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Model Forum / General / Models / September 2010Myford ML7 Headstock bearings
Hi, I just bought a ML7 and the spindle had a giant play. when I remove the bearings caps I found two shims made of paper stuffed along th metallic shims. I measured the shims with a dial capiler and all four is near the .4m mark. the paper was .2mm thick. I removed the papers and kept only the mettalic shims, the play ha gone, but the spindle was hard to turn by hand. I mixed some lithium grease with prussian blue, carefully spread th blue to a thin flim in the spindle bearings surface and... front lower: '[image http://img505.imageshack.us/img505/4966/frenteinferior.th.jpg] (http://img505.imageshack.us/my.php?image=frenteinferior.jpg) front upper: '[image: http://img18.imageshack.us/img18/9937/frentesuperior.th.jpg] (http://img18.imageshack.us/my.php?image=frentesuperior.jpg) back lower: '[image: http://img22.imageshack.us/img22/778/trasinferior.th.jpg] (http://img22.imageshack.us/my.php?image=trasinferior.jpg) back upper: '[image: http://img18.imageshack.us/img18/4420/trassuperior.th.jpg] (http://img18.imageshack.us/my.php?image=trassuperior.jpg) Note the blue just touched the upper half bearings ons the sides an nothing in the middle. the lower part had contact almos ins al surface. what sould I do -- luizdiefenbac > what sould I do? Put the paper shims back, sell it and buy a Boxford ?  SignatureBoo I mean how can I correct this problem? Can I scrape only the upper hal of the boths bearings, so that way the lower part retains the aligmen of the spindle -- luizdiefenbac > I mean how can I correct this problem? Can I scrape only the upper half > of the boths bearings, so that way the lower part retains the aligment > of the spindle? If it's got the original white metalled bearings (babbit) then I doubt there's enough metal there to scrape so your options are to either re-metal the bearings or replace the spindle and bearings with the updated parts from Myford which converts it to bronze bearings and, I believe, a hardened spindle. Martin Signaturemartin<dot here>whybrow<at here>ntlworld<dot here>com The best approach depends very much on how much money and effort you want spend on the machine. That, of course, will be influenced by the rest of its condition. It's all too easy to end up throwing good money after bad. >> I mean how can I correct this problem? Can I scrape only the upper half >> of the boths bearings, so that way the lower part retains the aligment >> of the spindle? > If it's got the original white metalled bearings (babbit) then I doubt > there's enough metal there to scrape so your options are to either re-metal > the bearings or replace the spindle and bearings with the updated parts from > Myford which converts it to bronze bearings and, I believe, a hardened > spindle. Twaddle. They are not lined steel shells, but solid, about 1/4" thick. It is hard to know why the machine was like that, unless the upper halves have been replaced but not fitted properly. I see nothing to be lost in fitting the top halves by scraping. SignatureCharles Lamont >>> I mean how can I correct this problem? Can I scrape only the upper half >>> of the boths bearings, so that way the lower part retains the aligment [quoted text clipped - 10 lines] > have been replaced but not fitted properly. I see nothing to be lost in > fitting the top halves by scraping. In that case Charles you've seen a Super 7 or an ML7 that's already been modified, original ML7s have white metal bearings, fact! Martin Signaturemartin<dot here>whybrow<at here>ntlworld<dot here>com >>>> I mean how can I correct this problem? Can I scrape only the upper half >>>> of the boths bearings, so that way the lower part retains the aligment [quoted text clipped - 14 lines] > modified, original ML7s have white metal bearings, fact! > Martin In case you doubt what I'm saying Charles, have a read of the ML7 spares list here http://www.myford.com/ML7_spares.html , look at the 4th and 5th items on the list. Martin >>>>> I mean how can I correct this problem? Can I scrape only the upper half >>>>> of the boths bearings, so that way the lower part retains the aligment [quoted text clipped - 18 lines] >items on the list. >Martin Charles is perfectly correct. The ML7 headstock bearings are not thinly Babbitt lined steel shells, as used in automotive crankshafts. They are solid Babbitt. Plenty of room for scraping if the mandrel accidentally wears larger:-) Mark Rand RTFM >>>>>> I mean how can I correct this problem? Can I scrape only the upper >>>>>> half [quoted text clipped - 30 lines] > Mark Rand > RTFM I realised very shortly after I replied that that's what Charles was saying. I stupidly assumed he was saying they all had solid bronze bearings. I guess I should remember that usenet and several beers do not mix! Martin Signaturemartin<dot here>whybrow<at here>ntlworld<dot here>com >Note the blue just touched the upper half bearings ons the sides and >nothing in the middle. the lower part had contact almos ins all >surface. > >what sould I do? Re-scrape the top halves with a bearing scraper until you can get good contact over most of the bearing without the shims. Then replace the paper shims with ones made from layers of aluminium kitchen foil. use enough layers so the mandrel will turn by hand when oiled, without significant effort and the total movement on the mandrel is less than .02mm when pushed up and down with about 20N of force. You can get replacement shim packs from Myford's, but the kitchen foil works as well, if not better, since it is .02mm rather than .05mm per-layer like the Myford shims. That should fix the problem. Mark Rand RTFM >> Note the blue just touched the upper half bearings ons the sides and >> nothing in the middle. the lower part had contact almos ins all [quoted text clipped - 8 lines] > movement on the mandrel is less than .02mm when pushed up and down with about > 20N of force. I'm not a Myford person, but <0.02 mm, or a thou? That's what I'd expect from a badly battered college machine! Imo it should be unnoticeable, or at least much less than one division, 0.01 mm or half-thou, as measured with a dial gauge. The next thought I had was, can't really tell without feeling them, but the shells look a bit scored. Is the shaft smooth? Third thought, the edges of the shell, where the blue appears and the shaft is loose, are almost vertical, and (un)shimming, or scraping, will only affect the top of the half-shell, not the sides/edges. Three-and-a-bit, rigidity of alignment in a lathe in the horizontal plane is much more important than in the vertical plane. A small vertical slop will create a much smaller variation in the thickness of the workpiece - a small horizontal slop will result in a variation in the thickness of the workpiece which is twice the slop. Fourth thought, where does the shim bear? where is it supposed to bear? is it supposed to bear on the edge, or around the bolt hole? If the latter, then if the bearing internal edge isn't shimmed, or perhaps is even skimmed, the closing pressure may also close in the edges of the shell. Fifth thought, Babbiting a bearing isn't hard, can be done on a kitchen stove, and it's quite fun to do (but get the right flux first!, damhikt). ( I did my first Babbitted bearing recently, successfully, but I have done a lot of soldering/brazing, and know about wetting and so on, so it may be a little harder for someone else - but it's a fun learning experience ) Sixth, dare I mention wedges? Thought not. :) > You can get replacement shim packs from Myford's, but the kitchen foil works > as well, if not better, since it is .02mm rather than .05mm per-layer like the > Myford shims. For bulking-up, use beer cans, which are mostly between 0.08 and 0.20 mm (eg Stella cans are about 0.10 mm thick, and surprisingly even considering how they are made, by drawing - the one I just measured was between 0.102 and 0.104 mm over most of it's surface, as was a second can). You can cut them with scissors, but ask the wife first. -- Peter F ac080938 had written this in response to http://rittercnc.com/modelengineering/Myford-ML7-Headstock-bearings-11749-.htm : You state that the metal shims are 0.4 mm thick which means that they haven't been played around with because these shims are in fact 8 layers of .002" shimstock and you can remove one layer at a time with a penknife. I think that I would have used a half-round scraper to ease the edges of the top bearing caps such that the spindle revolves fairly easily and then "blue up" to see if you get contact with the upper bearing surface. If this doesn't happen then remove ONE of the .002" shims from the shimstock and try again. You will probably have to scrape a little more to get an allround contact with both upper and lower bearings at the same time. DO NOT remove any material from the lower bearing caps at all, otherwise you will interfere with the spindle allignment. As a by the way, it is highly probable that an incorrect oil has been used causing this amount of wear. The oil used should be Esso Nuto H44 as Myford specify, which is a light hydraulic oil. I know that the equivalent is available. I would also advise you to obtain the Myford booklet on the ML7 which contains much information on maintainence, spare parts etc. It is available from Myford's in the UK. I own an ML7 myself which is 36 years old, has done an incredible amount of work, and which has had a bed regrind, but the original headstock bearings have never been touched and are just as good today as when I bought the lathe in 1973 (£260). Myford do sell new hardened spindles complete with bronse bearings for the ML7, but these are very expensive and should you have to change the spindle and bearings it might pay to buy second hand from one of the firms who are breaking up Myford lathes in the UK. Hope that this helps a little and will encourage you to "have a go". Antony ------------------------------------- > Hi, I just bought a ML7 and the spindle had a giant play. when I > removed > the > bearings caps I found two shims made of paper stuffed along the > metallic shims. > I measured the shims with a dial capiler and all four is near the .4mm > mark. the > paper was .2mm thick. > I removed the papers and kept only the mettalic shims, the play has > gone, but > the spindle was hard to turn by hand. > I mixed some lithium grease with prussian blue, carefully spread the > blue to a > thin flim in the spindle bearings surface and... > front lower: > '[image: [quoted text clipped - 9 lines] > '[image: http://img18.imageshack.us/img18/4420/trassuperior.th.jpg]' > (http://img18.imageshack.us/my.php?image=trassuperior.jpg) > Note the blue just touched the upper half bearings ons the sides and > nothing in > the middle. the lower part had contact almos ins all > surface. > what sould I do? ##-----------------------------------------------# Delivered via http://www.rittercnc.com Metalworking Forum Web and RSS access to your favorite newsgroup - uk.rec.models.engineering - 11474 messages and counting ##-----------------------------------------------## |
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