll often find the best tools designed specifically for composites use tungsten carbide grits or solid carbide drill bits which are extremely hard wearing.