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Post by Roger on Feb 22, 2019 16:25:25 GMT
As ever, there's a bit of history to what I was doing. I don't actually have a CNC mill; it's a CNC router which I built originally for woodworking. However, it is mainly built of welded steel with decent ballscrews and linear profile rails, and I wondered if it would be up to the job of cutting steel, using small cutters to suit the high-speed spindle (nominally 6K-24K RPM). After an experiment or two with cutters I had lying around, I bought some carbide cutters (2/3/4mm) designed for high-speed use with no coolant. I wasn't sure how well the 2mm cutters would stand up to this use but they've actually turned out to be much tougher than I expected. I do use the technique of roughing out with the larger cutters (usually the 4mm as it gives best cutting speeds) and then swapping to the 2mm to take out the corners, as far as possible. Your comments and my experience to date make me realise that I had forgotten that I could go down to 1mm in the same range of cutters. That would allow me to do tab-and-slot in the thinner steels for things like frame stays. I use Fusion 360 for CAD and CAM purposes and the CAM module is very good at generating tool paths for a smaller cutter to remove material that a larger roughing cutter left behind. It sounds like you're ideally placed for machining Sheet Steel, presumably you've got a much bigger working area than a milling machine has. I get the 1mm cutters from eBay, people like EW Equipment do them. Although you can use PCB cutters, they take an absolute age to cut because they are too long for our purposes, usually having 10mm of flute which you don't need. I think mine cost under £5 each, so that's not too expensive. Drilling the corners is quite a good techique too, even if you still only use 2mm cutters. It takes very little time to tidy them up with a needle file since the corner is nicely defined for you. Fusion360 seems to be very much more sophisticated than what I'm using. Mine has no knowledge of any cuts that have come before, so you're entirely on your own when it comes to spotting where the cutter is likely to take a larger bite of material. Still, it keeps me on my toes!
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Neale
Part of the e-furniture
5" Black 5 just started
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Post by Neale on Apr 2, 2019 9:27:34 GMT
A question for the more experienced loco builders out there...
I'm building my Black 5 to the DY design. I've made the tender axleboxes to drawing, then realised that there is no provision for lubrication. I've also now bought the Allsop Galatea tender drawings - another Stanier 4000 gallon tender design - and his axleboxes have oil reservoirs in the top with a small drilling down to the side of the axle bearing hole (presumably to avoid feeding into the loaded area at the top). Should there be a wick in the hole, felt pad in the oil reservoirs, or anything like that? Although I have the DY articles to go with his drawings, I don't have the Allsop articles from way back so no explanatory notes, unfortunately.
Comments welcome!
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Neale
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5" Black 5 just started
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Post by Neale on Sept 10, 2019 22:03:20 GMT
Hands up anyone who has built the DY Black 5 tender to DY design, where there are four bolts holding the brake shaft bearing flanges to the frames. Hands up anyone who has spotted that the real thing (both on works drawing and photos of real tenders) has five bolts. Probably just me, then...
Now I have seen the 5-bolt real thing, it's going to be out with the JB weld to fill a few holes and redrill a few more in the right place. It's not that I'm a super-scale junkie, but this would have been so easy to get right on the drawings for a trivial amount of work.
Ho hum - we live and learn! Mental note to look at photographs to check details before machining...
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barlowworks
Statesman
Now finished my other projects, Britannia here I come
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Post by barlowworks on Sept 10, 2019 22:35:43 GMT
Been there ,done that. The water pickup gear cross shaft outside bearing on the Britannia tender is drawn with three bolt fixings but the real thing has five. Luckily I spotted it before I made them.
Mike
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Post by David on Sept 11, 2019 5:48:31 GMT
Back to your much earlier message about lubrication, I'm sure it is common now to use cheap sealed bearings for tender axles if you have enough space to fit them. I'm sure you'll have the depth, but not sure about whether you can find one with an OD to fit within your axlebox. Unless you're sitting on it the tender won't be carrying much weight so a small ID isn't a problem.
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Neale
Part of the e-furniture
5" Black 5 just started
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Post by Neale on Sept 20, 2019 8:45:13 GMT
Thanks for the comment, David. After looking at various other designs, I machined a pocket in the top of the axlebox, then a vertical drilled hole from the pocket to just intersect the bore on the less loaded side. There will be a drilled hole in the spring retaining plate which sits on top of the axlebox to fill the pocket. I'll maybe put a bit of of wool in there to slow oil flow - I'll play that one by ear later.
Started making brake beams. "Cut three pieces 5.125" long" says DY in his article. I remembered this dimension from looking at the drawings, so cut the BMS bar accordingly. Clearly, DY read his drawings as well as I did and that dimension is between two flanges, not overall length. Fortunately, I had just enough bar left to cut three more blanks to the right length. One day, I shall start learning from my own experience...
"He who never made a mistake never made anything," they say. By that reckoning, I should have made a lot more than I have!
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