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Model Forum / General / Models / May 2008Regrinding live centres
I was looking out for a decent new MT2 live centre at Harrogate, there wasn't much about. Chesters had two qualities, the better one looked quite good but I was discouraged from giving them my money by the surly staff response to my enquiries. I came away instead with a job lot of three used ones from a well known dealer, he went through all his pile & we agreed most weren't up to much but these three looked good except that they needed regrinding. I was going to take two but he ended up offering me the three for a fiver each. Anyway, today I set about regrinding the points. I've got the benefit of a proper T&C grinder, but the same could be done on any grinder with some sort of XY table. I set one up in the universal head at the right angle and hoped they would rotate with the friction from the grinding wheel. Unfortunately this only worked with a heavy feed, ok for a roughing pass but no good for finishing. After a bit of contemplation I glued up a bit of 4mm O-ring cord into a belt of about 400mm length. Then found that one of my cordless drills has a bit of a notch on the keyless chuck which is just deep enough to act as a sort of pulley to keep the O-ring belt in position, provided it's kept somewhere near into line. It wouldn't be much of a job to turn up a crude pulley if the chuck wasn't so considerately designed. Then looping the belt over the nose of the live centre, and holding the cordless drill in such a position that the chuck 'pulley' kept the belt pressed against the static body of the centre, I was able to spin the centre point at a suitable sort of speed. I then had just enough hands to hold the cordless drill while pulling the trigger and work the table feeds on the grinder, job done in 5 minutes after the preparatory work. Yes the belt does have a few notches ground in in where it slipped off as my concentration wandered from one part of the excercise to another, but it is still intact after regrinding all three. I didn't have any spare hands to take a picture, though! Of course, if doing the job regularly a proper fixture would be worth making, but for a once-in-a-blue-moon job like this it would be a waste of time. Tim >I was looking out for a decent new MT2 live centre at Harrogate, there >wasn't much about. Chesters had two qualities, the better one looked [quoted text clipped - 35 lines] > >Tim Luckily the Old "Archer" that I have has a hole down the MT3 taper. A bit of M6 studding gained enough purchase to allow spinning with the cordless drill. SWMBO operated the drill whilst I ground using a cobbled up grinder made from a router. Worked OK. Main problem is the head of the centre is 65mm diameter and it often gets in the way <G> I will remember your option for a future "smaller diameter" centre. -- Richard Email address is valid but remove burrs before sending! > I was looking out for a decent new MT2 live centre at Harrogate, there > wasn't much about. Chesters had two qualities, the better one looked [quoted text clipped - 35 lines] > > Tim J&S 1300 cylindrical grinder with 3MT female in the live work head, swivle work head to require angle and grind to perfection. I'd do it for you but mine's still in storage!!!! Andrew I was thinking of putting mine (after getting a new bearing for it, but my center is a big and chunky one) in the headstock of the lathe, move my compound slide to 30degrees, and use a toolpost grinder (like I just did with my chuck jaws). Anything wrong with this? Is it a problem if the center free revolves (whilst also revolving when the lathe is switched on)?  SignatureBest regards, Dave Colliver. http://www.AshfieldFOCUS.com ~~ http://www.FOCUSPortals.com - Local franchises available >> I was looking out for a decent new MT2 live centre at Harrogate, > there [quoted text clipped - 55 lines] > > Andrew >I was thinking of putting mine (after getting a new bearing for it, but my >center is a big and chunky one) in the headstock of the lathe, move my [quoted text clipped - 3 lines] >Anything wrong with this? Is it a problem if the center free revolves >(whilst also revolving when the lathe is switched on)? My thinking was that the best result would be achieved with the body static and the centre revolving in its own bearings, any error then should be from the manufacture of the unit rather than the regrinding process. Others may have a different view. Cheers Tim >>I was thinking of putting mine (after getting a new bearing for it, but my >>center is a big and chunky one) in the headstock of the lathe, move my [quoted text clipped - 11 lines] >Cheers >Tim My sentiments exactly, that is why I did mine the way I did. -- Richard Email address is valid but remove burrs before sending! >>>I was thinking of putting mine (after getting a new bearing for it, but >>>my [quoted text clipped - 19 lines] > > Email address is valid but remove burrs before sending! I want a very small MT2 live centre and there is a design in Mr Sparey's Lathe book. My thought was to get a stub arbor as the starter for ten then machine to size and fit bearings. This is hobby use only and then occasional. Is there any flaw in this approach? Steve >I want a very small MT2 live centre and there is a design in Mr Sparey's >Lathe book. My thought was to get a stub arbor as the starter for ten then >machine to size and fit bearings. This is hobby use only and then >occasional. Is there any flaw in this approach? > >Steve Why do you need to fit bearings to the live centre? Just put the stub arbour in the headstock. Turn a 60 degree taper on it and use it in the headstock without removing it. Instant live centre :-) Next time you mount it in the headstock, turn another half thou off the taper to clean it up and ensure concentricity. Works very well for me once I discovered that no one seemed to be selling live centres any more. Mark Rand RTFM >>I want a very small MT2 live centre and there is a design in Mr Sparey's >>Lathe book. My thought was to get a stub arbor as the starter for ten then [quoted text clipped - 14 lines] >Mark Rand >RTFM Mark You're trying to confuse us by being pedantic and using 'proper' terminology <BG> Tim >>I want a very small MT2 live centre and there is a design in Mr Sparey's >>Lathe book. My thought was to get a stub arbor as the starter for ten then [quoted text clipped - 11 lines] >to clean it up and ensure concentricity. Works very well for me once I >discovered that no one seemed to be selling live centres any more. Mark, I may be missing some subtle point here, but there are plenty of live centres around, e.g. http://www.arceurotrade.co.uk/Catalogue/Centres http://www.chronos.ltd.uk/acatalog/Chronos_Catalogue_Lathe_Taper_Tooling_ _70.html The sets with interchangeable points may be a suitable solution for the OP. Thought about getting one for myself a few times. David SignatureDavid Littlewood > In article <393e3496elq2hc5f80pmjkl7b40t52d...@4ax.com>, Mark Rand > <ra...@internettie.co.uk> writes [quoted text clipped - 31 lines] > -- > David Littlewood Yeap, your missing a subtlety. The terminology 'live center' can (and I believe 'properly' is) indicating the one in the headstock, which turns with the work, as opposed to the dead center in the tail stock which doesnt. Dave >> In article <393e3496elq2hc5f80pmjkl7b40t52d...@4ax.com>, Mark Rand >> <ra...@internettie.co.uk> writes [quoted text clipped - 47 lines] > > Dave What I meant was a centre that rotates in the tailstock - a "running centre"? Steve >What I meant was a centre that rotates in the tailstock - a "running >centre"? > >Steve Call it a rotating centre and us pedants won't get our oil rags in a twist :-) The comment about no-one appearing to sell live (soft in this case) centres any more is true though) Mark Rand RTFM In article <3834a0a9-1a01-4472-a64e-e1dd5d737840@59g2000hsb.googlegroups.com>, dave sanderson <david.sanderson@bem.fki-et.com> writes >> I may be missing some subtle point here, but there are plenty of live >> centres around, e.g. [quoted text clipped - 18 lines] > >Dave Hm, not a terminology I have ever seen used before. to me, a dead centre is solid, a live centre has bearings and rotates independently of the taper it is in. This is also the terminology used in the tool catalogues. Dead centres come in two forms, soft (for use in the headstock, can be turned in situ to ensure absolute concentricity) and hard (for use in the tailstock, to resist wear as the part rotates against it). It is IMO worth using TC tipped ones for the latter, they resist scoring very much better. I understand it is the soft dead centres which have become difficult to source. David SignatureDavid Littlewood >In article ><3834a0a9-1a01-4472-a64e-e1dd5d737840@59g2000hsb.googlegroups.com>, dave >sanderson <david.sanderson@bem.fki-et.com> writes >>Yeap, your missing a subtlety. The terminology 'live center' can (and >>I believe 'properly' is) [quoted text clipped - 17 lines] > >David Your sources are wrong! Mark Rand RTFM >>>Dave >> [quoted text clipped - 13 lines] > >Your sources are wrong! Mark, Not understood. Are you disputing the terminology (in which case we'll have to agree to differ) or are you saying soft dead centres are easy to find (in which case some pointers might help those who are looking for them - not me, I have one and not yet felt the need to buy any more). David SignatureDavid Littlewood >Hm, not a terminology I have ever seen used before. In fact. One of these:- http://www.test-net.com/rotating-centre.jpg regards Mark Rand RTFM >J&S 1300 cylindrical grinder with 3MT female in the live work head, >swivle work head to require angle and grind to perfection. I'd do it >for you but mine's still in storage!!!! > >Andrew Andrew Thanks for the 'offer' <G> I do have a motorised universal head for my Cincinnati T&C grinder, but it's bl**dy heavy, it's on the floor, and trying to think it through logically decided that the method I used ought to give a truer result. As I said in another post, others may have differing views. Tim |
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