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Motorsport Fabrication Fundamentals: Angle Grinder

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Angle Grinder


00:00 - An essential item in any fabrication shop is an angle grinder or disc grinder as it's also referred to.
00:07 This is a high speed electric or pneumatic tool that drives a geared head at a right angle and allows us to attach either a grinding or a cutting disc via a threaded arbor.
00:17 For most of the more intensive cutting tasks that you'll be using an angle grinder for, the electric version is preferrable as it can provide more torque than the pneumatic variety.
00:28 Pneumatic grinders also require a serious air supply in order to keep up with sustained use.
00:33 A smaller shop compressor will often require you to pause your work to allow it to build pressure back up which can become frustrating as well as time consuming.
00:43 Electric grinders can be further broken down into mains powered or battery powered.
00:48 The battery powered versions offer the added convenience of not needing a power supply which is great if you're using one out of the workshop, however battery life can be a real downside.
01:00 If you're going to choose a battery powered option, then I'd suggest purchasing at least one spare battery so that you can always have one on charge which you're using the grinder.
01:08 If there's one tool that demands extreme care and respect, it's this one.
01:12 The angle grinder can be very dangerous and it must be operated with care as well as the correct personal protective equipment to minimise the chances of serious injury.
01:23 The angle grinder grabbing on the work piece and pulling you with it, or alternatively being pulled out of your hands isn't uncommon, particularly with the larger diameter angle grinders.
01:34 Other risks involve using damaged cutting or grinding discs.
01:37 It's always a good idea to visually inspect your disc for any damage or cracks prior to use.
01:42 Damaged discs can shatter at high RPM which can then spray shards of broken disc into yourself as well as the work piece.
01:50 Angle grinders are available in various sizes and the size dictates the diameter of grinding or cutting disc that can be fitted, ranging from 4 inch, all the way up to 9 inch.
02:01 On that note, it's pretty common for angle grinder sizes to be referred to in inches, even in countries where the metric system is normally used.
02:09 In motorsport fabrication, the most common angle grinder size you'll use is the 5 inch as it offers an increased depth of cut over the 4 inch grinder while still remaining easy to handle in tight situations.
02:22 You'll notice all angle grinders come with a guard that covers a section of the disc and many enthusiasts remove this for ease of use.
02:30 Unsurprisingly, that guard is there to protect you so it's critical that it stays attached and is positioned in a way that it sits between you and the work piece.
02:40 To get good results from an angle grinder, it's important that the right disc is selected for the work that we want to do.
02:47 The first things we need to consider is the material type we'll be working with.
02:51 There are different cutting discs and grinding discs for materials such as aluminium, steel, cast iron and stainless steel.
02:58 Using the specific cutting disc for the material that you're working with not only makes for a cleaner cut but will also limit the amount of cross material contamination that can often lead to corrosion or difficulties in the welding process later on.
03:13 Aluminium for example is very sensitive to contamination from ferrous material if it's been cut with the same disc that's been used to cut steel.
03:22 This can make it impossible to achieve a quality weld once the material has been cut.
03:27 For cutting, it's preferrable to use thin cutting discs that are available in 0.8 and 1.0 mm thicknesses.
03:36 These thin discs improve the accuracy of our cut while minimising heat distortion and they can speed up the cutting time by removing less material due to their reduced thickness.
03:46 The downside to using these thin discs is that they do have a shorter disc live and a lack of any lateral stability.
03:53 What this means is that it's possible to shatter a thin cut off disc if any lateral or twisting force is applied to it while we're cutting and this obviously can be very dangerous.
04:04 A common mistake that we see people make with cut off discs is trying to rush the cut by applying excessive force to the angle grinder.
04:12 This will get the job done but it will also prematurely wear out your cut off disc and it's going to produce more heat in the work piece.
04:20 Instead, what we want to do is let the weight of the angle grinder do the work for us and be a little patient, you'll get a better result and you'll save a fortune on cut off discs.
04:30 When we use an angle grinder for the purpose of grinding, there are a lot of different ways in which we can remove material.
04:37 The disc you choose is still dependent on the material you're grinding but there are also other factors to consider.
04:44 When we grind something, we're looking to remove material for the purpose of surface preparation, shaping or final metal finishing.
04:51 All these processes require a different style of disc.
04:55 There are conventional abrasive materials that are used to remove large amounts of material quickly, while providing a long disc life.
05:04 The downside of this style of disc is that the vibrations caused by its rigidity and the abrasiveness of the material makes for a very rough surface finish.
05:14 Flap discs on the other hand are generally the best abrasive grinding wheel for fast material removal, blending and final finishing.
05:21 Flap discs essentially incorporate multiple flaps of sandpaper which are supported by a rigid backing disc for strength.
05:29 The design of these flaps means that as they wear down through use, they reveal a fresh flap below for longer life.
05:36 Flap discs are available in a range of different grip values to allow for different surface finishes.
05:41 A very coarse 40 grit disc for example will allow a lot of material to be removed quickly but will also offer a rough surface finish.
05:49 On the other hand, an extra fine 120 grit flap disc will provide a smooth surface finish but won't remove a lot of material.
05:57 The outer edge of the flap disc is also available in either a sharp edge for getting into 90° pockets or a radiused outer edge for grinding out rounded pockets or for notching tube.
06:09 Another variation to the flap disc is a fibre sanding disc.
06:13 These are a two part disc that use a backing disc to mount to the grinder and a flexible fibre disc that attaches to the backing disc.
06:21 These are great to have in both fine and coarse variations for medium to light material removal, weld finishing and surface preparation.
06:29 The final disc we'll be looking at is the strip disc which uses a polyfibre composition with impregnated grain to remove things like rust, paint and other surface coatings.
06:39 The idea of a strip disc is to remove coatings and polish without removing any of the material underneath.
06:46 As you could imagine, it's advisable to have a selection of these discs on hand that you can swap between as you perform different jobs.
06:54 Since these discs also wear out as you use them, it's handy to have a good selection of spares stored away too.

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