J&S540 : some advice needed to assess plan bearing spindle - Page 2
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  1. #21
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    Hi Peter,

    Quote Originally Posted by Peter from Holland View Post
    To me it looks like that they mean thrust clearance of 0.01mm (axial clearance).
    Also this documentation is for a spindle with angle bearings it looks like.
    You are right, when they say "pull the wheel forwards" they mean towards the operator. I had misunderstood this. So 10 microns of axial clearance, which with a 10:1 taper would be 1 micron of diameter clearance or 0.5 microns of radial clearance.

    BTW in my post 10 it was your Studer we were talking about
    and my point was that if you have 50 microns of axial (end) play. with a 1:10 taper the endplay or diameter clearance is not 1/10 of axial play but 1/5 IMHO.
    I see what you mean, but I'm not sure that I agree. A 1:10 taper means that if we move the bearing by 10 microns axially, then the DIAMETER increases by 1 micron. A 50 micron motion increases the diameter by 5 microns. That leaves 2.5 microns of radial clearance, or 5 microns of diameter clearance, doesn't it?

    Cheers,
    Bruce

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    I checked it once more and you are right
    0.005mm endplay on a plain bearing??? That is tight

    Peter

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    Quote Originally Posted by Peter from Holland View Post
    0.005mm endplay on a plain bearing??? That is tight.
    On my Studer the axial play is 50 microns 0.050mm corresponding to 5 microns 0.005mm of diametrical play or 2.5 microns 0.0025mm of radial play. It seems to work fine, I didn't know that this was tight for a journal bearing.
    Last edited by ballen; 12-01-2021 at 05:48 PM.

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    Quote Originally Posted by ballen View Post
    On my Studer the axial play is 50 microns 0.050mm corresponding to 5 microns 0.005mm of diametrical play or 2.5 microns 0.0025mm of radial play. It seems to work fine, I didn't know that this was tight for a journal bearing.

    On your example post 19 the clearance on a accurate angle bearing was given as 0.01mm
    (I also wonder why no preload or at least 0.002-0,003mm like on a Schaublin lathe it was i think )

    So yes 0.005 on a plain bearing with much much more surface area is tight
    It needs a thinner as water oil under pressure I presume to get any lubrication

    Peter

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    Quote Originally Posted by Peter from Holland View Post
    On your example post 19 the clearance on a accurate angle bearing was given as 0.01mm .
    Yes, that's right. Post 19 was the J&S 540 instruction manual, and if we have understood correctly, it calls for only 10 microns 0.01mm of endplay. So if this has (for example) a 10:1 taper, that would correspond to just 1um = 0.001mm = 1 micron of diameter clearance or 0.5 microns of radial clearance! Could that be right? Are there any other J&S540 owners here, who have a solid journal bearing spindle and can confirm this small clearance?

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    oil thiner than water? water @40°c has a kinematic viscosity of 0.6579 mm2/s. where do you get thinner oil?

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    Quote Originally Posted by dian View Post
    oil thiner than water? water @40°c has a kinematic viscosity of 0.6579 mm2/s. where do you get thinner oil?

    Oke a bit exaggerated That is allowed on this forum I think
    But for the Abba with 0.01mm gap I have Drosera MS2 with a kinematic viscosity of 2 mm2/s.
    Would half the gap need half the viscosity??

    Peter

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    what is the size of the bearing and whats the speed range? (its not so simple.)

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    Quite a number of oil viscosities, sometimes clearance can be adjusted (a little ) with a different oil.
    Warm-up has to be considered for OD and endplay.

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    The manual I have has clearance measured cold as 0.0004" end float.
    It also says correct oil temp running is 20 degrees above ambient or 62 degrees (68 / 143F) which ever is colder.
    I run mobil velocite no3 in mine.

    Dave

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    Quote Originally Posted by small.planes View Post
    The manual I have has clearance measured cold as 0.0004" end float.
    Yes, that's the same as is given in post 19: 0.01mm = 0.0004" axial float.

    It also says correct oil temp running is 20 degrees above ambient or 62 degrees (68 / 143F) which ever is colder.
    I run mobil velocite no3 in mine.
    The manual page (post 19) reads "20C or 68F above ambient". But that's incorrect, because those two things are not the same! There are two possibilities:

    A) The manual page should read "bearing temperature 20C or 36F above ambient". The people writing the manual made the mistake of "translating" 20C as being 68F. However if F is temperature in Farenheit and C is temperature in Celsius, then

    F = 9C/5 + 32,

    so a temperature CHANGE of 20 Celsius results in a temperature CHANGE of 9x20/5 = 36 Farenheit.

    B) The manual page should read "bearing temperature 42 C or 75F above ambient". Based on what you wrote, I think this is what they meant. So if normal room temperature is 20C = 68F, then this would be a bearing temperature of 20+42 = 62C or 68+75 = 143F.

    Based on what you wrote, I am pretty sure that B is correct!
    Last edited by ballen; 12-20-2021 at 11:40 AM.

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    The manual says 20C above ambient:



    68F => 20C (I.e. a room temperature) so I think it probably means temp should be between 20C/36F above ambient and a maximum of 62/143 absolute.
    Given a shop temp of 20C that would be wheel head between 40 and 62, which feels like the right sort of range.

    On mine I haven't checked the temperature properly, just rested my hand on the wheel head, and its had the chill taken off, not really warm, but certainly not cold. (my shop is currently around 5C and rarely gets over 15C)

    Dave

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    Hi Dave,

    Quote Originally Posted by small.planes View Post
    Given a shop temp of 20C that would be wheel head between 40 and 62, which feels like the right sort of range.
    The manual page you have snapshotted in post #32 is different than the one that I snapshotted in post #19, and makes more sense. However it still contains an error. I agree with what you have written, and believe that the page should read as follows:

    Note: Normal running temperature of this wheelhead is approximately 20 Celsius (36 Farenheit) above ambient or 62C (144F), whichever is lower.

    For example:
    Ambient 20C = 68F: normal wheelhead temperature 40C = 104F
    Ambient 25C = 77F: normal wheelhead temperature 45C = 113F
    Ambient 30C = 86F: normal wheelhead temperature 50C = 122F
    Ambient 35C = 95F: normal wheelhead temperature 55C = 131F
    Ambient 40C = 104F: normal wheelhead temperature 60C = 140F
    Ambient 42C = 108F: normal wheelhead temperature 62C = 144F
    Ambient greater than 42C = 108F: normal wheelhead temperature 62C = 144F

    As a rule of thumb, you will get burned by touching something hotter than 70C, and touching 62C for a second or two should be no problem. So for a journal bearing J&S 5430, you should always be able to touch the wheelhead for a few seconds without getting burned.

    Cheers,
    Bruce

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    Hi Bruce, hi all !

    sorry for replying with such a delay: you have been active on this thread! & I was away for business. Thanks for the interesting insights on viscosity & the context info from similar spindle assemblies.

    Bruce, I totally agree with your analysis on the quite obvious mistake that was lingering in the manual section about operating temperatures.
    You will therefore like the following one:

    clipboard01_spindle_temp.jpg

    This is an extract from the oldest manual I have, that predates the extracts you commented, and that pertains to the model era of my 540 (~1960/61). It looks like they revised the wording in each manual edition but never got it right!
    As a comment/digression to your rule of thumb, 60°C is pretty damn hot, and although slightly below danger for skin injury, it has been set by french regulation as the limit for thermostats of domestic water boilers a few years ago. It will give you a hot tap water of about 56°C max, which I can personally hardly stand for more than a couple seconds.

    To address Peter's concern on sandblasting, I do not obey the same necessary breakeven challenges as a machine trader for whom fully disassembling a machine, stripping it to its bare casting, filling, sanding, priming & painting makes little if no sense and adds marginal value to an otherwise operational machine. I have extensive industrial experience, but do this for fun and home shop equipment, so time is almost out of the equation. Besides, this very machine, the 540, is in an exceptionally shabby state, much beyond the reach of any chemical or mechanical stripping: Many people would just scrap it. Btw, french law on usage of industrial grade chemicals strippers has become so stringent that most of what you can now source will strip old paint from a wooden door, but will not even stain heavy duty paints from the 60s/70s.
    I have been a bit brief on blasting as this was quite O.T. to this post, but my habit is to bead blast small/medium parts that I can process in my shop cabinet, and outsource larger parts to professionals, be they castings or panels/covers, etc. The company I work with has an extensive range of processes usable, all viewed as blasting , but very different in nature and generated impact energy:
    -They have an automatic conveyor where you put large/heavy (up to 1/2 ton) parts and it goes under a cataract of stainless beads at a rate of about 1 ton/linear conveyor meter. Parts then get turned to show a different face and run again under the cascade until fully processed. Very quick, inexpensive, and works fine with coarse parts, but it is BRUTAL. I used this for alternating saw and bandsaw base castings for example. Full machine gets processed in less than 10 mn, so it is quite cheap. It will make a mess of any sheet metal.
    -Then they have conventional blasting where an operator works in a dedicated over-pressured booth, an can work more intricate parts, casting internals, etc. They can modulate quite considerably the blast rate and access details, approach areas that you have masked out in advance (I fill all holes, & mask with aluminum sheet covers all mating areas, generally every area that is impacting geometry). A 800kg bandsaw I sent them not long ago with all castings prepared, masked, was processed internally/externally, with all covers, table etc . It was done in 40mn. It is more expensive (about 100€, I know I have friendly prices, but this gives a rough idea) but very decent if you wonder how long you would have to play with your paint stripping kit; Yes you have to put everything on a pallet, and use your trailor, etc...but still...
    -And when things get a bit more complicated/sensitive, eg when there are ways ground in the casting as is the case with such a grinder, I ask for vapor blasting of these areas. (They can sandblast the coarse areas first). It is significantly more expensive, but allows very cautious processing with impact energy that has nothing to see with regular sandblasting.
    For applications in my professional field I have been using this for years to shoot out contact cement from carrier plates of CCD sensors for which micron-level co-planarity is the rule. We never ran in any structure integrity mishaps so I consider this kind of process as quite respectful. A major drawback, beyond price (about 3 times higher hourly rate with this subcontractor), is that leaded paint/primer as is often found on these oldies is something they don't like to mess with and they will often refuse to deal with if they risk contaminating their wet process with your involuntary waste. Much more picky than the dry blasting process where stripped matter is quite easily separated.
    This really was off-topic ;-)

    So the largest machine parts will visit this contractor, but I will take the utmost care of the upper 1/3 of the base casting, and the cross slide will certainly be bead blasted at home. Not sure yet for the table as it is a bit large for my cabinet, and it has been significantly impacted by its life as a rainwater gutter and needs vigorous processing, while preserving the pretty good condition of the bottom face & slides.

    Cheers,
    Phil
    Last edited by kaiten; 12-23-2021 at 11:44 AM.

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    Hi Phil,

    Quote Originally Posted by kaiten View Post
    Bruce, I totally agree with your analysis on the quite obvious mistake that was lingering in the manual section about operating temperatures.
    You will therefore like the following one:
    Attachment 337671
    This is an extract from the oldest manual I have, that predates the extracts you commented, and that pertains to the model era of my 540 (~1960/61). It looks like they revised the wording in each manual edition but never got it right!
    I'm glad you agree, and would like to see your extract but the link above is broken.

    Cheers,
    Bruce

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    Phil

    I am glad to hear you know your way in sandblasting
    It would have been a mess if you put it through the turbine blaster
    I worked on a machine like that The worst is with cut wire as a blasting media

    We have a compagny near by specialized in paintstripping Eighter mecanicaly or chemicaly
    They have a multitude of options for cleaning
    TCI CLEANING industrieel reinigen en ontlakken

    Peter

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    Quote Originally Posted by ballen View Post

    I'm glad you agree, and would like to see your extract but the link above is broken.

    Hi Bruce,
    dunno what happened as I could still see the image on my end. Reuploaded & edited the post accordingly, hope this works now.

    Cheers,
    Phil

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    Hi Phil,

    Quote Originally Posted by kaiten View Post
    Reuploaded & edited the post accordingly, hope this works now.
    It works now, thank you. What a mess they made of this!!

    Anyone who comes across this in the future, and is confused, please see post 33 in this thread. There, I have written what J&S intended to say in their manuals, and kept trying to say, but never quite got it right.

    Cheers,
    Bruce

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    Hi Bruce !

    at the risk of really straying this post off topic, I have come across another inconsistency in the documentation I have at hand.
    I am investigating about wheel hubs : my 540 came with a single rust-encrusted wheel hub that is quite heavily pitted. Good thing though is that is took charge for the rain water exposure and the spindle taper still looks in very good condition.

    I am quite recent to all things 540-related, but I was left with the idea that the wheel hub OD was specified at 1"1/4.
    Browsing through the oldest manual I mentioned above, here is the specification section :

    clipboard01_wheelhead-spec.jpg

    It had me laugh for a second as they got it wrong again (1"1/4 is NOT 32mm but 31,75mm).
    It was fixed in later manual editions where grinding wheels are always specified for 31,75mm/1"1/4

    The trouble is I am proposed a bunch of wheel hubs that appear to be 32mm, not 31,75mm and I am wondering if I missed something. I have asked the seller for due diameter re-check, but have no confirmation yet.
    I have scrubbed this forum archive a bit and read about your heavy duty 2" wheel hubs, but did not come across anything 32mm.
    Does this ring any bell for the seasoned J&S users in here ?

    cheers all,... and merry Christmas !

    Phil

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    The J&S hubs should be 1 1/4" unless they are 'specials'. The trouble is that 32mm is also a standard size for more modern grinders.

    I had the problem the other way around. I bought some 1 1/4" wheels for my (new to me) bench grinder and then discovered that it needed 32mm ones. They would have fitted my J&S 1400 with no problems, but I did not want that type of wheel for it. I actually reamed out the holes to 32mm using a Rotabroach cutter that I already had. They are now fitted to the bench grinder.

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