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Thread: How to measure ways to how bad they are worn?

  1. #1
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    Default How to measure ways to how bad they are worn?

    I tried the search feature, but my search skills must be lacking....

    So, how do you check the ways to find out how how wore they are?

    It doesnt seem correct to put an indicator on the saddle and measure that way as the saddle may move and dip with the ways...right?

    So how?

  2. #2
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    it is a bit tricky and you've hit the reason why.....its difficult to know if something is flat or not over say 5' without something 5' long to compare it to. However when you're trying to assess wear on the ways, its usually in terms of order of magnitude - is the lathe worn out, rather than the exact amount meaning that much. Here's four ideas onhow to get a hint as to the wear on the ways -

    1) Indicating the ways can work as wear is going to be heaviest near the headstock. You want to set the indicator up with the carriage all the way to the right and the indicator reaching out far to the left of the carriage. This hopefully will reveal how much drop there is as the indicator goes from unworn section to worn. i almost always use a tenths indicator; not that a tenth of wear matters, but a tenths indicator makes picking up a few thou difference very obvious

    2) snug up the carriage lock in the area you think is low (heastock) and move the carriage to the other end. if you feel no difference in tightness the ways could be good - could because there is no guarantee this surface was accurate and parallel to the lathe ways to start with. If you can get at it you can quantify the difference with feeler gauges

    3) mic the thickness of the flat way to its underside - the underside surface on most is accurately made relative to the way as it is a bearing surface - it carries the plate or roller bearings that prevent the carriage from lifting

    4) visual and by feel. The V way will wear on the flanks but not the top. Significant wear will create a 'top hat' on the top of the V. You'll be able to feel this with a finger nail if there's a few thou wear.

    all i can think of for now
    Last edited by Mcgyver; 11-08-2010 at 11:08 AM.
    .

  3. #3
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    You need to, if you don't have more sophisticated equipment, find a "reference" surface that will NOT be worn, and compare those two along the bed.

    The comparison surface should be one that was finished at the factory, but that will not have worn since, or at least will not have worn "much".

    You can use the carriage as the base of comparison for the ways, since whatever is up with the ways is irrelevant unless it affects carriage movement.

    The reference surface might possibly be the tailstock flat way. Typically that is NOT worn at the extreme T/S end, and is NOT worn very close to the chuck.

    The carriage way is typically NOT worn at the extreme T/S end, but will be elsewhere.

    Therefore an indicator on carriage zeroed to the T/S way at the extreme T/S end will give you a picture of the carriage position relative to the T/S way along the bed.

    Since typically, the worst carriage way wear is at the H/S end, where the T/S way is NOT worn, you can usually check "overall" wear that way.

    In between, BOTH ways may be worn, and you might have some difficulty separating them. But it isn't impossible.

    Some operations in production may have worn the middle of teh carriage way much more than the H/S end or T/S end.

    That you might have trouble with.

    BUT if that is the case, then it is likely that the relatively fixed position of the carriage way wear is also associated with very little wear on the T/S way, simply because the T/S *could not* have been located where the cutter was, and so that area is very likely not worn by anything but chips falling.

    So overall, the T/S flat way is usually a pretty good reference surface.

    Some have used the flat tops of the V ways, but there isn't any guarantee that was a finished surface. It *probably* was finished just to make sure it was not a problem, and *may* have been finished by the same grinding operation simply as a convenience.

    But there is nothing stopping it from simply being left "as planed" or "as milled", which would leave you in doubt when it comes to small numbers of thous.

    if scraped, it probably is not reliable.

    other surfaces are very likely not reliable in any way.

    As for the "wear ridge" on the V ways..... NOT RELIABLE. S-B DO get the ridge on the V ways, Logan, for instance, DO NOT. So it is NOT a universal indicator.

  4. #4
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    The definitive answer to this question is in the classic book "Machine Tool Reconditioning" by Connelly. I strongly suggest checking it out of your local library before buying a copy, as this book is very expensive.

  5. #5
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    Never done the check myself but just a thought. If you had a test bar in the lathe running perfectly true of sufficient length to check the full travel of the carrage then a DI in the toolpost set on top of the test bar should show the amount of wear in the bed as you move the carrage along the bed. Welcome others thoughts on this method. Mounting the DI on the tailstock is another and using the tailstock ways as a reference is another previosly mentioned. In another life we rescued and old badly worn bed on a large Niles by mounting a grinder on the tailstock and grinding the ways to match the tailstock ways. Worked too. Peter
    Last edited by Oldbrock; 11-08-2010 at 01:08 PM.
    The difficult done right away. the impossible takes a little time.

  6. #6
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    And remember something to think about .If the way is worn so is the bottom of the saddle more so on the left hand side.

  7. #7
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    You have two simple ways to measure.
    But first I must ask "WHY" . If for your knowledge , then the first one only needs to be done. If you wish to rebuild the ways, then both will be needed.

    Starting at the headstock, put one inch marks along the ways with a good marker. Also make a chart, with the inch marks shown on one side

    First, put a known round rod of between 1 and 2 inches in diameter and 18 inches long between centers. Make sure the centerdrilled marks are dead on.
    Place a mag base indicator on the carraige OVER the front ways and indicate the bar, both on the top, and on the side. write down your readings
    Do the same when OVER the rear ways. The larger the Rod, the more accurate the reading. You now have a graph of the ways.
    the "side" readings tell you twist , which is usually the front way dropping and the rear way staying plumb.
    To eliminate error between head and tailstock, or to know if you have to compesate, Put a live center in the tailstock and indicate the "Housing".
    Now put the live center in the headstock or a 3 jawchuck and indicate the same again. any difference should be accounted for in your chart

    Second method is to remove the carriage from the lathe and also the top portion of the tailstock. Mount a dial indicator on the tailstock base and have at it.
    I rebuilt a lathe years ago by doing this, and mounted a die grinder on a angle slide on the base and I was able to use the pristeen tailstock slide/ways to regrind the carriage ways worked fine. Took time, but I was in a small town in Canada in the middle of winter and no access to a surface grinder

  8. #8
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    There are 2 tests/checks you can perform without the bed being level. They aren't perfect by any stretch of the imagination, but they'll give you some useful information. 1. Indicate the inside flat way off the carriage, this will give the straight down wear. 2. Indicate the inside face of the front V way from the tailstock, preferrably using the TS bottom as the indicator holder. Try to get the indicator as horizontal as possible, so that you can get some idea of how much the carriage moves away from the vertical centerline.
    These tests are to be regarded as approxiamations, you still don't know the true condition of the inside ways, and for that you'll need to approach this in a slightly different manner, which is outlined in the "Another New Toy" topic on the Monarch forum of Practical Machinist, about 2/3's of the way into the topic.
    Harry

  9. #9
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    You really can't count on the T/S ways anywhere but at the extremes..... you KNOW it didn't get to just in front of teh spindle, and you can be pretty sure it wasn't scuffed around much at the very end......

    Everywhere else, you are guessing. There could have been a repeating operation that required moving the T/S a lot on one area of the bed.... possibly repetitive deep hole drilling, etc, etc.

    So it is best not to get too excited about the T/S ways.

    It IS true that there is likely to be at least 20X as much carriage movement as T/S movement. Usually.

    But it is also probably more likely that the T/S was scuffed around with less oil under it than the carriage was. Oiling provisions for the T/S are often much less good than for the carriage. So it may nearly even out. More movement and more oil, vs less movement, but also less oil and more wear per move.

  10. #10
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    Quote Originally Posted by Rich Carlstedt
    First, put a known round rod of between 1 and 2 inches in diameter and 18 inches long between centers. Make sure the centerdrilled marks are dead on.
    Place a mag base indicator on the carraige OVER the front ways and indicate the bar, both on the top, and on the side. write down your readings
    Do the same when OVER the rear ways. The larger the Rod, the more accurate the reading. You now have a graph of the ways.
    the "side" readings tell you twist , which is usually the front way dropping and the rear way staying plumb.
    To eliminate error between head and tailstock, or to know if you have to compesate, Put a live center in the tailstock and indicate the "Housing".
    Now put the live center in the headstock or a 3 jawchuck and indicate the same again. any difference should be accounted for in your chart
    how do you know the error isn't from twist, tailstock set over, wear on the tailstock ways or tailstock height? Indicating the housing will be off because of gravity.....Peter same with your suggestion, how do you know the source of error is wear and not tailstock height, alignment, or bed twist or a combo of the three?

    The OP's Q leads one to believe he's inspecting rather than restoring.....there are a bunch of ways to get some hints , but to know exactly would require a straight edge blue and feeler gauges
    .

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