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| Another boring question... |
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| AdeV:
...or maybe it's a drilling or reaming question :D Picture, if you will, a block of aluminium approx 10"x22"x3" (255x560x75mm, or thereabouts). I need to drill three 5/8" (~16mm) holes, in fairly close proximity to each other, one of which will be through about 20" of the 22" long dimension. The other two holes will be shorter, but still ludicrously long; say 15" and 10", but I've not got exact depths yet. They'd be roughly central in the 10" dimension, and in the bottom 1" of the 3" dimension. Precise numbers aren't yet available, as the design work is not complete. Accuracy doesn't have to be in the "thousandths" range; 1/4" inaccuracy at the far end of the deep hole would be quite acceptable. I have 2 machines available to me: Bridgeport milling machine, and the Edgwick lathe (6.5" centre height). Assuming one can get cutters long enough.... I can see two obvious methods: 1) Mount the block on the lathe, and use a giant drill bit/reamer. Rather than having 1/2 ton of rectangular aluminium held in a chuck or somehow lashed to a face plate, it might be more prudent to make a jig to bolt the Ali block to the cross slide, and hold the cutter in the chuck; basically, make the lathe into a giant horizontal milling machine. 2) Tip the Bridgeport head on its side, and mill it out horizontally using a long drill bit/reamer. I'm pretty sure I can't get the height to use the mill in the vertical position; plus it would make mounting the work very difficult, and probably not terribly safe. My money's on #2; your thoughts would be much appreciated. Please don't tell me it can't be done - that's like a red rag to a bull... |
| DMIOM:
If you are going to drill it, I think you're in "gun drill" territory. However ..... without knowing the context on this workpiece, there might be another way that would be simple on the mill - or because of the eventual end use it might be totally inappropriate. One possibilility might be - don't use a 3" thick plate - use two 1.5" thick plates or a 1" and a 2" plate. Treat yourself to a 16mm ball nose cutter and then just mill matching semi-circular trenches in both plates (can be accurately placed and no 'wander' issues) and then bolt/dowel etc. them together? Dave |
| AdeV:
The context is, it's a dry sump for a racing car. I'd like to avoid using multiple pieces, because it's bad enough getting the seal between sump & engine, without having to seal the sump too... The ball nose cutter idea is a good one; I can mill most of each hole (trough, really) internally, and have an internal plate which covers them where required. Ironically, whilst discussing this with the "customer" (my old man; and if his works, I'll need one for me too :)), we came up with that idea as a possibility. It'd be nice, however, if they can be drilled in solid (then the cutouts into the sump would be added afterwards). |
| DMIOM:
--- Quote from: AdeV on January 31, 2010, 01:34:34 PM ---The context is, it's a dry sump for a racing car. ... --- End quote --- Well, unless you're into truck racing, I think you'll be wanting to mill most of it away anyway (unless you're making the first one with inbuilt ballast to help you win when you make no. 2!) - you mentioned 1/2 a ton in jest but I reckon that block will be over half a cwt. (nearer 30 kg?). Keeping a half-cwt block bolted to the bottom of an engine block might (a) be a challenge and (b) negate the weight-transfer? If its just for oilways, where the profile doesn't matter so much so long as its smooth, trench it out and also mill a rebate maybe 5mm wide and deep enough to take the plate, and taper the sides of the rebate to give a little relief, then drop a plate in and weld it? or make it wider & stiffer & bolt it down. Or - have a hollow sump pan and just secure oil pickup pipes? cheers / Dave |
| AdeV:
--- Quote from: DMIOM on January 31, 2010, 01:56:09 PM --- --- Quote from: AdeV on January 31, 2010, 01:34:34 PM ---The context is, it's a dry sump for a racing car. ... --- End quote --- Well, unless you're into truck racing, I think you'll be wanting to mill most of it away anyway (unless you're making the first one with inbuilt ballast to help you win when you make no. 2!) - you mentioned 1/2 a ton in jest but I reckon that block will be over half a cwt. (nearer 30 kg?). Keeping a half-cwt block bolted to the bottom of an engine block might (a) be a challenge and (b) negate the weight-transfer? --- End quote --- :D A lot of it will be milled away, yes; although a surprising amount may remain... The problem is, this is a BMW V8 engine, and the sump is a structural part of the engine; you're not even supposed to use a cork gasket, as this will allow too much bottom end movement. The original component was aluminium, so I'm not worried about that material; and I'll retain some material (both internal & external) to enhance its strength. I'd better draw a crap-o-cad tomorrow, to explain how the sump will look. Can't do it now as I don't have any CAD on this computer. --- Quote --- If its just for oilways, where the profile doesn't matter so much so long as its smooth, trench it out and also mill a rebate maybe 5mm wide and deep enough to take the plate, and taper the sides of the rebate to give a little relief, then drop a plate in and weld it? or make it wider & stiffer & bolt it down. Or - have a hollow sump pan and just secure oil pickup pipes? --- End quote --- The existing pan is shallow, and has a slight angle into a trough which runs maybe 3/4 the length of the pan. This trough contains 3 outlet pipes - front, middle and rear - which go to the triple oil pump. It's all welded together out of plate steel & a bit of box section; and whilst it's not particularly heavy; it's also not particularly straight, and it won't seal properly against the engine. As a result, it tends to drip oil, which marshals really don't like... Plan A was to use the mill to flatten out the mounting face of the existing sump, in the hope that it'll cure the leaks (and that remains the "if the aluminium one can't be done in time" option); however, that will leave parts of the mounting scary thin; with the risk of cracking/tearing & consequent oil loss. Plan A has become, make the aluminium one... --- Quote --- (unless you're making the first one with inbuilt ballast to help you win when you make no. 2!) --- End quote --- Hmmmm, I'm liking that idea.... :lol: [edit] PS: Those gun drills look like just the job for the long deep holes... I will investigate tomorrow. |
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