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Post by Roger on Nov 4, 2020 22:24:00 GMT
One last update tonight, this time the element end of the Test Boiler which will have a 1-1/4" BSPP thread. It thought it would be easier to create the tapping size on the mill while it's held in the right place. I added an extra clamp at the back which allowed me to move the side clamps to hold the middle down more securely. I'll set this up on the Lathe Faceplate and screw cut the thread. I haven't got a tap anywhere near that size. Fortunately I can get 11 TPI on the lathe, so that won't be a problem. 20201104_221826 by Roger Froud, on Flickr
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Post by 92220 on Nov 5, 2020 9:06:49 GMT
Hi Bob, Thanks for that, I've used them in the past, and also Lee Springs. Unfortunately, neither of these go below 0.2mm wire diameter, so it looks like I've already found the lightest springs I can buy. If I need anything lighter, I'll have to wind them myself. I could do that, but forming the ends neatly is far from easy. Hopefully these will be good enough. Hi Roger. I didn't realise you needed such a light spring. I now see why you had to go Chinese. Bob.
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Post by 92220 on Nov 5, 2020 9:23:29 GMT
Hi Roger. I notice you use a centre to locate your tap wrench when tapping on the mill. I couldn’t get on with that method, so looked at ways of beating the problem. The problem was that with the tiny taps I have (down to M0.60), pressing down on the centre, with the quill handle, just wasn’t sensitive enough to prevent tap breakages.This is what I now use and it works in the lathe too. I just drilled a hole concentric with the tap wrench body and fitted a 1/8” dia silver steel pin, with Loctite. The guide sleeve is just a piece of mild steel rod, with a 1/8” dia hole reamed through. I’ve also modified the larger tap wrenches as well, but with a 3/16” dia pin for the largest wrench. IMG_4366 by Robert Shephard, on Flickr IMG_4365 by Robert Shephard, on Flickr IMG_4364 by Robert Shephard, on Flickr IMG_4363 by Robert Shephard, on Flickr Bob.
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Post by Roger on Nov 5, 2020 9:50:47 GMT
Hi Roger. I notice you use a centre to locate your tap wrench when tapping on the mill. I couldn’t get on with that method, so looked at ways of beating the problem. The problem was that with the tiny taps I have (down to M0.60), pressing down on the centre, with the quill handle, just wasn’t sensitive enough to prevent tap breakages.This is what I now use and it works in the lathe too. I just drilled a hole concentric with the tap wrench body and fitted a 1/8” dia silver steel pin, with Loctite. The guide sleeve is just a piece of mild steel rod, with a 1/8” dia hole reamed through. I’ve also modified the larger tap wrenches as well, but with a 3/16” dia pin for the largest wrench. IMG_4366 by Robert Shephard, on Flickr IMG_4365 by Robert Shephard, on Flickr IMG_4364 by Robert Shephard, on Flickr IMG_4363 by Robert Shephard, on Flickr Bob. Hi Bob, The centre I use is one I made with a very light spring inside and a sliding point, I don't use the quill to apply pressure. I like the arrangement you have though, that looks very handy. The biggesst problem I found with very small taps is that it's tempting to use the tommy bar handle to turn the wrench. For anything below 2mm, I only ever grip the knurled part between my fingers so I can feel how much force I'm applying. Doing it that way I can't remember the last time I broke a tap.
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Post by 92220 on Nov 5, 2020 19:32:36 GMT
Hi Roger.
You can still rotate the wrench on the knurling rather than using the tommy bar. One thing I have found though, is that when you do use the tommy bar, the feel is very sensitive. I have used it for tapping 12 BA threads with no trouble at all. I have also used it to tap around 40 x M0.8 holes in 1mm nickel silver sheet, on my 9f backhead, without breaking a tap.
When you get down to these sizes, the thread depth is so small that there is almost no resistance to rotating the tap so it is just like a knife through butter. In fact I don't think I could tap such a small size without the support of the sliding sleeve in the chuck, without breaking taps. I've yet to try the M0.6 taps though. Must try, just to see if it is as easy. The problem might be the drilling of 0.4mm dia tapping holes though!
Bob.
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Post by Roger on Nov 5, 2020 20:09:40 GMT
Hi Roger. You can still rotate the wrench on the knurling rather than using the tommy bar. One thing I have found though, is that when you do use the tommy bar, the feel is very sensitive. I have used it for tapping 12 BA threads with no trouble at all. I have also used it to tap around 40 x M0.8 holes in 1mm nickel silver sheet, on my 9f backhead, without breaking a tap. When you get down to these sizes, the thread depth is so small that there is almost no resistance to rotating the tap so it is just like a knife through butter. In fact I don't think I could tap such a small size without the support of the sliding sleeve in the chuck, without breaking taps. I've yet to try the M0.6 taps though. Must try, just to see if it is as easy. The problem might be the drilling of 0.4mm dia tapping holes though! Bob. Hi Bob, I'm sure it's no problem on Brass, I've never used Nickel Silver so I don't know what that's like. I've had to tap Steel and Gauge Plate with small taps though, and there's considerable resistance that you need to feel for those. I think you'd come unstuck using the tommy bar for these more difficult materials. I do like the modification though, that's a really useful idea.
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Post by Roger on Nov 5, 2020 20:13:00 GMT
Almost there, that must be at least six passes, and a dozen rods in there already. I could really use some thicker welding wire for jobs like this, and a bit more current. Still, it's possible, and that's all that matters. 20201105_155643 by Roger Froud, on Flickr I'm calling this done. It's not pretty, but it's very strong. I've made sure it's fused to the sizes all the way down to the root and there are definitely no voids. Heaven knows what pressure it could withstand, but at least I won't have to even think about it. 20201105_200353 by Roger Froud, on Flickr
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Post by chris vine on Nov 5, 2020 20:18:05 GMT
From model engineering to nuclear submarines in one thread!!
In fact I think it is rather neat. It looks methodical and there should be any inclusions or pockets by the looks of things
Chris.
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Post by Roger on Nov 5, 2020 21:58:21 GMT
Thanks Chris, it certainly looks strong enough for a reactor vessel! I set this up roughly using the drill chuck in the tailstock to hold it somewhere close before clocking it up. I made this long boring bar years ago for some project or other. It has a square split sleeve for the toolpost and a cam arrangement to lock a round piece of HSS across the diameter for the tool. It's ideal for these big internal threads. I ground up the tool freehand using the universal thread gauge as the guide. It's plenty good enough for this sort of rough job. 20201105_213533 by Roger Froud, on Flickr Fortunately the mandrel has a large enough hole to swallow the element so I can try the fit for size. It saved me having to make a gauge. 20201105_213409 by Roger Froud, on Flickr So that just needed a spot face for the seal and a chamfer on the thread entry. I'll do the back of the thread by hand. 20201105_214751 by Roger Froud, on Flickr I'll have to watch out when I weld it on though, the edge of the spot face is a bit close to the edge. Still, it won't matter if I leave the weld a little short of that.
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dscott
Elder Statesman
Posts: 2,438
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Post by dscott on Nov 6, 2020 2:14:47 GMT
Lovely Welds Roger. Just got the latest Model Engineer and someone covers Flange-less Boilers!!! In copper, but they are not accepted by Boiler Inspectors so stick to what is normal. For steel Flangeless of course. You could always send yours for the ultimate pressure test after a few years. I am betting on well over 1000 LBs per square inch. Easy to reach using an oil pump They are powerful!
David and Lily.
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Post by Roger on Nov 6, 2020 9:07:02 GMT
Lovely Welds Roger. Just got the latest Model Engineer and someone covers Flange-less Boilers!!! In copper, but they are not accepted by Boiler Inspectors so stick to what is normal. For steel Flangeless of course. You could always send yours for the ultimate pressure test after a few years. I am betting on well over 1000 LBs per square inch. Easy to reach using an oil pump They are powerful! David and Lily. Hi David, I think you're in the right ball park for the pressure achievable. I'll probably take it up to 300PSI for the hydraulic test. Although 10mm wall thickness is ludicrous for this, it actually makes life so much easier because you don't need to worry about any stays and you don't need any bushes.
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Post by silverfox on Nov 6, 2020 13:27:00 GMT
Bob
Thanks for the mill tapping heads up ..... off to get a spare to butcher to make one
Ron
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Post by Roger on Nov 6, 2020 16:57:24 GMT
I'm using a couple of threaded bungs in the Water Gauge holes to line this up vertically but upside down... 20201106_115722 by Roger Froud, on Flickr ... with a clamp in the inside at the open end... 20201106_115730 by Roger Froud, on Flickr ... so I can machine the Blowdown Valve attachment details. This one is going to be a Banjo bolt, so no O-ring on this one, just a Spot Face. 20201106_123644 by Roger Froud, on Flickr The magnetic clock base has a handy Vee on one side so I'm using that to hold the foot in place. The Morse adaptor in the quill is being used to get it horizontal. 20201106_142441 by Roger Froud, on Flickr This doesn't need a huge weld, just one on the end to hold it on. 20201106_142500 by Roger Froud, on Flickr The one on the other end needs to be flat, so I'm using a chunky parallel for that. 20201106_143031 by Roger Froud, on Flickr Then it was just a matter of using the feet to hold it down while machining the rest of the top details. 20201106_164740 by Roger Froud, on Flickr I need to get all of these done and the inside cleaned out before welding the end on.
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Post by Deleted on Nov 6, 2020 17:12:03 GMT
Looking good Roger... the only problem is, you should have made 2.....
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jem
Elder Statesman
Posts: 1,065
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Post by jem on Nov 6, 2020 18:03:53 GMT
Aqualung cylinders are around 6 mm thick and take a pressure of 3000 psi, so I think that your boiler will stand well over 1000 psi, perhaps 5000 psi without much trouble, though welds will play some part in its strength. A bit late now, but an old fire extinguisher would probably make a very good boiler, they are OK up to 2000 psi or more.
best wishes
Jem
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Post by 92220 on Nov 6, 2020 19:35:15 GMT
Bob Thanks for the mill tapping heads up ..... off to get a spare to butcher to make one Ron Hi Ron. It also works well for tapping in the lathe. Bob.
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Post by Roger on Nov 6, 2020 21:41:39 GMT
Time to weld the element end in place. This is one complete run round. I tacked it in four places, then infilled with about 25mm runs between those, then filled in between those. I wanted to distribute the heat and stress around the whole shape. 20201106_200544 by Roger Froud, on Flickr Another complete pass, and yes, it doesn't seem to have filled up much. I've probably put another couple of complete 1.6mm rods into that. 20201106_211952 by Roger Froud, on Flickr And the same again here. It's slow progress, but it's a bit neater this time around now I've got a bit more practice. I have to stop every 20 minutes or so because the whole thing becomes rediculously hot. I'm filling the part next to the thread with more passes done a bit quicker so as to reduce the distorsion there. Hopefully it won't be an issue. 20201106_213409 by Roger Froud, on Flickr
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Post by jon38r80 on Nov 6, 2020 22:21:27 GMT
Nice looking welds, are you going to do any non destructive testing (dye pen for example) . Not sure that you shouldn’t have preheated the metal before welding. My limited experience of welding in multiple passes like that suggests you should. Then again my experience is very limited and a long time ago for work.
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Post by Roger on Nov 6, 2020 22:46:17 GMT
Nice looking welds, are you going to do any non destructive testing (dye pen for example) . Not sure that you shouldn’t have preheated the metal before welding. My limited experience of welding in multiple passes like that suggests you should. Then again my experience is very limited and a long time ago for work. Hi Jon, No, I'll just take it up to a really high hydraulic test pressure. I have no idea whether it needs preheating, it does heat up pretty quickly though. I did move around, rather than working continuously. I thought that would be better for distributing the stress. Anyway, we'll soon find out during the hydraulic test if it's a problem.
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Post by chris vine on Nov 7, 2020 11:41:35 GMT
Hi Roger,
Your wall thicknesses are similar to that used for hydraulic ram/cylinders. So I am sure you will be good for 5000, maybe even 10,000 psi!!
Chris.
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