Motorsport Fabrication Fundamentals: Cutting
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Cutting
12.11
| 00:00 | - There won't be too many fabrication projects that you'll take on which won't require some kind of cutting process and as such, this is an important skill for any fabricator to understand and master. |
| 00:12 | This may involve cutting an intricate shape out of sheet metal with an angle grinder or it may involve using a drop saw or band saw to cut tube for notching, bending and welding. |
| 00:22 | The options available to us when it comes to metal cutting are quite varied and the best option will come down to what you're cutting and what you're trying to achieve. |
| 00:32 | Particularly for more intricate shapes or ones where accuracy and repeatability is critical, we can employ a specialist metal cutting company to cut our designs using water jet or laser cutting methods. |
| 00:44 | The equipment required to do this is very expensive and well beyond the budgets of most fabricators however for a minimal outlay you can send a drawing, template or a CAD file to these companies and receive your precision cut parts on the courier just a day or two later. |
| 01:01 | This would usually be the best option if you're building multiple identical parts as the time saving can easily make the cost of the cutting service seem incredibly cheap. |
| 01:11 | It's also a great way of adding some tricky design elements to your fabricated parts which can add a professional touch. |
| 01:18 | I'm talking here about holes in slots to reduce weight but you could also incorporate a logo into the finished part with no more effort. |
| 01:26 | What we'll be looking at in this module are the more common cutting tasks that we'd use around the home workshop using equipment that is relatively affordable. |
| 01:34 | The 3 pieces of equipment that we'll be using here are the angle grinder, an abrasive drop saw and the band saw which cover the most common equipment most fabricators would have access to without breaking the budget. |
| 01:47 | We've already discussed the angle grinder in the fabrication tools section of this course but in this module we're going to put one to use to cut some steel tube and then to cut out a simple shape from some sheet metal. |
| 01:59 | For both tasks, we're going to use a cordless angle grinder fitted with a 1 mm cut off wheel. |
| 02:04 | These 1 mm cut off wheels allow us to perform clean and accurate cuts quickly and they don't put excessive heat into the material we're cutting. |
| 02:12 | There are a few basic precautions that we need to include here. |
| 02:16 | First, we want to inspect the condition of the cut off wheel and make sure that there's no damage or cracks evident. |
| 02:22 | A cracked cut off wheel can easily fly apart at high RPM and this can do some serious damage to anything in its path. |
| 02:29 | This is a good place to point out that cutting metal requires the right PPE to make sure you're properly protected in the event that something could go wrong. |
| 02:36 | Due to the sparks generated when cutting with an angle grinder, you'll want to wear overalls to protect your clothing or a fabrication apron for lighter duty tasks should suffice. |
| 02:46 | Ear and eye protection is also essential. |
| 02:49 | The angle grinder also has a moveable guard and it's important to make sure that this is oriented between you and the workpiece. |
| 02:56 | On our Milwaukee grinder for example, this guard can be quickly adjusted by pressing on a spring loaded lever. |
| 03:02 | On other grinders the guard may need to be physically loosened off using a tool, moved and then tightened again which does take a little bit more effort but it is well worth it. |
| 03:12 | Before cutting our tube we need to mark out where we're going to cut. |
| 03:15 | This is essential to give us a guide which will then allow us to achieve a straight cut through the tube and the easiest way to do this is to start by wrapping a line of tape around the tube at the point you wish to cut. |
| 03:27 | You can then use this tape as a guide to mark your cut line using a fine point sharpie marker. |
| 03:33 | Even though the sharpie marker provides a pretty sharp line to cut to, if the measurement that you're working to is critical, it's a good idea to decide which side of the mark you need to cut to and mark this accordingly with a cross mark so there's no chance of making a mistake. |
| 03:47 | We can now get our piece of tube in a vice and begin our cut. |
| 03:51 | We'll want to fit soft jaws to our vice for this purpose so that we don't end up with the jaws of our vice marking the outside of the tube. |
| 03:59 | We also need to be a little careful with how tightly we clamp the tube in the vice. |
| 04:03 | Obviously we don't want the tube to move but excessive pressure can deform thin wall tube so some care and common sense is required. |
| 04:11 | When we're using the angle grinder, we want to make sure that we're cutting on the correct side of the cut off disc. |
| 04:17 | If we look at the rotation of the disc, we want to make sure that it's rotating down and into the workpiece. |
| 04:24 | This will tend to draw the grinder into the tube and will also ensure that the sparks are directed backwards and down, away from our face. |
| 04:31 | Cutting with the grinder reversed will tend to push the grinder away from the workpiece towards us which could be dangerous. |
| 04:38 | Another point to make here is that when we're grinding, we need to be mindful of where the sparks off the grinder are going. |
| 04:44 | If these are concentrated onto our clothes or on a rag or something flammable on the workshop floor, it could cause a fire. |
| 04:52 | If they're directed towards a painted panel or automotive glass then they will leave pitting which will permanently damage the surface finish. |
| 05:00 | It's often surprising just how far these sparks can travel so a little care is required. |
| 05:06 | When we first start the cut, there's the possibility of the cut off wheel moving on the workpiece which affects our accuracy. |
| 05:13 | It's useful to steady the grinder initially by locating it on the workpiece with the hand that isn't operating the trigger. |
| 05:19 | Just touching the workpiece or vice with your fingers and stabilising the grinder with your thumb, can make a huge difference when initiating the cut. |
| 05:27 | Once we have the cut started, we can then hold the grinder with both hands and apply light pressure to allow the disc to do the cutting. |
| 05:35 | This doesn't require very much force from us and this is a place that a lot of novices can go wrong as forcing the angle grinder will just end up wearing out your cutting discs quicker and it will put more heat into the workpiece as well. |
| 05:49 | While we're cutting, we want to carefully watch the progress of our cut and adjust the angle grinder to follow the cut mark that we've made. |
| 05:56 | This will also require you to rotate the tube and reclamp it in the vice as the cut progresses. |
| 06:02 | Once we've finished the cut, we can remove the tube from the vice and deburr and dress the end of the tube. |
| 06:08 | There's a few options here but one of the quickest and easiest is to use a deburring tool to remove burrs from the inside and a linishing wheel to dress the end of the tube on the outside. |
| 06:18 | Alternatively you can achieve a great result with a fine file. |
| 06:21 | It's important to note that if we've used a cut off disc that may have been used for cutting ferrous materials, it shouldn't be used for cutting aluminium or stainless as this will leave contaminants in the material which can make welding very difficult later on. |
| 06:35 | Another area where the angle grinder and a 1 mm cut off wheel is often used is to cut shapes out of sheet metal. |
| 06:42 | The process here is the same where we start by tracing our shape onto the sheet metal. |
| 06:47 | This can be done with a sharpie marker however for anything with a fine tolerance, our preference is to scribe a mark onto the surface using a scriber. |
| 06:55 | This provides a very fine line that's easy to see and gives us a more accurate dimension than the sharpie. |
| 07:01 | The other advantage of scribing your cut line, as we've already discussed in a previous module, is that the scribe isn't going to be affected by heat, whereas the sharpie line can become hard to see if you get a lot of heat into your cut area. |
| 07:14 | One thing to be mindful of when cutting circular shapes with a cut off wheel is that we can't bend the cut off wheel while we're cutting, or we'd risk having the grinder disc shatter. |
| 07:24 | For this reason, we're best to cut circular shapes using a series of straight lines, before finishing the part on the linisher or with a hand file. |
| 07:32 | While the angle grinder is a great tool, there are other options, and particularly if you're going to progress to building roll cages or aluminium plumbing, a band saw or abrasive drop saw is a worthwhile addition to your workshop. |
| 07:44 | The drop saw is a cheaper option so is likely to be the more common choice when you're just starting out. |
| 07:49 | The advantage of either tool is that they allow us to perform fast and accurate cuts on our material, as well as being able to cut through the material faster than we can with an angle grinder, we'll also guarantee the cut is square to the tube which can help with the fit up to other pieces of tube. |
| 08:04 | To ensure these cuts are square though, it is essential to make sure that your material is supported at the same height as the saw. |
| 08:12 | For our band saw, we use an adjustable support with a horizontal roller on the top which makes it easy to support long lengths of material and quickly adjust the height of the support to suit our bandsaw. |
| 08:23 | Since the drop saw is usually going to sit on a workbench, it's sufficient to simply prop the end of the workpiece up with offcuts or scrap material that achieve the correct working height. |
| 08:33 | The bandsaw will give us a cleaner and more accurate cut with less chance of contaminating the workpiece, however these tend to be more expensive, starting at around the $1000 mark and moving up from there. |
| 08:45 | The drop saw on the other hand is much cheaper, starting at around $200 to $300, however it does have some distinct disadvantages. |
| 08:53 | First of all, it's essentially a large scale angle grinder using a similar abrasive disc only much larger in size and thicker. |
| 09:01 | This puts more heat into the workpiece than a bandsaw and will also produce a lot of sparks which will be injected behind the saw. |
| 09:08 | There also tends to be more run out or movement in the cutting disc which can make it a little more difficult to accurately start your cut. |
| 09:16 | If you're going to be working with aluminium, cutting it with a drop saw is not recommended because the soft aluminium material tends to clog the abrasive disc which reduces its effectiveness and also in extreme cases can potentially result in the disc failing. |
| 09:32 | The first step with either tool is to decide on the length of the material required and then mark this on the tube. |
| 09:38 | We can use a sharpie marker or a scriber to make this mark and as with the angle grinder, we want to be clear on which side of the cut mark we'll be cutting. |
| 09:46 | We can now locate the tube in the jaws of the bandsaw and bring the blade down to meet the tube. |
| 09:51 | This allows us to locate the tube correctly and confirm the accuracy of our cut position. |
| 09:56 | Once we're happy with the location we can lock up the material in the jaws and begin our cut. |
| 10:00 | Due to the slow cutting speed and the thin blade, very little heat is put into the material we're cutting with the bandsaw. |
| 10:07 | This means that lubricant isn't strictly necessary however it can still help extend the life of the blade and often these machines will have the option of running a lubricant feed to the cutting area. |
| 10:18 | Once complete we can remove the tube from the jaws and deburr and dress the end in the same way we've already looked at. |
| 10:24 | It's worth mentioning here that due to the blade construction and the slow speed of the operation, the cold saw can be used on both ferrous and non ferrous materials without any risk of problems from contamination. |
| 10:36 | Although the bandsaw might seem like a large investment, it can pay you back by saving you time and energy, especially when we're cutting a lot of tube. |
| 10:44 | Using the abrasive drop saw is very similar in operation however this requires us to manually apply pressure to move the abrasive disc through the workpiece. |
| 10:53 | Before we get into that though, you need to take a little care with the positioning of the disc versus our cutting location. |
| 11:00 | As mentioned, the disc tends to move around a little and the disc is physically thicker than the bandsaw. |
| 11:06 | We're going to need to account for this, particularly if the length of our workpiece is critical. |
| 11:11 | What we want to do is start by bringing the disc down onto our workpiece and locating it on our cut line. |
| 11:16 | We can then clamp the workpiece, lift the cutting disc and start the saw. |
| 11:20 | We want to carefully watch where the blade begins to connect the workpiece initially and we may need to loosen the clamp and make subtle changes in the location of the workpiece so that the disc begins to cut in exactly the right location. |
| 11:34 | Once we're happy with our location, we can apply light pressure to the saw, allowing the disc to do the cutting. |
| 11:40 | This is very similar to the angle grinder and excessive pressure just creates heat and wear in our disc. |
| 11:47 | You'll find that the initial cut is quite slow as the disc cuts through the horizontal surface of the piece of tube. |
| 11:53 | Once the initial cut is complete, the cut will progress a lot faster before slowing down again as the disc must cut through the horizontal portion at the bottom of the tube. |
| 12:02 | Lastly once complete we can remove the tube from the saw and deburr and dress the end as we've already seen. |
