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  1. #51
    Well what can I say but thanks again John, Irving

    Grinding the end of the shaft down worked a treat and was far quicker and easier than my suggestions.

    The offending article
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    And after a diet.....
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    In hind sight it was the obvious solution but having some say "yeah I've done that and it was fine" just gives you the confidence before you potentially turn a working bit into scrap.

    Going back to the bearings I have put the preload on them and it is still smooth but there is a definite bind/rub on one point of the rotation, does this sound like a problem?

    I have read on John Stevenson site that the bearings are hand marked with the precision and the high spot so they can be matched. Before i strip it all down again dose this sound like the solution?

    Thanks again and thanks in advance

  2. #52

    Glad things turned out well. There is always more than one way to skin a cat.

    If you can still have easy access to the ground off part, I would go around the square joint with a centre punch, just to make the gear a little more secure.

    Don't go having nightmares about the unequal pull off pressures just yet. I would wait until you can run the spindle up before taking any rash measures.

    Plenty of oil for lube, then let the spindle run for ten to fifteen minutes, checking on the bearing caps to make sure that things aren't overheating, warm is OK, hot is not.

    After that time, let it cool down for an hour or so, then recheck to see if it has the uneven drag.

    You have done so much work on it, it could be something as simple as a bit of oil varnish in either the races or on the rollers that is causing the problem. It only takes microns of thickness to show up as uneven.

    If it is still at fault, then investigate.

    Last edited by bogstandard; 22-06-2010 at 09:17 AM.

  3. #53
    yes I will centre punch the shaft now i know it clears OK, I've only got to undo the two screws and the apron is off again.

    I think I have also cured the problem with the binding. I just slackened of the preload and bearing caps, few light taps with a nylon hammer and tightened it all back up and it seems to be fine.

    I will still wait till i can power it up and give a good run before ultimately deciding if they are OK. If the preload is there to allow for the shaft expanding, would it not be better to adjust it when its hot and then slacken it off again when finished?or is it possible to over tighten and damage the bearings?

    Progress is extremely slow at the moment as i can only grab the odd 10-15mins here and there. Still praying for rain so I have an excuse to stay in the workshop all evening

  4. #54

    The preload is put on whilst cold, and after the spindle has warmed up, the pressure on the bearings should have been taken off, and you end up with no end float on the spindle.

    If you attempt to put the preload on whilst warm, you run the risk of the bearings being too tight when the spindle contract due to cooling, and that might set up a brinelling situation.


  5. #55
    The rain has arrived....... 3 hours of workshop time and the lathe is running. well sort of. I'm having a mare setting up the belt tension and alignment on the counter shaft. I fitted the metal atlas pulleys and shaft because it also has roller bearings but the end pulley is damaged and out of balance causing a vibration. I put the complete Halifax counter shaft on but now there is a nasty/annoying clanging noise coming for the spindle shaft. It seems to be the small amount of play where the final drive gear locks to the pulley assembly for normal speed. if i reduce the belt tension it helps a bit but i don't think then it would then be tight enough in use

    I have run it for quite a while and kept the oil topped up and the spindle spins freely but there is still a small amount of binding at one point. Is it likely that it is this slowing up that is causing the pulley to bang against the locating pin?

    If you attempt to put the preload on whilst warm, you run the risk of the bearings being too tight when the spindle contract due to cooling, and that might set up a brinelling situation.
    OK wont do that then

    Thanks in advance

  6. #56
    Solved the binding, the idler on the end of the spindle for the lead screw drive was loose

    Finally got the lead screw and reverse gear box working nicely, had to resort to using the Halifax gearbox with the atlas gears, 1st drive shaft and selector nob and plenty of grease.

    I tried machining the small pieces of ball screw that Gary gave me but not much luck

    I thought the tool post I had was very sturdy but seeing it move out of the way instead of cutting the screw proves otherwise.

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    So I'm going to put the tee slot table on, get a QCT and some new carbide tooling

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    The only problem is that I didnt get the gib. So my question is how can I get around this? will a small strip of brass be ok? something in the back of my mind tells me that only precision ground steel will do

  7. #57
    On my Atlas, they started off as ptfe gib strips (which I now think is standard issue), but they can be almost of anything, brass, bronze (recommended) or mild steel, and yes, they will need to be a nice constant thickness along the length. Nothing too exotic, but you do need to angle the narrow edges so that they sit in their position nice and snug, with only about 0.25mm (0.010") adjustment gap.
    Also put countersinks into the wide side for the grub screws to sit into and hold the strip in position even if the gib is slack.


  8. #58
    Thanks John, forgot about this little problem. I got sidetracked with the newest edition to the CNC family.

    Ptfe? I'm only familiar with the plumbers tape, can you get it as solid as well then? Any one with a surface grinder that could Knock me up a new gib strip? (not you John I know your not well,)

    Before I get too ahead of myself I also need to check headstock and tail stock alignment and carriage alignment, Ive seen various methods for each element but is there an order to which they should be checked and which is the best method given that I have completely striped and rebuilt it, Any pointers would be good (the bed was leveled with a precision level, not sure of the spec but moved at lot even when a rizzla paper was put underneath)

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