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Motorsport Fabrication Fundamentals: Dimple Dies, Punch and Flare Tools

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Dimple Dies, Punch and Flare Tools


00:00 - One of the aims of motorsport fabrication is to achieve increased strength and reduced weight and a great way to do this is through the use of a dimple die or a punch and flare tool.
00:10 The flared hole is a prevalent feature in a lot of sheet metal fabrication we see in motorsport.
00:15 A good example of this is the sheet metal gusset that's frequently used to connect the front lateral bars of a roll cage structure to the original body.
00:23 These often feature flared holes.
00:26 While just cutting holes in the gusset would achieve our aims of reduced weight, the gusset loses a lot of strength as a result but by adding a flare to these holes, we end up with a stronger and stiffer part.
00:37 These flared holes are the product of a dimple die or a punch and flare tool.
00:42 A dimple die is a specially machined two part die that's used on sheet metal or steel plate to achieve a 3D flare around the perimeter of the hole.
00:51 These dies are available in various sizes ranging from 12 mm right up to and over 100 mm and are usually machined from heat treated chromoly for a long working life.
01:02 The flared hole is achieved by first drilling a hole to the size of the die in the position we require then sandwiching the sheet metal between the two halves of the dimple die and pressing the die until it bottoms out.
01:13 It's possible to use a vice for this but we recommend the use of a small press as it makes pressing multiple dimple dies much easier.
01:22 The punch and flare tool is similar to the dimple die but it's designed for lighter sheet metal.
01:27 Like the dimple die this tool is made up of two parts but with the addition of a central bolt that pulls the two parts together.
01:34 Once our sheet metal part has a clearance hole for the centre bolt, we can sandwich it in between the upper punch which has a cutting face machined into it and the lower die that has the flare.
01:44 By tightening the central bolt, the punch will punch the inner hole and the flare will create the flare.
01:49 Punch and flare kits are available in both manual and hydraulic actuation but for a relatively small investment, the hydraulic actuated punch and flare kit definitely helps particularly when it comes to punching thicker sheet metal.
02:02 If you're looking at purchasing a kit, it's important to understand that there are two variations of flare style, radiused and tapered.
02:10 The radiused flare does present a slight advantage in rigidity and it also takes up less area than that of the tapered flare, however the tapered flare does have a more traditional look though and may suit the preferred aesthetic of some fabricators.
02:24 The only downside to these kits that are available off the shelf is that they're designed and machined to suit the largest advertised sheet metal thickness.
02:31 What this means is that a die set that's made for 3 mm sheet metal will bottom out and the flare will contact and press the 3 mm sheet metal evenly on all surfaces.
02:39 Take that same die set though and use it on 1 mm sheet metal and it'll bottom out before pressing the full draw of the flare and this may result in a less than perfect flare on thinner materials.

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