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| Making an accurate spindle with an innacurate chuck. |
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| Fergus OMore:
I was wandering about my hard drive and found that I have still got my copy of 'Spindles' in the Nexus Workshop series. I'd made a Quorn and a Kennet and so on and have a couple of lathe spindles made by a Mr G.Potts when he lived over in the Lake District. His other spindle was sold by Woking Models which is now Hemingwaykits. This brings me to cast iron and its behaviour. Woking when it was in North Queensferry sold plans and kits for Edgar Westbury's milling machine. I had all the bits except the head unit- the rest had been cast at Gateshead Tech where I later did my City and Guilds on retirement. Anyway, I bored the casting on a lot bigger lathe than my Pools there. All went well until I had split it so that it would clamp on the round column. So I split it- and it wouldn't go on. So I had to scrape it round- again. My later escapade was the George Thomas Universal Pillar Tool. Like most of us, I started on George's words and music in the forerunner to Workshop Techniques called 'The Universal Pillar Tool'. His mark 1 arms did exactly the same and GHT designed a Mark2 set which were not split and did not distort. So we come to none more advanced that Prof D H Chaddock and the Quorn. My first set of castings 'nipped' but I made cottars for the second set-which I have today. So you have chapter and verse now! N |
| The Steamer:
If your struggling to find good toll shops I suggest a trip down to Sheffield! there is quite literally hundreds of tool shops selling anything you can imagine! some have everything behind the counter so you have to ask for what you are looking for, others are just massive rooms FULL of every kind of tool you can imagine! I have literally spent hours sifting through chucks ect! |
| DavidA:
Just wondering, Have you gone right back to basics ? is there any run-out on your lathe mandrel nose. Does the backplate fit comfortably on the mandrel egister ? Dave. |
| S. Heslop:
--- Quote from: awemawson on November 22, 2013, 11:46:15 AM ---If you are measuring the front and rear faces as significantly none parallel then even after this period of times I'd get in touch and open negotiations as that situation would suggest that the chuck is not fit for purpose. If you explain that you've only just got round to mounting it then you never know they may take pity on you ..... --- End quote --- I keep making excuses but I really just don't want to deal with the hassle. I'm a little busy at the moment and it'd probably cost me half the price of the chuck just to ship it back to them. But I do appreciate the suggestions though. --- Quote from: Fergus OMore on November 22, 2013, 12:02:43 PM ---The first is 'cast iron' and by the very nature of the substance, both it and rolled steel can be very unstable. If you cut into either, the stresses will start to release. Correctly, cast iron should be rough cut to almost size and put out to weather in the factory yard. This what happened only a few miles from you when the 'Tyne' had factories. Again, when steel was red hot going through the rolling mills and came out, it had received built in stresses to be released later. Bright steel is worst whilst black steel is less unstable. --- End quote --- There's a place at the bottom of the Team Valley trading estate with big stacks of what look (to me) like unmachined cast iron pipe fittings. I wonder if they're being left to season. Still though, I'm aware that this stuff shifts a bit as it settles but i've never heard any real numbers to put it into perspective. I didn't imagine that cast iron could settle enough to make a 0.4mm difference on a large lump. --- Quote from: The Steamer on November 22, 2013, 03:48:14 PM ---If your struggling to find good toll shops I suggest a trip down to Sheffield! there is quite literally hundreds of tool shops selling anything you can imagine! some have everything behind the counter so you have to ask for what you are looking for, others are just massive rooms FULL of every kind of tool you can imagine! I have literally spent hours sifting through chucks ect! --- End quote --- I think my dad sometimes heads down that way for work. Maybe I could hitch a lift down some morning and take the bus about. Got any addresses for places worth going to? |
| Fergus OMore:
I've been retired( from TVTE) longer than I have ever worked :scratch: so I haven't a hint about what there is, However, I 'm sufficiently with it ( Quality control-wise) to say 20thous in what? Without going into the realms of engineering, you could have attempted to cut the chuck blank almost to size- and then heated it up to red hot- and let it stew until most of the stresses were relieved. Then you do your finish to size thing. However, I recall you making hats out of tin or something and stretching and shrinking with heat and cold is part and parcel of sheet metal work. For all practical purposes, it is the same thing. As a simple analogy , a central heating radiator or boiler will rattle and bang with expansions and contractions- after being in use for perhaps 20 years. A bit of railway line will alter in length with heat. If you are getting into fine measurement of precision tooling, you measure at a given temperature and that goes for viscosities as well. If you have a car you have a windscreen with tempered glass on both sides and normalised glass in the middle. If you damage a tiny bit of the outside, the inbuilt stresses will smash the screen. However, I still think that you might have a lathe that is trying to cope with poor alignment and or a chuck too heavy for the design. With a model makers lathe, you can throw it out of alignment by simply leaning on the tailstock. I'd better apologise but these are cold truths and perhaps are unwelcome. |
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